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CHAPTER 5: ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2 STRUCTURING THE ENGINEERING ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2.1 Summary of Design Line Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5.2.2 Scaling Relationships in Transformer Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

5.3 TECHNICAL DESIGN INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

5.3.1 Design Line 1 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

5.3.2 Design Line 2 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21

5.3.3 Design Line 3 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

5.3.4 Design Line 4 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

5.3.5 Design Line 5 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

5.3.6 Design Line 6 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24

5.3.7 Design Line 7 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

5.3.8 Design Line 8 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

5.3.9 Design Line 9 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

5.3.10 Design Line 10 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

5.3.11 Design Line 11 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

5.3.12 Design Line 12 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

5.3.13 Design Line 13 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31

5.4 MATERIAL AND LABOR INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-32

5.4.1 Material Prices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34

5.4.2 Material Inputs to the Design Software - Liquid-Immersed . . . . . . . . . . . . . . . . . . . . . . 5-35

5.4.3 Material Inputs to the Design Software - Dry-type . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-38

5.4.4 Labor Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-42

5.5 RESULTS OF THE ANALYSIS ON EACH DESIGN LINE . . . . . . . . . . . . . . . . . . . . . . . . . . 5-49

5.6 SIX EXAMPLE TRANSFORMER DESIGNS AND COST BREAKDOWNS . . . . . . . . . . . . . 5-63

5.6.1 Design Details Report for Non-Evaluated Transformer from Design Line 1 . . . . . . . . . 5-64

5.6.2 Design Details Report for Evaluated Transformer from Design Line 1 . . . . . . . . . . . . . 5-67

5.6.3 Design Details Report for Non-Evaluated Transformer from Design Line 7 . . . . . . . . . 5-71

5.6.4 Design Details Report for Evaluated Transformer from Design Line 7 . . . . . . . . . . . . . 5-75

5.6.5 Design Details Report for Non-Evaluated Transformer from Design Line 12 . . . . . . . . . 5-79

5.6.6 Design Details Report for Evaluated Transformer from Design Line 12 . . . . . . . . . . . . 5-83

5.7 TEAR-DOWN ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-87

LIST OF TABLES

Table 5.2.1 Product Classes and Number of kVA Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Table 5.2.2 Engineering Design Lines (DL) and Representative Units for Analysis . . . . . . . . . . . . . . . 5-3

Table 5.2.3 Liquid-Immersed Design Lines and Representative Units . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Table 5.2.4 Dry-Type, Low-Voltage Design Lines and Representative Units . . . . . . . . . . . . . . . . . . . 5-9

Table 5.2.5 Dry-Type, Medium-Voltage, Single-Phase Design Lines . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Table 5.2.6 Dry-Type, Medium-Voltage, Three-Phase Design Lines . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Table 5.2.7 Common Scaling Relationships in Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Table 5.3.1 A and B Grid Combinations used by Software to Generate Design Database . . . . . . . . . 5-15

Table 5.3.2 A and B Fan Combinations used by Software to Generate Design Database . . . . . . . . . . 5-16

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Table 5.3.3 Core Steel Grades, Thicknesses and Associated Losses . . . . . . . . . . . . . . . . . . . . . . . . . 5-17

Table 5.3.4 Core Configurations Used in Each Design Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Table 5.3.5 Design Option Combinations for the Representative Unit from Design Line 1 . . . . . . . . 5-20

Table 5.3.6 Design Option Combinations for the Representative Unit from Design Line 2 . . . . . . . . 5-21

Table 5.3.7 Design Option Combinations for the Representative Unit from Design Line 3 . . . . . . . . 5-22

Table 5.3.8 Design Option Combinations for the Representative Unit from Design Line 4 . . . . . . . . 5-23

Table 5.3.9 Design Option Combinations for the Representative Unit from Design Line 5 . . . . . . . . 5-24

Table 5.3.10 Design Option Combinations for the Representative Unit from Design Line 6 . . . . . . . . 5-25

Table 5.3.11 Design Option Combinations for the Representative Unit from Design Line 7 . . . . . . . . 5-26

Table 5.3.12 Design Option Combinations for the Representative Unit from Design Line 8 . . . . . . . . 5-27

Table 5.3.13 Design Option Combinations for the Representative Unit from Design Line 9 . . . . . . . . 5-28

Table 5.3.14 Design Option Combinations for the Representative Unit from Design Line 10 . . . . . . . . 5-29

Table 5.3.15 Design Option Combinations for the Representative Unit from Design Line 11 . . . . . . . . 5-30

Table 5.3.16 Design Option Combinations for the Representative Unit from Design Line 12 . . . . . . . . 5-31

Table 5.3.17 Design Option Combinations for the Representative Unit from Design Line 13 . . . . . . . . 5-32

Table 5.4.1 Manufacturer’s Material Prices for Liquid-Immersed Design Lines . . . . . . . . . . . . . . . . 5-35

Table 5.4.2 Marked-up Material Prices for Liquid-Immersed Units, 5-year Average Price Scenario . 5-36

Table 5.4.3 Summary Table of Fixed Material Costs for Liquid-Immersed Units . . . . . . . . . . . . . . . 5-38

Table 5.4.4 Manufacturer’s Material Prices for Dry-Type Design Lines . . . . . . . . . . . . . . . . . . . . . . 5-39

Table 5.4.5 Marked-up Material Prices for Dry-Type Units, 5-year Average Price Scenario . . . . . . . 5-40

Table 5.4.6 Summary Table of Fixed Material Costs for Dry-Type Units . . . . . . . . . . . . . . . . . . . . . 5-42

Table 5.4.7 Labor Markups for Liquid-Immersed and Dry-Type Manufacturers . . . . . . . . . . . . . . . . 5-43

Table 5.4.8 Summary of Labor Times for Liquid-Immersed Units . . . . . . . . . . . . . . . . . . . . . . . . . . 5-46

Table 5.4.9 Summary Table of Labor Times for Dry-Type Units . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-48

Table 5.6.1 Bill of Materials for Non-Evaluated Transformer from Design Line 1 . . . . . . . . . . . . . . 5-66

Table 5.6.2 Bill of Materials for Evaluated Transformer from Design Line 1 . . . . . . . . . . . . . . . . . . 5-70

Table 5.6.3 Bill of Materials for Non-Evaluated Transformer from Design Line 7 . . . . . . . . . . . . . . 5-74

Table 5.6.4 Bill of Materials for Evaluated Transformer frm Design Line 7 . . . . . . . . . . . . . . . . . . . 5-78

Table 5.6.5 Bill of Materials for Non-Evaluated Transformer from Design Line 12 . . . . . . . . . . . . . 5-82

Figure 5.6.6 Bill of Materials for Evaluated Transformer from Design Line 12 . . . . . . . . . . . . . . . . . 5-86

LIST OF FIGURES

Figure 5.3.1 A and B Combination Software Inputs used in the Engineering Analysis . . . . . . . . . . . . 5-16

Figure 5.3.2 Graphic of Single-Phase Core Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Figure 5.3.3 Graphic of Three-phase Core Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

Figure 5.3.4 Cruciform Core Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

Figure 5.4.1 Standard Method of Cost Accounting for Standards Rulemaking . . . . . . . . . . . . . . . . . . 5-32

Figure 5.5.1 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 1 . . . . . . . . . 5-50

Figure 5.5.2 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 2 . . . . . . . . . 5-51

Figure 5.5.3 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 3 . . . . . . . . . 5-52

Figure 5.5.4 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 4 . . . . . . . . . 5-53

Figure 5.5.5 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 5 . . . . . . . . . 5-54

Figure 5.5.6 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 6 . . . . . . . . . 5-55

Figure 5.5.7 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 7 . . . . . . . . . 5-56

Figure 5.5.8 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 8 . . . . . . . . . 5-57

Figure 5.5.9 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 9 . . . . . . . . . 5-58

Figure 5.5.10 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 10 . . . . . . . . 5-59

Figure 5.5.11 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 11 . . . . . . . . 5-60

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Figure 5.5.12 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 12 . . . . . . . . 5-61

Figure 5.5.13 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 13 . . . . . . . . 5-62

Figure 5.6.1 Manufacturer Selling Price Breakdown, Non-Evaluated Transformer from Design Line 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-67

Figure 5.6.2 Manufacturer Selling Price Breakdown, Evaluated Transformer from Design Line 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-71

Figure 5.6.3 Manufacturer Selling Price Breakdown, Non-Evaluated Transformer from Design Line 7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-75

Figure 5.6.4 Manufacturer Selling Price Breakdown, Evaluated Transformer from Design Line 7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-79

Figure 5.6.5 Manufacturer Selling Price Breakdown, Non-Evaluated Transformer from Design Line 12

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-83

Figure 5.6.6 Manufacturer Selling Price Breakdown, Evaluated Transformer from Design Line 12

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-87

Figure 5.6.7 Tear-down Plot Comparison, Design Line 7, 75kVA Three-phase Dry-type . . . . . . . . . . 5-89

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LIST OF ACRONYMS AND ABBREVIATIONS

A present value of future core losses ($/watt)

Al aluminum

ANOPR Advance Notice of Proposed Rulemaking

ANSI American National Standards Institute

B present value of future coil losses ($/watt)

BIL basic impulse insulation level

CSA Canadian Standards Association

Cu copper

DL design line (followed by a number indicating which design line)

DOE United States Department of Energy

H-O DR laser-scribed M3 core steel

Hz hertz

kV kilovolt

kVA kilovolt-ampere (transformer size rating)

LL load losses

M* M2, M3, M4, M6 - grade of core steel

NEMA National Electrical Manufacturers Association

NCI Navigant Consulting, Inc. (formerly Arthur D. Little, Inc.)

NL no-load losses

NOPR Notice of Proposed Rulemaking

OPS Optimized Program Service, Inc.

ORNL Oak Ridge National Laboratory

PC product class

SA1 Metglas amorphous core material

SEC Securities and Exchange Commission

TL total losses

US United States

V volts

Y wye-type transformer terminal connection

ZDMH mechanically scribed, deep-domain refined core steel

M phase

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 NEMA’s TP 1-2002 can be found online at www.nema.org.

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CHAPTER 5: ENGINEERING ANALYSIS

5.1 INTRODUCTION

This chapter provides the technical support documentation on the engineering analysis, evaluating

both liquid-immersed and dry-type distribution transformers. The purpose of the engineering analysis is to

estimate the relationship between the manufacturer’s selling price of a transformer and its corresponding

efficiency rating. This relationship serves as the basis for the subsequent cost-benefit calculations for

individual consumers, manufacturers, and the nation (see Chapter 8, Life-Cycle Cost and Payback Period

Analyses).

5.2 STRUCTURING THE ENGINEERING ANALYSIS

As discussed in the market and technology assessment (Chapter 3), distribution transformers are

classified by their insulation type (liquid-immersed or dry-type), the number of phases (single or three), the

primary voltage (low-voltage or medium-voltage for dry-types) and the basic impulse insulation level (BIL)

rating (for dry-types). Following this convention, the Department developed ten product classes, shown in

Table 5.2.1. These product classes were adapted from National Electrical Manufacturers Association’s

(NEMA) TP 1 classification system, though they do not follow the classification system precisely. NEMA’s

TP 1 classifies medium-voltage, dry-type distribution transformers into two product classes, <60 kilovolt (kV)

BIL and >60 kV BIL. Based on input from manufacturers, the Department elected to increase the

differentiation of medium-voltage, dry-type transformers, and create three product classes of BIL ratings: 20-

45 kV BIL, 46-95 kV BIL and >96kV BIL (see section 3.3). 

Within each of these product classes, distribution transformers are further classified by their kilovoltampere (kVA) rating. These kVA ratings are essentially size categories, indicating the power handling

capacity of the transformers. Due to the construction methods and material properties, efficiency levels vary

by both product class and kVA rating. For NEMA’s TP 1-2002a

, there are 99 kVA ratings across all the

product classes (see section 3.7.1). For the Department, because of the greater degree of differentiation

around the BIL rating in medium-voltage dry-type transformers, there are 115 kVA ratings across all the

product classes, as shown in Table 5.2.1

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Table 5.2.1 Product Classes and Number of kVA Ratings

Distribution Transformer Product Class kVA Range Number of kVA

Ratings

1. Liquid-immersed, medium-voltage, single-phase 10-833 13

2. Liquid-immersed, medium-voltage, three-phase 15-2500 14

3. Dry-type, low-voltage, single-phase 15-333 9

4. Dry-type, low-voltage, three-phase 15-1000 11

5. Dry-type, medium-voltage, single-phase, 20-45 kV BIL 15-833 12

6. Dry-type, medium-voltage, three-phase, 20-45 kV BIL 15-2500 14

7. Dry-type, medium-voltage, single-phase, 46-95 kV BIL 15-833 12

8. Dry-type, medium-voltage, three-phase, 46-95 kV BIL 15-2500 14

9. Dry-type, medium-voltage, single-phase, >96 kV BIL 75-833 8

10. Dry-type, medium-voltage, three-phase, >96 kV BIL 225-2500 8

Total 115

The Department recognized that it would be impractical to conduct a detailed engineering

analysis of the manufacturer’s selling price-efficiency relationship on all 115 kVA ratings, so it

sought to develop an approach that simplified the analysis while retaining reasonable levels of

accuracy. The Department consulted with industry representatives and transformer design engineers,

and developed an understanding of the construction principles for distribution transformers. It found

that many of the units share similar designs and construction methods. Thus, the Department

simplified the analysis by creating 13 engineering design lines, which group together kVA ratings

based on similar principles of design and construction. These 13 design lines subdivide the product

classes, to improve the accuracy of the engineering analysis. These 13 engineering design lines

differentiate the transformers by insulation type (liquid-immersed or dry-type), number of phases

(single or three), and primary insulation levels for medium-voltage dry-type (three different BIL

levels). 

The Department then selected one unit from each of the engineering design lines for study in

the engineering analysis and the LCC analysis (see Chapter 8), reducing the number of units for

analysis from 115 to 13. The Department then extrapolates the results of its analysis from the unit

studied to the other kVA ratings within that same engineering design line. This extrapolation is

conducted in the National Impacts Analysis (see Chapter 10). The technique used to extrapolate the

findings on the representative unit to the other kVA ratings within a design line is referred to as “the

0.75 scaling rule.” This rule states that, for similarly-designed transformers, costs of construction

and losses scale to the ratio of kVA ratings raised to the 0.75 power. The relationship is valid where

the optimum efficiency loading points of the two transformers being scaled are the same. An

example of how this scaling is applied appears in section 5.2.1 of this chapter. A technical discussion

on the derivation of the 0.75 scaling rule appears in Appendix 5-B.

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Table 5.2.2 presents the Department’s 13 design lines and the representative units selected

from each engineering design line for analysis. Descriptions of each of the design lines and the

rationale behind the selection of the representative units follow Table 5.2.2.

Table 5.2.2 Engineering Design Lines (DL) and Representative Units for Analysis

PC* DL Type of Distribution

Transformer

kVA

Range

Representative Unit for this

Engineering Design Line

1

1 Liquid-immersed, single-phase,

rectangular tank 10-167 50 kVA, 65/C, single-phase, 60Hz, 14400V primary,

240/120V secondary, rectangular tank

2 Liquid-immersed, single-phase,

round tank 10-167 25 kVA, 65/C, single-phase, 60Hz, 14400V primary,

120/240V secondary, round tank

3 Liquid-immersed, single-phase 250-833 500 kVA, 65/C, single-phase, 60Hz, 14400V

primary, 277V secondary

2

4 Liquid-immersed, three-phase 15-500 150 kVA, 65/C, three-phase, 60Hz, 12470Y/7200V

primary, 208Y/120V secondary

5 Liquid-immersed, three-phase 750-2500 1500 kVA, 65/C, three-phase, 60Hz,

24940GrdY/14400V primary, 408Y/277V secondary

3 6 Dry-type, low-voltage, singlephase 15-333 25 kVA, 150/C, single-phase, 60Hz, 480V primary,

120/240V secondary, 10kV BIL

4

7 Dry-type, low-voltage, threephase 15-150 75 kVA, 150/C, three-phase, 60Hz, 480V primary,

208Y/120V secondary, 10kV BIL

8 Dry-type, low-voltage, threephase 225-1000 300 kVA, 150/C, three-phase, 60Hz, 480V Delta

primary, 208Y/120V secondary, 10kV BIL

6

9 Dry-type, medium-voltage,

three-phase, 20-45kV BIL 15-500 300 kVA, 150/C, three-phase, 60Hz, 4160V Delta

primary, 480Y/277V secondary, 45kV BIL

10 Dry-type, medium-voltage,

three-phase, 20-45kV BIL 750-2500 1500 kVA, 150/C, three-phase, 60Hz, 4160V

primary, 480Y/277V secondary, 45kV BIL

8

11 Dry-type, medium-voltage,

three-phase, 46-95kV BIL 15-500 300 kVA, 150/C, three-phase, 60Hz, 12470V

primary, 480Y/277V secondary, 95kV BIL

12 Dry-type, medium-voltage,

three-phase, 46-95kV BIL 750-2500 1500 kVA, 150/C, three-phase, 60Hz, 12470V

primary, 480Y/277V secondary, 95kV BIL

10 13 Dry-type, medium-voltage,

three-phase, 96-150kV BIL 225-2500 2000 kVA, 150/C, three-phase, 60Hz, 12470V

primary, 480Y/277V secondary, 125kV BIL

* PC means Product Class (see Chapter 3 of the TSD). The analytical results for PC5, PC7 and PC9 are calculated

based on the results for their three-phase counterparts. The Department did not select any representative units from

the single-phase medium-voltage product classes (PC5, PC7 and PC9) because of their low sales volume.

Liquid-immersed transformers are divided into five engineering design lines, based on their

tank shape, number of phases and kVA ratings. The Department believes that this breakdown

enables the analysis to identify and capture a more accurate representation of the manufacturer’s

selling price and efficiency relationship. Dry-type distribution transformers are broken into eight

engineering design lines, primarily according to their BIL levels. The Department believes this level

of disaggregation is necessary to capture important differences in the price-efficiency relationship,

particularly as the BIL level varies. For example, a 300 kVA, three-phase, dry-type unit could be

classified in design lines 8, 9, 11, or 13 depending on whether the BIL rating is 10 kV (low-voltage),

20-45 kV, 46-95 kV, or 96-150 kV.

For design lines 9 through 13, the representative units selected for some of the dry-type

design lines may not be the standard BIL levels associated with a given primary voltage. The

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Department selected a slightly higher BIL level for the representative units from these design lines to

ensure that any minimum efficiency standard would not excessively penalize customers purchasing

transformers at higher BIL ratings within the range. For example, a 300 kVA with a 4160V primary

is called a “5kV class” transformer and would normally be built with a 30kV BIL level. However,

customers may also choose to order this transformer with 45kV BIL or 60kV BIL. If the candidate

minimum efficiency standard were set based upon a 30kV BIL, it may not be possible to achieve that

same efficiency rating for customers ordering 60kV BIL. Thus, the Department evaluated the middle

BIL level (in this example, 45kV BIL), making it slightly easier to comply for a lower BIL, and not

too difficult (or impossible) for the higher BIL.

The remainder of this section discusses each of the thirteen engineering design lines,

providing a description and explanation of the transformers covered.

Design Line 1. This is the basic, high-volume line for rectangular-tank, single-phase, liquidimmersed distribution transformers, ranging from 10 kVA to 167 kVA. Transformers in this design

line typically have BIL levels ranging from 30 kV to 150 kV, a tap configuration of four 21⁄2 percent

taps, two above and two below the nominal, a primary voltage less than 35 kV and a secondary

voltage less than or equal to 600 Volts (V).

The representative unit selected for design line 1 is a 50 kVA pad-mounted unit, as this is a

high shipment volume rating, and is approximately the middle of the kVA range for this design line

(10 kVA, 15 kVA, 25 kVA, 37.5 kVA, 50 kVA, 75 kVA, 100 kVA and 167 kVA). Engineering

design considerations and manufacturing differences led to the placement of 250 kVA and higher

rated units in design line 3.

Design Line 2. This is the basic, high-volume line for round-tank (pole mounted), singlephase, liquid-immersed distribution transformers, ranging from 10 kVA to 167 kVA. Although some

manufacturers tend to employ the same basic core/coil design for design line 1 and design line 2,

others may have design differences between pad-mounted and pole-mounted transformers. The

Department decided to analyze these two types of distribution transformers separately for the

engineering and Life Cycle Cost (LCC) analysis. Transformers in this design line typically have BIL

levels ranging from 30 kV and 150 kV, a tap configuration of four 21⁄2 percent taps, two above and

two below the nominal, a primary voltage less than 35 kV and a secondary voltage less than or equal

to 600 Volts (V). 

The representative unit selected design line 2 is a 25 kVA pole-mounted unit, as this is a

high-volume rating for pole-mounted transformers, and is on the lower end of the kVA range for this

design line (10 kVA, 15 kVA, 25 kVA, 37.5 kVA, 50 kVA, 75 kVA, 100 kVA and 167 kVA). 

Engineering design considerations and manufacturing differences led to the placement of 250 kVA

and higher rated units in design line 3.

Design Line 3. This design line groups together single-phase, round-tank, liquid-immersed

distribution transformers, ranging from 250 kVA to 833 kVA. Together, design lines 1 through 3

cover all the single-phase, liquid-immersed units (there are no standard kVA ratings between 167 and

250 kVA). Transformers in this design line typically have BIL levels ranging from 30 kV to 150 kV,

a tap configuration of four 21⁄2 percent taps, two above and two below the nominal, a primary

voltage less than 35 kV and a secondary voltage less than or equal to 600 Volts (V).

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The representative unit selected for design line 3 is a 500 kVA round-tank, as this is a

common rating and occurs in the middle of the kVA range for this design line (250 kVA, 333 kVA,

500 kVA, 667 kVA, and 833 kVA). Although high currents result with 277 Volt secondary at the

larger kVA ratings, high-current bushings are available, and a market does exist for these

transformers.

Design Line 4. Design line 4 represents rectangular tank, three-phase, liquid-immersed

distribution transformers, ranging from 15 kVA to 500 kVA. Transformers in this design line

typically have BIL levels ranging from 30 kV to 150 kV, a tap configuration of four 21⁄2 percent taps,

two above and two below the nominal, a primary voltage less than 35 kV and a secondary voltage

less than or equal to 600 Volts (V).

