5-i

CHAPTER 5: ENGINEERING ANALYSIS

TABLE OF CONTENTS

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

5.2 STRUCTURING THE ENGINEERING ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.2.1 Scaling Relationships in Transformer Manufacturing . . . . . . . . . . . . . . . . . . . . 5-9

5.3 TECHNICAL DESIGN INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

5.3.1 Design Line 1 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17

5.3.2 Design Line 2 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

5.3.3 Design Line 3 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

5.3.4 Design Line 4 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21

5.3.5 Design Line 5 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

5.3.6 Design Line 6 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

5.3.7 Design Line 7 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24

5.3.8 Design Line 8 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

5.3.9 Design Line 9 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

5.3.10 Design Line 10 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

5.3.11 Design Line 11 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

5.3.12 Design Line 12 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

5.3.13 Design Line 13 Representative Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

5.3.14 Summary of Design Line Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31

5.4 MATERIAL AND LABOR INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36

5.4.1 Material Inputs to the Design Software - Liquid-Immersed . . . . . . . . . . . . . . 5-37

5.4.2 Material Inputs to the Design Software - Dry-type . . . . . . . . . . . . . . . . . . . . . 5-41

5.4.3 Labor Cost Inputs to the Design Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-44

5.5 RESULTS OF THE ANALYSIS ON EACH DESIGN LINE . . . . . . . . . . . . . . . . . . . 5-45

5.6 TWO EXAMPLE TRANSFORMER DESIGNS AND COST BREAKDOWNS . . . 5-59

5.6.1 Results for DL3 Transformer, M6CuAl at $3 A and $1 B . . . . . . . . . . . . . . . . 5-59

5.6.2 Results for DL12 Transformer, M3CuCu at $3A and $1B . . . . . . . . . . . . . . . 5-64

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 . . . . . . 5-4

Table 5.2.3 Common Scaling Relationships in Transformers . . . . . . . . . . . . . . . . . . . . . . 5-10

Table 5.3.1 A and B Combinations used by Software to Generate Design Database . . . . . 5-13

Table 5.3.2 Core Steel Grades, Thicknesses and Associated Losses . . . . . . . . . . . . . . . . . 5-15

Table 5.3.3 Core Configurations Used in Each Design Line . . . . . . . . . . . . . . . . . . . . . . . 5-16

Table 5.3.4 Design Option Combinations for the Representative Unit from DL1 . . . . . . . 5-18

Table 5.3.5 Design Option Combinations for the Representative Unit from DL2 . . . . . . . 5-19

Table 5.3.6 Design Option Combinations for the Representative Unit from DL3 . . . . . . . 5-20

Table 5.3.7 Design Option Combinations for the Representative Unit from DL4 . . . . . . . 5-22

 EE-RM/STD-00-550 COMMENT 55
5-ii

Table 5.3.8 Design Option Combinations for the Representative Unit from DL5 . . . . . . . 5-23

Table 5.3.9 Design Option Combinations for the Representative Unit from DL6 . . . . . . . 5-24

Table 5.3.10 Design Option Combinations for the Representative Unit from DL7 . . . . . . . 5-25

Table 5.3.11 Design Option Combinations for the Representative Unit from DL8 . . . . . . . 5-26

Table 5.3.12 Design Option Combinations for the Representative Unit from DL9 . . . . . . . 5-27

Table 5.3.13 Design Option Combinations for the Representative Unit from DL10 . . . . . . 5-28

Table 5.3.14 Design Option Combinations for the Representative Unit from DL11 . . . . . . 5-29

Table 5.3.15 Design Option Combinations for the Representative Unit from DL12 . . . . . . 5-30

Table 5.3.16 Design Option Combinations for the Representative Unit from DL13 . . . . . . 5-31

Table 5.3.17 Liquid-Immersed Design Lines and Representative Units . . . . . . . . . . . . . . . 5-32

Table 5.3.18 Dry-Type, Low-Voltage Design Lines and Representative Units . . . . . . . . . . 5-33

Table 5.3.19 Dry-Type, Medium-Voltage, Single-Phase Design Lines . . . . . . . . . . . . . . . . 5-34

Table 5.3.20 Dry-Type, Medium-Voltage, Three-Phase Design Lines . . . . . . . . . . . . . . . . . 5-35

Table 5.4.1 Variable Material Inputs for Liquid-Immersed Units . . . . . . . . . . . . . . . . . . . 5-38

Table 5.4.2 Variable Tank Sizes for Design Line 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-39

Table 5.4.3 Summary Table of Fixed Material Costs for Liquid-Immersed Units . . . . . . . 5-40

Table 5.4.4 Variable Material Inputs for Dry-Type Units . . . . . . . . . . . . . . . . . . . . . . . . . . 5-41

Table 5.4.5 Summary Table of Fixed Material Costs for Dry-Type Units . . . . . . . . . . . . . 5-43

Table 5.4.6 Labor Markups for Liquid-Immersed and Dry-Type Manufacturers . . . . . . . . 5-44

Table 5.6.1 Bill of Materials for Example Design from DL3 Database . . . . . . . . . . . . . . . 5-62

Table 5.6.2 Bill of Materials for Example Design from DL12 Database . . . . . . . . . . . . . . 5-66

LIST OF FIGURES

Figure 5.4.1 Standard Method of Cost Accounting for Standards Rulemaking . . . . . . . . . 5-36

Figure 5.5.1 Scatter Plot of Manufacturer Selling Price and Efficiency for DL1 . . . . . . . . 5-46

Figure 5.5.2 Scatter Plot of Manufacturer Selling Price and Efficiency for DL2 . . . . . . . . 5-47

Figure 5.5.3 Scatter Plot of Manufacturer Selling Price and Efficiency for DL3 . . . . . . . . 5-48

Figure 5.5.4 Scatter Plot of Manufacturing Selling Price and Efficiency for DL4 . . . . . . . 5-49

Figure 5.5.5 Scatter Plot of Manufacturing Selling Price and Efficiency for DL5 . . . . . . . 5-50

Figure 5.5.6 Scatter Plot of Manufacturing Selling Price and Efficiency for DL6 . . . . . . . 5-51

Figure 5.5.7 Scatter Plot of Manufacturing Selling Price and Efficiency for DL7 . . . . . . . 5-52

Figure 5.5.8 Scatter Plot of Manufacturing Selling Price and Efficiency for DL8 . . . . . . . 5-53

Figure 5.5.9 Scatter Plot of Manufacturing Selling Price and Efficiency for DL9 . . . . . . . 5-54

Figure 5.5.10 Scatter Plot of Manufacturing Selling Price and Efficiency for DL10 . . . . . . 5-55

Figure 5.5.11 Scatter Plot of Manufacturing Selling Price and Efficiency for DL11 . . . . . . 5-56

Figure 5.5.12 Scatter Plot of Manufacturing Selling Price and Efficiency for DL12 . . . . . . 5-57

Figure 5.5.13 Scatter Plot of Manufacturing Selling Price and Efficiency for DL13 . . . . . . 5-58

Figure 5.6.1 Cost Breakdown for DL3 M6CuAl Design at $3A, $1B . . . . . . . . . . . . . . . . . 5-63

Figure 5.6.2 Cost Breakdown for DL12, M3CuCu Design at $3A, $1B. . . . . . . . . . . . . . . 5-67

 EE-RM/STD-00-550 COMMENT 55
5-iii

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)

M* M2, M3, M4, M6 - thickness 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

 EE-RM/STD-00-550 COMMENT 55
a

 During the first quarter of 2002, meetings were held with eight distribution transformer manufacturers, including ABB

Power Technology Products Division USA (both liquid-immersed plant and a dry-type plant), Acme Electric

Corporation, Cooper Power Industries, Federal Pacific Transformer Company, Howard Industries Inc., Jefferson Electric

Inc., Kuhlman Electric Corporation, and Square-D Company. The Department also met with AK Steel, a core steel

manufacturer.

5-1

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 efficiency level. This relationship serves as the basis for the subsequent costbenefit calculations for individual consumers, manufacturers, and the nation (see Chapter 8,

Life-Cycle Cost and Payback Period Analyses). Determining the cost-efficiency relationship

involves analysis of the options available to manufacturers for increasing the efficiency of a

distribution transformer.

The Department selected a modified design-option approach for the engineering analysis. 

The design-option approach normally involves selecting technology and/or material options for

transformer designs, and requesting that manufacturers provide estimated costs of transformers

built with these options at various efficiency levels. The modification applied to the designoption approach involved using a third party to create the designs for the transformer design

database and working with manufacturers to select appropriate design options and obtain correct

costing information.

In planning the structure of the engineering analysis, the Department visited the facilities

of nine distribution transformer manufacturers and one component supplier.a

 Together,

representatives of these companies contributed more than 60 hours of presentations, technical

information, and plant tours to the engineering analysis. Topics discussed at these meetings

included the structure of the engineering analysis, product classifications, product design,

materials handling, market dynamics, high-efficiency designs, and manufacturers’ concerns

relating to the rulemaking.

The Department recognizes that the results in this chapter are not the definitive answer to

the question of the relationship between a manufacturer’s cost and the efficiency of the

transformer. These results assume an ideal situation, where manufacturers do not incur any

increased retooling, redesign, marketing or special handling costs associated with changing

materials or core/coil dimensions. The Department requests that reviewers, and particularly

manufacturers, submit comments on what additional costs they may incur if minimum efficiency

standards are introduced. Identification of additional costs will be important in subsequent stages

of the rulemaking process (e.g., manufacturer impact analysis (MIA)).

 EE-RM/STD-00-550 COMMENT 55
5-2

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 kVA rating. The range and number of kilovolt-amp (kVA) ratings varies by product class,

as shown in Table 5.2.1. For NEMA’s TP 1-2002, 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, there are 115 kVA ratings across all the product classes. 

These kVA ratings are essentially size categories, indicating the power handling capacity of the

transformers. Due to the physical principles of construction and material properties, efficiency

levels vary by both product class and kVA rating.

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

 EE-RM/STD-00-550 COMMENT 55
5-3

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

analysis of the cost-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 (one or three), and primary insulation levels (three different BIL levels for medium

voltage dry-types). 

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). It then extrapolated the results

of this analysis from the unit studied to the other kVA ratings in that engineering design line. 

This reduced the number of units for analysis from 115 to 13. The technique used to extrapolate

the findings 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 can be 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.

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.

