1 | Building Technologies Program eere.energy.gov 

# NOPR Rulemaking Stage

Framework Document Preliminary Analysis NOPR Final Rule Date

Screening Analysis Engineering Analysis

Energy Use and End

- Use Load Characterization
Shipments Analysis National Impact Analysis Markups for Equipment Price Determination

Life

- Cycle Cost and Payback Period Analysis Market & Technology Assessment

Manufacturer Impact Analysis Compliance Date2 | Building Technologies Program eere.energy.gov 

# Goals of the Engineering Analysis

Downstream Analyses

• Life

- Cycle Cost and Payback Period Analysis

• National Impact Analysis Manufacturer Selling Price

– Efficiency RelationshipManufacturerSelling Price

Efficiency Level 

## • To evaluate design options that improve efficiency.

• To characterize manufacturer selling price (MSP) versus efficiency for higher

- efficiency distribution transformers.3 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Methodology

 Subdivide 10 equipment class groupings into 14 design lines based on similar principles of design. Identify rep units.

 Identify design option combinations to characterize the spectrum of possible efficiencies.

 Identify materials prices, markups, labor requirements, and other cost components for each design option combination.

 Use Optimized Program Service (OPS) software to model optimized designs based on several hundred A and B values

.

 Develop efficiency levels (ELs) that span the range of efficiency from the baseline to the maximum technologically feasible.

 Scale results to other equipment classes not analyzed. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Model Optimized

Designs Based on A’s and B’s

Develop ELs

Scale to Equipment Classes Not

Analyzed4 | Building Technologies Program eere.energy.gov 

# Engineering Design Lines and Representative Units

• Subdivide equipment classes into 14 engineering design lines based on similar principles of design and construction.

– Five liquid

- immersed,

– Three LVDT, and

– Six MVDT.



## • Span a range of kVA ratings for which the 0.75 scaling rule would provide accurate results.

• Select one representative unit from each engineering design line. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed5 | Building Technologies Program eere.energy.gov 

# Low Voltage, Dry Type Equipment Class to Design Line Mapping

Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed6 | Building Technologies Program eere.energy.govEquipmentClassDesign Line


### Type of Distribution Transformer kVA Range Representative Unit

3 6 Dry

- type, low

- voltage, single

- phase 15

– 333 25 kVA, 150 **°** C, single

- phase, 60Hz, 480V primary, 120/240V secondary, 10kV BIL

4 7 Dry

- type, low

- voltage, three

- phase 15

– 150 75 kVA, 150 **°** C, three

- phase, 60Hz, 480V primary, 208Y/120V secondary, 10kV BIL

8 Dry

- type, low

- voltage, three

- phase 225

– 1000 300 kVA, 150 **°** C, three

- phase, 60Hz, 480V Delta primary, 208Y/120V secondary, 10kV BIL 

# Low

- Voltage, Dry

- Type Design Lines and Representative Units7 | Building Technologies Program eere.energy.gov 

# Identify Transformer Design Option Combinations

• Select design option combinations.

– Vary core configurations, core steels, and winding materials.

– Capture most common designs and maximum efficiency. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s 

### Design Option Designs Considered

Core Configuration (Type) Wound core distributed gap; Stacked butt

- lap; Stacked full miter; Step

- lap miter; Stacked cruciform miter.

Core Configuration (Construction) **1**

**- Phase:**  Shell and Core type. **3**

**- Phase:**  3

- legged, 5

- legged and Symmetric Core.

Core Steels **Silicon steel:** M12, M6, M5, M4, M3, M2. **Domain refined silicon steel:** H

- 0 DR (dry

- type), ZDMH (liquid

- immersed). **Amorphous steel:** SA1 (Dry

- type and Liquid)

Winding materials Copper; Aluminum. Scale to Equipment Classes Not

Analyzed8 | Building Technologies Program eere.energy.gov 

# Identify Transformer Design Option Combinations (Continued)

Design Option Core Material Conductor Primary Conductor Secondary Core/Coil Design Type