The representative unit selected for design line 4 is a 150 kVA transformer, as this is a

common rating in this design line and occurs approximately in the middle of the kVA range (15 kVA,

30 kVA, 45 kVA, 75 kVA, 112.5 kVA, 150 kVA, 225 kVA, 300 kVA, and 500 kVA). 

Design Line 5. Design line 5 represents rectangular tank, three-phase, liquid-immersed

distribution transformers, ranging from 750 kVA to 2500 kVA. Together, design lines 4 and 5 cover

all the three-phase, liquid-immersed units (there are no standard kVA ratings between 500 and 750

kVA). Transformers in this design line typically have BIL levels ranging from 95 kV to 150 kV, a

tap configuration of four 21⁄2 percent taps, two above and two below the nominal, a primary voltage

less than 35 kV and a secondary voltage less than or equal to 600 Volts (V). 

The representative unit selected for this design line is a 1500 kVA transformer, as this is a

common rating in this size range, and occurs in the middle of the kVA range for this design line (750

kVA, 1000 kVA, 1500 kVA, 2000 kVA, and 2500 kVA).

Design Line 6. Design line 6 represents single-phase, low-voltage, ventilated dry-type

distribution transformers, ranging from 15 kVA to 333 kVA. Transformers in this design line

typically have BIL ratings of 10 kV and a “universal” tap arrangement, meaning six 21⁄2 percent taps,

two above and four below the nominal. The Department selected this tap arrangement based on

recommendations from manufacturers who produce transformers at these ratings. The primary and

secondary voltages are both 600 V or below.

The representative unit selected for design line 6 is 25 kVA, as this is a common rating in this

size range, and occurs toward the low end of the kVA ratings for this design line (15 kVA, 25 kVA,

37.5 kVA, 50 kVA, 75 kVA, 100 kVA, 167 kVA, 250 kVA, 333 kVA). 

Design Line 7. Design line 7 represents three-phase, low-voltage, ventilated dry-type

distribution transformers, ranging from 15 kVA to 150 kVA. Because the kVA range of three-phase

ratings is broad and construction techniques differ, the Department split the range of three-phase,

low-voltage, dry-type transformers into design line 7 and design line 8, so the engineering differences

in core-coil design and manufacturing would be more readily apparent. Transformers in this design

line typically have BIL ratings of 10 kV and a “universal” tap arrangement, meaning six 21⁄2 percent

taps, two above and four below the nominal. The primary and secondary voltages are both 600 V or

below.

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The representative unit selected for design line 7 is a 75 kVA transformer, as this is a

common rating in this size range, and occurs in the middle of the kVA ratings for this design line (15

kVA, 30 kVA, 45 kVA, 75 kVA, 112.5 kVA, 150 kVA). 

Design Line 8. Design line 8 represents three-phase, low-voltage, ventilated dry-type

distribution transformers, ranging from 225 kVA to 1000 kVA. Transformers in this design line

typically have BIL ratings of 10 kV and a “universal” tap arrangement, meaning six 21⁄2 percent taps,

two above and four below the nominal. The primary and secondary voltages are both 600 V or

below. 

The representative unit selected for this design line is a 300 kVA transformer, as this is a

common rating in this size range, and occurs toward the lower end of the range of kVA ratings

included in this design line (225 kVA, 300 kVA, 500 kVA, 750 kVA, and 1000 kVA). 

Design Line 9. Design line 9 represents three-phase, medium-voltage, ventilated dry-type

distribution transformers, ranging from 15 kVA to 500 kVA. To accommodate the broad kVA

range and to allow for engineering differences in construction principles and associated costs, the

Department split the three-phase, medium-voltage, dry-type units into design lines 9 and 10. 

Transformers in this design line typically have primary voltages less than or equal to 5 kV with a BIL

rating between 20 kV and 45 kV. The secondary voltage is less than or equal to 600 V and the tap

arrangement is typically four 21⁄2 percent taps, two above and two below the nominal. 

The representative unit selected for design line 9 is 300 kVA, as this is a common rating in

this size range, and occurs near the high end of the kVA ratings for this design line (15 kVA, 30

kVA, 45 kVA, 75 kVA, 112.5 kVA, 150 kVA, 225 kVA, 300 kVA, and 500 kVA).

Design Line 10. Design line 10 represents three-phase, medium-voltage, ventilated dry-type

distribution transformers, ranging from 750 kVA to 2500 kVA. Transformers in this design line

typically have primary voltages less than or equal to 5 kV with a BIL rating between 20 kV and 45

kV. The secondary voltage is less than or equal to 600 V and the tap arrangement is typically four

21⁄2 percent taps, two above and two below the nominal.

The representative unit selected for this design line is a 1500 kVA transformer, as this is a

common rating, and occurs in the middle of the kVA range for this design line (750 kVA, 1000 kVA,

1500 kVA, 2000 kVA, and 2500 kVA). 

Design Line 11. Design line 11 represents three-phase, medium-voltage, ventilated dry-type

distribution transformers, ranging from 15 kVA to 500 kVA. This design line parallels design line 9,

with a higher primary insulation level, 46 kV to 95 kV BIL. Because dry-type transformer designs

and, more importantly, the efficiency of those designs, is strongly influenced by changes in BIL, the

Department considered these higher BIL ratings separately. The typical tap arrangement is four 21⁄2

percent taps, two above and two below the nominal. The primary voltage is typically less than or

equal to 15 kV and the secondary voltage is less than or equal to 600 V. 

The kVA ratings in design line 11 are 15 kVA, 30 kVA, 45 kVA, 75 kVA, 112.5 kVA, 150

kVA, 225 kVA, 300 kVA and 500 kVA. The shipments for this design line are concentrated in the

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225 kVA through 500 kVA rating; therefore, the Department selected the 300 kVA rating as the

representative unit for analysis.

Design Line 12. Design line 12 represents three-phase, medium-voltage, ventilated dry-type

distribution transformers, ranging from 750 kVA to 2500 kVA. This design line parallels design line

10, with a higher primary insulation level, 46 kV to 95 kV BIL. The typical tap arrangement is four

21⁄2 percent taps, two above and two below the nominal. The primary voltage is typically less than or

equal to 15 kV and the secondary voltage is less than or equal to 600 V. 

The representative unit selected for this design line is a 1500 kVA transformer, as it is a

common rating in this size range and BIL rating, and it occurs in the middle of kVA range covered

by this design line (750 kVA, 1000 kVA, 1500 kVA, 2000 kVA, and 2500 kVA). 

Design Line 13. As a further extension on the dry-type, three-phase, medium-voltage BIL

ranges, the Department analyzed 96 kV to 150 kV BIL, in a design line ranging from 225 kVA to

2500 kVA. The 225 kVA rating is considered to be the lowest kVA rating where one would expect

to see a unit with a BIL greater than 110 kV. The typical tap arrangement is four 21⁄2 percent taps,

two above and two below the nominal. The primary voltage is typically less than or equal to 35 kV

and the secondary voltage is less than or equal to 600 V.

This third set of dry-type, three-phase, medium-voltage distribution transformers spans a

smaller range of kVA ratings, 225 kVA to 2500 kVA. As most of the sales activity in this design

line occurs in the higher kVA ratings, the representative unit selected for design line 13 is a 2000

kVA transformer. This unit is a common rating in this size range, occurs toward the high end of the

range covered by this design line (225 kVA, 300 kVA, 500 kVA, 750 kVA, 1000 kVA, 1500 kVA,

2000 kVA and 2500 kVA). NEMA recommended considering this rating in the Department’s

analysis. (NEMA, No. 7 at p. 5)

In addition to the three product classes for dry-type, medium-voltage, three-phase

distribution transformers (for which there are five engineering design lines) presented in Table 5.2.1,

there are three product classes for single-phase, dry-type, medium-voltage units. As discussed in

Chapter 3, the shipment volume for the single-phase, dry-type, medium voltage is very low, and thus

it does not warrant the level of effort involved in conducting analysis on these specific units. The

Department decided instead to scale the analysis findings from three-phase units to the single-phase

units by dividing by three. In this way, the Department was able to concentrate resources and

improve the accuracy in other, higher volume and more important distribution transformer product

classes.

5.2.1 Summary of Design Line Coverage

The following four tables summarize the coverage of each of the design lines in relation to

the various product classes and kVA ratings. The abbreviation DL stands for design line, and the

row in the table where the phrase “Rep Unit” appears indicates the kVA rating of the representative

unit from that design line. For example, DL 1 stands for design line 1, spanning from 10 to 167 kVA

liquid-type, single-phase. The label “Rep Unit” appears in row 50 kVA, indicating that the 50 kVA

is the representative unit for DL 1. Similarly, the representative unit for DL 2 is the 25 kVA unit. 

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Product Class 1 

Liquid-Immersed, 

Single-Phase 

 Product Class 2 

Liquid-Immersed, 

Three-Phase 

kVA Rectang. 

Tank 

Round 

Tank kVA Design 

Lines 

10 15 

15 30 

25 45 

37.5 75 

50 112.5 

75 150 

100 225 

167 300 

250 500 

333 750 

500 1000 

667 1500 

833 2000 

 2500 DL 1 DL 2 DL 3 

Rep Unit 

Rep Unit 

DL 4 

Rep Unit 

DL 5 

Rep Unit 

Rep Unit 

There are five liquid-immersed design lines, three single-phase and two three-phase, as shown

in Table 5.2.3. To capture any design differences between a single-phase pole vs. pad-mounted

transformer, the Department analyzed units in both DL 1 and DL 2, spanning the same kVA ratings

(10 kVA to 167 kVA). On the three-phase liquid-immersed side, there is no overlap between those

two design lines.

Table 5.2.3 Liquid-Immersed Design Lines and Representative Units

Table 5.2.4 presents the low-voltage, dry-type design lines. For single-phase units, one

design line spans all nine kVA ratings. For the three-phase units, two design lines cover the 11 kVA

ratings in that product class. There is no overlap in the design lines for low-voltage dry-type

transformers.

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Product Class 3 

Dry-Type, Low-Voltage, 

Single-Phase

Product Class 4 

Dry-Type, Low-Voltage, 

Three-Phase

kVA Design Line kVA Design Line 

15 15 

25 30 

37.5 45 

50 75 

75 112.5 

100 150 

167 225 

250 300 

333 500 

 750 

 1000 DL 6 

Rep Unit 

DL 7 

Rep Unit 

DL 8 

Rep Unit 

Table 5.2.4 Dry-Type, Low-Voltage Design Lines and Representative Units

Table 5.2.5 presents product classes (abbreviated “PC” in this table) for medium-voltage,

single-phase, dry-type units. As discussed in section 3.4, National Shipment Estimate, these units

have an extremely low shipment volume. All three product classes shown in Table 5.2.5 together

represent less than one-third of one percent of dry-type shipments on both a per-unit and an MVAcapacity basis. Thus, the Department did not consider it appropriate to conduct analysis of any units

from these three product classes.

As an alternative to investing time and resources analyzing these low-volume units, the

Department used the results from the medium voltage three-phase dry-type units (presented in Table

5.2.6) and divided those findings by three, creating virtual (calculated) representative units (labeled

as “Virtual RU” in the table) for these three product classes. The Department used the

representative units from design lines 9, 10, 11, 12 and 13. These virtual representative units are

shown in their respective rows, following the application of the quotient. For example, in the single

phase (20–45kV BIL) column, the representative unit from DL 9 is a three-phase 300 kVA unit, so it

scales to a single-phase, 100 kVA unit in Table 5.2.5. 

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Dry-Type, Medium-Voltage, Single-Phase

kVA

PC 5* 

Low BIL 

20-45kV 

PC 7 

Med BIL 

46-95kV 

PC 9 

High BIL 

>96kV 

15 - 

25 - 

37.5 - 

50 - 

75 

100 

167 

250 

333 

500 

667 

833 

DL9 / 3 

Virtual RU

DL11 / 3 

Virtual RU

DL13 / 3 

Virtual RU

Virtual RU

DL10 / 3 

Virtual RU

DL12 / 3 

Table 5.2.5 Dry-Type, Medium-Voltage, Single-Phase Design Lines

Table 5.2.6 presents the product classes (abbreviated “PC” in this table) for the mediumvoltage, three-phase, dry-type distribution transformers and each of the design lines and respective

representative units. For the higher volume and larger range of kVA ratings, the Department used

two separate design lines for each, to maintain accuracy. However, for the very high BIL levels

($96kV BIL), one design line (DL 13) covers all the ratings from 225kVA to 2500kVA. Within DL

13, the Department does not extrapolate the results of this unit to ratings lower than 150kVA

because there were no shipments at these ratings in the shipments analysis and it is very unlikely that

they would be built.

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Dry-Type, Medium-Voltage, Three-Phase

kVA PC 6 

Low BIL 

20-45kV 

PC 8 

Med BIL 

46-95kV 

PC 10 

High BIL 

>96kV 

15 - 

30 - 

45 - 

75 - 

112.5 - 

150 - 

225 

300 

500 

750 

1000 

1500 

2000 

2500 

DL 9 

DL 11 

DL 13 

Rep Unit Rep Unit DL 10 

DL 12 

Rep Unit Rep Unit 

Rep Unit 

Table 5.2.6 Dry-Type, Medium-Voltage, Three-Phase Design Lines

5.2.2 Scaling Relationships in Transformer Manufacturing

The Department simplified the engineering analysis by creating design lines, selecting

representative units from these design lines, and scaling the results of the analysis on these

representative units within their respective design lines. This section briefly introduces the scaling

relationship the Department used to extrapolate the findings on the representative units to the other

kVA ratings. A more detailed discussion of the derivation of the 0.75 scaling rule is provided in

Appendix 5B.

The scaling formulae are mathematical relationships that exist between the kVA ratings and

the physical size, cost, and performance of transformers. The size-versus-performance relationships

arise from fundamental equations describing a transformer's voltage and kVA rating. For example,

when the kVA rating, voltage, and frequency are fixed, the product of the conductor current density,

core flux density, core cross-sectional area, and total conductor cross-sectional area is constant. 

To illustrate this point, consider a transformer with five fixed variables: frequency, magnetic

flux density, current density, and BIL rating. If one enlarges (or decreases) the kVA rating, then the

only parameters free to vary are the core cross-section and the core window area through which the

windings pass. Thus, to increase (or decrease) the kVA rating, the dimensions for height, width, and

depth of the core/coil assembly scale equally in all directions. Analysis of this scaling relationship

reveals that each of the linear dimensions varies as the ratio of kVA ratings to the 1⁄4 power. 

Similarly, areas vary as the ratios of kVA ratings to the 1⁄2 power and volumes vary as the ratio of the

kVA ratings to the 3⁄4 or 0.75 power, hence the term "0.75 scaling rule." Application of the 0.75

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scaling rule assumes that the efficiency profile of a given transformer will have the same shape as the

transformer being scaled. Table 5.2.7 depicts the most common scaling relationships in transformers.

Table 5.2.7 Common Scaling Relationships in Transformers

Parameter Being Scaled Relationship to kVA Rating 

(varies with ratio of kVAx

)

Weight (kVA1/kVA0)

3/4

Cost (kVA1/kVA0)

3/4

Length (kVA1/kVA0)

1/4

Width (kVA1/kVA0)

1/4

Height (kVA1/kVA0)

1/4

Total Losses (kVA1/kVA0)

3/4

No-load Losses (kVA1/kVA0)

3/4

The following three relationships are true as the kVA rating increases or decreases, if the type

of transformer (liquid-immersed or dry-type, single-phase or three-phase), the primary voltage, the

core configuration, the core material, the core flux density, and the current density (amperes per

square inch of conductor cross-section) in both the primary and secondary windings are all held

constant:

1. The physical proportions are constant (same relative shape),

2. The eddy loss proportion is essentially constant, and

3. The insulation space factor (voltage or BIL) is constant.

In practical applications, it is rare to find that all of the above are constant over even limited

ranges; however, over a range of one order of magnitude in both directions (e.g., from 50 kVA to 5

kVA or from 50 kVA to 500 kVA), the scaling rules shown in Table 5.2.7 can be used to establish

reasonable estimates of performance, dimensions, costs, and losses. In practice, these rules can be

applied over even wider ranges to estimate general performance levels. The Department’s

application of the 0.75 scaling rule in this analysis is always less than an order of magnitude.

To illustrate how the scaling laws are used, consider two transformers with kVA ratings of S0

and S1. The no-load losses (NL) and total losses (TL) of these two transformers would be depicted

as NL0 and TL0, and NL1 and TL1. Then the relationships between the NL and TL of the two

transformers could be shown as follows:

NL1 = NL0 × (S1 / S0)0.75 Eq. 5.1

where:

NL1 = no-load losses of transformer “1,”

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NL0 = no-load losses of transformer “0,”

S1 = kVA rating of transformer “1,” and

S0 = kVA rating of transformer “0.”

and

TL1 = TL0 × (S1 / S0)0.75 Eq. 5.2

where:

TL1 = total losses of transformer “1,” and

TL0 = total losses of transformer “0.”

Equations 5.1 and 5.2 can be manipulated algebraically to show that the load loss also varies

to the 0.75 power. Starting with the concept that total losses equals no-load losses plus load losses,

we can derive the relationship for load loss (LL), and show that it also scales to the 0.75 power. 

Specifically:

LL1 = TL1 - NL1 Eq. 5.3

where:

LL1 = load losses of transformer “1”

Inserting the TL1 and NL1 terms into this equation, we find:

LL1 = (TL0 × (S1 / S0)0.75) - (NL0 × (S1 / S0)0.75) Eq. 5.4

LL1 = (TL0 - NL0 )× (S1 / S0)0.75 Eq. 5.5

LL1 = (LL0 ) × (S1 / S0)0.75 Eq. 5.6

Where:

LL0 = load losses of transformer “0.”

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Thus, the 0.75 scaling rule can be applied to estimate the losses of a transformer, given the

losses and kVA rating of a reference (analyzed) unit. However, in order for this rule to be

applicable, the transformer type must be the same, and key parameters—such as the type of core

material, core flux density, and conductor current density in the high and low voltage

windings—must be fixed. Additionally, use of the 0.75 scaling rule assumes that the efficiency

profile of a given transformer will have the same shape as the transformer being scaled. Please note

that a detailed discussion on the derivation of the 0.75 scaling rule is provided in Appendix 5B. 

The Department uses the 0.75 scaling rule to scale the analysis findings on each of the

representative units within the 13 design lines to the 102 kVA ratings that were not analyzed. The

scaling rule is applied within the design lines in the national impact analysis (Chapter 10), where the

Department calculates efficiency ratings for the 102 kVA ratings not analyzed.

5.3 TECHNICAL DESIGN INPUTS

For all thirteen representative units, the engineering analysis explores the relationship

between the manufacturer selling prices and corresponding transformer efficiencies. The Department

contracted Optimized Program Service (OPS) in Ohio, a software company specializing in

transformer design since 1969. Using a range of input parameters and material prices, the OPS

software produces a design. This design has specific information about the core and coil, including

physical characteristics, dimensions, material requirements and mechanical clearances, as well as a

complete electrical analysis of the final design. This optimized, practical transformer design, bill of

materials and an electrical analysis report contains sufficient information for a manufacturer to build

this unit. The software’s output is used to generate an estimated cost of manufacturing materials and

labor, which is then converted to a manufacturer selling price by applying markups.

The electrical analysis report estimates the performance of the transformer design (including

efficiency) at 25 percent, 35 percent, 50 percent, 65 percent, 75 percent, 100 percent, 125 percent,

and 150 percent of nameplate load. The software output provides a clear understanding of the

relationship between cost and efficiency because it provides detailed data on design variances, as well

as a bill of materials, labor costs, and efficiency. The software does not capture retooling costs

associated with changing production designs for a specific manufacturer. In some cases however,

the Department captured tooling costs associated with manufacturing mitered cores by applying

adders to the steel price. 

One of the inputs to the design software consisted of a range of what are known in the

industry as A and B evaluation combinations (see section 3.6, Total Ownership Cost Evaluation). 

The combination of A and B inputted to the design software mimics a distribution transformer

purchase order. The A parameter represents a customer's present value of future losses in the

transformer core (no-load losses). The B value represents a customer's present value of future losses

in the windings (load losses). The B parameter is never larger than A, as this would imply a

specification for a transformer whose average load would be more than 100 percent of the nameplate

load. The A and B values take into account a range of factors that usually vary from customer to

customer. 

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The A and B values are expressed in terms of dollars per watt of loss. The greater the values

of A and B, the greater the importance a customer attaches to the value of future transformer losses. 

As A and B values increase, the customer places greater importance on reducing the watts of core

and winding losses, respectively, and so the customer chooses a more energy efficient transformer.

The Department used broad ranging combinations of A and B evaluation formulae (presented

in Table 5.3.1 and Table 5.3.2) to create a complete set of efficiency levels for each design option

combination analyzed. The efficiency levels span from a low first-cost unit to a maximum

technologically feasible (“max-tech”) design. For the low first-cost design, the A and B evaluation

values are both $0/watt, indicating that the customer does not attach any financial value to future

losses in the core or coil of the transformer. For the maximum technologically feasible design, the A

and B evaluation values are very high, pushing the software to design at the highest efficiencies

achievable.

The Department created its combinations of A and B evaluation formulae combining two

techniques to ensure there were sufficient designs in the database for the analysis. The first

technique, as in the ANOPR, the Department created a ‘grid’ of A and B combinations. The ‘grid’

technique involves increasing the value of A by a step value, and then increasing the B value from

zero to that value of A using a different step value. Thus, if A has incremental steps of $0.25 and B

has steps of $0.20, the combinations will work as follows: ($0.00, $0.00), ($0.25, $0.00), ($0.25,

$0.20), ($0.50, $0.00), ($0.50, $0.20), ($0.50, $0.40), ($0.75, $0.00), and so on. Table 5.3.1

presents the ranges and incremental steps for the A and B combinations used in the three grids.