 EE-RM/STD-00-550 COMMENT 55
5-4

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

PC* DL Type of Distribution

Transformer

kVA

Range

Voltage

Taps

Secondary

Voltages

Engineering Design Line

Representative Unit

1

1

Liquid-immersed,

medium-voltage, singlephase, rectangular tank10-100 ±2-2.5% 240/120 to

600V

50kVA, 65/C, single-phase, 60Hz,

7200V primary, 240/120V

secondary, rectangular tank

2

Liquid-immersed,

medium-voltage, singlephase, round tank10-100 ±2-2.5% 120/240 to

600V

25kVA, 65/C, single-phase, 60Hz,

24940GrdY/14400V primary,

120/240V secondary, round tank

3

Liquid-immersed,

medium-voltage, singlephase167-833 ±2-2.5% 120/240 to

600V

500kVA, 65/C, single-phase, 60Hz,

14400/24940YV primary, 

277/480YV secondary

2

4

Liquid-immersed,

medium-voltage, threephase15-500 ±2-2.5% 208Y/120 to

600V

150kVA, 65/C, three-phase, 60Hz,

12470Y/7200V primary,

208Y/120V secondary

5

Liquid-immersed,

medium-voltage, threephase750-2500 ±2-2.5% 208Y/120 to

600Y/347V

1500kVA, 65/C, three-phase, 60Hz,

24940GrdY/14400V primary, 

480Y/277V secondary

3 6 Dry-type, low-voltage,

single-phase 15-333 Universal** 120/240 to

600V

25kVA, 150/C, single-phase, 60Hz,

480V primary, 120/240V secondary,

10kV BIL

4

7 Dry-type, low-voltage,

three-phase 15-150 Universal** 208Y/120 to

600Y/347V

75kVA, 150/C, three-phase, 60Hz,

480V primary, 208Y/120V

secondary, 10kV BIL

8 Dry-type, low-voltage,

three-phase 225-1000 Universal** 208Y/120 to

600Y/347V

300kVA, 150/C, three-phase, 60Hz,

480V Delta primary, 208Y/120V

secondary, 10kV BIL

6

9

Dry-type, mediumvoltage, three-phase,

20-45kV BIL

15-500 ±2-2.5% 208Y/120 to

600Y/347V

300kVA, 150/C, three-phase, 60Hz,

4160V primary, 480Y/277V

secondary, 45kV BIL

10

Dry-type, mediumvoltage, three-phase,

20-45kV BIL

750-2500 ±2-2.5% 208Y/120 to

600Y/347V

1500kVA, 150/C, three-phase,

60Hz, 4160V primary, 480Y/277V

secondary, 45kV BIL

8

11

Dry-type, mediumvoltage, three-phase,

60-95kV BIL

15-500 ±2-2.5% 208Y/120 to

600Y/347V

300kVA, 150/C, three-phase, 60Hz,

12470V primary, 480Y/277V

secondary, 95kV BIL

12

Dry-type, mediumvoltage, three-phase,

60-95kV BIL

750-2500 ±2-2.5% 208Y/120 to

600Y/347V

1500kVA, 150/C, three-phase,

60Hz, 12470V primary, 480Y/277V

secondary, 95kV BIL

10 13

Dry-type, mediumvoltage, three-phase,

110-150kV BIL

225-2500 ±2-2.5% 208Y/120 to

600Y/347V

2000kVA, 150/C, three-phase,

60Hz, 12470V primary, 480Y/277V

secondary, 125kV BIL

* PC means Product Class (see Chapter 3 of the TSD). PC5, PC7 and PC9 are based on their three-phase

counterparts. They were not addressed in the detailed engineering analysis because of their low sales volume.

** Universal Taps are two above and four below 2.5 percent

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 cost-efficiency relationship between units as the

 EE-RM/STD-00-550 COMMENT 55
5-5

BIL level varies. For example, a 300 kVA, three-phase, dry-type unit can appear in design lines

8, 9, 11, or 13 depending on whether the BIL level is 10 kV, 20-45 kV, 60-95 kV, or 110-150

kV.

For design lines 9 through 13, it should be noted that 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 Department selected a slightly higher BIL level for the representative units

from these design lines to ensure that any candidate minimum efficiency standard would not

excessively penalize customers purchasing higher BIL levels. 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 also order a 5kV class 300 kVA with 45kV BIL or 60kV BIL. If the

candidate minimum efficiency standard were set at 30kV BIL, it may be prohibitively difficult to

achieve that same candidate standard level for customers ordering 60kV BIL. Thus, the

Department elected to evaluate the middle BIL level (in this example, 45kV BIL), making it

slightly easier for the lower BIL, and not too difficult for the higher BIL, to achieve compliance.

The remainder of this section discusses the 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,

liquid-immersed distribution transformers, ranging from 10 kVA to 100 kVA. The BIL level of

the windings ranges between 30 kV and 150 kV, and the tap arrangement is four 21⁄2 percent, two

above and two below normal. The primary voltage is less than 35 kV and the secondary voltage

is 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 and 100 kVA). Also, NEMA

recommended a 50 kVA rating for the Department’s analysis. Engineering design and

manufacturing differences led to the omission of 167 kVA and higher rated units, which are

considered part of 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 100 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. The BIL level of the windings ranges between

30 kV and 150 kV, and the tap arrangement is four 21⁄2 percent, two above and two below

normal. The primary voltage is less than 35 kV and the secondary voltage is less than or equal to

600 V. 

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

high-volume rating for round-tanks, and is approximately in the middle of the kVA range for this

 EE-RM/STD-00-550 COMMENT 55
5-6

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

NEMA recommended that the Department consider a 25 kVA pole-mounted unit in its analysis.

(NEMA, No. 7 at p. 5) Engineering design and manufacturing differences led to the omission of

167 kVA and higher rated units, which are considered part of design line 3.

Design Line 3. This design line groups together single-phase, round-tank, liquidimmersed distribution transformers, ranging from 167 kVA to 833 kVA. Together, design lines

1 through 3 cover all the single-phase, liquid-immersed units (there are no units produced

between 100 and 167 kVA). The BIL level of the windings ranges between 30 kV and 150 kV,

and the tap arrangement is four 21⁄2 percent, two above and two below normal. The primary

voltage is less than 35kV and the secondary voltage is less than or equal to 600V.

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

common rating and occurs approximately in the middle of the kVA range for this design line

(167 kVA, 250 kVA, 333 kVA, 500 kVA, 667 kVA, and 833 kVA). Although high currents

result with 277/480Y 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. The BIL level of the windings

range between 30 kV and 150 kV, and the tap arrangement is four 21⁄2 percent, two above and

two below normal. The primary voltage is less than 35 kV and the secondary voltage is less than

or equal to 600 V.

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

common rating and occurs approximately in the middle of the kVA range 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 5. Design line 5 represents rectangular tank, three-phase, liquid-immersed

distribution transformers, ranging from 750 kVA to 2500 kVA. Design lines 4 and 5 cover all

the three-phase, liquid-immersed units (there are no units produced between 500 and 750 kVA). 

The BIL level of the windings ranges between 95 kV and 150 kV, and the tap arrangement is four

21⁄2 percent, two above and two below normal. The primary voltage is less than 35 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 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. The BIL of the windings is 10 kV,

and the tap arrangement is “universal,” meaning six 21⁄2 percent, two above and four below

normal. The Department selected this tap arrangement based on recommendations from

 EE-RM/STD-00-550 COMMENT 55
5-7

manufacturers who produce transformers at these ratings. The primary voltage is 600 V or

below. The secondary voltage is less than 600 V. 

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. 

The primary windings are less than or equal to 600V, with a BIL of 10 kV. The secondary

voltage is less than 600 V. The tap arrangement is universal, meaning six 21⁄2 percent, two above

and four below normal.

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

common rating in this size range, 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), and NEMA recommended this rating

for analysis.

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

distribution transformers, ranging from 225 kVA to 1000 kVA. The primary windings are less

than or equal to 600V, with a BIL of 10kV. The secondary voltage is less than 600V. The tap

arrangement is universal, meaning six 21⁄2 percent, two above and four below normal. 

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 low 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 drytype 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 complete three-phase, medium-voltage, dry-type units into design

lines 9 and 10. The primary voltage is less than or equal to 5 kV, and the BIL is between 20 kV

and 45 kV. The secondary voltage is less than or equal to 600 V. The tap arrangement is four

21⁄2 percent, two above and two below normal. 

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, 225 kVA, 300 kVA, and 500 kVA).

Design Line 10. Design line 10 represents three-phase, medium-voltage, ventilated drytype distribution transformers, ranging from 750 kVA to 2500 kVA. The primary voltage is less

 EE-RM/STD-00-550 COMMENT 55
5-8

than or equal to 5kV, and the BIL is between 20kV and 45kV. The secondary voltage is less than

or equal to 600V. The tap arrangement is four 21⁄2 percent, two above and two below normal. 

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 (750kVA,

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

Design Line 11. Design line 11 represents three-phase, medium-voltage, ventilated drytype distribution transformers, ranging from 15 kVA to 500 kVA. This design line parallels

design line 9, with a higher primary insulation level, 60 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 tap

arrangement is four 21⁄2 percent, two above and two below normal. The primary voltage is 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 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 drytype distribution transformers, ranging from 750 kVA to 2500 kVA. This design line parallels

design line 10, with a higher primary insulation level, 60 kV to 95 kV BIL. The tap arrangement

is four 21⁄2 percent, 2 above and 2 below normal. The primary voltage is 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 110 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 tap arrangement is four 21⁄2

percent, two above and two below normal. The primary voltage is less than 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), and NEMA recommended this rating for analysis.

 EE-RM/STD-00-550 COMMENT 55
5-9

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 Scaling Relationships in Transformer Manufacturing

As discussed in the previous section, 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. 

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 and voltage frequency is 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 a fixed 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 are scaled equally in all directions. Analysis of this

scaling relationship reveals that each of the linear dimensions vary 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" (see

Appendix 5B). Table 5.2.3 depicts the most common scaling relationships in transformers.

 EE-RM/STD-00-550 COMMENT 55
5-10

Table 5.2.3 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 (distribution or power 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 5.2.3 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.

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,”

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

 EE-RM/STD-00-550 COMMENT 55
5-11

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”

Plugging 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.”

 EE-RM/STD-00-550 COMMENT 55
5-12

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

losses and kVA rating of a reference 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.

For dditional information on the derivation of the 0.75 scaling rule, see Appendix 5B. The

Department used the 0.75 scaling rule to scale the analysis findings on each of the representative

units within the 13 design lines. It applied the scaling rule to the design lines in the national

impact analysis (Chapter 10), where it scaled losses and other properties from the 13 units to the

102 kVA ratings it did not analyze.

5.3 TECHNICAL DESIGN INPUTS

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

the manufacturing selling prices and corresponding transformer efficiencies. To study this

relationship, the Department contracted a transformer design software company called Optimized

Program Service, Inc. (OPS) to create a database of designs that span the range of efficiency

levels for each of the units being analyzed. The Department learned during its visits to the nine

distribution transformer manufacturing facilities in early 2002 that many companies developed

and use their own, proprietary design software to develop new transformer designs for their

customers.

The design software creates an optimized, practical transformer design, bill of materials

and an electrical analysis report based on a set of input specifications and design parameters. 

The software produces information about the core and coil design that would enable a

manufacturer to build this unit, such as core dimensions, high- and low-voltage windings,

insulation, cooling ducts, and labor. The software generates an estimated cost of manufacturing

materials and labor, which is then converted to a sales 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. 

The Department will research these retooling costs in the MIA, following the ANOPR public

workshop and when appropriate will incorporate these costs in future engineering analyses.

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 values supplied to the design software mimics hundreds of

distribution transformer purchase orders. The A parameter represents a customer's net present

value of future losses in the transformer core (no-load losses) and the B represents a customer's

net present value of future losses in the windings (load losses). These values take into account a

 EE-RM/STD-00-550 COMMENT 55
5-13

range of factors depending on the customer. The B parameter is never larger than A, as this

would mean a user was specifying a transformer whose average load would be more than 100

percent of nameplate load.

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, and so the customer chooses a more efficient

transformer. 