1 M12 Al Al 3

- leg stacked butt

- lap
2 M12 Cu Al 3

- leg stacked butt

- lap
3 M6 Al Al 3

- leg stacked butt

- lap
4 M6 Al Al 3

- leg stacked full miter
5 M4 Cu Al 3

- leg stacked full miter
6 M3 Al Al 3

- leg stacked full miter
7 M3 Al Al 3

- leg step

- lap miter
8 M3 Al Al 3

- leg distributed gap core 9 H

- 0 DR Al Al 3

- leg stacked full miter
10 H

- 0 DR Al Al 3

- leg step

- lap miter
11 ZDMH Al Al 3

- leg distributed gap core
12 H

- 0 DR Cu Cu 3

- leg stacked full miter
13 SA1 Al Al 5

- leg distributed gap core
14 SA1 Cu Cu 5

- leg distributed gap core Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s 

## Example of Design Option Combinations Analyzed
DL7: 75 kVA low

- voltage dry

- type, three

- phase.

Scale to Equipment Classes Not

Analyzed9 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Markups and Labor Rate

• DOE determined materials prices and labor requirements through conversations with manufacturers and experts.

• DOE determined markups and labor rates from census data, SEC filings, and manufacturer interviews. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s 

### Markup / Cost Input Markup Notes

Scrap and handling 2.5 % Standard scrap and handling; applied to materials
1.5 % Prefabricated amorphous cores

4.0 % Additional scrap on fully mitered cores
Factory overhead 12.5 % Applied to materials

Shipping $ 0.28 / pound Added prior to profit markup; Approximately 4

– 8% of MSP Fully

- burdened hourly labor rate $ 51.52 Applied to total labor hours

Non

- production 25 % Applied to total cost for SG&A, R&D, warranty/risk provisions, and profit factor Scale to Equipment Classes Not

Analyzed10 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Modeling Optimized Designs

• Optimized Program Service (OPS) software conducts design runs.

• As an input to the OPS software, economic parameters (A and B values) are varied to simulate a range of customer orders, creating a database of transformer designs.

• Approximately 2,500 unique designs for each of the fourteen representative units within each of the fourteen design lines. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed11 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Modeling Optimized Designs

• OPS design software output includes:

– Construction and winding instructions for the core and coil (e.g., core dimensions, high

- and low

- voltage windings, tap locations, insulation, cooling ducts, and labor).

– Bill of materials and electrical analysis report.



## • Material, labor costs and markups are combined to determine the manufacturer’s selling price (MSP).

• Temperature

- corrected efficiency determined from OPS software electrical analysis report. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed12 | Building Technologies Program eere.energy.gov 

## • DOE was unable to identify a company that could model symmetric core designs.

• DOE gathered information on symmetric cores through manufacturer interviews, published literature, and limited designs provided by manufacturers.

– Using these data sources, DOE roughly estimated the cost

efficiency relationship of symmetric core designs.



## • DOE did receive limited design data from manufacturers of symmetric core transformers, and may issue some analysis to the extent that it is able. 

# Engineering Analysis: Symmetric Core Designs

Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed13 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Develop efficiency Levels

• DOE identified efficiency levels (ELs) that span the range of distribution transformer efficiencies from the baseline to the maximum technologically feasible efficiency.

• Factors DOE considered in setting ELs: Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s



## Benchmark efficiency levels (e.g., NEMA Premium) Equally spaced efficiency increments Harmonization across single

- phase and the per

- phase kVA equivalent three

- phase design lines.

Scale to Equipment Classes Not

Analyzed14 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Modeled Designs from DL1

Rep Unit from DL1: 50 kVA liquid

- immersed, single

- phase, pad

- mounted

$1,500 $2,000 $2,500 $3,000 $3,500 $4,000

99.00% 99.10% 99.20% 99.30% 99.40% 99.50% 99.60%Manufacturer Selling Price ($)

Efficiency at 50% Load, Temperature Corrected M5_CuAl_dgw_sh
M3_AlAl_dgw_sh M3_CuAl_dgw_sh
M2_AlAl_dgw_sh M2_CuAl_dgw_sh
ZDMH_AlAl_dgw_sh ZDMH_CuCu_dgw_sh SA1_AlAl_dgw_sh SA1_CuCu_dgw_sh

CSLs CSL 0 CSL 1 CSL 2 CSL 3 CSL 4 CSL 5 CSL 615 | Building Technologies Program eere.energy.gov 

# Developing Trial Standard Levels for the NOPR

• If DOE issues a NOPR, it will select trial standard levels (TSLs) based on groupings of ELs, such as:

– Per

- phase harmonization, minimum LCC, and maximum NPV.