Table 5.3.1 A and B Grid Combinations used by Software to Generate Design Database

Grid

Number

A values 

and increments

B values 

and increments

Resultant # of

(A, B) combinations

1 $0 to $2 by 0.25 steps $0 to $2 by 0.20 steps 47

2 $2.50 to $8 by 0.50 steps $0 to $8 by 0.40 steps 157

3 $9 to $16 by 1.00 steps $3 to $8 by 0.50 steps 85

The second technique for generating A and B evaluation formulae in the Engineering

Analysis was new for the NOPR. The Department understands that the ratio of A to B represents an

implicit loading for the transformer. Therefore, the Department created a set of (A, B) values in

which the B is calculated from the A. The B term is calculated as the A times the percent load

squared. In other words, if A equals $1 and we are interested in calculating the appropriate B for a

50 percent RMS load, then it would be $1 times (0.50)^2, or $0.25. So the combination of ($1.00,

$0.25) represents approximately a 50 percent RMS load. As with the “grid”, the A values increased

with a step function, and B values were calculated as fractions of A so that the ratio of A to B

encompassed the RMS loading points that were identified in the Department’s loading analysis (i.e.,

35% and 50%). Calling this approach the “fan”, the B values were calculated for each A at the

following RMS loading points: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% and

60%. Table 5.3.2 presents the range of the two fan combinations used in the NOPR.

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Figure 5.3.1 A and B Combination Software Inputs used in the Engineering Analysis

Table 5.3.2 A and B Fan Combinations used by Software to Generate Design Database

Fan

Number

A values 

and increments

B values 

and increments

Resultant # of 

(A,B) combinations

1 $0 to $2 by 0.50 steps 5% to 60% implicit loading by 5% steps 47

2 $3 to $16 by 1.00 steps 5% to 60% implicit loading by 5% steps 182

When used together, these two techniques created a broad spectrum of A and B

combinations as inputs to the OPS software. Figure 5.3.1 illustrates the coverage of designs for the

518 A and B combinations.

Occasionally, the design software generated the same transformer design for two different $A

and $B combinations, creating duplicate designs in the engineering analysis database. Later, in the

LCC analysis, the Department removed any duplicate designs from the engineering database.

The Department understands that there are many ways to build a transformer, even with

constant kVA and voltage ratings. For instance, manufacturers can vary the core steels (e.g., M2,

M3, M6), the winding materials (aluminum or copper), and core configurations (shell or core-type). 

Within each of the design lines discussed in the sections starting at 5.3.1, the Department provides

tables listing the design option combinations that it used to analyze each of the representative units. 

Depending on customer needs, the cost of materials, the capital equipment in their facility, and the

skills of their labor force, manufacturers make decisions on how to manufacture a given transformer

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using different core configurations, core steels and winding materials. To capture this variation in

designs, DOE analyzed the thirteen representative units using five to eleven different design option

combinations of core type, core steel and winding material. As discussed in the technology

assessment (see Chapter 3), core steel is produced in a range of qualities (from an efficiency

perspective). M2 core steel is grain-oriented and has thin laminations, and consequently has very

low losses. M43 core steel is not grain-oriented and is rolled in much thicker laminations, thus

contributing to higher core losses. Table 5.3.3 lists all the steel types used in the analysis, and

properties associated with these steels, including nominal thickness and core losses per pound of

steel. Note that the core losses per pound of steel are given as a function of the magnetic flux

density, measured in Tesla.

Table 5.3.3 Core Steel Grades, Thicknesses and Associated Losses

Steel

Grade

Nominal

Thickness 

inches

Core Loss at 60 Hz

Watts per Pound at

magnetic flux density*

Notes / Remarks

M43 0.0185 2.10 Watts/lb at 1.5 T Non-oriented grain silicon steel

M36 0.0185 2.00 Watts/lb at 1.5 T Non-oriented grain silicon steel

M19 0.0185 1.65 Watts/lb at 1.5 T Non-oriented grain silicon steel

M6 0.014 0.66 Watts/lb at 1.5 T

0.94 Watts/lb at 1.7 T Grain-oriented silicon steel

M5 0.012 0.53 Watts/lb at 1.5 T

0.83 Watts/lb at 1.7 T Grain-oriented silicon steel

M4 0.011 0.51 Watts/lb at 1.5 T

0.74 Watts/lb at 1.7 T Grain-oriented silicon steel

M3 0.009 0.45 Watts/lb at 1.5 T

0.70 Watts/lb at 1.7 T Grain-oriented silicon steel

M2 0.007 0.41 Watts/lb at 1.5 T Grain-oriented silicon steel

H0 0.009 0.60 Watts/lb at 1.7 T “High permeability” grade silicon steel

SA1 0.001 0.08 Watts/lb at 1.3 T Amorphous core steel (silicon and boron); flux

density limitation - testing at 1.3 T

ZDMH 0.009 0.34 Watts/lb at 1.5 T

0.46 Watts/lb at 1.7 T

Imported silicon steel, magnetic domain- refined

by mechanical process 

* Watts of loss per pound of core steel are only comparable at the same magnetic flux density (measured in Tesla)

In addition to selecting a core steel, the manufacturer’s selection of a core design may also

contribute to the overall efficiency of a transformer. A transformer facility may be optimized to

work around one or two core configurations. Table 5.3.4 provides a list of all the core

configurations used for each of the 13 design lines. The Department selected these configurations, in

combinations with the range of core steels and winding materials, to represent the most common

construction methods for these kVA ratings in the US market. Note that for design lines 2, 3, 6, 7,

8, and 9, the Department analyzed two different core construction configurations.

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Table 5.3.4 Core Configurations Used in Each Design Line

Design Line # Phases Core Configurations Used in the Engineering Analysis

DL 1 1 Wound core - distributed gap, shell-type

DL 2 1 Wound core - distributed gap, shell-type or core-type

DL 3 1 Wound core - distributed gap, shell-type or core-type

DL 4 3 Wound core - distributed gap, 5-leg

DL 5 3 Wound core - distributed gap, 5-leg

DL 6 1 Stacked, butt-lap, shell-type or core-type

DL 7 3 Stacked, butt-lap or mitered joint, 3-leg

DL 8 3 Stacked, butt-lap or mitered joint, 3-leg

DL 9 3 Stacked, butt-lap or mitered joint, 3-leg

DL 10 3 Stacked, cruciform, mitered joint, 3-leg

DL 11 3 Stacked, mitered joint, 3-leg

DL 12 3 Stacked, cruciform, mitered joint, 3-leg

DL 13 3 Stacked, cruciform, mitered joint, 3-leg

For the single-phase representative units, the configurations used are either core-type or

shell-type. This applies whether the core consists of stacked or wound laminations of core steel. For

wound cores, manufacturers generally employ a technique known as ‘distributed gap.’ This means

that each lamination of core steel wound around the form will have a start and finish point (the

‘gap’), staggered with respect to the laminations on either side. Distributed gap core construction

techniques are used to minimize the performance impact of the lamination joint gaps (reducing the

exciting current) and, by locating inside the coil window, reduces the transformer’s operating sound

level. Figure 5.3.2 illustrates the two types of single-phase core configurations.

Three-phase transformers can have three-legged, four-legged, five-legged or Evans cores. Of

these, in the engineering analysis, the Department considered the three-legged construction

techniques for the three-phase dry-types and five-legged construction for the three-phase liquidimmersed. Figure 5.3.3 below illustrates the difference between the three-legged and the five-legged

core construction techniques. A three-legged core is assembled from stacked laminations, the joints

 

Figure 5.3.2 Graphic of Single-Phase Core Configurations

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of which can be butt-lapped or mitered. Where there is an economic need to reduce core losses,

particularly in keeping with the use of more efficient grades of core steel (M2 or M3), the mitered

core tends to be selected. The Department recognizes that there are a variety of approaches to

mitered core construction - “scrapless T-mitering,” “full-mitering,” and “step-mitering.” The

Department modeled the scrapless T and full-mitered cores. 

For larger kVA ratings, design economics may cause the selection of a cruciform core

section, where multiple lamination widths are stacked in increasing and then decreasing widths to

create a circular core form (or “log”) around which the windings are placed. Figure 5.3.4 illustrates

the cruciform core by showing a cross-section. This figure shows four different widths of steel being

used, but there can be fewer or more widths, depending on the design. By using a core configuration

that better follows the contours of the windings, losses are again reduced, resulting in a more

efficient transformer. The use of the three-legged core usually depends on the primary winding being

delta-connected. If the primary winding is wye-connected, as is frequently the case for pad-mounted

transformers used in underground distribution, the core configuration needs to be four-legged or

five-legged.

The five-legged core is assembled from four wound-core loops, and is the common

configuration for liquid-filled three-phase distribution transformers having a wye-wye voltage

Figure 5.3.3 Graphic of Three-phase Core Configurations

Figure 5.3.4 C r u c i f o r m C o r e

Cross-Section

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connection. Again, this occurs for pad-mounted transformers used in underground distribution. The

individual core loops have distributed gaps as explained for single-phase wound-core transformers.

5.3.1 Design Line 1 Representative Unit 

Design line 1 (DL 1) represents rectangular-tank, liquid-immersed, single-phase distribution

transformers, ranging from 10 kVA to 167 kVA. The representative unit selected for this design line

is a 50kVA pad-mounted unit. The following are the technical specifications which constitute input

parameters to the OPS design software:

KVA: 50 (liquid-immersed, rectangular-tank)

Primary: 14400 Volts at 60 Hz

Secondary: 240/120V

T Rise: 65/C

Ambient: 20/C

Winding Configuration: Lo-Hi-Lo (Shell-Type)

Core: Wound core - distributed gap

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 1.0–3.5 percent

For DL 1, DOE selected eight construction combinations (called “design option

combinations”), based on input from manufacturers and other technical experts. The core selected

was shell-type, because the application is for a pad-mounted unit, and this shape is well suited to a

rectangular tank. With the exception of the max tech/high efficiency designs, DOE selected eight

design option combinations to represent the most common construction practices for this

representative unit. 

Table 5.3.5 Design Option Combinations for the Representative Unit from Design Line 1

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) Shell - DG Wound Core

M6 Cu (wire) Al (strip) Shell - DG Wound Core

M3 Al (wire) Al (strip) Shell - DG Wound Core

M3 Cu (wire) Al (strip) Shell - DG Wound Core

M2 Cu (wire) Al (strip) Shell - DG Wound Core

M2 Cu (wire) Cu (strip) Shell - DG Wound Core

ZDMH Cu (wire) Cu (strip) Shell - DG Wound Core

SA1 (Amorphous) Cu (wire) Cu (strip) Shell - DG Wound Core

The Department analyzed each of the eight design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 4,144 designs.

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5.3.2 Design Line 2 Representative Unit 

Design line 2 (DL 2) represents round-tank, liquid-immersed, single-phase distribution

transformers, ranging from 10 kVA to 167 kVA. The representative unit selected for this design line

is a 25kVA pole-mounted unit. The following are the technical specifications which constitute input

parameters to the OPS design software:

KVA: 25 (liquid-immersed, round-tank)

Primary: 14400 Volts at 60 Hz (125 kV BIL)

Secondary: 120/240V

T Rise: 65/C

Ambient: 20/C

Winding Configuration: Lo-Hi-Lo (Shell-Type), Lo-Hi (Core-Type, for amorphous core)

Core: Wound core - distributed gap

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 1.0–3.5 percent

For DL 2, DOE selected ten design option combinations, based on input from manufacturers

and other technical experts. With the exception of the max tech/high-efficiency designs, DOE

selected these design option combinations to represent the most common construction practices for

the representative unit.

Table 5.3.6 Design Option Combinations for the Representative Unit from Design Line 2

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) Shell - DG Wound Core

M6 Cu (wire) Al (strip) Shell - DG Wound Core

M4 Al (wire) Al (strip) Shell - DG Wound Core

M4 Cu (wire) Al (strip) Shell - DG Wound Core

M3 Cu (wire) Al (strip) Shell - DG Wound Core

M3 Cu (wire) Cu (strip) Shell - DG Wound Core

M2 Cu (wire) Al (strip) Shell - DG Wound Core

M2 Cu (wire) Cu (strip) Shell - DG Wound Core

ZDMH Cu (wire) Cu (strip) Shell - DG Wound Core

SA1 (Amorphous) Cu (wire) Cu (strip) Core - DG Wound Core

The Department analyzed each of the ten design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 5,180 designs.

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5.3.3 Design Line 3 Representative Unit 

Design line 3 (DL 3) represents round-tank, liquid-immersed, single-phase distribution

transformers, ranging from 250 kVA to 833 kVA. The representative unit selected for this design

line is a 500kVA round-tank. The following are the technical specifications which constitute input

parameters to the OPS design software:

KVA: 500 (liquid-immersed, round-tank)

Primary: 14400 Volts at 60 HZ (150kV BIL)

Secondary: 277 Volts

T Rise: 65/C

Ambient: 20/C

Winding Configuration: Lo-Hi-Lo (Shell-Type), Lo-Hi (Core-Type, for amorphous core)

Core: Wound core - distributed gap

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 2.5–5.75 percent

For DL 3, the Department selected seven design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE chose design option combinations to represent the

most common construction practice for this representative unit. 

Table 5.3.7 Design Option Combinations for the Representative Unit from Design Line 3

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) Shell - DG Wound Core

M4 Cu (wire) Al (strip) Shell - DG Wound Core

M3 Cu (wire) Al (strip) Shell - DG Wound Core

M2 Cu (wire) Al (strip) Shell - DG Wound Core

M2 Cu (wire) Cu (strip) Shell - DG Wound Core

ZDMH Cu (wire) Cu (strip) Shell - DG Wound Core

SA1 (Amorphous) Cu (wire) Cu (strip) Core- DG Wound Core

The Department analyzed each of the seven design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 3,626 designs.

5.3.4 Design Line 4 Representative Unit 

Design line 4 (DL 4) represents rectangular tank, liquid-immersed, three-phase distribution

transformers, ranging from 15 kVA to 500 kVA. The representative unit selected for this design line

is a 150kVA transformer. The following are the technical specifications that constitute input

parameters to the OPS design software:

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KVA: 150 (liquid-immersed, pad mount)

Primary: 12470Y/7200 Volts at 60 HZ (95kV BIL)

Secondary: 208Y/120 Volts

T Rise: 65/C

Ambient: 20/C

Terminal Configuration: ANSI/IEEE C57.12.26, Loop Feed

Winding Configuration: Lo-Hi (Core-Type)

Core: Wound core - distributed gap, 5-leg

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 1.5–3.0 percent

For DL 4, DOE selected seven design option combinations of core steel and winding types

based on input from manufacturers and other technical experts. With the exception of the max

tech/high efficiency designs, DOE selected these design option combinations to represent the most

common construction practice for the representative unit.

Table 5.3.8 Design Option Combinations for the Representative Unit from Design Line 4

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) 5-Leg DG Core

M4 Al (wire) Al (strip) 5-Leg DG Core

M3 Cu (wire) Al (strip) 5-Leg DG Core

M2 Cu (wire) Al (strip) 5-Leg DG Core

M2 Cu (wire) Cu (strip) 5-Leg DG Core

ZDMH-price 1 Cu (wire) Cu (strip) 5-Leg DG Core

SA1 (Amorphous) Cu (wire) Cu (strip) 5-Leg DG Core

The Department analyzed each of the seven design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 3,626 designs.

5.3.5 Design Line 5 Representative Unit 

Design line 5 (DL 5) represents rectangular tank, liquid-immersed, three-phase distribution

transformers, ranging from 750 kVA to 2500 kVA. The representative unit selected for this design

line is a 1500kVA transformer. The following are the technical specifications that constitute input

parameters to the OPS design software:

KVA: 1500 (liquid-immersed, pad mount)

Primary: 24940GrdY/14400 Volts (125kV BIL)

Secondary: 480Y/277 Volts

T Rise: 65/C

Ambient: 20/C

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Terminal Configuration: ANSI/IEEE C57.12.26, Loop Feed

Winding Configuration: Lo-Hi (Core-Type)

Core: Wound core - distributed gap, 5-leg

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 4.5-7.0 percent

For DL 5, the Department selected seven design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE selected these design option combinations to represent

the most common construction practices for the representative unit.

Table 5.3.9 Design Option Combinations for the Representative Unit from Design Line 5

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M4 Al (wire) Al (strip) 5-Leg DG Core

M4 Cu (wire) Al (strip) 5-Leg DG Core

M3 Cu (wire) Al (strip) 5-Leg DG Core

M2 Cu (wire) Al (strip) 5-Leg DG Core

M2 Cu (wire) Cu (strip) 5-Leg DG Core

ZDMH Cu (wire) Cu (strip) 5-Leg DG Core

SA1 (Amorphous) Cu (wire) Cu (strip) 5-Leg DG Core

The Department analyzed each of the seven design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 3,626 designs.

5.3.6 Design Line 6 Representative Unit 

Design line 6 (DL 6) represents ventilated dry-type, single-phase, low-voltage distribution

transformers, ranging from 15 kVA to 333 kVA. The representative unit selected for this design line

is a 25 kVA transformer. The following are the technical specifications that constitute input

parameters to the OPS design software:

KVA: 25 (dry-type)

Phases: Single

Primary: 480 Volts at 60 Hz (10 kV BIL)

Secondary: 120/240 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi (For Core-Type), Lo-Lo-Hi (For Shell-Type)

Core: Stacked, butt-lap

Taps: Six 21⁄2 percent, two above and four below the nominal

Impedance Range: 3.0–6.0 percent

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For DL 6, DOE selected nine design option combinations of core steel and winding material,

based on input from manufacturers and other technical experts. With the exception of the max

tech/high-efficiency designs, DOE selected these design option combinations to represent the most

common construction practice for the representative unit. 

Table 5.3.10 Design Option Combinations for the Representative Unit from Design Line 6

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M43, 26 gauge Al (wire) Al (wire) Stacked Core Buttlap

M36, 26 gauge Al (wire) Al (wire) Stacked Core Buttlap

M19, 26 gauge Al (wire) Al (wire) Stacked Core Buttlap

M6 Al (wire) Al (wire) Stacked Core Buttlap

M3 Cu (wire) Al (wire) Stacked Core Buttlap

H-O DR* Cu (wire) Cu (wire) Stacked Core Buttlap

M6 Al (wire) Al (wire) Stacked Shell Buttlap

M3 Cu (wire) Al (wire) Stacked Shell Buttlap

H-O DR* Cu (wire) Cu (wire) Stacked Shell Buttlap

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

The Department analyzed each of the nine design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 4,662 designs.

5.3.7 Design Line 7 Representative Unit 

Design line 7 (DL 7) represents ventilated dry-type, three-phase, low-voltage distribution

transformers, ranging from 15 kVA to 150 kVA. The representative unit selected for this design line

is a 75 kVA transformer. The following are the technical specifications that constitute input

parameters to the OPS design software:

KVA: 75 (dry-type)

Phases: Three

Primary: 480 Volts at 60 Hz (10 kV BIL)

Secondary: 208Y/120 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, butt-lap; Stacked, mitered

Taps: Six 21⁄2 percent, two above and four below the nominal

Impedance Range: 3.0–6.0 percent

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For DL 7, DOE selected eight design option combinations of core steel and winding material,

based on input from manufacturers and other technical experts. With the exception of the max

tech/high-efficiency designs, DOE selected these design option combinations to represent the most

common construction practice for the representative unit. 

Table 5.3.11 Design Option Combinations for the Representative Unit from Design Line 7

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M36, 26 gauge Al (wire) Al (wire) 3-Leg Stacked Buttlap

M19, 26 gauge Al (wire) Al (wire) 3-Leg Stacked Buttlap

M6 Al (wire) Al (wire) 3-Leg Stacked Buttlap

M6 Al (wire) Al (wire) 3-Leg Stacked Scrapless T-miter

M6 Al (wire) Al (wire) 3-Leg Stacked Full Miter**

M4 Cu (wire) Al (wire) 3-Leg Stacked Full Miter

M3 Cu (wire) Al (wire) 3-Leg Stacked Full Miter

H-O DR* Cu (wire) Cu (wire) 3-Leg Stacked Full Miter

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

** Full Miters are not step-miters, but are mitered joints for all three legs. These cores are stacked three by three. 

The Department analyzed each of the seven design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 4,144 designs.

5.3.8 Design Line 8 Representative Unit 

Design line 8 (DL 8) represents ventilated dry-type, three-phase, low-voltage distribution

transformers, ranging from 225 kVA to 1000 kVA. The representative unit selected for this design

line is a 300 kVA transformer. The following are the technical specifications that constitute input

parameters to the OPS design software:

KVA: 300 (dry-type)

Phases: Three

Primary: 480V at 60 Hz (10 kV BIL) Delta Connected

Secondary: 208Y/120 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, butt-lap; Stacked, mitered

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 3.0–6.5 percent

For DL 8, the Department selected five design option combinations of core steel and winding

material, based on input from manufacturers and other technical experts. With the exception of the

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max tech/high-efficiency designs, DOE selected these design option combinations to represent the

most common construction practice for the representative unit. 

Table 5.3.12 Design Option Combinations for the Representative Unit from Design Line 8

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M19, 26 gauge Al (wire) Al (wire) 3-Leg Stacked Buttlap

M6, 29 gauge Al (wire) Al (strip) 3-Leg Stacked Buttlap

M6, 29 gauge Cu (wire) Cu (strip) 3-Leg Stacked Full Miter**

M3 Cu (wire) Al (strip) 3-Leg Stacked Full Miter

H-O DR* Cu (wire) Cu (strip) 3-Leg Stacked Full Miter

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

** Full Miters are not step-miters, but are mitered joints for all three legs. These cores are stacked three by three. 

The Department analyzed each of the six design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 3,108 designs.

5.3.9 Design Line 9 Representative Unit 

Design line 9 (DL 9) represents ventilated dry-type, three-phase, medium-voltage distribution

transformers with a 20–45kV BIL, ranging from 15 kVA to 500 kVA. The representative unit

selected for this design line is a 300 kVA transformer. The following are the technical specifications

that constitute input parameters to the OPS design software:

KVA: 300 (dry-type)

Phases: Three

Primary: 4160V at 60 Hz (45 kV BIL) Delta Connected

Secondary: 480Y/277 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, butt-lap; Stacked, mitered

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 3.0–6.0 percent

For DL 9, the Department selected five design option combinations of core steel and winding

material, based on input from manufacturers and other technical experts. With the exception of the

max tech/high-efficiency designs, DOE selected these design option combinations to represent the

most common construction practice for the representative unit. 