For the engineering analysis, the Department used broad ranges of A and B evaluation

values (presented in Table 5.3.1) resulting in a comprehensive range of efficiency levels for each

design option combination of core steel and winding material. During the 2002 site visits,

manufacturers helped develop the range of A and B values used in the analysis. These values

result in the spectrum of efficiencies represented in transformer orders from customers, as well as

a low first-cost design and 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 being

bought. For the maximum technologically feasible design, the A and B evaluation values are

sufficiently high to push the design to the highest efficiency achievable, and are different for the

liquid-immersed and dry-type distribution transformers.

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

Transformers A values and increments B values and increments Resultant number of 

(A, B) combinations

Liquid-immersed

DLs: 1 - 5

$0 to $8 by 0.5 steps

$8 to $16 by 1.0 steps*

$0 to $3 by 0.25 steps

$3 to $6 by 0.5 steps*

179

63*

Dry-type

DLs: 6 - 13

$0 to $12 by 0.5 steps $0 to $8 by 0.5 steps 289

*Note: The Department conducted extended analyses on the A and B values for the liquid-immersed units when it

determined that max tech designs had not been captured with an $8 A and a $3 B. The Department applied the

extended analysis only to certain core steels for a representative unit, as manufacturers would not build transformers

with certain steels at such high evaluation conditions.

As an example of how the software used increments of A and B value combinations,

consider design line 1. For one construction method of the 50-kVA liquid-immersed

transformer, the software would be given A values starting at zero and increasing by 50-cent

increments and B values starting at zero and increasing by 25-cent increments. Because B is

never greater than A, the combinations of ($A, $B) designs for this design line were ($0.00,

$0.00), ($0.50, $0.00), ($0.50, $0.25), ($0.50, $0.50), ($1.00, $0.00), ($1.00, $0.25), ($1.00,

$0.50), and so on, totaling 179 different combinations of ($A, $B). The department carried out

this evaluation for each core-coil combination considered in the analysis. Furthermore, if this

core-coil combination studied under an extended analysis (to reach max tech), it would have ($A,

$B) designs starting at ($8.00, $3.00) and increasing by $1 increments on the A and 50 cent

increments on the B up to $16 and $6, respectively. Thus, the ($A, $B) combinations for those

 EE-RM/STD-00-550 COMMENT 55
5-14

core-coil combinations to which an extended analysis was applied were ($8.00, $3.50), ($8.00,

$4.00), ($8.00, $4.50) and so on, for an additional 63 designs. 

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

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

Department removed these duplicate designs from the resultant database, as they might introduce

some bias in the LCC analysis resulting from a greater prevalence of a particular design.

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 using different core configurations, core steels and

winding materials. To capture this variation in designs, DOE analyzed each representative unit

using five to eleven 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 very 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 5.3.2 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.

 EE-RM/STD-00-550 COMMENT 55
5-15

Table 5.3.2 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

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 domainrefined 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 5.3.3 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 6 and 7, the Department analyzed two different core configurations.

 EE-RM/STD-00-550 COMMENT 55
5-16

Table 5.3.3 Core Configurations Used in Each Design Line

Design Line # Phases Core Configuration

DL1 1 Shell-type, wound core - distributed gap

DL2 1 Shell-type, wound core - distributed gap

DL3 1 Shell-type, wound core - distributed gap

DL4 3 Wound core - distributed gap, 5-leg

DL5 3 Wound core - distributed gap, 5-leg

DL6 1 Shell-type and core-type, stacked, butt-lap

DL7 3 Stacked, butt-lap, 3-leg; or Evans wound core- distributed gap

DL8 3 Stacked, butt-lap, 3-leg

DL9 3 Stacked, butt-lap, 3-leg

DL10 3 Stacked, mitered joint, 3-leg

DL11 3 Stacked, mitered joint, 3-leg

DL12 3 Stacked, cruciform, mitered joint, 3-leg

DL13 3 Stacked, cruciform, mitered joint, 3-leg

For the single-phase representative units, the configuration is either core-type or shelltype. This applies whether the core consists of stacked or wound laminations of core steel. For

the 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 previous and the following lamination. The distributed

gap is 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.

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

Of these, in the engineering analysis, the Department considered the 3-legged, the 5-legged and

the Evans. A three-legged core is assembled from stacked laminations. The joints can be buttlapped 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. Also, for larger kVA ratings, design economics may cause the selection of a

cruciform core section, consisting of multiple lamination widths in order to create a circular core

form around which the windings are placed. By using a core configuration that better follows the

contours of the windings, losses are again reduced, making 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.

 EE-RM/STD-00-550 COMMENT 55
5-17

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

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.

The Evans core is sometimes employed for small dry-type transformers in the 600V class. 

It consists of two inner wound cores which link the three winding assemblies. Enveloping these

two inner cores is a larger wound core which passes through the windows of the two outside

windings.

5.3.1 Design Line 1 Representative Unit 

Design line 1 (DL1) represents rectangular-tank, liquid-immersed, single-phase

distribution transformers, ranging from 10 kVA to 100 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 design software:

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

Primary: 7200 Volts at 60 Hz

Secondary: 240/120V

T Rise: 65/C

Ambient: 20/C

Winding Configuration: Lo-Hi-Lo

Core: Wound core - distributed gap

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

Impedance Range: 1.5–3.5 percent

For DL1, DOE selected ten 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 ten design option combinations to represent the most common construction practices for

this representative unit. It analyzed design option combinations 2, 8, 9 and 10 with both the

normal range of A and B factors and the extended A and B factors to capture the maximum

technologically feasible efficiency design. 

 EE-RM/STD-00-550 COMMENT 55
5-18

Table 5.3.4 Design Option Combinations for the Representative Unit from DL1

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design

Type

1 M2 Cu Al Shell

2* M2 Cu Cu Shell

3 M3 Al Al Shell

4 M3 Cu Al Shell

5 M3 Cu Cu Shell

6 M6 Al Al Shell

7 M6 Cu Al Shell

8*,** SA1 (Amorphous) Cu Cu Core

9*,*** ZDMH - price 1 Cu Cu Shell

10*,*** ZDMH - price 2 Cu Cu Shell

* Design option combinations 2, 8, 9 and 10 were studied with the extended $A and $B analysis, as these are

considered the likely core/coil combinations for high evaluation formulae. This extended analysis means that, in

addition to the $0-8A and $0-3B, $8-16A and $3-6B were also analyzed.

** For amorphous metal cores, a magnetic flux density of 13.4 kilogauss and a 0.82 space factor were used.

*** ZDMH (mechanically scribed core steel) was analyzed at both a U.S. price and a Mexican/Canadian price, since

Mexico and Canada do not apply a 31 percent import duty on ZDMH. See section 3.5.3.

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 2,027 designs (after the removal of any

duplicate designs).

5.3.2 Design Line 2 Representative Unit 

Design line 2 (DL2) represents round-tank, liquid-immersed, single-phase distribution

transformers, ranging from 10 kVA to 100 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 design software:

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

Primary: 24940GrdY/14400 Volts at 60 Hz (125 kV BIL)

Secondary: 120/240V

T Rise: 65/C

Ambient: 20/C

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

Core: Wound core - distributed gap

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

Impedance Range: 1.0–3.5 percent

 EE-RM/STD-00-550 COMMENT 55
5-19

For DL2, DOE selected ten design option combinations, based on input from

manufacturers and other technical experts. The Department selected shell-type core

configuration because this is commonly used by manufacturers for a 25 kVA transformer. 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. It

analyzed design option combinations 1, 3, 8, 9 and 10 with both the normal range of A and B

factors and the extended A and B factors to capture the maximum technologically feasible

efficiency design. 

Table 5.3.5 Design Option Combinations for the Representative Unit from DL2

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1* M2 Cu Al Shell

2 M3 Cu Al Shell

3* M3 Cu Cu Shell

4 M4 Al Al Shell

5 M4 Cu Al Shell

6 M6 Al Al Shell

7 M6 Cu Al Shell

8*,** SA1 (Amorphous) Cu Cu Core

9*,*** ZDMH - price 1 Cu Cu Shell

10*,*** ZDMH - price 2 Cu Cu Shell

* Design option combinations 1, 3, 8, 9 and 10 were studied with the extended $A and $B analysis, as these are

considered the likely core/coil combinations for high evaluation formulae. This extended analysis means that, in

addition to the $0-8A and $0-3B, $8-16A and $3-6B were also analyzed.

** For amorphous metal cores, a magnetic flux density of 13.4 kilogauss and a 0.82 space factor were used.

*** ZDMH (mechanically scribed core steel) was analyzed at both a U.S. price and a Mexican/Canadian price, since

Mexico and Canada do not apply a 31 percent import duty on ZDMH. See section 3.5.3.

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 2,100 designs (after removal of duplicate

designs).

5.3.3 Design Line 3 Representative Unit 

Design line 3 (DL3) represents round-tank, liquid-immersed, single-phase distribution

transformers, ranging from 167 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 design software:

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

 EE-RM/STD-00-550 COMMENT 55
5-20

Primary: 14400/24940Y Volts at 60 HZ (150kV BIL)

Secondary: 277/480Y Volts

T Rise: 65/C

Ambient: 20/C

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

Core: Wound core - distributed gap

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

Impedance Range: 2.5–5.75 percent

For DL3, the Department selected eight design option combinations of core steel and

winding material, based on input from manufacturers and other technical experts. The core

selected was shell-type, because this is commonly used by industry for this rating. 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. The Department

analyzed design option combinations 5, 6, 7 and 8 with both the normal range of A and B factors

and the extended A and B factors to capture the maximum technologically feasible efficiency

design. 

Table 5.3.6 Design Option Combinations for the Representative Unit from DL3

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M6 CU AL Shell

2 M4 AL AL Shell

3 M3 CU AL Shell

4 M2 CU AL Shell

5* M2 CU CU Shell

6*,** SA1 (Amorphous) CU CU Shell

7*,*** ZDMH - price 1 CU CU Shell

8*,*** ZDMH - price 2 CU CU Shell

* Design option combinations 5, 6, 7, and 8 were studied with the extended $A and $B analysis, as these are

considered the likely core/coil combinations for high evaluation formulae. This extended analysis means that, in

addition to the $0-8A and $0-3B, $8-16A and $3-6B were also analyzed.

** For amorphous metal cores, a magnetic flux density of 13.4 kilogauss and a 0.82 space factor were used.

*** ZDMH (mechanically scribed core steel) was analyzed at both a U.S. price and a Mexican/Canadian price, since

Mexico and Canada do not apply a 31 percent import duty on ZDMH. See section 3.5.3.

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 1,674 designs (after removal of duplicate

designs)

 EE-RM/STD-00-550 COMMENT 55
5-21

5.3.4 Design Line 4 Representative Unit 

Design line 4 (DL4) 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 design software:

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 or Lo-Hi-Lo

Core: Wound core - distributed gap, 5-leg

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

Impedance Range: 2.5–3.0 percent

For DL4, DOE selected nine 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. It analyzed the design option

combinations 3, 6, 7, 8 and 9 with both the normal range of A and B factors and the extended A

and B factors to capture the maximum technologically feasible efficiency design. 