## • These TSLs may consider any interaction between equipment classes.

• DOE will select its proposed standard level in the NOPR from the list of TSLs developed. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed16 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Scaling Results

• DOE scaled the total losses (TL) from a representative unit to other unanalyzed kVA ratings (S) within a design line using the 0.75 Scaling Rule:

TL 1 

## = TL 0 

## x (S 1 

## / S 0 

## ) 0.75



## • Costs of construction and losses can be scaled when design parameters are held constant, including:

– frequency, magnetic flux density, current density and insulation level. Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s 

### Design Line 7 (LVDT, 3

- phase, 15

– 150 kVA): 75 kVA Representative Unit

15 kVA 30 kVA 45 kVA 75 kVA 112.5 kVA 150 kVA Scale Results

Scale to Equipment Classes Not

Analyzed17 | Building Technologies Program eere.energy.gov18 | Building Technologies Program eere.energy.gov 

# Backup Slides Backup Slides19 | Building Technologies Program eere.energy.gov 

# Liquid

- Immersed Equipment Class to Design Line Mapping

Rectangular Round Tank Tank 10 15 25 37.5

50 75 100 167 250 333 500 667 833 Equipment Class 1 Liquid-Immersed, Single-Phase

kVADL 1DL 2DL 3 Rep Unit Rep Unit

Rep Unit 

### Design Lines 15 30 45 75 112.5

150 225 300 500 750 1000 1500 2000 2500

Equipment Class 2 Liquid-Immersed, Three-Phase

kVADL 4DL 5 Rep Unit Rep Unit Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs

Scale to Equipment Classes Not

Analyzed Model Optimized

Designs Based on A’s and B’s20 | Building Technologies Program eere.energy.gov 

# Low

- Voltage Dry

- Type Equipment Class to Design Line Mapping

kVA Design Line

15
25
37.5

50
75
100
167
250
333 Equipment Class 3 Dry-Type, Low Voltage, Single-PhaseDL 6 

## Rep Unit kVA Design Line
15
30
45
75
112.5

150
225
300
500
750
1000 Equipment Class 4 Dry-Type, Low Voltage, Three-PhaseDL 7 

### Rep UnitDL 8 

### Rep Unit Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs

Scale to Equipment Classes Not

Analyzed Model Optimized

Designs Based on A’s and B’s21 | Building Technologies Program eere.energy.gov 

# Medium

- Voltage Dry

- Type Equipment Class to Design Line Mapping

Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs

Scale to Equipment Classes Not

Analyzed Model Optimized

Designs Based on A’s and B’s 

### EC 6 EC 8 EC 10
20-45kV 46-95kV >96kV
15

- 30

- 45

- 75

- 112.5

-

150

- 225
300
500
750
1000
1500
2000
2500 Dry-Type, Medium Voltage, Three-PhaseDL 9DL 11DL 13 (A & B)DL 10DL 12 

### Rep Unit

Rep Unit Rep Unit

Rep Unit Rep Unit Rep Unit22 | Building Technologies Program eere.energy.govEquipmentClassDesignLine 

### Type of Distribution Transformer kVA Range Representative Unit

1 1 Liquid

- immersed, single

- phase, rectangular tank 10

– 167 50 kVA , 65 ° C, single

- phase, 60Hz, 14400V primary, 240/120V secondary, rectangular tank

2 Liquid

- immersed, single

- phase, round tank 10

– 167 25 kVA , 65 ° C, single

- phase, 60Hz, 14400V primary, 120/240V secondary, round tank

3 Liquid

- immersed, single

- phase 250

– 833 500 kVA , 65 ° C, single

- phase, 60Hz, 14400V primary, 277V secondary 

# Liquid

- Immersed Design Lines and Representative Units23 | Building Technologies Program eere.energy.gov 

# Liquid

- Immersed Design Lines and Representative UnitsEquipmentClassDesignLine 

### Type of Distribution Transformer kVA Range Representative Unit

2 4 Liquid

- immersed, three

- phase 15

– 500 150 kVA , 65 ° C, three

- phase, 60Hz, 12470Y/7200V primary, 208Y/120V secondary

5 Liquid

- immersed, three

- phase 750

– 2500 1500 kVA , 65 ° C, three

- phase, 60Hz, 24940GrdY/14400V primary, 480Y/277V secondary24 | Building Technologies Program eere.energy.gov 