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Table 5.3.13 Design Option Combinations for the Representative Unit from Design Line 9

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6, 29 gauge Al (wire) Al (wire) 3-Leg Stacked Buttlap

M6, 29 gauge Cu (wire) Cu (wire) 3-Leg Stacked Full Miter**

M5 Al (wire) Al (wire) 3-Leg Stacked Full Miter

M3 Cu (wire) Al (strip) 3-Leg Stacked Full Miter

H-O DR* Cu (wire) Cu (strip) 3-Leg Stacked Full Miter

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

** Full Miters are not step-miters, but are mitered joints for all three legs. These cores are stacked three by three. 

The Department analyzed each of the five design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 2,590 designs.

5.3.10 Design Line 10 Representative Unit 

Design line 10 (DL 10) represents dry-type, three-phase, medium-voltage distribution

transformers with a 20–45kV BIL, ranging from 750 kVA to 2500 kVA. The representative unit

selected for this design line is a 1500 kVA transformer. The following are the technical

specifications that constitute input parameters to the OPS design software:

KVA: 1500 (dry-type)

Phases: Three

Primary: 4160V at 60 Hz (45 kV BIL)

Secondary: 480Y/277 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, cruciform, mitered joint

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 4.0-6.0 percent

For DL 10, the Department selected five design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE selected these design option combinations to represent

the most common construction practice for the representative unit. 

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Table 5.3.14 Design Option Combinations for the Representative Unit from Design Line 10

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) 3-Leg Mitered Cruciform

M6 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

M4 Cu (wire) Al (strip) 3-Leg Mitered Cruciform

M3 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

H-O DR* Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

The Department analyzed each of the five design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 2,590 designs.

5.3.11 Design Line 11 Representative Unit 

Design line 11 (DL 11) represents dry-type, three-phase, medium-voltage distribution

transformers with a 46–95kV BIL, ranging from 15 kVA to 500 kVA. The representative unit

selected for this design line is a 300 kVA transformer. The following are the technical specifications

that constitute input parameters to the OPS design software:

KVA: 300 (dry-type)

Phases: Three

Primary: 12470 Volts at 60 Hz (95 kV BIL)

Secondary: 480Y/277 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, mitered joint

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 3.0-7.0 percent

For DL 11, the Department selected five design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE selected these design option combinations to represent

the most common construction practice for the representative unit. 

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Table 5.3.15 Design Option Combinations for the Representative Unit from Design Line 11

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) 3-Leg Stacked Full Miter**

M6 Cu (wire) Cu (strip) 3-Leg Stacked Full Miter

M4 Cu (wire) Al (strip) 3-Leg Stacked Full Miter

M3 Cu (wire) Cu (strip) 3-Leg Stacked Full Miter

H-O DR* Cu (wire) Cu (strip) 3-Leg Stacked Full Miter

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

** Full Miters are not step-miters, but are mitered joints for all three legs. These cores are stacked three by three. 

The Department analyzed each of the five design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 2,590 designs.

5.3.12 Design Line 12 Representative Unit 

Design line 12 (DL 12) represents dry-type, three-phase, medium-voltage distribution

transformers with a 46–95kV BIL, ranging from 750 kVA to 2500 kVA. The representative unit

selected for this design line is a 1500 kVA transformer. The following are the technical

specifications that constitute input parameters to the OPS design software:

KVA: 1500 (dry-type)

Phases: Three

Primary: 12470 Volts at 60 Hz (95 kV BIL)

Secondary: 480Y/277 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, cruciform, mitered joint

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 4.0–7.0 percent

For DL 12, the Department selected five design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE selected these design option combinations to represent

the most common construction practice for the representative unit. 

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Table 5.3.16 Design Option Combinations for the Representative Unit from Design Line 12

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) 3-Leg Mitered Cruciform

M6 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

M4 Cu (wire) Al (strip) 3-Leg Mitered Cruciform

M3 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

H-O DR* Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

The Department analyzed each of the five design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 2,590 designs.

5.3.13 Design Line 13 Representative Unit 

Design line 13 (DL 13) represents dry-type, three-phase, medium-voltage distribution

transformers with a $96kV BIL, ranging from 225 kVA to 2500 kVA. The representative unit

selected for this design line is a 2000 kVA transformer. The following are the technical

specifications that constitute input parameters to the OPS design software:

KVA: 2000 (dry-type)

Phases: Three

Primary: 12470 Volts at 60 Hz (125 kV BIL)

Secondary: 480Y/277 Volts

T Rise: 150/C

Ambient: 20/C

Winding Configuration: Lo-Hi

Core: Stacked, cruciform, mitered joint

Taps: Four 21⁄2 percent, two above and two below the nominal

Impedance Range: 4.0–7.0 percent

For DL 13, the Department selected five design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. With the exception

of the max tech/high-efficiency designs, DOE selected these design option combinations to represent

the most common construction practice for the representative unit. 

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Direct

Labor

Direct

Labor Direct

Material

Direct

Material Overhead Overhead Selling Selling General &

Admin.

General &

Admin. R & D R & D Interest Interest

Indirect Labor

Full Production Cost 1 Non-Production Cost

Indirect Material

Maintenance

Depreciation

Taxes

Insurance related

to assets

Mkt. research

Advertising

POS promotion

Sales person

salary + travel

+ commission

Logistics

- Warehousing

- Delivery

- Record

 keeping

- Order entry/

 processing

Costs of

service &

staff units

General

corporate

costs

- comp. etc.

Costs

associated

with efforts

to find new

or improved

products or

production

processes

Costs

of

borrowing

funds

1 Tax Reform Act of 1986, essentially, requires companies to measure cost of goods sold as the full production cost of the goods sold.

Full Cost of Product Full Cost of Product

Code

compliance

Modernization

Cust. service

Figure 5.4.1 Standard Method of Cost Accounting for Standards Rulemaking

Table 5.3.17 Design Option Combinations for the Representative Unit from Design Line 13

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

M6 Al (wire) Al (strip) 3-Leg Mitered Cruciform

M6 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

M4 Cu (wire) Al (strip) 3-Leg Mitered Cruciform

M3 Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

H-O DR* Cu (wire) Cu (strip) 3-Leg Mitered Cruciform

* H-O DR is laser-scribed core steel, and represents the max tech for dry-type units.

The Department analyzed each of the five design option combinations using the matrix of A

and B values described in Table 5.3.1, creating 2,590 designs.

5.4 MATERIAL AND LABOR INPUTS

The Department uses a standard method of cost accounting to determine the costs associated

with manufacturing. This methodology is illustrated in Figure 5.4.1, where production costs and

non-production costs are combined to determine the manufacturer’s selling price of a product.

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The full production cost and the non-production cost equal the manufacturer’s selling price

of the product. Full production cost is a combination of direct labor, direct materials, and overhead. 

The overhead contributing to full production cost includes indirect labor, indirect material,

maintenance, depreciation, taxes, and insurance related to company assets. Non-production cost

includes the cost of selling (market research, advertising, sales representatives, logistics), general and

administrative costs, research and development, interest payments and profit factor (not shown). 

Because profit factor is included in the non-production cost, the sum of production and nonproduction costs is an estimate of the manufacturer’s selling price.

The Department developed estimates of the costs listed in Figure 5.4.1 from the U.S.

Industry Census Data Reports for 1992 and 1997, manufacturer interviews, and SEC 10-K reports

for ACME Electric Corporation, Powell Industries, Inc., Magnetek, Inc., and Hammond

Manufacturing Company Limited. These estimates were then refined through meetings and dialogue

with transformer manufacturers in early 2002. The following markups resulted:

• Scrap and handling factor: 2.5 percent markup. This markup applies to variable materials

(e.g., core steel, windings, insulation). It accounts for the handling of material (loading into

assembly or winding equipment) and the scrap material that cannot be used in the production

of a finished transformer (e.g., lengths of wire too short to wind, trimmed core steel).

• Mitered scrap factor: 4.0 percent markup. An additional scrap markup applies to steel used

in full-mitered cores. This markup represents material cut from the notch in the yoke.

• Factory overhead: 12.5 percent markup. Factory overhead includes all the indirect costs

associated with production, indirect materials and energy use (e.g., annealing furnace), taxes,

and insurance. The Department only applies factory overhead to the direct material

production costs.

• Non-production: 25 percent markup. This markup reflects costs including selling, general

and administrative, R&D, interest payments, and profit factor. The Department applies the

non-production markup to the sum of direct material, direct labor, and factory overhead. 

The following example shows how the Department applied the markups to the materials, and

how it determined the manufacturer selling price. Consider a 300kVA 45kV BIL three-phase drytype transformer designed for a $1.50 A and a $0.60 B. This design has $3,048 of materials,

including M6 core steel, copper primary and secondary windings, and all the transformer hardware. 

There are approximately 26 hours of labor involved in manufacturing this design, resulting in a labor

cost of $1,147. The factory overhead on this design is $381, as it is only applied to the material cost

(i.e., 12.5 percent of $3,048). The non-production cost is $1,144, as the 25 percent is applied to the

material, labor, and factory overhead costs (i.e., 25 percent of $3,048 + $1,147 + $381). Thus, in

total, DOE estimates this 300kVA three-phase transformer to have a manufacturer selling price of

$5,720. 

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5.4.1 Material Prices

The Department received considerable input from manufacturers concerning recent increases

in the cost of materials, particularly core steel. The Department uses prices of core steel, conductor,

mineral oil, insulation and other materials as an input to the transformer design software used for the

engineering analysis. As the price of one material increases or decreases relative to the other

materials, the software will modify its design and increase or decrease the amount of that material

while balancing other design parameters, creating a cost-optimized transformer. Material pricing is

also critical because the manufacturer’s selling prices calculated in the engineering analysis are based

on a bill of materials that includes specifications for pounds of steel, pounds of conductor, gallons of

mineral oil, tank dimensions and so on. Therefore, as material prices increase, so will the

manufacturer’s selling price. Furthermore, as discussed in Chapter 3, energy-efficient transformers

tend to incorporate more materials (e.g., pounds of core steel, pounds of conductor), making the

impact of more expensive materials even more significant at higher efficiencies.

The Department contracted Optimized Program Service (OPS) to develop material price

estimates for the engineering analysis. OPS used data from their own records as well as data

provided by transformer manufacturers and material suppliers and wholesalers. The resulting prices

are intended to be representative of a standard quantity order for a medium- to large-scale U.S.

transformer manufacturer. The Department conducted the engineering analysis using two material

price scenarios - 1) a five-year average of the material prices (in constant 2004 dollars) from 2000,

2001, 2002, 2003, and 2004 and 2) a more recent material price sensitivity, using material prices

from the first quarter of 2005. The consideration of a second set of material prices in the engineering

analysis was directly in response to comments received during the review of the ANOPR analysis

that material prices are increasing rapidly and the historical lows of recent past were unlikely to be

experienced again. The results of the first quarter 2005 engineering analysis are presented in

Appendix 5C.

The Department noted that the most critical material input to a distribution transformer,

electrical core steel, had increased by more than 100% for some M-grades between the five-year

average price and the first quarter of 2005 (see Table 5.4.1 on the next page). For this reason, the

Department researched the grain-oriented electrical steel market to gain a better understanding of the

main players and some of the factors influencing this significant price increase (see Appendix 3A). 

In the life-cycle cost (LCC) analysis (see Chapter 8), the Department presents results on its

sensitivity analyses conducted on various LCC inputs, which includes material prices. In Chapter 8,

the Q1 2005 material price is referred to as the “high” price scenario and the 2000-2004 average

price scenario is called the “medium” price scenario. The Department then developed a hypothetical

"low" price scenario in order to establish a lower bound for the LCC sensitivity analysis. The low

price scenario is based on material prices in 2002 (the calender year with the lowest $/pound for M6

core steel) and reduces all the material prices in that year by 15%. These material prices can be

found in the material price tables presented in this section. The resulting low-price scenario

manufacturer selling prices are provided in the LCC spreadsheets

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5.4.2 Material Inputs to the Design Software - Liquid-Immersed

Table 5.4.1 presents the material prices for a typical liquid-immersed transformer manufacturer in the first q

hypothetical low material prices (for the LCC material price sensitivity, presented in Chapter 8) and the 2000-2004 prices (all in constant 2004 dollars). The highlighted columns are the prices that were used in the engineering analyTable 5.4.1 Manufacturer’s Material Prices for Liquid-Immersed Design Lines

Material Q1 2005 $/lb. 2002 -15% 2004$/lb. 5-Year Average 2004$/lb. 2004 2004$/lb. 2003 2004$/lb. 2002 2004$/lb

M2 core steel 1.71 0.76 0.95 0.95 0.88 0.89 M3 core steel 1.63 0.65 0.80 0.80 0.78 0.76 M4 core steel 1.56 0.64 0.76 0.75 0.72 0.75 M6 core steel 1.42 0.57 0.70 0.69 0.69 0.67 ZDMH (mechanically-scribed core steel) 2.75 1.23 1.47 1.50 1.42 1.45 SA1 (amorphous) - finished core, volume production 2.50 1.51 1.80 1.89 1.78 1.78 Copper wire, formvar, round #10-20 2.25 1.11 1.55 2.10 1.48 1.31 Copper wire, enameled, round #7-10 flattened 2.21 1.09 1.51 2.05 1.45 1.28 Copper wire, enameled, rectangular sizes 2.65 1.18 1.76 2.51 2.02 1.39 Aluminum wire, formvar, round #9-17 1.56 1.15 1.43 1.53 1.41 1.35 Aluminum wire, formvar, round #7-10 1.58 1.16 1.46 1.54 1.43 1.36 Copper strip, thickness range 0.020-0.045 2.92 1.86 2.32 2.50 2.24 2.19 Copper strip, thickness range 0.030-0.060 2.84 1.79 2.24 2.44 2.15 2.11 Aluminum strip, thickness range 0.020-0.045 1.66 1.30 1.54 1.60 1.58 1.53 Aluminum strip, thickness range 0.045-0.080 1.69 1.24 1.45 1.51 1.49 1.46 Kraft insulating paper with diamond adhesive 1.56 1.32 1.59 1.56 1.54 1.55 

Tank steel 0.50 0.29 0.35 0.35 0.33 0.34 Mineral oil 2.40 1.45 1.71 1.80 1.73 1.71 

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The raw material prices presented in Table 5.4.1 are then marked-up using the manufacturer’s internal mark

section 5.4. For example, a raw material price of $1.00/lb. would be marked-up to $1.44/lb., reflecting the handling percent), the factory overhead (12.5 percent), and the non-production markup (25 percent). The marked-up materias inputs to the transformer design software. During the manufacturer site visits in early 2002, the Department fouconsistent with that of several manufacturers who operate their own, proprietary transformer design software. Tablmark-up steps being applied to the 5-year average material price scenario (2000-2004).Table 5.4.2 Marked-up Material Prices for Liquid-Immersed Units, 5-year Average Price Scenario

Item and Description

Material

Price*

Scrap 

& Handling

Factory

Overhead

N

Prod

M2 core steel $0.95 1.025 1.125 1M3 core steel $0.80 1.025 1.125 1M4 core steel $0.76 1.025 1.125 1M6 core steel $0.70 1.025 1.125 1ZDMH (mechanically-scribed core steel, finished core) $1.47 + 0.30 1.015 1.125 1

SA1 (amorphous material) - finished core, volume production $1.80 + 0.30 1.015 1.125 1Copper wire, formvar, round #10-20 (DL 1,2,4) $1.55 1.025 1.125 1Copper wire, enameled, round #7-10 flattened (DL 3,5) $1.51 1.025 1.125 1Copper wire, enameled, rectangular sizes (DL 3) $1.76 1.025 1.125 1Aluminum wire, formvar, round #9-17 (DL 1,2,4) $1.43 1.025 1.125 1Aluminum wire, formvar, round #7-10 (DL 3,5) $1.46 1.025 1.125 1Copper strip, thickness range 0.02-0.045 (DL 1,2,4) $2.32 1.025 1.125 1Copper strip, thickness range 0.030-0.060 (DL 3,5) $2.24 1.025 1.125 1Aluminum strip, thickness range 0.02-0.045 (DL 1,2,4) $1.54 1.025 1.125 1Aluminum strip, thickness range 0.045-0.080 (DL 3,5) $1.45 1.025 1.125 1Kraft insulating paper with diamond adhesive $1.59 1.025 1.125 1Tank Steel $0.35 1.025 1.125 1Mineral oil (per gallon) $1.71 - 1.125 1

* Five year average (2000 through 2004) for materials expressed in 2004$ per lb. ZDMH and SA1 include $0.30/lb adder for finished 

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Several manufacturers commented to the Department that the U.S. has a 31% anti-dumping

import duty on core steel produced in Japan. One of the core steels considered by the Department as

a high-efficiency grade steel for the liquid-immersed wound-core units was ZDMH. ZDMH is a

mechanically scribed, grain-oriented electrical steel. The process for manufacturing this steel is

patented, and it is only produced in Japan. For the Advance Notice of Proposed Rulemaking

(ANOPR) analysis, the Department considered two price points for ZDMH, one reflecting what a

U.S. manufacturer would pay with the import duty and the other reflecting what a manufacturer in

Mexico or Canada would pay (no duty). The duty only applies to ZDMH raw material, it does not

apply to the material if ‘substantial rework’ were done prior to importation (e.g., building a

transformer or a core outside the U.S. and then importing it). The Department is concerned that if

ZDMH offered a more cost-effective set of liquid-immersed designs for standards compliance, it may

give manufacturers outside the U.S. a competitive advantage over domestic manufacturers.

For the NOPR analysis, the Department modified its use of ZDMH pricing in the engineering

analysis due to input received from several manufacturers. These companies indicated to the

Department that if ZDMH offered the most cost-effective liquid-immersed designs, then they would

out-source core fabrication to a Mexican or Canadian company and import finished cores. Finished

ZDMH cores are not subject to the importation duty, thus the ZDMH price did not include the 31%

import duty, but did include an adder for core processing. The MIA (see Chapter 12) discusses the

effect of this scenario on U.S. transformer manufacturer employment.

In addition to the aforementioned materials that vary during the design optimization process

(e.g., core steel, windings, insulation, etc.), there are other direct materials inputs that are fixed costs

and generally do not influence the design or vary with efficiency rating. These include direct

materials such as the high- and low-voltage bushings and the core clamps. Estimates of the tank

fabrication cost are also prepared, based on the optimized transformer design (the software considers

this variable) and the labor necessary to build the tank. Table 5.4.2, on the next page, summarizes all

the estimated fixed material costs and estimates of the tank costs for each of the five liquid-immersed

design lines.

For design line 1, a 50kVA single-phase pad-mounted unit, the high-voltage bushings are

two universal bushing wells, 15 kV, 95 BIL, 14400V, costing $7 each. The low-voltage bushings

are three threaded copper studs, 240/120V, 50 kVA, costing $20 for the set. Internal hardware

costs includes a core clamp, nameplate, and other miscellaneous hardware costing $25.65. The

finished tank size (and associated cost) varies by design, but the average is approximately $130.

For design line 2, a 25kVA single-phase pole-mounted unit, the high-voltage terminal is a

single wet-process porcelain bushing assembly, 15 kV, 125 BIL, costing $6.00. The low-voltage

terminals are three molded polymer bushings, 120/240V, 25 kVA, costing $8.00 for the set. Internal

hardware costs include a core clamp, nameplate, and other miscellaneous hardware, costing $19.15. 

The finished tank sizes (height and diameter) vary by design, but the average is approximately $70.

For design line 3, a 500kVA single-phase unit, the high-voltage connector is a single wetprocess porcelain bushing, 25 kV, 125 BIL, costing $6.00. The low-voltage bushings are two fourhole “J” Spade 500kVA, 277V, costing $60 for the set. The internal hardware includes a core clamp

($30), nameplate ($0.65) and miscellaneous hardware ($20), totaling $50.65. The design software

optimized the tank cost with each design, including radiators (external cooling) for this kVA rating. 

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The resultant finished round tank has a diameter of 33" to 52", with an average cost of

approximately $500 (including radiators).

For design line 4, a 150kVA three-phase, pad-mounted unit, the high-voltage bushings are

three externally clamped universal high-voltage bushing wells, 8.3/14.4 kV, 95 BIL, costing $7 each. 

The low-voltage bushings are three copper studs at $8 each. The internal hardware includes core

clamps ($30), nameplate ($0.65) and miscellaneous hardware ($45), totaling $75.65 The optimized

finished tank sizes measure 50 inches high and vary in width and depth. The finished rectangular,

welded tank has an average cost of approximately $360.

For design line 5, a 1500kVA three-phase, pad-mounted unit, the high-voltage bushings are

three externally clamped universal high-voltage bushing wells, 15.2/26.3 kV, 125kV BIL, costing

$20 each. The low-voltage bushings are four externally clamped bushings, each having six-hole

spade, costing $160 for the set. The internal hardware includes core clamps ($60), nameplate

($0.65) and miscellaneous hardware ($45), totaling $105.65. The optimized finished tank sizes

measure 70 inches high and vary in width and depth. The finished rectangular, welded tank,

including radiators as specified by the design software, has an average cost of approximately $800.

Table 5.4.3 Summary Table of Fixed Material Costs for Liquid-Immersed Units

Item DL 1 DL 2 DL 3 DL 4 DL 5

High voltage bushings $14 $6 $6 $21 $60

Low voltage bushings $20 $8 $60 $24 $160

Core clamp, nameplate, and misc. hardware $25.65 $19.15 $50.65 $75.65 $105.65

Transformer tank average cost* $130 $70 $500 $360 $800

* Transformer tank steel is used in the design optimization software and varies with the efficiency (and size) of each

design. DL3 and DL5 include calculated costs of radiators, which are scaled for each design based on the required

cooling surface area.

5.4.3 Material Inputs to the Design Software - Dry-type

Table 5.4.3 presents the material prices for a typical dry-type transformer manufacturer in the

first quarter 2005, the hypothetical low material prices (for the LCC material price sensitivity,

presented in Chapter 8) and the 2000-2004 five-year average prices (all in constant 2004 dollars). 

The highlighted columns are the prices used in the engineering analysis.

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Table 5.4.4 Manufacturer’s Material Prices for Dry-Type Design Lines

Material Q1 2005 $/lb. 2002 -15% 2004$/lb. 5-Year Average 2004$/lb. 2004 2004$/lb. 2003 2004$/lb. 2002 2004$/lb. 