 EE-RM/STD-00-550 COMMENT 55
5-22

Table 5.3.7 Design Option Combinations for the Representative Unit from DL4

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design

Type

1 M6 AL AL 5-Leg Core

2 M4 AL AL 5-Leg Core

3* M3 CU AL 5-Leg Core

4 M3 CU CU 5-Leg Core

5 M2 CU AL 5-Leg Core

6* M2 CU CU 5-Leg Core

7*,** SA1 (Amorphous) CU CU 5-Leg Core

8*,*** ZDMH-price 1 CU CU 5-Leg Core

9*,*** ZDMH-price 2 CU CU 5-Leg Core

* Design option combinations 3, 6, 7, 8, and 9 were studied with the extended $A and $B analysis, as these are

considered the likely core/coil combinations for high evaluation formulae. This extended analysis means that, in

addition to the $0-8A and $0-3B, $8-16A and $3-6B were also analyzed.

** For amorphous metal cores, a magnetic flux density of 13.4 kilogauss and a 0.82 space factor were used.

*** ZDMH (mechanically scribed core steel) was analyzed at both a U.S. price and a Mexican/Canadian price, since

Mexico and Canada do not apply a 31 percent import duty on ZDMH. See section 3.5.3.

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 1,906 designs (after removal of duplicate

designs).

5.3.5 Design Line 5 Representative Unit 

Design line 5 (DL5) 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 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

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

Winding Configuration: Lo-Hi

Core: Wound core - distributed gap, 5-leg

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

Impedance Range: 5.75 percent

 EE-RM/STD-00-550 COMMENT 55
5-23

For DL5, the Department 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 practices for the representative unit. It

analyzed design option combinations 4, 5, 6, 7, and 8 with both the normal range of A and B

factors and the extended A and B factors to capture the maximum technologically feasible

efficiency design.

Table 5.3.8 Design Option Combinations for the Representative Unit from DL5

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design

Type

1 M4 AL AL 5-Leg Core

2 M4 CU AL 5-Leg Core

3 M3 AL AL 5-Leg Core

4* M3 CU AL 5-Leg Core

5* M2 CU AL 5-Leg Core

6*,** SA1 (Amorphous) CU CU 5-Leg Core

7*,*** ZDMH - price 1 CU CU 5-Leg Core

8*,*** ZDMH - price 2 CU CU 5-Leg Core

* Design option combinations 4, 5, 6, 7, and 8 were studied with the extended $A and $B analysis, as these are

considered the likely core/coil combinations for high evaluation formulae. This extended analysis means that, in

addition to the $0-8A and $0-3B, $8-16A and $3-6B were also analyzed.

** For amorphous metal cores, a magnetic flux density of 13.4 kilogauss and a 0.82 space factor were used.

*** ZDMH (mechanically scribed core steel) was analyzed at both a U.S. price and a Mexican/Canadian price, since

Mexico and Canada do not apply a 31 percent import duty on ZDMH. See section 3.5.3.

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 1,742 designs (after removal of duplicate

designs).

5.3.6 Design Line 6 Representative Unit 

Design line 6 (DL6) 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 design software:

KVA: 25 (dry-type)

Phases: Single

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

Secondary: 120/240 Volts

 EE-RM/STD-00-550 COMMENT 55
5-24

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 normal

Impedance Range: 3.0–6.0 percent

For DL6, DOE selected ten 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 5.3.9 Design Option Combinations for the Representative Unit from DL6

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M43, 26 gauge AL (wire) AL (wire) Core

2 M36, 26 gauge AL (wire) AL (wire) Core

3 M19, 26 gauge AL (wire) AL (wire) Core

4 M6 AL (wire) AL (wire) Core

5 M3 CU (wire) AL (strip) Core

6 H-O DR CU (wire) CU (strip) Core

7 M6 AL (wire) AL (wire) Shell

8 M19 AL (wire) AL (wire) Shell

9 M3 CU (wire) AL (strip) Shell

10 H-O DR* CU (wire) CU (strip) Shell

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

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 2,597 designs (after removal of duplicate

designs).

5.3.7 Design Line 7 Representative Unit 

Design line 7 (DL7) 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 design software:

KVA: 75 (dry-type)

 EE-RM/STD-00-550 COMMENT 55
5-25

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; Evans Wound, DG

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

Impedance Range: 3.0–6.0 percent

For DL7, DOE 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 practice for the representative unit. 

Table 5.3.10 Design Option Combinations for the Representative Unit from DL7

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M19, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

2 M36, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

3 M43, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

4 M6 AL (wire) AL (wire) 3 - Leg Stacked

5 M6 AL (wire) AL (wire) 3 - Leg Evans

6 M3 CU (wire) AL (strip) 3 - Leg Evans

7 H-O DR* CU (wire) CU (strip) 3 - Leg Evans

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

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 1,874 designs (after removal of duplicate

designs).

5.3.8 Design Line 8 Representative Unit 

Design line 8 (DL8) 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 design software:

KVA: 300 (dry-type)

Phases: Three

 EE-RM/STD-00-550 COMMENT 55
5-26

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

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

Impedance Range: 3.0–6.0 percent

For DL8, 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. 

Table 5.3.11 Design Option Combinations for the Representative Unit from DL8

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M19, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

2 M6, 29 gauge AL (wire) AL (strip) 3 - Leg Stacked

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

4 M3 CU (wire) AL (strip) 3 - Leg Stacked

5 H-O DR* CU (wire) CU (strip) 3 - Leg Stacked

* 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 1,393 designs (after removal of duplicate

designs).

5.3.9 Design Line 9 Representative Unit 

Design line 9 (DL9) 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 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

 EE-RM/STD-00-550 COMMENT 55
5-27

Core: Stacked, butt-lap

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

Impedance Range: 3.0–6.0 percent

For DL9, the Department selected six 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 5.3.12 Design Option Combinations for the Representative Unit from DL9

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M36, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

2 M19, 26 gauge AL (wire) AL (wire) 3 - Leg Stacked

3 M6, 29 gauge AL (wire) AL (wire) 3 - Leg Stacked

4 M6, 29 gauge CU (wire) CU (wire) 3 - Leg Stacked

5 M3 CU (wire) AL (strip) 3 - Leg Stacked

6 H-O DR* CU (wire) CU (strip) 3 - Leg Stacked

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

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 1,620 designs (after removal of duplicate

designs).

5.3.10 Design Line 10 Representative Unit 

Design line 10 (DL10) 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 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, Mitered

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

Impedance Range: 5.7 percent

 EE-RM/STD-00-550 COMMENT 55
5-28

For DL10, 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. 

Table 5.3.13 Design Option Combinations for the Representative Unit from DL10

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M6 AL (wire) AL (strip) Stacked

2 M6 CU (wire) CU (strip) Stacked

3 M4 CU (wire) AL (strip) Stacked

4 M3 CU (wire) CU (strip) Stacked

5 H-O DR* CU (wire) CU (strip) Stacked

* 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 1,400 designs (after removal of duplicate

designs).

5.3.11 Design Line 11 Representative Unit 

Design line 11 (DL11) 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 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 normal

Impedance Range: 5.0–7.0 percent

For DL11, 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. 

 EE-RM/STD-00-550 COMMENT 55
5-29

Table 5.3.14 Design Option Combinations for the Representative Unit from DL11

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M6 AL (wire) AL (strip) Stacked

2 M6 CU (wire) CU (strip) Stacked

3 M4 CU (wire) AL (strip) Stacked

4 M3 CU (wire) CU (strip) Stacked

5 H-O DR* CU (wire) CU (strip) Stacked

* 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 1,375 designs (after removal of duplicate

designs).

5.3.12 Design Line 12 Representative Unit 

Design line 12 (DL12) 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 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 normal

Impedance Range: 5.0–8.0 percent

For DL12, 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. 

 EE-RM/STD-00-550 COMMENT 55
5-30

Table 5.3.15 Design Option Combinations for the Representative Unit from DL12

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M6 AL (wire) AL (strip) Stacked

2 M6 CU (wire) CU (strip) Stacked

3 M4 CU (wire) AL (strip) Stacked

4 M3 CU (wire) CU (strip) Stacked

5 H-O DR* CU (wire) CU (strip) Stacked

* 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 1,344 designs (after removal of duplicate

designs).

5.3.13 Design Line 13 Representative Unit 

Design line 13 (DL13) 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 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 normal

Impedance Range: 5.0–8.0 percent

For DL13, 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. 

 EE-RM/STD-00-550 COMMENT 55
5-31

Table 5.3.16 Design Option Combinations for the Representative Unit from DL13

Design Option

Combination

Core Material High Voltage

Conductor

Low Voltage

Conductor

Core Design Type

1 M6 AL (wire) AL (strip) Stacked

2 M6 CU (wire) CU (strip) Stacked

3 M4 CU (wire) AL (strip) Stacked

4 M3 CU (wire) CU (strip) Stacked

5 H-O DR* CU (wire) CU (strip) Stacked

* 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 1,335 designs (after removal of duplicate

designs).

5.3.14 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, DL1 stands for design line 1, spanning

from 10 to 100kVA liquid-type, single-phase. The label “Rep Unit” appears in row 50kVA,

indicating that the 50kVA is the representative unit for DL1. Similarly, the representative unit

for DL2 is the 25kVA unit. 

 EE-RM/STD-00-550 COMMENT 55
5-32

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

 Single-Phase Three-Phase

Product Class 1 Product Class 2

Liquid-Immersed, Liquid-Immersed, DL 1 DL 2 DL 3

Rep Unit

Rep Unit

Rep Unit

DL 4

Rep Unit

DL 5

Rep Unit

As Table 5.3.17 shows, both design line 1 and design line 2 span the single-phase liquidimmersed units from 10 kVA to 100 kVA.

Table 5.3.17 Liquid-Immersed Design Lines and Representative Units

 EE-RM/STD-00-550 COMMENT 55
5-33

kVa

Design 

Lines kVa

Design 

Lines

15 15

25 30

37.5 45

50 75

75 112.5

100 150

167 225

250 300

333 500

750

1000

Single-Phase Three-Phase

Product Class 3 Product Class 4

Dry-Type, Low-Voltage Dry-Type, Low-Voltage DL 

6

Rep Unit

Rep Unit

DL 7 DL 8

Rep Unit

Table 5.3.18 presents the low-voltage, dry-type design lines and the product classes they cover. 

For single-phase units, one design line spans all nine kVA ratings while, for the three-phase

units, two design lines cover the 11 kVA ratings in that product class. There is no overlap of

design lines for these two product classes.

Table 5.3.18 Dry-Type, Low-Voltage Design Lines and Representative Units

 EE-RM/STD-00-550 COMMENT 55
5-34

kVa

PC 5* 

Low BIL 

20-45 kV

PC 7 

Med BIL 

46-95 kV

PC 9 

High BIL 

>96 kV

10 -

25 -

37.5 -

50 -

75

100

167

250

333

500

667

833

Dry-Type, Medium-Voltage, Single-Phase DL 9 / 3 DL 11 / 3

Virtual RU

DL 13 / 3

DL 10 / 3

DL 12 / 3

Virtual RU

Virtual RU

Virtual RU

Virtual RU

Table 5.3.19 presents product classes (abbreviated “PC” in this table) for mediumvoltage, 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

5.3.18 together represent less than one-third of one percent of dry-type shipments on both a perunit and an MVA-capacity basis. Thus, the Department did not consider it appropriate to

conduct three design lines of analysis for each of the BIL ratings shown.