# Low

- Voltage Dry

- Type Design Lines and Representative UnitsEquipmentClassDesignLine 

### Type of Distribution Transformer kVA Range Representative Unit

3 6 Dry

- type, low

- voltage, single

- phase 15

– 333 25 kVA , 150 ° C, single

- phase, 60Hz, 480V primary, 120/240V secondary, 10kV BIL

4 7 Dry

- type, low

- voltage, three

- phase 15

– 150 75 kVA , 150 ° C, three

- phase, 60Hz, 480V primary, 208Y/120V secondary, 10kV BIL

8 Dry

- type, low

- voltage, three

- phase 225

– 1000 300 kVA , 150 ° C, three

- phase, 60Hz, 480V Delta primary, 208Y/120V secondary, 10kV BIL25 | Building Technologies Program eere.energy.gov 

# Medium

- Voltage Dry

- Type Design Lines and Representative UnitsEquipmentClassDesignLine 

### Type of Distribution Transformer kVA Range Representative Unit

6 9 Dry

- type, medium

voltage, three

- phase, 20

- 45kV BIL 15

– 500 300 kVA , 150 ° C, three

- phase, 60Hz, 4160V Delta primary, 480Y/277V secondary, 45kV BIL

10 Dry

- type, medium

voltage, three

- phase, 20

- 45kV BIL 750

– 2500 1500 kVA , 150 ° C, three

- phase, 60Hz, 4160V primary, 480Y/277V secondary, 45kV BIL

8 11 Dry

- type, medium

voltage, three

- phase, 46

- 95kV BIL 15

– 500 300 kVA , 150 ° C, three

- phase, 60Hz, 12470V primary, 480Y/277V secondary, 95kV BIL

12 Dry

- type, medium

voltage, three

- phase, 46

- 95kV BIL 750

– 2500 1500 kVA , 150 ° C, three

- phase, 60Hz, 12470V primary, 480Y/277V secondary, 95kV BIL

10 13 (A & B) Dry

- type, medium

voltage, three

- phase, 96

- 150kV BIL 225

– 2500 300 kVA , 150 ° C, three

- phase, 60Hz, 24940V primary, 480Y/277V secondary, 125kV BIL
2000 kVA , 150 ° C, three

- phase, 60Hz, 24940V primary, 480Y/277V secondary, 125kV BIL26 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Materials Prices for Core Steels

Material Units 2010 Price **[2010$]** 2006 Price **[2010$]** 2008 Price **[2010$]**
M12 core steel $/lb 1.03 0.85 1.60

M6 core steel $/lb 1.46 0.94 2.19

M5 core steel $/lb 1.51 0.99 2.24

M4 core steel $/lb 1.59 1.03 2.30

M3 core steel $/lb 1.88 1.06 2.60 M3 core steel ( Lite Carlite ) $/lb 1.95 1.47 2.44

M2 core steel $/lb 2.00 1.32 2.79 M2 core steel ( Lite Carlite ) $/lb 2.10 1.58 2.63 ZDMH (mechanically

- scribed core steel) $/lb 2.05 1.41 3.22

H

- 0 DR core steel (laser scribed) $/lb 2.06 1.41 3.23 SA1 (amorphous) finished core, volume production $/lb 2.38 1.72 3.6427 | Building Technologies Program eere.energy.gov 

## Engineering Analysis: Materials Prices for Liquid

- Immersed Design Lines

Material Units 2010 Price **[2010$]** 2006 Price **[2010$]** 2008 Price **[2010$]** Copper wire, formvar , round #10

- 20 $/lb 4.87 3.33 5.97 Copper wire, enameled, round #7

- 10 $/lb 4.84 3.31 5.93 Copper wire, enameled, rectangular sizes $/lb 4.97 3.41 6.09 Aluminum wire, formvar, round #9

- 17 $/lb 3.07 2.30 3.91 Aluminum wire, formvar, round #7

- 10 $/lb 2.57 1.93 3.28 Copper strip, thickness range 0.02

- 0.045 $/lb 4.97 3.41 6.09 Copper strip, thickness range 0.030

- 0.060 $/lb 4.97 3.41 6.09 Aluminum strip, thickness range 0.02

- 0.045 $/lb 2.08 1.56 2.67 Aluminum strip, thickness range 0.045

- 0.080 $/lb 2.08 1.56 2.67 Kraft insulating paper with diamond adhesive $/lb 1.52 1.17 1.93
Mineral oil $/gal 3.35 1.94 3.84 Tank Steel $/lb 0.38 0.32 0.60 