H-O DR core steel (laser-scribed) 1.85 0.82 0.99 1.00 0.92 0.97 M3 core steel 1.63 0.65 0.80 0.80 0.78 0.76 M4 core steel 1.56 0.64 0.76 0.75 0.72 0.75 M5 core steel 1.47 0.60 0.72 0.73 0.63 0.70 M6 core steel 1.42 0.57 0.70 0.69 0.69 0.67 M19 core steel (26 gauge) 0.82 0.43 0.56 0.55 0.52 0.51 M36 core steel (29 gauge) 0.69 0.42 0.50 0.53 0.49 0.49 M36 core steel (26 gauge) 0.65 0.36 0.45 0.51 0.44 0.42 M43 core steel (26 gauge) 0.58 0.36 0.43 0.48 0.43 0.42 Copper wire, rectangular 0.1 x 0.2, Nomex wrap 2.69 1.39 2.00 2.72 2.24 1.63 Aluminum wire, rectangular 0.1 x 0.2, Nomex wrap 2.05 1.71 2.06 2.04 2.01 2.01 Copper strip, thickness range 0.020-0.045 2.92 1.86 2.32 2.50 2.24 2.19 Aluminum strip, thickness range 0.020-0.045 1.66 1.30 1.54 1.60 1.58 1.53 Nomex insulation (per pound) 18.00 15.38 18.11 18.00 17.76 18.09 Cequin insulation (per pound) 12.00 10.54 11.99 12.00 12.18 12.40 Impregnation (per gallon) 19.00 14.93 17.80 18.00 17.26 17.57 Enclosure Steel (per pound) 0.50 0.29 0.35 0.35 0.33 0.34 Winding combs (per pound) 10.00 8.79 10.24 10.00 10.15 10.34 

On the following pages, all the material prices entered into the design software for dry-type distribution transformers a

these tables, the Department marked up the material prices before being entering them into the design software.

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Table 5.4.5 Marked-up Material Prices for Dry-Type Units, 5-year Average Price Scenario

Item and Description Material Price* Scrap & Handling Factory Overhead N

Prod

H-O DR core steel (laser-scribed) $0.99 1.025 1.125 1M3 core steel $0.80 1.025 1.125 1M4 core steel $0.76 1.025 1.125 1M5 core steel $0.72 1.025 1.125 1M6 core steel $0.70 1.025 1.125 1M19 core steel (26 gauge) $0.56 1.025 1.125 1M36 core steel (29 gauge) $0.50 1.025 1.125 1M36 core steel (26 gauge) $0.45 1.025 1.125 1M43 core steel (26 gauge) $0.43 1.025 1.125 1Copper wire, rectangular 0.1 x 0.2, Nomex wrapped $2.00 1.025 1.125 1Aluminum wire, rectangular 0.1 x 0.2, Nomex wrapped $2.06 1.025 1.125 1Copper strip, thickness range .02-.045 $2.32 1.025 1.125 1Aluminum strip, thickness range .02-.045 $1.54 1.025 1.125 1Nomex insulation (per pound) $18.11 1.025 1.125 1Cequin insulation (per pound) $11.99 1.025 1.125 1Impregnation (per gallon) $17.80 - 1.125 1

Enclosure steel (per pound) $0.35 1.025 1.125 1Winding Combs (per pound) $10.24 1.025 1.125 1

* Five year average (2000 through 2004) for materials expressed in 2004$ per lb. Average compiled by Paul Goethe, Optimized Progra

As stated in section 5.3, the OPS software does not take into account retooling costs associated with chang

Therefore, to partially capture these differential costs in design lines that had both buttlap and mitered designs, the Dadders in design lines 7, 8, and 9. The adders specified an extra ten cents per pound of core steel for full-mitered defive cents per pound of core steel for T-mitered designs. More detailed costing of the retooling costs for mitering ein the manufacturer impact analysis (see Chapter 12). 

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Similar to the liquid-immersed designs, there are fixed (and some partially variable) hardware

costs associated with dry-type distribution transformers. These are discussed individually and then

summarized in Table 5.4.6.

For design line 6, a 25 kVA single-phase, low-voltage, dry-type, the fixed hardware costs are

$4 for the low-voltage and high-voltage terminals. The mounting frame for attaching the core/coil

assembly to the transformer enclosure is estimated as $9.25. The fiberglass dog-bone duct-spacers

used for this design line cost $0.24 per foot. The miscellaneous hardware costs were estimated to be

$4.50. The ventilated enclosure, a 14-gauge steel enclosure, base, and mounting feet varies with the

size of the core-coil assembly, however it costs approximately $65.

For design line 7, a 75 kVA three-phase, low-voltage, dry-type, the fixed hardware costs are

$9 for the high-voltage terminal board with connection points. The low voltage bus-bar is estimated

to be seven feet at $1.50 per foot, or $10.50. The mounting frame that attaches the core/coil

assembly to the transformer enclosure is estimated to cost $19. The fiberglass dog-bone ductspacers used for this design line are $0.32 per foot. The miscellaneous hardware costs were

estimated at $7. The ventilated enclosure, a 14-gauge steel enclosure, base, and mounting feet varies

with the size of the core-coil assembly, however it costs approximately $70.

For design line 8, a 300 kVA three-phase, low-voltage, dry-type, the high-voltage terminal

boards cost $27. The low-voltage bus-bar is estimated to be nine feet at $2.50 per foot, or $22.50. 

The mounting frame that attaches the core/coil assembly to the transformer enclosure costs

approximately $36. The fiberglass dog-bone duct-spacers used for this design line cost $0.42 per

foot. The miscellaneous hardware costs were estimated at $12. The ventilated enclosure, a 14-gauge

steel enclosure, base, and mounting feet varies with the size of the core-coil assembly, however it

costs approximately $175. 

For design line 9, a 300 kVA three-phase medium-voltage dry-type at 45 kV BIL, the lowvoltage and high-voltage terminal set costs $75. The low-voltage bus-bar is estimated to be eight

feet at $10 per foot, or $80. The mounting frame that attaches the core/coil assembly to the

transformer enclosure costs approximately $36. The fiberglass dog-bone duct-spacers used for this

design line cost $0.42 per foot. The miscellaneous hardware costs were estimated at $25. The

ventilated enclosure, a 14-gauge steel enclosure, base, and mounting feet varies with the size of the

core-coil assembly, however it costs approximately $175.

For design line 10, a 1500 kVA three-phase medium-voltage dry-type at 45 kV BIL, the lowvoltage and high-voltage terminal set costs $120. The low voltage bus-bar is estimated to be

fourteen feet at $10 per foot, or $140. The mounting frame that attaches the core/coil assembly to

the transformer enclosure costs approximately $120. The fiberglass dog-bone duct-spacers used for

this design line cost $0.52 per foot. The miscellaneous hardware costs were estimated at $42. The

ventilated enclosure, a 12-gauge steel enclosure, base, and mounting feet varies with the size of the

core-coil assembly, however it costs approximately $600.

For design line 11, a 300 kVA three-phase medium-voltage dry-type at 95 kV BIL, the lowvoltage and high-voltage terminal set costs $100. The high-voltage terminal boards cost $27. The

low-voltage bus-bar is estimated to be ten feet at $8 per foot, or $80. The mounting frame that

attaches the core/coil assembly to the transformer enclosure costs $42. The fiberglass dog-bone

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duct-spacers used for this design line cost $0.42 per foot. The miscellaneous hardware costs were

estimated at $32. The ventilated enclosure, a 14-gauge steel enclosure, base, and mounting feet

varies with the size of the core-coil assembly, however it costs approximately $300. 

For design line 12, a 1500 kVA three-phase medium-voltage dry-type at 95 kV BIL, the lowvoltage and high-voltage terminal set costs $135. The high-voltage terminal boards cost $27. The

low-voltage bus-bar is estimated to be sixteen feet at $12 per foot, or $192. The mounting frame

that attaches the core/coil assembly to the transformer enclosure costs $125. The fiberglass dogbone duct-spacers used for this design line cost $0.56 per foot. The miscellaneous hardware costs

were estimated at $54. The ventilated enclosure, a 12-gauge steel enclosure, base, and mounting

feet varies with the size of the core-coil assembly, however it costs approximately $770.

For design line 13, a 2000 kVA three-phase medium-voltage dry-type at 125 kV BIL, the

low-voltage and high-voltage terminal set costs $150. The high-voltage terminal boards cost $27. 

The low-voltage bus-bar is estimated to be eighteen feet at $15 per foot, or $270. The mounting

frame that attaches the core/coil assembly to the transformer enclosure costs $175. The fiberglass

dog-bone duct-spacers used for this design line cost $0.60 per foot. The miscellaneous hardware

costs were estimated at $60. The ventilated enclosure, a 12-gauge steel enclosure, base, and

mounting feet varies with the size of the core-coil assembly, however it costs approximately $835. 

Table 5.4.6 Summary Table of Fixed Material Costs for Dry-Type Units

Item DL 6 DL 7 DL 8 DL 9 DL 10 DL 11 DL 12 DL 13

LV and HV terminals (set) $4 n/a n/a $75 $120 $100 $135 $150

HV terminal board(s) n/a $27 $27 $27 $27 $27 $27 $27

LV bus-bar n/a $10.50 $22.50 $80 $140 $80 $192 $270

Core/coil mounting frame $9.25 $19 $36 $36 $120 $42 $125 $175

Nameplate $0.65 $0.65 $0.65 $0.65 $0.65 $0.65 $0.65 $0.65

Dog-bone duct-spacer (ft.) $0.24 $0.32 $0.42 $0.42 $0.52 $0.42 $0.56 $0.60

Winding combs (lb.) n/a n/a n/a n/a n/a $10.24 $10.24 $10.24

Misc. hardware $4.50 $7 $12 $25 $42 $32 $54 $60

Enclosure (12, 14 gauge) ~$65 ~$125 ~$175 ~$250 ~$600 ~$300 ~$770 ~$835

5.4.4 Labor Costs

Labor costs constitute a critical aspect of the cost of manufacturing a distribution

transformer. The Department used the same hourly labor cost for both liquid and dry-type

distribution transformers. The Department developed the hourly cost of labor using a similar

approach to the development of the cost of materials; however, it used different markups with the

exception of the non-production markup. The Department developed the markups shown in Table

5.4.7 after reviewing publicly available information and consulting with industry experts familiar with

transformer manufacturing in the U.S.

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Table 5.4.7 Labor Markups for Liquid-Immersed and Dry-Type Manufacturers

Item description Markup percentage Rate per hour

Labor cost per hour* $ 14.31

Indirect Production** 33% $ 19.03

Overhead*** 30% $ 24.74

Fringe† 21% $ 29.93

Assembly Labor Up-time†† 43% $ 42.77

Non-Production Mark-up††† 25% $ 53.46

Cost of Labor Input to Software $ 53.46

* Cost per hour is from U.S. Census Bureau, 1997 Economic Census of Industry, published September 1999, Table 5,

page 9. Data for NAICS code 3353111 "Power and distribution transformers, except parts" Production workers hours

and wages.

** Indirect Production Labor (Production managers, quality control, etc.) as a percent of direct labor on a cost basis. 

Navigant Consulting, Inc. (NCI) estimate.

*** Overhead includes commissions, dismissal pay, bonuses, vacation, sick leave, and social security contributions. 

NCI estimate.

†

 Fringe includes pension contributions, group insurance premiums, workers compensation. Source: U.S. Census

Bureau, 1997 Economic Census of Industry, published September 1999, Table 3, page 8. Data for NAICS code

335311 "Power, Distribution and Specialty Transformer Manufacturing," Total fringe benefits as a percent of total

compensation for all employees (not just production workers).

†† Assembly labor up-time is a factor applied to account for the time that workers are not assembling product and/or

reworking unsatisfactory units. The markup of 42 percent represents a 70 percent utilization (multiplying by 100/70).

NCI estimate.

††† Non-production markup reflects non-production costs, including selling, general, and administrative, R&D,

interest payments, and profit factor markups. Source: US Industry Census Data for 1992 and 1997; SEC 10-K reports

for Acme, Powell, Magnetek and Hammond; Manufacturer interviews, 2002. 

There are several labor steps involved in manufacturing a liquid-immersed transformer. The

Department prepared estimates of the amount of labor involved, some varying with the transformer

design and others fixed on a per unit basis. These steps are described below, and the amount of time

dedicated to each are given in Table 5.4.6.

• Cutting, Forming, and Annealing - this task involves cutting the core steel to lengths on a

distributed-gap core cutting machine, forming the resulting “donut” of core steel into a

rectangular shape in a hydraulic press, and then annealing the core in a high temperature

annealing furnace. The labor involved in these activities is calculated based on the weight of

core (pounds) multiplied by a constant, which varies with the lamination thickness of the core

steel. For DL1, DL2, and DL4, on M6 designs the constant is 0.08, on M4 its 0.10, M3 is

0.125 and M2 is 0.16. For DL3 and DL5, on M6 designs the constant is 0.05, M4 is 0.07,

M3 is 0.09, and M2 is 0.11. For the prefabricated cores - ZDMH and SA1 (Amorphous

material), the labor for cutting, forming and annealing is set to zero.

• Primary Winding - this task encompasses the hours of labor necessary for winding the

primary conductor of the transformer. It includes set-up time as well as winding time. The

labor hours vary with the number of turns (per phase) for the primary winding. For DL1,

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DL2, and DL4 the winding time is 0.0001 hours per turn. For these smaller kVA ratings

(and smaller cores), this rate is very low because some of the larger liquid-immersed

manufacturers wind multiple coils simultaneously on the same winding machine. This

manufacturing approach improves throughput and productivity at the facility. The rate of

0.0001 hours per turn equates to approximately one-third of a second per turn. On DL3 and

DL5, due to the larger coil size associated with these units, the winding time is 0.002 hours

per turn (approximately 7.2 seconds per turn).

• Secondary Winding - this task involves the hours of labor necessary for winding the

secondary of the transformer. It includes set-up time as well as winding time. On a

distribution transformer (step-down) the number of secondary turns is always less than the

primary. For the liquid-immersed units which are taking a relatively high primary voltage and

dropping to below 600V, the turns ratio can be as large as 100:1. For this reason, the hours

per turn of the secondary are considerably higher than the primary both because there are

fewer turns over which to amortize the set-up time as well as a slower winding rate for the

secondary which has larger cross-sectional area than the primary. For DL1, DL2 and DL4,

the hours per turn of the secondary are 0.015 (54 seconds per turn) and for DL3 and DL5,

the hours per turn are 0.02 (72 seconds per turn).

• Lead Dressing - once a wound coil is taken off the winding machine, work must be

performed on the leads to prepare them for the next manufacturing step. Enamel is removed

to enable good electrical connection and an insulating tubing is slipped over the cable. This is

a fixed amount of labor, and does not vary with efficiency or design. The estimated times are

0.5 hours for DL1 and DL4, 0.07 hours for DL2, 0.35 hours for DL3 and 1.0 hour for DL5.

• Coil Varnishing and Baking - once they are complete, the coils are vacuum dipped in varnish

and baked in an oven to cure the varnish and enhance the integrity of the coil. This task

varies slightly with kVA rating, but does not vary with efficiency. The estimated times are

0.10 hours for DL1, 0.07 hours for DL2, 0.15 hours for DL3, 0.17 hours for DL4 and 0.25

hours for DL5.

• Core Assembly (“Lacing”) - this task involves assembling and banding the annealed wound

core laminations around varnished windings. The annealed bundle of core steel is

disassembled from the inside out by grabbing approximately 1/4 inch bundles, then

reassembling the core steel around the coils. Once all the laminations are reassembled, the

core material is then clamped to maintain the structure. The activity involves feeding a

banding strip around the core material and using a locking clamp to compress and contain the

core material. The labor rate varies with stack height and lamination thickness for each

design. The time for core assembly is approximately 0.5 hours for DL1, 0.3 hours for DL2,

1.5 hours for DL3, 1 hour for DL4 and 3.5 hours for DL5.

• Tanking and Impregnating - this task involves inserting and fastening the core/coil assembly

into the tank. Then, a vacuum is pulled and oil is introduced to the tank. The vacuum and oil

step on round tanks is done through a lid attached to the top of the unit. On the rectangular

and pad-mounted tanks, the vacuum is pulled in a chamber, thus it takes a little longer per

unit. Finally, tap changers and bushings are mounted, and bolted connections made. The

time for this activity does not vary with design or efficiency, but it does vary by kVA rating

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and tank shape. The estimates of labor time for the five liquid-immersed design lines are: 0.5

hours for DL1, 0.11 hours for DL2, 0.3 hours for DL3, 0.62 hours for DL4 and 1.4 hours for

DL5. 

• Inspection - this activity involves verifying that the transformer is assembled properly and is

up to manufacturer's quality specification. This task includes inspecting the lead dressing,

lead tie-up, and other quality certification specifications. The time for this activity does not

vary with design or efficiency, but it does vary by kVA rating. The estimates of labor time

are 0.10 hours for DL1 and DL3, 0.05 hours for DL2, 0.15 hours for DL4 and 0.20 hours for

DL5.

• Preliminary Test - this step involves conducting a test to ensure that the core/coil meets the

specified turns ratio, polarity, core loss, etc. The time for this activity does not vary with

design or efficiency, but it does vary by kVA rating. The estimates of labor time are 0.10

hours for DL1, DL3 and DL4; 0.03 hours for DL2 and 0.15 hours for DL5.

• Final Test - this activity involves testing of the final, assembled unit, with the core/coil

assembly immersed in oil. This test verifies that the unit meets the guaranteed values,

including core and coil losses, impedance, and dielectric tests. The time for this activity does

not vary with design or efficiency, but it does vary by kVA rating. The estimates of labor

time are 0.15 hours for DL1 and DL3, 0.07 hours for DL2, 0.20 hours for DL4 and 0.25

hours for DL5.

• Marking and Miscellaneous - this task involves preparing any extra markings around the

bushings or on the surface of the transformer and other miscellaneous labor associated with

preparing the finished transformer for the customer. The time for this activity does not vary

with design or efficiency, but it does vary by kVA rating. The estimates of labor time are

0.28 hours for DL1, 0.07 hours for DL2, 0.35 hours for DL3, 0.31 hours for DL4, and 0.75

hours for DL5.

• Pallet Loading - this activity involves preparing the transformer for shipping to the customer. 

This includes loading the finished transformer onto a pallet, banding the transformer to the

pallet, wrapping and all other necessary steps for shipping. The time for this activity does not

vary with design or efficiency, but it does vary by kVA rating. The estimates of labor time

are 0.27 hours for DL1, 0.06 hours for DL2, 0.5 hours for DL3 and DL4, and 3 hours for

DL5.

Table 5.4.8 summarizes the estimates of labor time discussed in this section that were used

for the five liquid-immersed units.

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Table 5.4.8 Summary of Labor Times for Liquid-Immersed Units

Labor Activity DL 1

hrs.

DL 2

hrs.

DL 3

hrs.

DL 4

hrs.

DL 5 

hrs.

Cutting, Forming, & Annealing ~1.00 ~0.75 ~4.00 ~3.00 ~8.50

Primary Winding (hrs/turn) 0.0001 0.0001 0.002 0.0001 0.002

Secondary Winding (hrs/turn) 0.015 0.015 0.020 0.015 0.020

Lead Dressing 0.50 0.07 0.35 0.50 1.00

Baking Coils 0.10 0.07 0.15 0.17 0.25

Core Assembly ~0.50 ~0.30 ~1.50 ~1.00 ~3.50

Tanking and Impregnating 0.50 0.11 0.30 0.62 1.40

Inspection 0.10 0.05 0.10 0.15 0.20

Preliminary Test 0.10 0.03 0.10 0.10 0.15

Final Test 0.15 0.07 0.15 0.20 0.25

Pallet Loading 0.27 0.06 0.50 0.50 3.00

Marking and Misc. 0.28 0.07 0.35 0.31 0.75

• Core Stacking - this task involves the labor associated with stacking (assembling) the cut

steel laminations into a distribution transformer core. The amount of labor for this task varies

by kVA rating, stack height and whether the core is grain-oriented or non-oriented. Thus the

labor for core stacking varies with efficiency of the transformer. Approximate labor hours for

core stacking vary from a short as 0.15 hours / inch for a 25 kVA single-phase low-voltage to

0.9 hours / inch for a 2000 kVA three-phase medium-voltage.

• Primary Winding - this task encompasses the hours of labor necessary for winding the

primary conductor of the transformer. It includes set-up time as well as winding time. The

labor hours vary with the number of turns (per phase) for the primary winding. For DL6, the

winding time is the quickest, with 0.001 hours/turn. DL7 is slightly longer with 0.0015

hours/turn. The 300kVA units, DL8, DL9 and DL11 all have the same 0.01 hours/turn. The

1500kVA units, DL10, DL12 and the 2000kVA DL13 all have the same winding time,

0.0125 hours/turn. 

• Secondary Winding - this task involves the hours of labor necessary for winding the

secondary of the transformer. It includes set-up time as well as winding time. The hours per

turn of the secondary are considerably higher than the primary because there are fewer turns

over which to amortize the set-up time as well as a slower winding rate for the secondary

which has larger cross-sectional area. The hours per turn vary from 0.01 to 0.125, depending

on the kVA rating (design line).

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• Lead Dressing - once a wound coil is taken off the winding machine, work must be

performed on the leads to prepare them for the next manufacturing step. Enamel is removed

to enable good electrical connection and an insulating tubing is slipped over the cable. For a

given kVA rating, this is a fixed amount of labor, and does not vary with efficiency or design. 

The range is from 0.15 to 1.0 hours per unit.

• Assembly - this task involves installing the wound cores onto the partially assembled core,

and then lacing the top (yoke) laminations to complete the core. It also includes the time to

set all the core clamps and complete the core/coil assembly. The Department assumed that

the assembly time varies by kVA rating, but does not vary by design within a kVA rating. 

For example, the assembly time for a 1500kVA three-phase unit is estimated at 6 hours while

the assembly time for a 75kVA three-phase unit is estimated at one hour. 

• Inspection - this activity involves verifying that the transformer is assembled properly and is

up to manufacturer's quality specification. This task includes inspecting the lead dressing,

lead tie-up, and other quality certification specifications. The time for this activity does not

vary with design or efficiency, but it does vary by kVA rating. The time estimates vary from

0.05 hours (3 minutes) for the smaller kVA ratings to 0.25 hours (15 minutes) for the larger

units.