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 5.3.19) 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 DL9 is a three-phase 300 kVA

unit, so it scales to a single-phase, 100 kVA unit in Table 5.3.19.

Table 5.3.19 Dry-Type, Medium-Voltage, Single-Phase Design Lines

*PC is an abbreviation for Product Class

 EE-RM/STD-00-550 COMMENT 55
5-35

kVa

PC 6 

Low BIL 

20-45 kV

PC 8 

Med BIL 

46-95 kV

PC 10 

High BIL 

>96 kV

15 -

30 -

45 -

75 -

112.5 -

150 -

225

300

500

750

1000

1500

2000

2500

Dry-Type, Medium-Voltage, Three-Phase DL 9 DL 11

Rep Unit

DL 13

DL 10 

DL 12 

Rep Unit

Rep Unit

Rep Unit

Rep Unit

Table 5.3.20 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 (DL13) covers all the ratings from 225kVA to

2500kVA. As stated earlier, it is extremely unlikely that a three-phase, dry-type transformer with

a BIL $96kV and a power rating less than 150kVA would be built.

Table 5.3.20 Dry-Type, Medium-Voltage, Three-Phase Design Lines

 EE-RM/STD-00-550 COMMENT 55
5-36

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

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 full cost of a product.

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. Together, the full production cost and the non-production cost

equal the full cost 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).

For the purposes of the rulemaking, the Department estimated manufacturer internal

markups from U.S. Industry Census Data for 1992 and 1997; and SEC 10-K reports for Acme,

Powell, Magnetek and Hammond. The Department then vetted these estimated markups with

 EE-RM/STD-00-550 COMMENT 55
5-37

manufacturers during a series of consultative meetings held in early 2002. The following

markups resulted:

• Scrap 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).

• Factory overhead: 12.5 percent markup. Factory overhead includes all the indirect costs

associated with production, indirect materials and energy use, 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 sales and

general administrative, R&D, interest payments, and profit factor. The Department

applies the non-production markup to the sum of the direct material production, the direct

labor, and the factory overhead. 

The following example shows how the Department applied the markups to the materials,

and how it determined the total production cost. Consider a 300kVA 45kV BIL three-phase drytype transformer designed for a $1.50 A and a $0.50 B. This design has $2,902 of materials,

including M6 core steel, copper primary and secondary windings, and all the transformer

hardware. There are approximately 12.5 hours of labor involved in manufacturing this design,

resulting in a labor cost of $532. The factory overhead on this design is $362, as it is only

applied to the material cost (i.e., 12.5 percent of $2902). The non-production cost is $949, as the

25 percent is applied to the material, labor, and factory overhead costs (i.e., 25 percent of $2902

+ $532 + $362). Thus, in total, DOE estimates this 300kVA three-phase transformer to have a

manufacturer selling price of $4,747. 

5.4.1 Material Inputs to the Design Software - Liquid-Immersed

In addition to the design parameters described in section 5.3, the other critical inputs to

the design software are material costs. As the price of one material increases or decreases

relative to the other materials, the design software will adjust the design to increase or decrease

the content of that material. The design software uses the final marked-up cost of materials as

input to the optimization process. In other words, rather than use the raw material cost of $1.00

per pound of core steel, the software uses $1.44 per pound, to reflect a small handling and scrap

factor (2.5 percent), the factory overhead (12.5 percent), and the non-production markup (25

percent). During its manufacturer site visits in early 2002, the Department found this approach to

be consistent with that of several manufacturers who operate their own, proprietary design

software. 

The following pages describe all the material prices entered into the design software for

liquid-immersed distribution transformers. As shown in these tables, the Department marked up

the material prices before entering them into the design software.

 EE-RM/STD-00-550 COMMENT 55
5-38

Table 5.4.1 Variable Material Inputs for Liquid-Immersed Units

Item and Description

Material Cost*Scrap andHandling**FactoryOverhead***Nonproduction****Input to designsoftware

M2 core steel $1.05 1.025 1.125 1.25 $1.51

M3 core steel $0.95 1.025 1.125 1.25 $1.37

M4 core steel $0.85 1.025 1.125 1.25 $1.23

M6 core steel $0.80 1.025 1.125 1.25 $1.15

ZDMH (mechanically-scribed core steel), non-US

price

$1.40 1.025 1.125 1.25 $2.02

ZDMH (mechanically-scribed core steel), US price

with import tariff

$1.83 1.025 1.125 1.25 $2.64

SA1 (amorphous material) - finished core, priced at

volume production

$1.70 1.1 1.125 1.25 $2.62

Copper wire, formvar, round #10-20 (DL1,2,4) $1.30 1.025 1.125 1.25 $1.87

Copper wire, enameled, round #7-10 flattened (DL3,5) $1.30 1.025 1.125 1.25 $1.87

Copper wire, enameled, rectangular sizes (DL3) $1.50 1.025 1.125 1.25 $2.16

Aluminum wire, formvar, round #9-17 (DL1,2,4) $1.36 1.025 1.125 1.25 $1.96

Aluminum wire, formvar, round #7-10 (DL3,5) $1.36 1.025 1.125 1.25 $1.96

Copper strip, thickness range 0.02-0.045 (DL1,2,4) $2.40 1.025 1.125 1.25 $3.46

Copper strip, thickness range 0.030-0.060 (DL3,5) $2.40 1.025 1.125 1.25 $3.46

Aluminum strip, thickness range 0.02-0.045 (DL1,2,4) $1.30 1.025 1.125 1.25 $1.87

Aluminum strip, thickness range 0.045-0.080 (DL3,5) $1.30 1.025 1.125 1.25 $1.87

Kraft insulating paper with diamond adhesive $1.54 1.025 1.125 1.25 $2.22

Mineral oil $1.52 1.025 1.125 1.25 $2.19

* Purchasing price to manufacturers from suppliers of raw materials necessary for building a transformer. Source:

Paul Goethe, OPS, 2001; Manufacturer interviews, 2002.

** Handling and scrap is a multiplier factor that 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). Source: Paul Goethe, OPS; Manufacturer interviews, 2002.

*** Factory overhead includes all indirect costs associated with production, energy use (e.g., furnace), light bulbs,

insurance on factory and equipment, etc. Source: US Industry Census Data for 1992 and 1997; SEC 10-K reports for

Acme, Powell, Magnetek and Hammond; Manufacturer interviews, 2002.

**** Material markup reflects non-production costs, including sales and general 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.

 EE-RM/STD-00-550 COMMENT 55
5-39

The Department obtained prices of all core steels used in the analysis for a standard

quantity order from a major U.S. core steel manufacturer. Due to a U.S. policy to apply an

import tariff to core steels from Japan and Italy, the Department considered a dual-price point for

a special Japanese core steel called ‘ZDMH’ in this analysis, to understand how significant

changes in the cost of core steel may impact the rulemaking process. Given a recent

administrative decision to remove steel import tariffs, DOE will review the need for this dualprice point in the Notice of Proposed Rulemaking (NOPR) analysis. 

ZDMH is a mechanically-scribed core steel that has beneficial low-loss properties that

can survive the high-temperature stress-relief annealing process conducted on wound cores

during manufacture. However, this high-efficiency technology option is only available from one

supplier in Japan. Thus, as discussed in section 3.5.3, two prices are necessary because finished

transformers imported from Mexico and Canada would not be subject to the tariff. The

Department analyzed designs at both price points, to ensure that the standard would not result in

a competitive advantage to non-US manufacturers due to the import duty on ZDMH core steel. 

The wire and strip prices shown in Table 5.4.1 were obtained from a major U.S. wire

manufacturer.

In addition to these variable materials which the design software considers when

preparing its optimized designs, there are other materials that are fixed and do not influence the

design of the product. These include materials like the transformer cabinet, the high- and lowvoltage bushings, and the core clamps. Table 5.4.3, on the next page, outlines all the estimated

fixed material 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, 7200V, costing $7 for the set. The low-voltage

bushings are three copper studs, 240/120V, 50 kVA, at $8 for the set. The fuse system specified

is a bayonet fuse holder, fuse and isolation link, costing $35. The internal hardware includes a

core clamp, tap changer, nameplate, and other miscellaneous hardware costing $28.65. The

Department varied the finished tank sizes for design line 1, ranging in price from $210 for the

smallest size to $250 for the largest. Table 5.4.2 shows the five tank sizes used in design line 1. 

The Department based tank-size selections on the dimensions of the core-coil assembly, and

based the oil used in the design on the core-coil assembly displacement of the tank volume.

Table 5.4.2 Variable Tank Sizes for Design Line 1

Tanks Length Height Depth Volume 

(cubic inches)*

Volume

(gal)*

Price 

($)

Weight 

(lbs)

A 32 24 13 8,320 36.0 $210 167

B 32 24 15 9,600 41.6 $220 174

C 32 24 17 10,880 47.1 $230 181

D 32 24 19 12,160 52.6 $240 188

E 32 24 21 13,440 58.2 $250 195

* Note that the volume calculation is less a four inch air-gap in the height of the tank.

 EE-RM/STD-00-550 COMMENT 55
5-40

For design line 2, a 25kVA single-phase pole-mounted unit, the high-voltage terminals

are two porcelain bushing assemblies, 15 kV, 125 BIL, costing $12.00 for the set. The lowvoltage terminals are three porcelain bushings, 120/240V, 25 kVA, at $8.00 for the set. The

Department specified no fuse system for this representative unit. The internal hardware includes

a core clamp, tap changer, nameplate, and other miscellaneous hardware, costing $28.65. The

finished tank sizes are determined by the design software. Rather than use five discrete sizes as

in design line 1, the software calculates tank size based on core/coil clearances and oil

requirements. The price for a 25kVA pole-mounted tank is held constant at $120.

For design line 3, a 500kVA single-phase unit, the high-voltage connectors are two

porcelain bushings, 25 kV, 125 BIL, costing $20 for the set. The low-voltage bushings are two

polymer 500kVA, 277V, costing $40 for the set. The internal hardware includes a core clamp

($30), tap changer ($15), and nameplate and miscellaneous hardware ($20), totaling $65. As

with design line 2, the software was allowed to vary the tank size. The finished round tank has a

diameter of 26" to 30" with external cooling, and has a fixed cost of $500.

For design line 4, a 150kVA three-phase, pad-mounted unit, the high-voltage bushings

are six universal bushing wells, 8.3/14.4 kV, 95 BIL, costing $21 each. The low-voltage

bushings are four copper studs at $12 each. The fuse system installed is a bayonet fuse holder,

fuse, and isolation link, costing $105. The internal hardware includes core clamps ($45), tap

changer ($40), and nameplate and miscellaneous hardware ($45), totaling $130. The finished

tank sizes were determined by the design software, measuring 48 inches high and 54 inches wide,

and varying the depth. The finished rectangular welded tank costs $650.

For design line 5, a 1500kVA three-phase, pad-mounted unit, the high-voltage bushings

are six universal bushing wells, 15.2/26.3 kV, 125kV BIL, costing $42 for the set. The lowvoltage bushings are four copper studs, costing $12 each. The fuse system installed is a bayonet

fuse holder, fuse, and isolation link costing $105. The internal hardware includes core clamps

($45), tap changer ($40), and nameplate and miscellaneous hardware ($45), totaling $130. The

finished tank sizes were determined by the design software, measuring 60 inches high and 57

inches wide, and varying the depth. The finished rectangular welded tank costs $800.

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

Item DL1 DL2 DL3 DL4 DL5

High voltage bushings $7 $12 $20 $21 $42

Low voltage bushings $8 $8 $40 $12 $12

Fuse system $35 none none $105 $105

Core clamp, tap changer,

misc. hardware

$28.65 $28.65 $65 $130 $130

Transformer tank $210-250 $120 $500 $650 $800

 EE-RM/STD-00-550 COMMENT 55
5-41

5.4.2 Material Inputs to the Design Software - Dry-type

On the following pages, all the material costs entered into the design software for drytype distribution transformers are given. As shown in these tables, the Department marked up

the material costs before being entering them into the design software.

Table 5.4.4 Variable Material Inputs for Dry-Type Units

Item and Description

Material Cost*Scrap andHandling**FactoryOverhead***Nonproduction****Input to designsoftware

H-O DR core steel (laser-scribed) $1.15 1.025 1.125 1.25 $1.66

M3 core steel $0.95 1.025 1.125 1.25 $1.37

M4 core steel $0.85 1.025 1.125 1.25 $1.23

M6 core steel $0.80 1.025 1.125 1.25 $1.15

M19 core steel (26 gauge) $0.70 1.025 1.125 1.25 $1.01

M36 core steel (26 gauge) $0.46 1.025 1.125 1.25 $0.66

M43 core steel (26 gauge) $0.39 1.025 1.125 1.25 $0.56

Copper wire, rectangular 0.1 x 0.2, Nomex

wrapped

$1.60 1.025 1.125 1.25 $2.31

Aluminum wire, rectangular 0.1 x 0.2,

Nomex wrapped

$2.00 1.025 1.125 1.25 $2.88

Copper strip, thickness range .02-.045 $2.40 1.025 1.125 1.25 $3.46

Aluminum strip, thickness range .02-.045 $1.30 1.025 1.125 1.25 $1.87

Nomex insulation (per pound) $17.50 1.025 1.125 1.25 $25.22

Impregnation (per gallon) $18.00 1.025 1.125 1.25 $25.95

Winding Combs (per pound) $10.00 1.025 1.125 1.25 $14.41

* Purchasing price to manufacturers from suppliers of raw materials necessary for building a transformer. Source:

Paul Goethe, OPS, 2001; Manufacturer interviews, 2002.

** Handling and scrap is a multiplier factor that 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). Source: Paul Goethe, OPS; Manufacturer interviews, 2002.

*** Factory overhead includes all indirect costs associated with production, energy use (e.g., furnace), light bulbs,

insurance on factory and equipment, etc. Source: US Industry Census Data for 1992 and 1997; SEC 10-K reports for

Acme, Powell, Magnetek and Hammond; Manufacturer interviews, 2002.

**** Material mark up reflects non-production costs, including sales and general 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.

 EE-RM/STD-00-550 COMMENT 55
5-42

In addition to the variable inputs presented in Table 5.4.4, there is one input material that

varied for each of the design lines: the dog-bone cooling duct spacer. The number and

placement of cooling ducts is determined by the design software during the design process;

however, the size (height) of the duct is defined as a design input. In addition to presenting some

of the fixed material costs, Table 5.4.5 presents the input costs per foot for the duct-spacers used. 

For design line 6, a 25kVA 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 costs $9.25. The fiberglass dog-bone ductspacers used for this design line cost $0.24 per foot. The miscellaneous hardware costs were set

at $4.50. The enclosure itself, a 14-gauge steel enclosure, base, and mounting feet cost $100. 

The cost of the enclosure was held constant while the actual dimensions were allowed to vary

with the core-coil assembly size. 

For design line 7, a 75kVA three-phase, low-voltage, dry-type, the fixed hardware costs

are $6 for the low-voltage and high-voltage terminals. The low voltage bus-bar is estimated to be

six feet at $1.50 per foot, or $9. The mounting frame that attaches the core/coil assembly to the

transformer enclosure costs $19. The fiberglass dog-bone duct-spacers used for this design line

cost $0.32 per foot. The miscellaneous hardware costs were estimated at $6. The enclosure itself,

a 14-gauge steel enclosure, base, and mounting feet cost $125. The cost of the enclosure was

held constant while the actual dimensions were allowed to vary with the core-coil assembly size. 

For design line 8, a 300 kVA three-phase, low-voltage, dry-type, the low-voltage and

high-voltage terminal set costs $19. 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 $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 enclosure itself, a 14-

gauge steel enclosure, base, and mounting feet cost $175. The cost of the enclosure was held

constant while the actual dimensions were allowed to vary with the core-coil assembly size. 

For design line 9, a 300 kVA three-phase medium-voltage dry-type at 45kV BIL, the lowvoltage and high-voltage terminal set costs $75. The low-voltage bus-bar is estimated to be nine

feet at $6 per foot, or $54. The mounting frame that attaches the core/coil assembly to the

transformer enclosure costs $36. The fiberglass dog-bone duct-spacers used for this design line

cost $0.24 per foot. The miscellaneous hardware costs were estimated at $25. The enclosure

itself, a 14-gauge steel enclosure, base, and mounting feet cost $175. The cost of the enclosure

was held constant while the actual dimensions were allowed to vary with the core-coil assembly

size. 

For design line 10, a 1500 kVA three-phase medium-voltage dry-type at 45kV BIL, the

low-voltage and high-voltage terminal set costs $120. The low voltage bus-bar is estimated to be

ten feet at $14 per foot, or $140. The mounting frame that attaches the core/coil assembly to the

transformer enclosure costs $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 enclosure

 EE-RM/STD-00-550 COMMENT 55
5-43

itself, a 12-gauge steel enclosure, base, and mounting feet cost $500. The cost of the enclosure

was held constant while the actual dimensions were allowed to vary with the core-coil assembly

size. 

For design line 11, a 300 kVA three-phase medium-voltage dry-type at 95kV BIL, the

low-voltage and high-voltage terminal set costs $75. 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 duct-spacers used for this design line

cost $0.24 per foot. The miscellaneous hardware costs were estimated at $32. The enclosure

itself, a 14-gauge steel enclosure, base and mounting feet cost $200. The cost of the enclosure

was held constant while the actual dimensions were allowed to vary with the core-coil assembly

size. 

For design line 12, a 1500 kVA three-phase medium-voltage dry-type at 95kV BIL, the

low-voltage and high-voltage terminal set costs $120. The low-voltage bus-bar is estimated to be

fourteen feet at $12 per foot, or $168. The mounting frame that attaches the core/coil assembly

to the transformer enclosure costs $125. The fiberglass dog-bone duct-spacers used for this

design line cost $0.56 per foot. The miscellaneous hardware costs were estimated at $42. The

enclosure itself, a 12-gauge steel enclosure, base and mounting feet cost $600. The cost of the

enclosure was held constant while the actual dimensions were allowed to vary with the core-coil

assembly size. 

For design line 13, a 2000 kVA three-phase medium-voltage dry-type at 125kV BIL, the

low-voltage and high-voltage terminal set costs $150. 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 $56. The

enclosure itself, a 12-gauge steel enclosure, base and mounting feet cost $750. The cost of the

enclosure was held constant while the actual dimensions were allowed to vary with the core-coil

assembly size. 

Table 5.4.5 Summary Table of Fixed Material Costs for Dry-Type Units

Item DL6 DL7 DL8 DL9 DL10 DL11 DL12 DL13

LV and HV terminals (set) $4 $6 $19 $75 $120 $75 $120 $150

LV bus-bar n/a $9 $22.50 $54 $140 $80 $168 $270

Core/coil mounting frame $9.25 $19 $36 $36 $120 $42 $125 $175

Dog-bone duct-spacer (ft.) $0.24 $0.32 $0.42 $0.24 $0.52 $0.24 $0.56 $0.60

Misc. hardware $4.50 $6 $12 $25 $42 $32 $42 $56

Enclosure (12, 14 gauge) $100 $125 $175 $175 $500 $200 $600 $750

 EE-RM/STD-00-550 COMMENT 55
5-44

5.4.3 Labor Cost Inputs to the Design Software

Labor costs constitute a critical aspect of the cost of manufacturing a distribution

transformer. As an input to the design software, 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 except for the non-production markup. The Department developed the

markups shown in Table 5.4.6 after reviewing publicly available information and consulting with

industry experts familiar with transformer manufacturing in the U.S.

Table 5.4.6 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 sales and general 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. 

 EE-RM/STD-00-550 COMMENT 55
5-45

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 cost and efficiency relationships for each of the 13

design lines. Each dot on the plots represents one unique design created by the software at a

given manufacturer 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, and A/B combination. In Appendix 5A, additional scatter plots for the

engineering analysis results for the 13 representative units are presented, including watts of core

and coil loss by price and the weight by price. On the Department’s website, the actual values

behind these plots are available in two Microsoft Excel® workbooks, one for liquid-immersed

and one for dry-type units. See: 

http://www.eere.energy.gov/buildings/appliance_standards/commercial/dist_transformers.html

Figure 5.5.1 presents a plot of the manufacturer sales prices and efficiency levels for the

full database of designs for the representative unit from design line 1. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• Designs achieving the highest efficiencies at the lowest costs are based on M2 and M3

steel cores. Of these cores, the M3CuAl offers the least-cost option for improving

efficiency, but is limited to an efficiency of 99.3 percent.

• The all-copper windings available with the M2CuCu and M3CuCu options allow for

somewhat higher efficiencies, but the costs escalate rapidly above 99.3 percent efficiency.

• The ZDUS (ZDMH core steel) has higher costs associated with increasing efficiency than

do other cores.

• The amorphous metal (SA1) core dramatically extends the available efficiency for the

transformers beyond 99.6 percent, but at a significant cost.

 EE-RM/STD-00-550 COMMENT 55
5-46

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

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 ($)

SA1CuCu

M2CuAl

M2CuCu

M3AlAl

M3CuAl

M3CuCu

M6AlAl

M6CuAl

ZDUSCuCu

Figure 5.5.1 Scatter Plot of Manufacturer Selling Price and Efficiency for DL1

 EE-RM/STD-00-550 COMMENT 55
5-47

Figure 5.5.2 Scatter Plot of Manufacturer Selling Price and Efficiency for DL2

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The TP-1 standard of 98.7 percent can be achieved with several design option

combinations, including M6AlAl and M4AlAl.

• The ZDUS core has higher costs associated with increasing efficiency relative to the other

design option combinations.

• In most cases, the maximum efficiency available with conventional core steels is

approximately 99.2 percent. However, the amorphous metal (SA1) provides efficiencies

up to about 99.5 percent.

• For this kVA rating, the SA1 core has a very steep cost curve associated with increasing

efficiency.

 EE-RM/STD-00-550 COMMENT 55
5-48

Figure 5.5.3 Scatter Plot of Manufacturer Selling Price and Efficiency for DL3

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The Japanese deep-domain refined core steel (ZDMH) design option combination,

ZDUSCuCu, has higher costs associated with increasing efficiency relative to the other

design options.

• 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 99.8 percent, with an available range from about 99.5 percent to nearly 99.8

percent.

• Beyond the efficiencies available with other cores, the amorphous core has a flat cost

with increasing efficiency up to about 99.6 percent. Beyond that, the costs begin to rise

exponentially.