• Preliminary Test - this step involves conducting a test to ensure that the core/coil meets the

specified turns ratio, polarity, core loss, etc. The time for this activity does not vary with

design or efficiency, but it does vary by kVA rating. The estimates of labor time range from

0.05 hours (3 minutes) for the smaller kVA ratings to 0.5 hours (30 minutes) for the larger

units.

• Final Test - this activity involves testing of the final, assembled unit, with the core/coil

assembly immersed in oil. This test verifies that the unit meets the guaranteed values,

including core and coil losses, impedance, and dielectric tests. The time for this activity does

not vary with design or efficiency, but it does vary by kVA rating. Similar to the preliminary

test, the labor time estimates range from 0.1 hours (6 minutes) for the smaller kVA ratings

0.75 hours (45 minutes) for the larger units.

• Marking and Miscellaneous - this task involves preparing any extra markings on the terminal

board or on the surface of the transformer, and other miscellaneous labor associated with

preparing the finished transformer for the customer. The time for this activity does not vary

with design or efficiency, but it does vary by kVA rating. The labor estimate ranges from

0.20 hours at the low end to 2.2 hours at the higher kVA ratings.

• Packing - this activity involves preparing the transformer for shipping to the customer. This

includes loading the finished transformer onto a pallet, banding the transformer to the pallet,

wrapping and all other necessary steps for shipping. The time for this activity does not vary

with design or efficiency, but it does vary by kVA rating. The time estimate ranges from 0.20

hours at the low end to 2.0 hours at the higher kVA ratings.

• Enclosure Manufacturing - this task encompasses a labor estimate for all activity associated

with the cutting, forming, assembly, priming, painting, and preparation of the enclosure. This

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labor estimate varies with the kVA rating, spanning from 0.75 hours for the 25kVA singlephase up through 8 hours for the 1500 and 2000kVA cabinets.

Table 5.4.7 presents the hours of labor needed to complete each step in the manufacturing

process for all design lines containing dry-type transformers.

Table 5.4.9 Summary Table of Labor Times for Dry-Type Units

Labor Activity DL 6

hrs.

DL 7

hrs.

DL 8

hrs.

DL 9

hrs.

DL 10

hrs.

DL 11

hrs.

DL 12

hrs.

DL 13

hrs.

Core Stacking (hrs/inch) 0.15 -

0.25

0.25 -

0.35

0.28 -

0.38

0.45-

0.55

0.70 0.70 0.80 0.90

Primary Winding (hrs/turn) 0.001 0.0015 0.01 0.01 0.0125 0.01 0.0125 0.0125

Secondary Winding (hrs/turn) 0.01 0.011 0.035 0.035 0.125 0.035 0.125 0.125

Lead Dressing 0.15 0.25 0.50 0.60 1.00 0.60 1.00 1.00

Assembly 0.35 1.00 2.50 3.00 6.00 4.00 6.00 6.00

Inspection 0.05 0.05 0.10 0.10 0.25 0.10 0.25 0.25

Preliminary Test 0.05 0.05 0.10 0.10 0.50 0.15 0.50 0.50

Final Test 0.10 0.10 0.15 0.15 0.75 0.25 0.75 0.75

Enclosure Manufacturing 0.75 1.50 3.00 5.00 8.00 5.00 8.00 8.00

Packing 0.20 0.20 1.00 1.00 2.00 1.00 2.00 2.00

Marking and Misc. 0.20 0.20 0.60 0.70 2.20 0.80 2.20 2.20

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5.5 RESULTS OF THE ANALYSIS ON EACH DESIGN LINE

This section provides a visual representation of the results of the engineering analysis. The

scatter plots in this section show the relationship between the manufacturer’s selling price and

efficiency for each of the 13 design lines. Each dot on the plots represents one unique design created

by the software at a given manufacturer’s selling price and efficiency level. The placement of each

dot (and the uniqueness of each design) is dictated by the design option combinations (core steel and

windings), core shape, A/B combination and the variable design parameters generated by the design

software. In addition to the results provided in this section, the Department also prepared additional

scatter plots depicting results of the engineering analysis results for the 13 representative units,

including watts of core and coil loss and the weight by efficiency (see Appendix 5A). 

As discussed earlier in this chapter, the Department received several comments on the

ANOPR analysis that material prices, and particularly core steel, were experiencing a rapid increase. 

Therefore, in addition to its analysis on a five year average material price (2000 through 2004)

presented here, the Department also conducted a current price scenario of the first quarter 2005. 

The engineering analysis results of the Q1 2005 material price scenario are presented in Appendix

5C, along with a comparison between these material prices and the five year average. The

Department also calculated a hypothetical low materials price scenario, which represents a 15%

reduction over the 2002 materials prices (year in which M6 had the lowest $/pound between 2000

and 2004). The results of the low price scenario are included in the LCC spreadsheets, where they

are used for an LCC sensitivity analysis.

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Figure 5.5.1 presents a plot of the manufacturer selling prices and efficiency levels for the full

database of designs for the representative unit from design line 1, a 50kVA single-phase liquidimmersed pad-mounted distribution transformer. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

• NEMA’s TP 1-2002 efficiency level of 98.9 percent is met by most M3 and M2 core designs. 

However, many of the M6 core designs exhibit efficiencies below this level.

• The amorphous metal (SA1) core extends the available efficiency for the transformers beyond

99.6 percent, but at a significant cost.

500

1,000

1,500

2,000

2,500

3,000

98.40% 98.60% 98.80% 99.00% 99.20% 99.40% 99.60% 99.80%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_sh

M6CuAl_sh

M3AlAl_sh

M3CuAl_sh

M2CuAl_sh

M2CuCu_sh

ZDMHCuCu_sh

SA1CuCu_sh

Figure 5.5.1 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 1

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Figure 5.5.2 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 2, a 25kVA single-phase liquidimmersed pole-mounted distribution transformer. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

• The NEMA TP 1-2002 standard of 98.7 percent can be achieved with several design option

combinations, including M3CuAl and M3CuCu.

• In most cases, the maximum efficiency available with conventional silicon core steels is

approximately 99.2 percent. However, the amorphous metal (SA1) provides efficiencies up

to about 99.5 percent.

400

600

800

1,000

1,200

1,400

1,600

1,800

98.00% 98.20% 98.40% 98.60% 98.80% 99.00% 99.20% 99.40% 99.60% 99.80%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_sh

M6CuAl_sh

M4AlAl_sh

M4CuAl_sh

M3CuAl_sh

M3CuCu_sh

M2CuAl_sh 

M2CuCu_sh

ZDMHCuCu_sh

SA1CuCu_co

Figure 5.5.2 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 2

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Figure 5.5.3 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 3, a 500kVA single-phase liquidimmersed distribution transformer with radiators. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

• All design option combinations have designs that meet or exceed the NEMA TP 1-2002

efficiency of 99.3 percent.

• In most cases, the maximum efficiency available is limited to approximately 99.6 percent. 

However, the amorphous metal design option combination provides efficiencies up to about

99.75 percent, with an available range from about 99.35 percent to nearly 99.75 percent.

1,000

3,000

5,000

7,000

9,000

11,000

13,000

15,000

98.90% 99.00% 99.10% 99.20% 99.30% 99.40% 99.50% 99.60% 99.70% 99.80%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_sh

M4CuAl_sh

M3CuAl_sh

M2CuAl_sh

M2CuCu_sh

ZDMHCuCu_sh

SA1CuCu_co

Figure 5.5.3 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 3

 EE-RM/STD-00-550 COMMENT 83
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Figure 5.5.4 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 4, a 150kVA three-phase liquidimmersed distribution transformer. The efficiency levels shown in this plot represent transformers at

50 percent of nameplate load and are corrected for temperature. The following observations can be

made about this scatter plot:

• At the lower efficiencies, the M6 and M4 steel cores offer a low-cost option for increasing

efficiency, but do not meet the NEMA TP 1-2002 efficiency standard of 98.9 percent.

• The amorphous metal design option combination extends the available efficiency for the

transformers up to 99.6 percent, but at a significant cost.

1,500

2,500

3,500

4,500

5,500

6,500

7,500

98.20% 98.40% 98.60% 98.80% 99.00% 99.20% 99.40% 99.60% 99.80%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_co

M4AlAl_co

M3CuAl_co

M2CuAl_co

M2CuCu_co

ZDMHCuCu_co

SA1CuCu_co

Figure 5.5.4 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 4

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Figure 5.5.5 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 5, a 1500kVA three-phase liquidimmersed distribution transformer. The efficiency levels shown in this plot represent transformers at

50 percent of nameplate load and are corrected for temperature. The following observations can be

made about this scatter plot:

• Every design option combination has designs that meet the NEMA TP 1-2002 efficiency of

99.3 percent, however many of the M6 and M4 core designs exhibit efficiencies lower than

99.3 percent.

• Beyond 99.5 percent, the SA1 core provides additional efficiency with increased cost. 

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

98.90% 99.00% 99.10% 99.20% 99.30% 99.40% 99.50% 99.60% 99.70% 99.80%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M4AlAl_co

M4CuAl_co

M3CuAl_co

M2CuAl_co

M2CuCu_co

ZDMHCuCu_co

SA1CuCu_co

Figure 5.5.5 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 5

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Figure 5.5.6 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 6, a 25kVA single-phase low-voltage

dry-type transformer. The efficiency levels shown in this plot represent transformers at 35 percent of

nameplate load and are corrected for temperature. The following observations can be made about

this scatter plot:

• The least-expensive cores, M43, M36, and M19, do not meet the minimum efficiency level

for NEMA’s TP 1-2002 for a 25kVA low-voltage, dry-type, single-phase of 98.0 percent.

• The H-O DR steel cores provide the highest efficiency but are limited to about 99.0 percent

efficiency. At these higher efficiency levels, the cost of the transformers rises exponentially

with little or no gain in efficiency.

200

400

600

800

1,000

1,200

1,400

94.50% 95.00% 95.50% 96.00% 96.50% 97.00% 97.50% 98.00% 98.50% 99.00% 99.50%

Efficiency at 35% load, Temperature Corrected

Manufacturer Selling Price ($)

M43AlAl_co_bl

M36AlAl_co_bl

M19AlAl_co_bl

M6AlAl_co_bl

M3CuAl_co_bl

HOCuCu_co_bl

M6AlAl_sh_bl

M3CuAl_sh_bl

HOCuCu_sh_bl

Figure 5.5.6 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 6

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Figure 5.5.7 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 7, a 75kVA three-phase low-voltage

dry-type transformer. The efficiency levels shown in this plot represent transformers at 35 percent of

nameplate load and are corrected for temperature. The following observations can be made about

this scatter plot:

• The M3CuAl transformer has essentially the same costs and efficiency gains as the HOCuCu

transformer. However, the H-O DR transformer provides a slightly higher efficiency than

the M3 transformer.

• The M19 and M36 cores do not achieve the minimum efficiency rating of 98.0 percent

under NEMA’s TP 1-2002 for a 75kVA three-phase LV dry-type transformer.

500

1,000

1,500

2,000

2,500

3,000

3,500

95.00% 95.50% 96.00% 96.50% 97.00% 97.50% 98.00% 98.50% 99.00% 99.50%

Efficiency at 35% load, Temperature Corrected

Manufacturer Selling Price ($)

M36AlAl_bl

M19AlAl_bl

M6AlAl_bl

M6AlAl_mtt

M6AlAl_mtf

M4CuAl_mtf

M3CuCu_mtf

HOCuCu_mtf

Figure 5.5.7 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 7

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Figure 5.5.8 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 8, a 300kVA three-phase low-voltage

dry-type transformer. The efficiency levels shown in this plot represent transformers at 35 percent of

nameplate load and are corrected for temperature. The following observations can be made about

this scatter plot:

• The HOCuCu transformer does not appear to have any cost benefit over the M3CuAl

transformer. At 99.0 percent efficiency, a transformer with the M3 steel core offers the

least cost and at higher efficiencies has costs equal to those of the H-O DR core steel.

• The M19 core steel can not reach the minimum efficiency of 98.6 percent under NEMA’s

TP 1-2002.

2,000

3,000

4,000

5,000

6,000

7,000

8,000

96.00% 96.50% 97.00% 97.50% 98.00% 98.50% 99.00% 99.50% 100.00%

Efficiency at 35% load, Temperature Corrected

Manufacturer Selling Price ($)

M19AlAl_bl

M6AlAl_bl

M6CuCu_mtf

M3CuAl_mtf

HOCuCu_mtf

Figure 5.5.8 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 8

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Figure 5.5.9 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 9, a 300kVA three-phase mediumvoltage dry-type transformer with a 45kV BIL. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

• NEMA’s TP 1-2002 efficiency level for this unit is 98.6 percent efficient. This level can be

achieved by using M6 or better core steels.

• Rapid increase in price is realized in the M3 and H-O DR core steels, as the efficiency level

increases. For example, moving a fraction of an efficiency level (e.g., from 99.00 percent to

99.5 percent) can almost double the price.

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

12,000

98.20% 98.40% 98.60% 98.80% 99.00% 99.20% 99.40% 99.60%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_bl M6CuCu_mt

M5AlAl_mt M3CuAl_mt

HOCuCu_mt

Figure 5.5.9 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 9

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Figure 5.5.10 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 10, a 1500kVA three-phase mediumvoltage dry-type transformer with a 45kV BIL. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

· NEMA’s TP 1-2002 efficiency level of 99.1 percent is met by M4, M3 and HO core steel

designs.

· As the efficiency increases, the laser-scribed (H-O DR) and M3 steel cores have similar costs.

7,000

12,000

17,000

22,000

27,000

32,000

37,000

42,000

98.60% 98.70% 98.80% 98.90% 99.00% 99.10% 99.20% 99.30% 99.40% 99.50% 99.60%

Efficiency at 50% load, Temperature Corrected

Manufacture Selling Price ($)

M6AlAl_cf

M6CuCu_cf

M4CuAl_cf

M3CuCu_cf

HOCuCu_cf

Figure 5.5.10 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 10

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Figure 5.5.11 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the design line 11, a 300kVA three-phase medium-voltage dry-type

transformer with a 95kV BIL. The efficiency levels shown in this plot represent transformers at 50

percent of nameplate load. The following observations can be made about this scatter plot:

· The least-cost high-efficiency design path at 50 percent load varies between the M3, M4, and

H-O DR cores steel design option combinations.

· The M6 cores offer the least-cost options only at the lowest efficiency levels. In general, the

transformers that use the M6 core steel are not the most cost-effective option available, and

many of the M6 designs do not meet the NEMA TP 1-2002 efficiency level of 98.5 percent.

4,000

6,000

8,000

10,000

12,000

14,000

16,000

97.60% 97.80% 98.00% 98.20% 98.40% 98.60% 98.80% 99.00% 99.20% 99.40%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6CuCu_mt

M4CuAl_mt

M3CuCu_mt

HOCuCu_mt

M6AlAl_mt

Figure 5.5.11 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 11

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Figure 5.5.12 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 12, a 1500kVA three-phase mediumvoltage dry-type transformer with a 95kV BIL. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load. The following observations can be made about this

scatter plot:

· NEMA’s TP 1-2002 efficiency level of 99.0 percent is met by M4, M3 and HO core steel

designs.

· Above 99.3 percent efficiency, the H-O DR steel design option combination has a slight cost

advantage over the M3 core. 

15,000

20,000

25,000

30,000

35,000

40,000

45,000

98.60% 98.80% 99.00% 99.20% 99.40% 99.60%

Efficiency at 50% load, Temperature Corrected

Manufacturer Selling Price ($)

M6AlAl_cf

M6CuCu_cf

M4CuAl_cf

M3CuCu_cf

HOCuCu_cf

Figure 5.5.12 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 12

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12,000

22,000

32,000

42,000

52,000

62,000

98.90% 99.00% 99.10% 99.20% 99.30% 99.40% 99.50% 99.60% 99.70%

Efficiency at 50% load, Temperature Corrected

Manfuacturer Selling Price ($)

M6AlAl_cf

M6CuCu_cf

M4CuAl_cf

M3CuCu_cf

HOCuCu_cf

Figure 5.5.13 Scatter Plot of Manufacturer Selling Price and Efficiency for Design Line 13

Figure 5.5.13 presents a plot of the manufacturer sales prices and efficiency levels for the full

database of designs for the representative unit from design line 13, a 2000kVA three-phase mediumvoltage dry-type transformer with a 125kV BIL. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load and are corrected for temperature. The following

observations can be made about this scatter plot:

· NEMA’s TP 1-2002 efficiency level of 99.0 percent is met by all core steel design option

considerations considered by the Department.

· At efficiency levels of 99.3 percent and above, the M3 steel core and H-O DR steel cores

have similar costs and efficiency gains.

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5.6 SIX EXAMPLE TRANSFORMER DESIGNS AND COST BREAKDOWNS

This section presents some of the OPS transformer designs from the Department’s

Engineering Analysis database. As discussed earlier, to prepare a cost-efficiency relationship on

selected representative units, the Department contracted Optimized Program Service (OPS), a

software company specializing in transformer design since 1969. Using a range of input parameters

and material prices, more than 45,000 transformer designs were created by OPS for the

Department’s analysis. For each design, the software generates specific information about the core

and coil, including physical characteristics, dimensions, material requirements and mechanical

clearances, as well as a complete electrical analysis of the final design. For information on OPS and

their software, visit their website: http://www.opsprograms.com/home.html

To illustrate the typical output from the OPS software, two designs from each of the three

superclasses (i.e., liquid-immersed, low-voltage dry-type and medium-voltage dry-type) are

presented in this section. As these practical designs illustrate, the software output is used to create a

bill of materials, which is marked-up to arrive at the manufacturer’s selling price. The OPS software

provides an electrical analysis including efficiency, which, when plotted with the manufacturer’s

selling price, constitutes the primary output of the engineering analysis.

The six distribution transformers presented are two each from three design lines - 1, 7 and 12. 

Across all the design lines, the complete database of designs contains 46,102 distribution transformer

specification and winding sheets, bills of materials, and performance reports. This design database is

then used by the LCC analysis (see Chapter 8) as it simulates purchases of distribution transformers

in the marketplace.

Design Line 1: 50 kVA single-phase, liquid-immersed

• M6 core steel with an aluminum primary and secondary windings (M6AlAl) at a $0.00 A and

a $0.00 B evaluation formula.

• M3 core steel with a copper primary winding and an aluminum secondary winding (M3CuAl)

at a $1.50 A and a $0.38 B evaluation formula.

Design Line 7: 75 kVA three-phase, low-voltage dry-type 

• M6 buttlap core steel with aluminum primary and secondary windings (M6AlAl) at a $0.00 A

and a $0.00 B evaluation formula.

• M6 t-mitered core steel with aluminum primary and secondary windings (M6AlAl) at a $1.50

A and a $0.14 B evaluation formula.

Design Line 12: 1500 kVA three-phase, medium-voltage dry-type 

• M6 core steel with aluminum primary and secondary windings (M6AlAl) at a $0.00 A and a

$0.00 B evaluation formula.

• M3 core steel with copper primary and secondary windings (M3CuCu) at a $0.50 A and a

$0.08 B evaluation formula. 

For the six designs presented, the design detail report is followed by a bill of materials

showing the cost calculation, and a pie chart providing a breakdown of the final selling price.

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5.6.1 Design Details Report for Non-Evaluated Transformer from Design Line 1

A design specification report for a 50kVA single-phase liquid-immersed transformer appears

below. This design incorporates M6 core steel, with an aluminum primary and an aluminum

secondary. The evaluation factors for this design are $0.00 A and $0.00 B. The bill of materials and

associated breakdown of costs for this design are also reported, after the design and electrical

analysis reports.

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3- 1 5:40: 6

DG-CORE SHELL TYPE TRANSFORMER NL1PM6ALAL 

FREQUENCY 60.0 KVA RATING 50.00 @ 100.00% DUTY CYCLE

CORE DG-M6 M 6 THICKNESS .0140

 D: 6.738 E: 2.073 F: 3.104 G: 7.476 EFF. AREA 26.952 WEIGHT 203.850

WINDING FORM: INS. DIM. 6.988 X 4.331 THICKNESS .072 LENGTH 6.976

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 .0267X 6.2262 AL 31.83 25.47 .375 6.204

P1 1 #14.5 ROUND AL 5643.34 35.83 .375 18.182

S2 .0267X 6.2262 AL 57.67 46.13 .375 11.238

NUMBER OF COILS 1 TOTAL BARE CONDUCTOR WEIGHT 35.558

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 15.0 15 1.0 1(.00500) 1(.03000) .471

P1 1800.0 1710.0 1890.0 21 92.0 3(.00500) 1(.10000) 1.677

S2 15.0 15 1.0 1(.00500) 1(.05000) .471

 TOTAL BUILD(%) 92.51

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 1755.0( 14040.00) 1845.0( 14760.00) 1890.0( 15120.00)

WNDG INTERNAL DUCTS(100.00) %EFF EXTERNAL DUCTS(100.00) %EFF

----------------------------------------------------------------

S1 3 .125 X .125 IN. END 

P1 6 .125 X .125 IN. END .125 X .125 IN. END 

S2 1 .125 X .125 IN. END .125 X .125 IN. END 

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 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 14400.00 13680.00 15120.00 34.5 3.541 27.52329 1293.

S1 118.32 10.0 208.330 .00256 1253. 1.4

S2 117.77 10.0 208.330 .00463 1253. 1.9

 F.L. N.L.