 EE-RM/STD-00-550 COMMENT 55
5-49

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

97.50% 98.00% 98.50% 99.00% 99.50% 100.00%

Efficiency at 50% Load, Temperature Corrected (%)

Manufacturer Selling Price ($)

SA1CuCu

M2CuAl

M4AlAl

M3CuAl

M2CuCu

M6AlAl

ZDUSCuCu

M3CuCu

Figure 5.5.4 Scatter Plot of Manufacturing Selling Price and Efficiency for DL4

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several 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.

• Between 99.0 percent and 99.4 percent, the M2 and M3 steel cores are a cost-efficient

option for increasing efficiency. For these cores there is no significant difference

between the all-copper and copper-aluminum windings.

• The ZDUS core has a higher cost associated with increasing efficiency relative to the

other steel core offerings.

• The amorphous metal design option combination extends the available efficiency for the

transformers up to 99.6 percent, but at a significant cost.

 EE-RM/STD-00-550 COMMENT 55
5-50

5000

10000

15000

20000

25000

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 ($)

SA1CuCu

M2CuAl

M4AlAl

M3CuAl

M4CuAl

ZDUSCuCu

M3AlAl

Figure 5.5.5 Scatter Plot of Manufacturing Selling Price and Efficiency for DL5

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load. Several observations

can be made about this scatter plot:

• All the cores, except for the ZDUS, provide a low-cost option for increased efficiency

between 99.2 percent and 99.5 percent. However, the optimal core and winding

combination at a given efficiency rating vary.

• Beyond 99.5 percent, the SA1 core provides additional efficiency with increased cost. 

However, the units with the lowest manufacturer selling prices follow a similar general

trend displayed by the other cores.

• From the least expensive to the most expensive, there is more than a three-fold difference

in the manufacturer’s sales price.

 EE-RM/STD-00-550 COMMENT 55
5-51

400

600

800

1000

1200

1400

1600

94.00% 95.00% 96.00% 97.00% 98.00% 99.00%

Efficiency at 35% Load, Temperature Corrected (%)

Manufacturer Selling Price ($)

M43AlAlCo M36AlAlCo

M19AlAlCo M6AlAlCo

M3CuAlCo HOCuCuCo

M19AlAlSh M6AlAlSh

M3CuAlSh HOCuCuSh

Figure 5.5.6 Scatter Plot of Manufacturing Selling Price and Efficiency for DL6

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. The efficiency levels

shown in this plot represent transformers at 35 percent of nameplate load and are corrected for

temperature. Some 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

continues to rise with little or no gain in efficiency.

• The M3 and M6 cores provide the least-cost option, from 97.5 percent to 98.5 percent, for

increasing efficiency.

 EE-RM/STD-00-550 COMMENT 55
5-52

Figure 5.5.7 Scatter Plot of Manufacturing Selling Price and Efficiency for DL7

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. The efficiency levels

shown in this plot represent transformers at 35 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The M3CuAlEv (Evans core) transformer has essentially the same costs and efficiency

gains as the HOCuCuEv transformer. However, the H-O DR transformer provides a

slightly higher efficiency than the M3 transformer.

• At the higher efficiency levels, the cost of the transformers continues to rise with little or

no gain in efficiency.

• The M19 and M43 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.

 EE-RM/STD-00-550 COMMENT 55
5-53

Figure 5.5.8 Scatter Plot of Manufacturing Selling Price and Efficiency for DL8

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. The efficiency levels

shown in this plot represent transformers at 35 percent of nameplate load and are corrected for

temperature. Several 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.

• At the higher efficiency levels, the cost of the transformers continues to rise with little or

no gain in efficiency.

• The M19 core steel does not provide the minimum efficiency of 98.6 percent under

NEMA’s TP 1-2002.

 EE-RM/STD-00-550 COMMENT 55
5-54

3000

4000

5000

6000

7000

8000

9000

10000

96.50% 97.00% 97.50% 98.00% 98.50% 99.00% 99.50%

Efficiency at 50% Load, Temperature Corrected (%)

Manufacturer Selling Price ($)

M36AlAl

M19AlAl

M6AlAl

M3CuAl

HOCuCu

M6CuCu

Figure 5.5.9 Scatter Plot of Manufacturing Selling Price and Efficiency for DL9

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The least-expensive units employ the least-expensive core steels, M36 and M19. 

• Even though extremely high evaluation formulas are being applied to M36 and M19

steels (i.e., $12A and $8B), the efficiencies are unable to improve beyond 98 percent.

• NEMA’s TP 1-2002 efficiency level for this unit is 98.6 percent efficient. This level

cannot be achieved using the less expensive M36 and M19 core steels. 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 99.25 percent) can double the price.

• The increased performance and higher price of all-copper windings is shown when the

M6AlAl design option combination is compared with the M6CuCu, although, at several

efficiency points, M3CuAl appears to be a lower-cost option than M6CuCu.

 EE-RM/STD-00-550 COMMENT 55
5-55

Figure 5.5.10 Scatter Plot of Manufacturing Selling Price and Efficiency for DL10

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The M4 core steel combined with the copper-aluminum windings (M4CuAl) offers a

more cost-effective design option than the all-copper or all-aluminum windings available

with the M6 cores.

• As the efficiency increases, the laser-scribed (H-O DR) and M3 steel cores have similar

costs.

 EE-RM/STD-00-550 COMMENT 55
5-56

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

97.40% 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 ($)

M4CuAl

M6AlAl

M3CuCu

HOCuCu

M6CuCu

Figure 5.5.11 Scatter Plot of Manufacturing Selling Price and Efficiency for DL11

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. The efficiency levels shown in this plot represent

transformers at 50 percent of nameplate load. Several 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. 

• Many design option combinations are possible that comply with the NEMA TP 1-2002

efficiency level of 98.5 percent for this 300kVA, three-phase medium-voltage dry-type

unit at 95kV BIL.

 EE-RM/STD-00-550 COMMENT 55
5-57

10000

15000

20000

25000

30000

35000

40000

45000

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 (%)

Manufacturer Selling Price ($)

M4CuAl

M6AlAl

M3CuCu

HOCuCu

M6CuCu

Figure 5.5.12 Scatter Plot of Manufacturing Selling Price and Efficiency for DL12

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load. Several observations

can be made about this scatter plot:

• The M4 core steel combined with the copper-aluminum windings (M4CuAl) offers a

more cost-effective design option than the all-copper or all-aluminum windings available

with the M6 cores.

• Above 99.3 percent efficiency, the H-O DR steel design option combination has a slight

cost advantage over the M3 core. Both provide a maximum efficiency of about 99.5

percent with similar costs.

• In general, the transformers that use the M6 core steel are not the most cost-effective

option available. 

 EE-RM/STD-00-550 COMMENT 55
5-58

20000

25000

30000

35000

40000

45000

50000

55000

60000

98.50% 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 (%)

Manufacturer Selling Price ($)

M4CuAl

M6AlAl

M3CuCu

HOCuCu

M6CuCu

Figure 5.5.13 Scatter Plot of Manufacturing Selling Price and Efficiency for DL13

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. The efficiency levels

shown in this plot represent transformers at 50 percent of nameplate load and are corrected for

temperature. Several observations can be made about this scatter plot:

• The M3CuCu transformer offers the least-cost option over an extended range of

efficiencies, from slightly less than 99.0 percent up to nearly 99.5 percent.

• The HOCuCu transformer does not appear to yield any cost reduction relative to the

M3CuCu transformer. At efficiency levels of 99.2 percent and above, the M3 steel core

and H-O DR steel cores have similar costs and efficiency gains.

• The transformers that use the M6 steel are limited to an efficiency of about 99.25 percent

and are only cost-effective up to about 99.0 percent.

 EE-RM/STD-00-550 COMMENT 55
5-59

5.6 TWO EXAMPLE TRANSFORMER DESIGNS AND COST BREAKDOWNS

To provide some detail and establish credibility with its engineering analysis costefficiency database developed by the design software, the Department selected two designs from

its database of over 20,000 to present in this section. Transformer engineers can review the

design reports, and assess the quality of the designs. The two distribution transformers presented

are the cost-optimized designs for two units, one each from design line 3 and design line 12. 

Across all the design lines, the complete database of designs contains 22,387 distribution

transformer specification and winding sheets, bills of materials, and performance reports. This

database is the output from the engineering analysis that is used in the LCC analysis.

Design Line 3: 500 kVA single-phase, liquid-immersed, M6 core steel with an copper

primary and an aluminum secondary (M6CuAl) at a $3.00 A and a $1.00 B evaluation formula.

Design Line 12: 1500 kVA three-phase, medium-voltage dry-type, M3 core steel with

primary and secondary copper windings (M3CuCu) at a $3.00 A and a $1.00 B evaluation

formula. 

For both 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.

5.6.1 Results for DL3 Transformer, M6CuAl at $3 A and $1 B

A design specification report for a 500kVA single-phase liquid-immersed transformer

appears below. This design incorporates M6 core steel, with a copper primary and aluminum

secondary. The evaluation factors for this design are $3.00 A and $1.00 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

 2002- 3-22 9: 2:45

DG-CORE SHELL TYPE TRANSFORMER L3SM6CUAL

FREQUENCY 60.0 KVA RATING 499.85 @ 100.00% DUTY CYCLE

CORE DG-M6 M 6 THICKNESS .0140

 D: 9.680 E: 4.083 F: 4.315 G:21.577 EFF. AREA 76.285 WEIGHT1354.749

WINDING FORM: INS. DIM. 10.180 X 8.541 THICKNESS .122 LENGTH 21.265

 EE-RM/STD-00-550 COMMENT 55
5-60

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 2X 1(.0512X20.5148) AL 48.50 44.77 .375 119.358

P1 .1269X .2614 CU 3552.43 60.06 .750 442.697

NUMBER OF COILS 1 TOTAL BARE CONDUCTOR WEIGHT 562.055

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 13.0 13 1.0 1(.02000) 1(.15000) 1.571

P1 676.0 642.2 709.8 10 71.0 6(.00500) 1(.15000) 1.589

 TOTAL BUILD(%) 87.37

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 659.1( 14040.00) 692.9( 14760.00) 709.8( 15120.00)

WNDG INTERNAL DUCTS(100.00) %EFF EXTERNAL DUCTS(100.00) %EFF

----------------------------------------------------------------

S1 3 .188 X .188 IN. END

P1 3 .188 X .188 IN. END .188 X .188 IN. FULL

 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 34.977 .89491 1082.

S1 275.04 10.0 1805.000 .00031 860. .7

 F.L. N.L.

FLUX DENS. 16.175 16.240 LEAKAGE INDUCTANCE MHYS 56.817

CORE LOSS 987.255 999.001 POWER FACTOR 1.0000

COIL LOSS 2908.687 .011 IMPEDANCE % 5.23

EXCIT. VA 1328.606 1364.913 EFFICIENCY % 99.23

EXCIT. CURR. .092 .095 TANK OIL GAL 69.04

AMBIENT TEMP. 20.00 NOMINAL LENGTH 24.96

TEMP.RISE 65.00 NOMINAL DEPTH 21.06

OPERATING TEMP. 85.00 NOMINAL HEIGHT 29.74

 AVG. OIL RISE: 50.