FLUX DENS. 17.120 17.262 LEAKAGE INDUCTANCE MHYS 217.723

CORE LOSS 174.699 179.762 POWER FACTOR 1.0000

COIL LOSS 828.787 .028 IMPEDANCE % 2.54

EXCIT. VA 367.167 417.373 EFFICIENCY % 98.03

EXCIT. CURR. .025 .029 TANK OIL GAL 41.86

AMBIENT TEMP. 20.00 NOMINAL LENGTH 14.50

TEMP.RISE 65.00 NOMINAL DEPTH 16.20

OPERATING TEMP. 85.00 NOMINAL HEIGHT 11.62

 2

 COND. I R LOSS = 806.3795

 COND. EDDY CURRENT LOSS = 2.2476

 OTHER STRAY LOSS = 20.1595

 K VALUE = 1.0000

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .35 98.24 .341 .504 .608 45.690 28.6

 35 .50 98.49 .484 .703 .854 90.911 33.6

 50 .75 98.54 .717 1.004 1.234 192.395 44.2

 65 1.03 98.43 .980 1.307 1.633 341.577 58.6

 75 1.22 98.32 1.156 1.509 1.901 464.858 65.0

 100 1.64 98.03 1.545 2.018 2.542 828.772 65.0

 125 2.07 97.70 1.938 2.531 3.188 1299.377 65.0

Table 5.6.1 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for a nonevaluated transformer from design line 1, a 50kVA single-phase, liquid-immersed, pad-mount M6

design, with an aluminum primary and an aluminum secondary. This design was generated using a

$0.00A and $0.00B.

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Bill of Materials and Labor for liquid-immersed, single-phase, pad-mount, 50kVA

A$ Input $0.00

B$ Input $0.00

Efficiency at 50% load 98.56%

Material item Type quantity $ each $ total

Core steel* (lb) M6-.014 204 0.70$ 143.49 $ 

Primary winding* (lb) Aluminum wire, formvar, round #9-17 18 1.43 $ 26.00 $ 

Secondary windings* (lb) Aluminum strip, thickness range 0.02-0.045 17 1.54 $ 26.90 $ 

Winding form & insulation* (lb) Kraft insulating paper with diamond adhesive 4 1.59 $ 5.59 $ 

Oil (gal) - 42 1.71 $ 71.57 $ 

Tank - 1 132.95 $ 132.95 $ 

Core clamp - 1 15.00 $ 15.00 $ 

Nameplate - 1 0.65 $ 0.65 $ 

Bushings HV & LV 1 34.00 $ 34.00 $ 

Misc. hardware - 1 10.00 $ 10.00 $ 

Scrap factor 1.0% $ 2.02

Total Material Cost $ 468.17

Labor item hours rate $ total

Lead dressing 0.50 42.77 21.39 $ 

Inspection 0.10 42.77 4.28 $ 

Baking coils 0.10 42.77 4.28 $ 

Tanking and impregnating 0.50 42.77 21.39 $ 

Preliminary test 0.10 42.77 4.28 $ 

Final test 0.15 42.77 6.42 $ 

Pallet loading 0.27 42.77 11.55 $ 

Marking and miscellaneous 0.28 42.77 11.98 $ 

Winding the primary 0.19 42.77 8.08 $ 

Winding the secondary 0.45 42.77 19.25 $ 

Cutting, forming, and annealing 0.38 42.77 16.31 $ 

Core assembly 0.29 42.77 12.23 $ 

Handling and slitting factor (on material) 1.50% $ 3.03

Total Labor 3.306 42.77 144.44 $ 

Manufacturing Cost (Material + Labor) $ 612.61

Factory Overhead (Materials only) 12.5% $ 58.52

Non-production Cost Markup 25.0% $ 167.78

Manufacturer Selling Price $ 838.91

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

This bill of materials is based on non-rounded core dimensions.

Table 5.6.1 Bill of Materials for Non-Evaluated Transformer from Design Line 1

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Figure 5.6.1 provides a summary of the costs contributing to the total selling price of the

non-evaluated transformer from design line 1. For this design, approximately 56 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 17 percent of the price,

and together, the factory overhead and selling price account for 27 percent.

5.6.2 Design Details Report for Evaluated Transformer from Design Line 1

A design specification report for a 50kVA single-phase liquid-immersed transformer appears

below. This design incorporates M3 core steel, with a copper primary and an aluminum secondary. 

The evaluation factors for this design are $1.50 A and $0.38 B. The bill of materials and associated

breakdown of costs for this design are also reported, after the design and electrical analysis reports.

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3- 1 8:52:41

DG-CORE SHELL TYPE TRANSFORMER NL1PM3CUAL 

FREQUENCY 60.0 KVA RATING 50.00 @ 100.00% DUTY CYCLE

CORE DG-M3 M 3 THICKNESS .0090

 D: 7.635 E: 1.786 F: 3.048 G: 7.372 EFF. AREA 25.909 WEIGHT 188.488

WINDING FORM: INS. DIM. 7.885 X 3.758 THICKNESS .072 LENGTH 6.872

Core/Coils

23%

Other Material

33%

Labor

17%

Factory Overhead

7%

Selling Factor

20%

Figure 5.6.1 Manufacturer Selling Price Breakdown, Non-Evaluated

Transformer from Design Line 1

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 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 .0305X 6.1220 AL 35.24 26.43 .375 7.697

P1 1X 1 #16 ROUND H CU 6087.06 36.23 .375 45.437

S2 .0305X 6.1220 AL 61.30 45.97 .375 13.387

NUMBER OF COILS 1 TOTAL BARE CONDUCTOR WEIGHT 66.520

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 16.0 16 1.0 1(.00500) 1(.03000) .563

P1 1920.0 1824.0 2016.0 19 107.0 4(.00500) 1(.10000) 1.423

S2 16.0 16 1.0 1(.00500) 1(.05000) .563

 TOTAL BUILD(%) 91.85

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 1872.0( 14040.00) 1968.0( 14760.00) 2016.0( 15120.00)

WNDG INTERNAL DUCTS(100.00) %EFF EXTERNAL DUCTS(100.00) %EFF

----------------------------------------------------------------

S1 3 .125 X .125 IN. END 

P1 6 .125 X .125 IN. END .125 X .125 IN. END 

S2 1 .125 X .125 IN. END .125 X .125 IN. END 

 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 14400.00 13680.00 15120.00 34.5 3.532 25.60013 1824.

S1 118.40 10.0 208.330 .00253 1118. 1.3

S2 117.91 10.0 208.330 .00439 1118. 1.8

 F.L. N.L.

FLUX DENS. 16.706 16.836 LEAKAGE INDUCTANCE MHYS 245.843

CORE LOSS 105.561 108.891 POWER FACTOR 1.0000

COIL LOSS 779.995 .008 IMPEDANCE % 2.70

EXCIT. VA 219.090 238.628 EFFICIENCY % 98.26

EXCIT. CURR. .015 .017 TANK OIL GAL 41.23

AMBIENT TEMP. 20.00 NOMINAL LENGTH 13.24

TEMP.RISE 65.00 NOMINAL DEPTH 16.98

OPERATING TEMP. 85.00 NOMINAL HEIGHT 10.94

 2

 COND. I R LOSS = 758.5084

 COND. EDDY CURRENT LOSS = 2.5240

 EE-RM/STD-00-550 COMMENT 83
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5-69

 OTHER STRAY LOSS = 18.9627

 K VALUE = 1.0000

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .33 98.81 .313 .565 .646 41.814 21.3

 35 .47 98.92 .446 .791 .908 83.412 26.5

 50 .69 98.88 .663 1.130 1.310 176.975 37.5

 65 .95 98.72 .907 1.471 1.728 314.794 52.2

 75 1.15 98.58 1.088 1.700 2.018 435.534 64.2

 100 1.55 98.26 1.461 2.273 2.702 779.984 65.0

 125 1.96 97.92 1.832 2.851 3.389 1222.869 65.0

Table 5.6.2 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for an

evaluated transformer from design line 1, a 50kVA single-phase, liquid-immersed, pad-mount M3

design, with a copper primary and an aluminum secondary. This design was generated using a

$1.50A and $0.38B.

 EE-RM/STD-00-550 COMMENT 83
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5-70

Bill of Materials and Labor for liquid-immersed, single-phase, pad-mount, 50kVA

A$ Input $1.50

B$ Input $0.38

Efficiency at 50% load 98.87%

Material item Type quantity $ each $ total

Core steel* (lb) M3-.009 188 0.80 $ 150.79 $ 

Primary winding* (lb) Copper wire, formvar, round #10-20 45 1.55 $ 70.29 $ 

Secondary windings* (lb) Aluminum strip, thickness range 0.02-0.045 21 1.54 $ 32.52 $ 

Winding form & insulation* (lb) Kraft insulating paper with diamond adhesive 4 1.59 $ 6.98 $ 

Oil (gal) - 41 1.71 $ 70.50 $ 

Tank - 1 131.88 $ 131.88 $ 

Core clamp - 1 15.00 $ 15.00 $ 

Nameplate - 1 0.65 $ 0.65 $ 

Bushings HV & LV 1 34.00 $ 34.00 $ 

Misc. hardware - 1 10.00 $ 10.00 $ 

Scrap factor 1.0% $ 2.61

Total Material Cost $ 525.22

Labor item hours rate $ total

Lead dressing 0.50 42.77 21.39 $ 

Inspection 0.10 42.77 4.28 $ 

Baking coils 0.10 42.77 4.28 $ 

Tanking and impregnating 0.50 42.77 21.39 $ 

Preliminary test 0.10 42.77 4.28 $ 

Final test 0.15 42.77 6.42 $ 

Pallet loading 0.27 42.77 11.55 $ 

Marking and miscellaneous 0.28 42.77 11.98 $ 

Winding the primary 0.20 42.77 8.62 $ 

Winding the secondary 0.48 42.77 20.53 $ 

Cutting, forming, and annealing 0.55 42.77 23.41 $ 

Core assembly 0.26 42.77 11.23 $ 

Handling and slitting factor (on material) 1.50% $ 3.91

Total Labor 3.491 42.77 153.24 $ 

Manufacturing Cost (Material + Labor) $ 678.46

Factory Overhead (Materials only) 12.5% 65.65$ 

Non-production Cost Markup 25.0% $ 186.03

Manufacturer Selling Price $ 930.14

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

This bill of materials is based on non-rounded core dimensions.

Table 5.6.2 Bill of Materials for Evaluated Transformer from Design Line 1

 EE-RM/STD-00-550 COMMENT 83
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5-71

Figure 5.6.2 provides a summary of the costs contributing to the total selling price of the

evaluated transformer from design line 1. For this design, approximately 57 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 16 percent of the price,

and together, the factory overhead and selling price account for 27 percent.

5.6.3 Design Details Report for Non-Evaluated Transformer from Design Line 7

The following design report provides information on one of several designs prepared to study

the representative unit from design line 7. This is a 75kVA, three-phase, low-voltage, dry-type unit. 

The design shown here (out of the 4,144 designs in the database) is for M6 buttlap core steel with

aluminum primary and secondary windings, and a $0.00 A and $0.00 B.

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3-12 10:28: 6

STRIP 3-PHASE TYPE TRANSFORMER L7M6aa-BL 

FREQUENCY 60.0 KVA RATING 74.94 @ 100.00% DUTY CYCLE

CORE 3.565" STRP STACK 5.170 GRADE M 6 THICKNESS .0140

WINDOW: 2.685 X 9.432 EFF. AREA 17.787 WEIGHT 309.153 

WINDING FORM:INS. DIM. 3.690 X 5.295 THICKNESS .070 LENGTH 9.307

Core/Coils 

27%

Other Material

30%

Labor

16%

Factory Overhead

7%

Selling Factor

20%

Figure 5.6.2 Manufacturer Selling Price Breakdown, Evaluated

Transformer from Design Line 1

 EE-RM/STD-00-550 COMMENT 83
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5-72

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 .1731X .6924 AL 44.65 21.43 .250 6.174

P1 .0934X .3736 AL 269.40 30.79 .250 10.755

NUMBER OF COILS 3 TOTAL BARE CONDUCTOR WEIGHT 50.786

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 25.0 3 11.0 1(.00001) 1(.00700) .549

P1 100.0 90.0 105.0 5 21.0 1(.00001) 1(.00001) .517

 TOTAL BUILD(%) 89.82

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 92.5( 444.00) 95.0( 456.00) 97.5( 468.00)

 102.5( 492.00) 105.0( 504.00)

WNDG INTERNAL DUCTS( 95.00) %EFF EXTERNAL DUCTS( 95.00) %EFF

----------------------------------------------------------------

S1 1 .563 X .563 IN. END 

P1 2 .563 X .563 IN. END .563 X .563 IN. END 

WNDG INT. DUCT AREA EXT. DUCT AREA TOTAL DUCT AREA

---------------------------------------------------------

S1 147.2432 80.0211 227.2643

P1 371.1016 365.4896 736.5912

 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 480.00 D 432.00 504.00 4.0 53.987 .10566 1585.

S1 116.02 W 4.0 208.180 .00506 1765. 3.4

 F.L. N.L.

FLUX DENS. 15.398 15.691 LEAKAGE INDUCTANCE MHYS .737

CORE LOSS 300.676 312.222 POWER FACTOR 1.0000

COIL LOSS 2559.344 .136 IMPEDANCE % 4.54

EXCIT. VA 752.681 761.771 EFFICIENCY % 96.32

EXCIT. CURR. .523 .529 OPEN ALT. DUCT 3 .00

AMBIENT TEMP. 20.00 NOMINAL LENGTH 18.75

TEMP.RISE 150.00 NOMINAL DEPTH 12.48

OPERATING TEMP. 170.00 NOMINAL HEIGHT 16.56

 WINDING: S1 P1 

 TEMP RISE: 150. 150.

 2

 EE-RM/STD-00-550 COMMENT 83
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5-73

 COND. I R LOSS = 2478.1850

 COND. EDDY CURRENT LOSS = 6.8138

 OTHER STRAY LOSS = 74.3455

 K VALUE = 1.0000

 WIRE WRAP PER COIL

WNDG THICKNESS WEIGHT

-------------------------

P1 .00500 .43372

S1 .00500 .13070

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .58 97.79 .582 .772 .967 113.283 38.5

 35 .83 98.00 .826 1.078 1.358 224.670 42.8

 50 1.23 97.96 1.219 1.541 1.964 473.697 52.4

 65 1.69 97.70 1.663 2.008 2.607 840.287 66.5

 75 2.04 97.45 2.001 2.322 3.065 1166.596 79.1

 100 3.20 96.52 3.089 3.125 4.394 2402.231 127.1

 125 5.06 94.91 4.857 3.970 6.273 4728.370 216.0

Table 5.6.3 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for a nonevaluated transformer from design line 7, a 75kVA three-phase, low-voltage, dry-type M6 design,

with an aluminum primary and an aluminum secondary. This design uses a butt-lap core

configuration, and was generated using a $0.00A and $0.00B.

 EE-RM/STD-00-550 COMMENT 83
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5-74

Bill of Materials and Labor for low, voltage, dry-type, 3-phase, 75kVA

A$ Input $0.00

B$ Input $0.00

Efficiency at 35% load 97.98%

Material item Type quantity $ each $ total

Core Steel* (lb) M6-.014 309 0.70 $ 216.40 $ 

Primary winding* (lb) Aluminum wire, rectangular 0.1 x 0.2, Nomex w 32 2.06 $ 66.38 $ 

Secondary winding* (lb) Aluminum wire, rectangular 0.1 x 0.2, Nomex w 19 2.06 $ 38.11 $ 

Winding form & insulation* (lb) Nomex insulation 1 18.11 $ $ 24.03

Enclosure 14-gauge steel 1 123.75 $ $ 123.75

Core Clamp - 1 19.00$ $ 19.00

Duct Spacers - 19 0.32 $ $ 5.95

Nameplate - 1 0.65 $ $ 0.65

LV Buss Bar (ft.) - 7 1.50$ 10.50 $ 

HV Terminal Board - 3 9.00 $ 27.00 $ 

Impregnation (gal.) - 0.8 17.80 $ $ 14.93

Misc. Hardware - 1 7.00 $ $ 7.00

Scrap factor 1.0% $ 3.45

Total Material Cost $ 557.16

Labor item hours rate $ total

Lead dressing 0.25 42.77 10.69 $ 

Inspection 0.05 42.77 2.14 $ 

Preliminary test 0.05 42.77 2.14 $ 

Final test 0.10 42.77 4.28 $ 

Packing 0.20 42.77 8.55 $ 

Marking and miscellaneous 0.20 42.77 8.55 $ 

Enclosure manufacturing 1.50 42.77 64.16 $ 

Winding the primary 0.47 42.77 20.21 $ 

Winding the secondary 0.83 42.77 35.29 $ 

Core stacking 1.81 42.77 77.39 $ 

Core assembly 1.00 42.77 42.77 $ 

Handling and slitting factor (on material) 1.50% $ 5.17

Total Labor 6.46 42.77 281.34 $ 

Manufacturing Cost (Material + Labor) $ 838.49

Factory Overhead (Materials only) 12.5% $ 69.64

Non-production Cost Markup 25.0% $ 227.03

Manufacturer Selling Price $ 1,135.17

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

This bill of materials is based on non-rounded core dimensions.

Table 5.6.3 Bill of Materials for Non-Evaluated Transformer from Design Line 7

 EE-RM/STD-00-550 COMMENT 83
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5-75

Figure 5.6.3 provides a summary of the costs contributing to the total selling price of the

non-evaluated transformer from design line 7. For this design, approximately 49 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 25 percent of the price,

and together, the factory overhead and selling price account for 26 percent.

5.6.4 Design Details Report for Evaluated Transformer from Design Line 7

A design specification report for a 75kVA three-phase, low-voltage, dry-type transformer

appears below. This design incorporates M6 t-mitered core steel, with an aluminum primary and an

aluminum secondary. The evaluation factors for this design are $1.50 A and $0.14 B. The bill of

materials and associated breakdown of costs for this design are also reported, after the design and

electrical analysis reports

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3-12 4:44: 4

STRIP 3-PHASE TYPE TRANSFORMER L7M6ALALTMiter 

FREQUENCY 60.0 KVA RATING 74.94 @ 100.00% DUTY CYCLE

CORE 3.422" STRP STACK 4.599 GRADE M 6 THICKNESS .0140

WINDOW: 3.705 X 10.874 EFF. AREA 15.188 WEIGHT 296.940 

WINDING FORM:INS. DIM. 3.547 X 4.724 THICKNESS .070 LENGTH 10.749

Core/Coils

28%

Other Material

21%

Labor

25%

Factory Overhead

6%

Selling Factor

20%

Figure 5.6.3 Manufacturer Selling Price Breakdown, Non-Evaluated

Transformer from Design Line 7

 EE-RM/STD-00-550 COMMENT 83
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5-76

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 1X 2(.1456X .5826) AL 50.65 20.26 .250 9.974

P1 .1278X .3835 AL 324.87 30.94 .250 18.351

NUMBER OF COILS 3 TOTAL BARE CONDUCTOR WEIGHT 84.975

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 30.0 4 7.5 1(.00001) 1(.00700) .623

P1 120.0 108.0 126.0 6 24.0 1(.00001) 1(.00001) .827

 TOTAL BUILD(%) 85.80

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 111.0( 444.00) 114.0( 456.00) 117.0( 468.00)

 123.0( 492.00) 126.0( 504.00)

WNDG INTERNAL DUCTS( 95.00) %EFF EXTERNAL DUCTS( 95.00) %EFF

----------------------------------------------------------------

S1 1 .563 X .563 IN. END 

P1 2 .563 X .563 IN. END .563 X .563 IN. END 

WNDG INT. DUCT AREA EXT. DUCT AREA TOTAL DUCT AREA

---------------------------------------------------------

S1 99.2988 58.5992 157.8980

P1 319.1871 402.3261 721.5132

 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 480.00 D 432.00 504.00 4.0 53.640 .09004 1113.

S1 116.64 W 4.0 208.180 .00403 1239. 2.8

 F.L. N.L.

FLUX DENS. 15.063 15.314 LEAKAGE INDUCTANCE MHYS 1.065

CORE LOSS 239.558 247.624 POWER FACTOR 1.0000

COIL LOSS 2111.250 .042 IMPEDANCE % 5.25

EXCIT. VA 444.479 459.371 EFFICIENCY % 96.96

EXCIT. CURR. .309 .319 OPEN ALT. DUCT 3 .00

AMBIENT TEMP. 20.00 NOMINAL LENGTH 21.38

TEMP.RISE 150.00 NOMINAL DEPTH 12.93

OPERATING TEMP. 170.00 NOMINAL HEIGHT 17.72

 WINDING: S1 P1 

 TEMP RISE: 150. 150.

 2

 EE-RM/STD-00-550 COMMENT 83
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5-77

 COND. I R LOSS = 2037.1360

 COND. EDDY CURRENT LOSS = 12.9997

 OTHER STRAY LOSS = 61.1141

 K VALUE = 1.0000

 WIRE WRAP PER COIL

WNDG THICKNESS WEIGHT

-------------------------

P1 .00500 .57064

S1 .00500 .25054

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .48 98.22 .479 1.110 1.209 93.850 38.4

 35 .69 98.38 .680 1.552 1.694 186.261 42.7

 50 1.03 98.33 1.004 2.217 2.434 392.678 52.3

 65 1.42 98.11 1.370 2.889 3.197 696.014 66.4

 75 1.72 97.90 1.647 3.340 3.724 965.461 78.9

 100 2.68 97.12 2.537 4.488 5.155 1980.615 126.4

 125 4.21 95.80 3.962 5.684 6.928 3867.327 213.4

Table 5.6.4 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for an

evaluated transformer from design line 7, a 75kVA three-phase, low-voltage dry-type M6 design,

with an aluminum primary and an aluminum secondary. This design uses a “scrapless” t-mitered core

construction, and was generated using a $0.00A and $0.00B. Note that the M6 core steel

incorporates a $0.05 per pound mark-up to account for costs associated with tooling for the tmitering core-cutting equipment.

 EE-RM/STD-00-550 COMMENT 83
DRAFT

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5-78

Bill of Materials and Labor for low, voltage, dry-type, 3-phase, 75kVA

A$ Input $1.50

B$ Input $0.14

Efficiency at 35% load 98.36%

Material item Type quantity $ each $ total

Core Steel* (lb) M6-.014 297 0.75 $ 222.71 $ 

Primary winding* (lb) Aluminum wire, rectangular 0.1 x 0.2, Nomex w 55 2.06 $ 113.26 $ 

Secondary winding* (lb) Aluminum wire, rectangular 0.1 x 0.2, Nomex w 30 2.06 $ 61.56 $ 

Winding form & insulation* (lb) Nomex insulation 1 18.11 $ $ 25.76

Enclosure 14-gauge steel 1 126.26 $ $ 126.26

Core Clamp - 1 19.00 $ $ 19.00

Duct Spacers - 21 0.32 $ $ 6.88

Nameplate - 1 0.65 $ $ 0.65

LV Buss Bar (ft.) - 7 1.50$ 10.50 $ 

HV Terminal Board - 3 9.00 $ 27.00 $ 

Impregnation (gal.) - 1.1 17.80 $ $ 18.87

Misc. Hardware - 1 7.00 $ $ 7.00

Scrap factor 1.0% $ 4.23

Total Material Cost $ 643.67

Labor item hours rate $ total

Lead dressing 0.25 42.77 10.69 $ 

Inspection 0.05 42.77 2.14 $ 

Preliminary test 0.05 42.77 2.14 $ 

Final test 0.10 42.77 4.28 $ 

Packing 0.20 42.77 8.55 $ 

Marking and miscellaneous 0.20 42.77 8.55 $ 

Enclosure manufacturing 1.50 42.77 64.16 $ 

Winding the primary 0.57 42.77 24.25 $ 

Winding the secondary 0.99 42.77 42.34 $ 

Core stacking 1.61 42.77 68.84 $ 

Core assembly 1.00 42.77 42.77 $ 

Handling and slitting factor (on material) 1.50% $ 6.35

Total Labor 6.52 42.77 285.07 $ 

Manufacturing Cost (Material + Labor) $ 928.74

Factory Overhead (Materials only) 12.5% $ 80.46

Non-production Cost Markup 25.0% $ 252.30

Manufacturer Selling Price $ 1,261.50

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

This bill of materials is based on non-rounded core dimensions.

Table 5.6.4 Bill of Materials for Evaluated Transformer frm Design Line 7

 EE-RM/STD-00-550 COMMENT 83
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5-79

Figure 5.6.4 provides a summary of the costs contributing to the total selling price of the

evaluated transformer from design line 7. For this design, approximately 51 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 23 percent of the price,

and together, the factory overhead and selling price account for 26 percent.

5.6.5 Design Details Report for Non-Evaluated Transformer from Design Line 12

The following design report provides information on one of several designs prepared to study

the representative unit from design line 12. This is a 1500kVA, three-phase, medium-voltage, drytype unit at 95kV BIL. The design shown here (out of the 2,590 designs in the database) is for M6

core steel with aluminum primary and secondary windings, and a $0.00A and $0.00B.

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3-12 12:58: 9

STRIP CRUC 3-PHASE TYPE TRANSFORMER L12M6ALAL 

FREQUENCY 60.0 MVA RATING 1.50 @ 100.00% DUTY CYCLE

CORE 9.929" CRUC STACK 9.929 GRADE M 6 THICKNESS .0140

WINDOW: 14.442 X 50.208 EFF. AREA 75.247 WEIGHT 5565.141 

WINDING FORM:INS. DIM. 10.457 X 10.457 THICKNESS .156 LENGTH 48.208

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

Core/Coils

31%

Other Material

20%

Labor

23%

Factory Overhead

6%

Selling Factor

20%

Figure 5.6.4 Manufacturer Selling Price Breakdown, Evaluated

Transformer from Design Line 7

 EE-RM/STD-00-550 COMMENT 83
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Transformer_DRAFT_TSD_Chapter5_version08-01-05.wpd 

5-80

----------------------------------------------------------------------

S1 2X 1(.0167X38.2076) AL 46.38 42.82 5.000 69.450

P1 1X 2(.0668X .2318) AL 3407.39 66.57 5.750 116.001

NUMBER OF COILS 3 TOTAL BARE CONDUCTOR WEIGHT 556.355

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 13.0 13 1.0 1(.01000) 1(.20000) 2.805

P1 585.0 555.8 614.3 15 1.0 1(.00001) 1(.00001) 1.182

 TOTAL BUILD(%) 84.56

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 570.4( 12158.25) 599.6( 12781.75) 614.3( 13093.50)

 DISK INFORMATION

 -----------------

WNDG DISK WIDTH VOLTS/DISK BREAK TAPS SPACE

-------------------------------------------------------

P1 42 .493 311.750 .750 2(.50) 38( .375)

WNDG INTERNAL DUCTS( 90.00) %EFF EXTERNAL DUCTS( 90.00) %EFF

----------------------------------------------------------------

S1 3 .750 X .750 IN. FULL

P1 2 .750 X .750 IN. FULL

WNDG INT. DUCT AREA EXT. DUCT AREA TOTAL DUCT AREA

---------------------------------------------------------

S1 6800.8820 1617.2770 8418.1580

P1 .0000 2519.9360 5176.6380

 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 12470.00 D 11846.50 13093.50 18.0 40.735 1.56703 1402.

S1 273.07 W 4.0 1804.300 .00049 1412. 1.4

 F.L. N.L.

FLUX DENS. 16.320 16.472 LEAKAGE INDUCTANCE MHYS 45.571

CORE LOSS 4645.135 4734.112 POWER FACTOR 1.0000

COIL LOSS 19994.840 .493 IMPEDANCE % 5.76

EXCIT. VA 8824.361 9869.501 EFFICIENCY % 98.38

EXCIT. CURR. .236 .264 OPEN ALT. DUCT 3 .00

AMBIENT TEMP. 20.00 NOMINAL LENGTH 73.11

TEMP.RISE 141.46 NOMINAL DEPTH 22.49

OPERATING TEMP. 161.46 NOMINAL HEIGHT 70.06

 EE-RM/STD-00-550 COMMENT 83
DRAFT

Transformer_DRAFT_TSD_Chapter5_version08-01-05.wpd 

5-81

 CRUCIFORM PLATE WIDTHS

 W1 W2 W3 W4 W5

 9.929 8.843 7.394 5.579 3.281

 STACK HEIGHTS

 H1 H2 H3 H4 H5

 3.283 1.149 .907 .725 .542

 RESULTANT GROSS AREA: 77.977 CIRCLE AREA FILL: % 90.8

 MIN. WINDING FORM INSIDE DIAMETER: 10.457

 WINDING: S1 P1 

 TEMP RISE: 141. 116.

 2

 COND. I R LOSS = 19188.2900

 COND. EDDY CURRENT LOSS = 39.0233

 OTHER STRAY LOSS = 767.5314

 K VALUE = 1.0000

TEMP. AT LOW TAP 

----------------

S1 141.46

P1 121.72

 WIRE WRAP PER COIL

WNDG THICKNESS WEIGHT

-------------------------

P1 .00600 8.72106

 o

AT REFERENCE TEMP. 170.0

----------------------------

COIL LOSS = 20441.770

IMPEDANCE % = 5.763

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .25 98.51 .241 1.402 1.423 944.956 47.0

 35 .36 98.76 .344 1.958 1.988 1890.136 54.1

 50 .55 98.85 .514 2.794 2.841 4033.891 68.2

 65 .78 98.79 .708 3.634 3.702 7212.068 86.3

 75 .94 98.71 .852 4.196 4.282 10014.870 100.3

 100 1.44 98.38 1.275 5.612 5.755 19994.840 141.5

 125 2.08 97.91 1.805 7.048 7.275 35411.180 190.8

Table 5.6.5 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for a non-

 EE-RM/STD-00-550 COMMENT 83
DRAFT

Transformer_DRAFT_TSD_Chapter5_version08-01-05.wpd 

5-82

evaluated transformer from design line 12, a 1500kVA three-phase, medium-voltage, dry-type design

with M6 core steel and an aluminum primary and secondary. This design was generated using a

$0.00A and $0.00B.

Bill of Materials and Labor for medium voltage, dry-type, 3-phase, 1500kVA

A$ Input $0.00

B$ Input $0.00

Efficiency at 50% load 98.81%

Material item Type quantity $ each $ total

Core steel* (lb) M6-.014 5565 0.70 $ 3,895.60 $ 

Primary winding* (lb) Aluminum wire, rectangular 0.1 x 0.2, Nomex w 348 2.06 $ 715.95 $ 

Secondary winding* (lb) Aluminum strip, thickness range 0.02-0.045 208 1.54 $ 321.35 $ 

Winding form & insulation* (lb) Nomex insulation 110 18.11 $ 1,997.39 $ 

Enclosure 12-gauge steel 1 748.06$ $ 748.06

Core clamp - 1 125.00 $ $ 125.00

Nameplate - 1 0.65 $ $ 0.65

LV buss bar (ft.) - 16 12.00$ $ 192.00

HV tap board - 3 9.00 $ $ 27.00

HV terminals - 1 135.00$ $ 135.00

Winding combs (lb.) - 70 10.24$ $ 717.80

Duct spacers (ft.) 1318 0.56 $ 738.24 $ 

Impregnation (gal.) - 25 17.80$ $ 443.74

Misc. hardware - 1 54.00 $ $ 54.00

Scrap factor 1.0% $ 69.30

Additional scrap on core** 4.0% $ 155.82

Total Material Cost $ 10,336.91

Labor item hours rate $ total

Lead dressing 1.00 42.77 42.77 $ 

Inspection 0.25 42.77 10.69 $ 

Preliminary test 0.50 42.77 21.39 $ 

Final test 0.75 42.77 32.08 $ 

Packing 2.00 42.77 85.54 $ 

Enclosure manufacturing 8.00 42.77 342.16 $ 

Marking and miscellaneous 2.20 42.77 94.09 $ 

Winding the primary 23.03 42.77 985.18 $ 

Winding the secondary 2.93 42.77 125.10 $ 

Core stacking 7.94 42.77 339.73 $ 

Core assembly 6.00 42.77 256.62 $ 

Handling and Slitting Factor (on material) 1.50% $ 103.95

Total Labor 54.603 42.77 2,439.31 $ 

Manufacturing Cost (Material + Labor) $ 12,776.21

Factory Overhead (Materials only) 12.5% $ 1,292.11

Non-production Cost Markup 25.0% $ 3,517.08

Manufacturer Selling Price $ 17,585.41

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

** additional scrap on core due to mitering process.

This bill of materials is based on non-rounded core dimensions.

Table 5.6.5 Bill of Materials for Non-Evaluated Transformer from Design Line 12

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Figure 5.6.5 provides a summary of the costs contributing to the total selling price of the

non-evaluated transformer from design line 12. For this design, approximately 59 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 14 percent of the price,

and together, the factory overhead and selling price account for 27 percent.

5.6.6 Design Details Report for Evaluated Transformer from Design Line 12

A design specification report for a 1500kVA three-phase, medium-voltage, dry-type

transformer appears below. This design incorporates M3 core steel, with copper primary and

secondary windings. The evaluation factors for this design are $0.50 A and $0.08 B. The bill of

materials and associated breakdown of costs for this design are also reported, after the design and

electrical analysis reports

OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2005- 3-12 19:22:57

STRIP CRUC 3-PHASE TYPE TRANSFORMER L12M3CUCU 

FREQUENCY 60.0 MVA RATING 1.50 @ 100.00% DUTY CYCLE

CORE 9.936" CRUC STACK 9.936 GRADE M 3 THICKNESS .0090

WINDOW: 13.354 X 50.940 EFF. AREA 74.572 WEIGHT 5550.538 

WINDING FORM:INS. DIM. 10.464 X 10.464 THICKNESS .156 LENGTH 48.940

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

Core/Coils 

28%

Other Material

31%

Labor

14%

Factory Overhead

7%

Selling Factor

20%

Figure 5.6.5 Manufacturer Selling Price Breakdown, Non-Evaluated

Transformer from Design Line 12

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S1 2X 1(.0096X38.9404) CU 45.72 42.20 5.000 129.011

P1 1X 2(.0512X .1778) CU 3301.91 64.51 5.750 226.486

NUMBER OF COILS 3 TOTAL BARE CONDUCTOR WEIGHT 1075.046

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 13.0 13 1.0 1(.01000) 1(.20000) 2.620

P1 585.0 555.8 614.3 15 1.0 1(.00001) 1(.00001) .948

 TOTAL BUILD(%) 85.20

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 570.4( 12158.25) 599.6( 12781.75) 614.3( 13093.50)

 DISK INFORMATION

 -----------------

WNDG DISK WIDTH VOLTS/DISK BREAK TAPS SPACE

-------------------------------------------------------

P1 42 .510 311.750 .750 2(.50) 38( .375)

WNDG INTERNAL DUCTS( 90.00) %EFF EXTERNAL DUCTS( 90.00) %EFF

----------------------------------------------------------------

S1 3 .750 X .750 IN. FULL

P1 2 .750 X .750 IN. FULL

WNDG INT. DUCT AREA EXT. DUCT AREA TOTAL DUCT AREA

---------------------------------------------------------

S1 6962.6350 1621.1610 8583.7960

P1 .0000 2516.7880 4898.1040

 ELECTRICAL ANALYSIS

 -------------------

 FULL-LOAD TAP VOLTS TEST LOAD RESIST. CURRNT

WNDG VOLTS LOW HIGH KV CURRENT @20 C. DENS. %REG

----------------------------------------------------------------------

P1 12470.00 D 11846.50 13093.50 18.0 40.680 1.51120 2286.

S1 273.23 W 4.0 1804.300 .00050 2411. 1.4

 F.L. N.L.

FLUX DENS. 16.477 16.622 LEAKAGE INDUCTANCE MHYS 44.500

CORE LOSS 3261.498 3377.035 POWER FACTOR 1.0000

COIL LOSS 19285.360 .285 IMPEDANCE % 5.61

EXCIT. VA 7133.554 7726.391 EFFICIENCY % 98.52

EXCIT. CURR. .191 .207 OPEN ALT. DUCT 3 .00

AMBIENT TEMP. 20.00 NOMINAL LENGTH 69.87

TEMP.RISE 138.10 NOMINAL DEPTH 21.58

OPERATING TEMP. 158.10 NOMINAL HEIGHT 70.81

 CRUCIFORM PLATE WIDTHS

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 W1 W2 W3 W4 W5

 9.936 8.849 7.399 5.583 3.284

 STACK HEIGHTS

 H1 H2 H3 H4 H5

 3.285 1.150 .907 .726 .542

 RESULTANT GROSS AREA: 78.085 CIRCLE AREA FILL: % 90.8

 MIN. WINDING FORM INSIDE DIAMETER: 10.465

 WINDING: S1 P1 

 TEMP RISE: 138. 117.

 2

 COND. I R LOSS = 18519.0200

 COND. EDDY CURRENT LOSS = 25.5813

 OTHER STRAY LOSS = 740.7608

 K VALUE = 1.0000

TEMP. AT LOW TAP 

----------------

S1 138.10

P1 122.59

 WIRE WRAP PER COIL

WNDG THICKNESS WEIGHT

-------------------------

P1 .00600 6.62868

 o

AT REFERENCE TEMP. 170.0

----------------------------

COIL LOSS = 19877.280

IMPEDANCE % = 5.620

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .24 98.88 .232 1.364 1.384 907.508 41.9

 35 .35 99.03 .332 1.907 1.935 1818.703 49.2

 50 .53 99.05 .497 2.723 2.768 3887.590 63.8

 65 .75 98.96 .684 3.542 3.608 6955.772 82.2

 75 .91 98.86 .823 4.091 4.173 9660.987 96.4

 100 1.39 98.52 1.231 5.473 5.610 19285.400 138.1

 125 2.00 98.05 1.742 6.873 7.090 34129.490 187.9

Table 5.6.6 provides the bill of materials which was calculated from the OPS design details

report. This bill of materials uses the raw material prices given in this Chapter for fixed and variable

materials used in building the transformer. These materials are then marked-up at the bottom of the

table to arrive at the manufacturer’s selling price. This table provides the bill of materials for an

evaluated transformer from design line 12, a 1500kVA three-phase, medium-voltage, dry-type

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transformer built with M3 core steel and copper primary and secondary windings. This design was

generated using a $0.50A and $0.08B.

Bill of Materials and Labor for medium voltage, dry-type, 3-phase, 1500kVA

A$ Input $0.50

B$ Input $0.08

Efficiency at 50% load 99.02%

Material item Type quantity $ each $ total

Core steel* (lb) M3-.009 5551 0.80 $ 4,440.43 $ 

Primary winding* (lb) Copper wire, rectangular 0.1 x 0.2, Nomex wrap 679 2.00 $ 1,361.68 $ 

Secondary winding* (lb) Copper strip, thickness range 0.02-0.045 387 2.32 $ 897.92 $ 

Winding form & insulation* (lb) Nomex insulation 110 18.11 $ 1,997.49 $ 

Enclosure 12-gauge steel 1 733.94 $ $ 733.94

Core clamp - 1 125.00 $ $ 125.00

Nameplate - 1 0.65 $ $ 0.65

LV buss bar (ft.) - 16 12.00 $ $ 192.00

HV tap board - 3 9.00 $ $ 27.00

HV terminals - 1 135.00 $ $ 135.00

Winding combs (lb.) - 62 10.24 $ $ 631.23

Duct spacers (ft.) - 1306 0.56 $ 731.11 $ 

Impregnation (gal.) - 23 17.80 $ $ 411.17

Misc. hardware - 1 54.00 $ $ 54.00

Scrap factor 1.0% $ 86.98

Additional scrap on core** 4.0% $ 177.62

Total Material Cost $ 12,003.20

Labor item hours rate $ total

Lead dressing 1.00 42.77 42.77 $ 

Inspection 0.25 42.77 10.69 $ 

Preliminary test 0.50 42.77 21.39 $ 

Final test 0.75 42.77 32.08 $ 

Packing 2.00 42.77 85.54 $ 

Enclosure manufacturing 8.00 42.77 342.16 $ 

Marking and miscellaneous 2.20 42.77 94.09 $ 

Winding the primary 23.03 42.77 985.18 $ 

Winding the secondary 2.93 42.77 125.10 $ 

Core stacking 7.95 42.77 339.97 $ 

Core assembly 6.00 42.77 256.62 $ 

Handling and Slitting Factor (on material) 1.50% 130.46 $ 

Total Labor 54.608 42.77 2,466.05 $ 

Manufacturing Cost (Material + Labor) $ 14,469.25

Factory Overhead (Materials only) 12.5% $ 1,500.40

Non-production Cost Markup 25.0% $ 3,992.41

Manufacturer Selling Price $ 19,962.07

* indicates those items to which the scrap factor (1.0%) and the handling and slitting factor (1.5%) are applied.

** additional scrap on core due to mitering process.

This bill of materials is based on non-rounded core dimensions.

Figure 5.6.6 Bill of Materials for Evaluated Transformer from Design Line 12

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Figure 5.6.6 provides a summary of the costs contributing to the total selling price of the

evaluated transformer from design line 12. For this design, approximately 60 percent of the final

manufacturer selling price is direct material and scrap. Labor accounts for 12 percent of the price,

and together, the factory overhead and selling price account for 28 percent.

5.7 TEAR-DOWN ANALYSIS

The Department purchased, tested, disassembled and analyzed six transformers from design

line 7 for the engineering analysis. This tear-down analysis was conducted for two reasons: 1) to

demonstrate the predictive accuracy of the OPS software and 2) to validate the NOPR designs. 

Design line 7 was selected because it has the largest energy savings potential and because the

representative unit (75 kVA three-phase low-voltage dry-type) is readily available from wholesale

distributors. This section discusses the tear-down analysis on the six transformers and the results.

The Department purchased six transformers in early 2004, two ‘matched pairs’ from three

manufacturers. The two transformers from each manufacturer represented a low first-cost unit and a

NEMA TP-1 / Energy Star® unit. The transformers were shipped directly to the testing facility,

Transformer Engineering Corporation (TEC) in Cleveland, Ohio. TEC has been a manufacturer of

custom designed transformers, inductors, and other electro-magnetic components since 1937. TEC

has a 50,000 square-foot facility in Cleveland, which includes a top-notch testing laboratory.

The Department reviewed several manufacturer catalogues and identified matched pairs of

low-first cost and NEMA TP-1 units. These units were purchased from a local distributor, and

shipped to TEC for testing. In Cleveland, the transformers were subjected to the following tests:

Core/Coils

33%

Other Material

27%

Labor

12%

Factory Overhead

8%

Selling Factor

20%

Figure 5.6.6 Manufacturer Selling Price Breakdown, Evaluated

Transformer from Design Line 12

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• Core loss test

• Conductor resistance

• Conductor loss test

• Temperature test

Data was recorded for each of these tests, documenting all the critical performance metrics

for each of the six designs. The transformers were then carefully disassembled, with attention being

paid to the construction techniques, including type of steel and conductor. All the pieces were

weighed, and physical attributes such as core dimensions and number of turns were recorded. All of

these physical dimensions were then put into the OPS software, to model the transformer that had

just been disassembled. The OPS software then used its electrical analysis program to predict the

values that had been measured in the laboratory. This step validated the predictive capability of the

software for generating performance metrics associated with its modeled designs. The OPS software

accurately predicted the efficiency (including the core and coil losses), the impedance, the

inductance, and all the transformer performance metrics.

Next, when the NOPR engineering analysis designs were completed, the Department used the

results of the tear-down analysis to create a manufacturer’s selling price. In other words, using

measured variables such as the pounds of core steel and pounds of conductor, the Department costed

out the torn-down units using the same 2000-2004 average material prices and mark-ups, just as was

done for the engineering analysis. The Department then plotted these six dots on the NOPR

manufacturer’s selling price-efficiency curve generated for design line 7. Figure 5.6.7 presents the

plot of these torn-down units. The six transformer tear-downs align perfectly with the design line 7

cost-efficiency curve.

 EE-RM/STD-00-550 COMMENT 83
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0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

94.50% 95.00% 95.50% 96.00% 96.50% 97.00% 97.50% 98.00% 98.50% 99.00% 99.50%

Efficiency at 35% load

Manfacturer Selling Price ($)

M36AlAl_bl

M19AlAl_bl

M6AlAl_bl

M6AlAl_mtt

M6AlAl_mtf

M4CuAl_mtf

M3CuCu_mtf

HOCuCu_mtf

Teardowns

TP-1: 98.0%

Manufacturer A:

Low Eff M36_bl

Manufacturer B:

Low Eff M19_bl

Manufacturer C: 

Low Eff M36_bl

Manufacturer B:

High Eff M6_bl Manufacturer C:

High Eff M5_mt

Manufacturer A:

 High Eff M6_mt

Figure 5.6.7 Tear-down Plot Comparison, Design Line 7, 75kVA Three-phase Dry-type

 EE-RM/STD-00-550 COMMENT 83