 TOP OIL RISE: 76.6

TANK DIMENSIONS

-------------------

LENGTH = 25.963

DEPTH = 22.061

OIL HEIGHT = 41.743

 2

 EE-RM/STD-00-550 COMMENT 55
5-61

COND. I R LOSS = 2662.5920

COND. EDDY CURRENT LOSS = 166.2170

OTHER STRAY LOSS = 79.8778

K VALUE = 1.0000

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .13 99.08 .123 1.303 1.309 168.913 39.1

 35 .19 99.24 .174 1.821 1.829 335.370 44.1

 50 .29 99.32 .258 2.599 2.612 705.026 54.7

 65 .41 99.32 .346 3.379 3.396 1226.960 65.0

 75 .48 99.30 .399 3.899 3.920 1633.676 65.0

 100 .67 99.23 .533 5.203 5.230 2908.687 65.0

 125 .89 99.12 .666 6.510 6.544 4553.014 65.0

 150 1.12 99.00 .801 7.821 7.862 6569.333 65.0

Following is the breakdown of costs, or the 'bill of materials,' associated with this design,

M3 core steel, with an aluminum primary and copper secondary.

 EE-RM/STD-00-550 COMMENT 55
5-62

Bill of Materials and Labor for 1 phase, 500kVA liquid-type round-tank

A$ Input $3.00

B$ Input $1.00

Material item Type Quantity $ each $ total

Core Steel* (lb) M6 1355 0.64 $ $ 867.04

Primary winding* (lb) Copper 443 1.30 $ $ 575.51

Secondary windings* (lb) Aluminum 119 1.30 $ $ 155.17

Winding form & insulation* (lb) Kraft Paper 25 1.54 $ $ 39.18

Oil (gal) - 70 1.50 $ $ 104.94

Tank round 1 506.35 $ $ 506.35

Core Clamp - 1 30.00 $ $ 30.00

Tap Changer - 1 15.00 $ $ 15.00

Bushings HV & LV 1 60.00 $ $ 60.00

Misc. Hardware - 1 20.65 $ $ 20.65

Handling and Scrap Factor 2.5% $ 40.92

Total Material Cost $ 2,414.76

Labor item hours rate $ total

Setup & wind primary 1.42 42.77 60.72 $ 

Setup & wind secondary 0.90 42.77 38.29 $ 

Banding core metal 0.50 43.77 21.89 $ 

Assembly (coils, yoke & clamping) 0.75 42.77 32.08 $ 

Lead dressing 0.35 42.77 14.97 $ 

Inspection 0.10 42.77 4.28 $ 

Preliminary and Final Test 0.25 42.77 10.69 $ 

Shipment Packing and Marking 0.55 42.77 23.52 $ 

Miscellaneous (incl. VPI) 0.30 42.77 12.83 $ 

Total Labor 5.115 42.77 218.76 $ 

Manufacturing Cost (Material + Labor) $ 2,633.52

Factory Overhead (Materials only) 12.5% $ 301.84

Selling Factor 25.0% $ 733.84

Manufacturer Selling Price $ 3,669.21

* indicates those items to which the handling and scrap factor (2.5%) is applied

Table 5.6.1 Bill of Materials for Example Design from DL3 Database

 EE-RM/STD-00-550 COMMENT 55
5-63

Figure 5.6.1 Cost Breakdown for DL3

M6CuAl Design at $3A, $1B

Figure 5.6.1 provides a summary of the costs contributing to the total selling price of the

DL3 representative unit. For this design, approximately 66 percent of the final manufacturer

selling price of an M3, aluminum primary and copper secondary, is direct material and scrap. 

Labor accounts for 6 percent of the price, and overheads account for 28 percent.

 EE-RM/STD-00-550 COMMENT 55
5-64

5.6.2 Results for DL12 Transformer, M3CuCu at $3A and $1B

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, mediumvoltage, dry-type unit at 95kV BIL. The design shown here (out of the 1,344 designs in the

database) is for M3 core steel with a copper primary and secondary, and a $3.00A and $1.00B.

 OPTIMIZED PROGRAM SERVICE

 CLEVELAND OHIO 101800

 2002- 8- 9 11:35: 2

STRIP CRUC 3-PHASE TYPE TRANSFORMER L12M3CUCU 

FREQUENCY 60.0 MVA RATING 1.50 @ 100.00% DUTY CYCLE

CORE 10.063" CRUC STACK 10.063 GRADE M 3 THICKNESS .0090

WINDOW: 15.241 X 47.372 EFF. AREA 76.894 WEIGHT 5591.294 

WINDING FORM:INS. DIM. 10.598 X 10.598 THICKNESS .156 LENGTH 45.372

 COIL SPECIFICATIONS

 -------------------

WNDG WIRE LENGTH MEAN TURNS MARGIN WT

----------------------------------------------------------------------

S1 3X 1(.0124X37.3721) CU 51.62 44.24 4.000 276.774

P1 .1190X .3225 CU 3850.89 69.86 5.750 557.192

NUMBER OF COILS 3 TOTAL BARE CONDUCTOR WEIGHT 2501.897

WNDG TURNS LO TAP HI TAP LAYRS T/L LAYR INS SEC. INS BUILD

----------------------------------------------------------------------

S1 14.0 14 1.0 1(.00700) 1(.20000) 3.112

P1 630.0 598.5 661.5 14 1.0 1(.00001) 1(.00001) 1.890

 TOTAL BUILD(%) 90.23

WNDG TAPS: TURNS( VOLTS)

----------------------------------------------------------

P1 614.3( 12158.25) 645.8( 12781.75) 661.5( 13093.50)

 DISK INFORMATION

 -----------------

WNDG DISK WIDTH VOLTS/DISK BREAK TAPS SPACE

-------------------------------------------------------

P1 48 .338 272.781 .375 2(.38) 44( .375)

WNDG INTERNAL DUCTS( 95.00) %EFF EXTERNAL DUCTS( 95.00) %EFF

----------------------------------------------------------------

S1 4 .625 X .625 IN. FULL

P1 2 .625 X .625 IN. FULL

 EE-RM/STD-00-550 COMMENT 55
5-65

WNDG INT. DUCT AREA EXT. DUCT AREA TOTAL DUCT AREA

---------------------------------------------------------

S1 9931.7920 1671.3810 11603.1700

P1 .0000 2278.9760 5815.4850

 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 40.431 .83551 1077.

S1 274.72 W 4.0 1804.300 .00030 1297. .9

 F.L. N.L.

FLUX DENS. 14.882 14.971 LEAKAGE INDUCTANCE MHYS 58.391

CORE LOSS 2794.702 2841.611 POWER FACTOR 1.0000

COIL LOSS 10076.760 .039 IMPEDANCE % 7.16

EXCIT. VA 3808.522 3899.871 EFFICIENCY % 99.15

EXCIT. CURR. .102 .104 OPEN ALT. DUCT 3 .00

AMBIENT TEMP. 20.00 NOMINAL LENGTH 75.91

TEMP.RISE 76.58 NOMINAL DEPTH 24.32

OPERATING TEMP. 96.58 NOMINAL HEIGHT 67.50

 WINDING: S1 P1 

 TEMP RISE: 77. 63.

 2

 COND. I R LOSS = 8916.1750

 COND. EDDY CURRENT LOSS = 803.9380

 OTHER STRAY LOSS = 356.6469

 K VALUE = 1.0000

 WIRE WRAP PER COIL

WNDG THICKNESS WEIGHT

-------------------------

P1 .00800 9.64374

%LOAD %REG %EFF %IR %IX %IZ COIL LOSS TEMP. RISE

------------------------------------------------------------------------

 25 .15 99.10 .128 1.786 1.790 554.804 30.5

 35 .21 99.26 .181 2.496 2.502 1096.539 33.9

 50 .33 99.32 .264 3.563 3.573 2281.396 40.9

 65 .47 99.31 .354 4.632 4.646 3953.208 49.7

 75 .57 99.28 .418 5.346 5.363 5365.097 56.5

 100 .86 99.15 .594 7.137 7.162 10076.760 76.6

 125 1.21 98.97 .797 8.937 8.973 16764.860 100.6

 150 1.64 98.74 1.033 10.748 10.798 25853.470 128.2

 EE-RM/STD-00-550 COMMENT 55
5-66

Bill of Materials and Labor for 3 phase, 1500kVA dry-type, 95kV BIL

A$ Input $3.00

B$ Input $1.00

Material item Type Quantity $ each $ total

Winding Form* (lb) Nomex 29.71 17.50 $ $ 519.84

Core Steel* (lb) M3 5591 0.95 $ 5,311.73 $ 

Primary winding* (lb) Copper - Wire 1672 1.60 $ 2,674.52 $ 

Secondary winding* (lb) Copper - Strip 830 2.40 $ 1,992.77 $ 

Winding Insulation* (lb) Nomex 71 17.50 $ $ 1,245.05

Winding Comb* (lb) 91 10.00 $ $ 908.77

Duct Spacer* (ft) Dog-bone 1553 0.56 $ $ 869.73

Enclosure 14 gauge 1 600.00 $ $ 600.00

Mounting Frame - 1 125.00 $ $ 125.00

Buss-bar (ft) - 14 12.00 $ $ 168.00

Start & finish terminals HV & LV 15 8.00 $ $ 120.00

Varnish impregnation (gal) 27 18.00 $ $ 485.43

Misc. Hardware - 1 42.00 $ $ 42.00

Handling and Scrap Factor 2.5% $ 338.06

Total Material Cost $ 15,400.90

Labor item hours rate $ total

Setup & wind primary (3 phase) 4.96 42.77 212.19 $ 

Setup & wind secondary (3 phase) 2.85 42.77 122.05 $ 

Stacking core metal 8.05 42.77 344.32 $ 

Assembly (coils, yoke & clamping) 6.00 42.77 256.62 $ 

Lead dressing (3 phase) 1.00 42.77 42.77 $ 

Inspection 0.25 42.77 10.69 $ 

Preliminary and Final Test 1.25 42.77 53.46 $ 

Shipment Packing and Marking 2.20 42.77 94.09 $ 

Miscellaneous (incl. VPI) 2.00 42.77 85.54 $ 

Total Labor 28.565 42.77 1,221.74 $ 

Manufacturing Cost (Material + Labor) $ 16,622.64

Factory Overhead (Materials only) 12.5% $ 1,925.11

Selling Factor 25.0% $ 4,636.94

Manufacturer Selling Price $ 23,184.69

* indicates those items to which the handling and scrap factor (2.5%) is applied

Table 5.6.2 Bill of Materials for Example Design from DL12 Database

Table 5.6.2 provides a breakdown of costs, or the “bill of materials,” associated with this

design, 1500kVA three-phase medium-voltage (95kV BIL) dry-type with M3 core steel and

copper primary and secondary windings. The evaluation factors for this design are $3.00 A and

$1.00 B.

 EE-RM/STD-00-550 COMMENT 55
5-67

Figure 5.6.2 Cost Breakdown for DL12, M3CuCu

Design at $3A, $1B.

Figure 5.6.2 provides a summary of the costs contributing to the total selling price of the

transformer detailed above. Approximately 67 percent of the final selling price is material-based:

core, coil, insulation, and other materials. Labor accounts for approximately 5 percent of the

price, and overheads account for about 28 percent.

 EE-RM/STD-00-550 COMMENT 55