## Conductor and Miscellaneous Prices28 | Building Technologies Program eere.energy.gov 

# Engineering Analysis: Materials Prices for Dry

- Type Design Lines

Material Units 2010 Price **[2010$]** 2006 Price **[2010$]** 2008 Price **[2010$]** Copper wire, rectangular 0.1 x 0.2, Nomex wrapped $/lb 4.52 3.07 5.53 Aluminum wire, rectangular 0.1 x 0.2, Nomex wrapped $/lb 2.97 2.23 3.78 Copper strip, thickness range 0.02

- 0.045 $/lb 4.97 3.41 6.09 Aluminum strip, thickness range 0.02

- 0.045 $/lb 2.08 1.56 2.67
Nomex insulation $/lb 24.50 13.72 29.03 Cequin insulation $/lb 5.53 3.84 6.09 Impregnation $/gal 22.55 17.16 27.31 Winding combs $/lb 12.34 6.08 15.41 Enclosure Steel $/lb 0.38 0.32 0.60 

## Conductor and Miscellaneous Prices29 | Building Technologies Program eere.energy.gov 

# Developing Trial Standard Levels for the NOPR

Choose Rep. Design Lines and Units

Select Higher Efficiency Design Options

Develop Cost Inputs

Develop ELs Model Optimized

Designs Based on A’s and B’s

Scale to Equipment Classes Not

Analyzed 

## • Illustration of how TSLs are selected based on groupings of ELs:

– Combine liquid

- immersed design lines using maximum EL available that does not use amorphous metal.

Design Line EL

1 2

2 2

3 3

4 2

5 2 TSL 130 | Building Technologies Program eere.energy.gov 

# NOPR Rulemaking Stage

Framework Document Preliminary Analysis NOPR Final Rule Date

Screening Analysis Engineering Analysis

Energy Use and End

- Use Load Characterization
Shipments Analysis National Impact Analysis Markups for Equipment Price Determination

Life

- Cycle Cost and Payback Period Analysis Market & Technology Assessment

Preliminary Manufacturer Impact Analysis Compliance Date31 | Building Technologies Program eere.energy.gov 

# Purpose

• Market and Technology Assessment

– Characterize the distribution transformer market and industry.

– Identify the technology options to improve distribution transformer efficiency.

– Establish equipment classes.



## • Screening Analysis

– Screen out technology options that DOE will not consider in the engineering analysis for distribution transformers based on several criteria.32 | Building Technologies Program eere.energy.gov 

## Relationship of Market and Technology Assessment to Other Analyses

Market and Technology Assessment **Equipment Classes** 

**Technology options**  **to improve efficiency**

Screening Analysis

**Design options**  **to improve efficiency**

Engineering Analysis33 | Building Technologies Program eere.energy.gov 

# Equipment Classes

• DOE divides covered equipment into classes by:

– The Type of energy used,

– The Capacity, or

– Any performance

- related features that affect consumer utility or efficiency.



## • DOE considered 10 equipment class groupings by dividing the population of distribution transformers based upon:

– Type of transformer insulation: liquid

- immersed or dry

- type
,

– Number of phases: single or three

,

– Voltage class: low or medium (for dry

- type units only) , and

– Basic impulse insulation level (BIL): (for MVDT units only)

.34 | Building Technologies Program eere.energy.gov 

# Distribution Transformers Equipment Class Groupings

There are 115 discrete kVA ratings across the ten equipment class groupings (ECG)

ECG Insulation Phases Voltage BIL kVA Range

1 Liquid

- Immersed Single Medium

--- 10

- 833 kVA

2 Liquid

- Immersed Three Medium

--- 15

- 2500 kVA

3 Dry

- Type Single Low

--- 15

- 333 kVA

4 Dry

- Type Three Low

--- 15

- 1000 kVA

5 Dry

- Type Single Medium 20

- 45 kV BIL 15

- 833 kVA

6 Dry

- Type Three Medium 20

- 45 kV BIL 15

- 2500 kVA

7 Dry

- Type Single Medium 46

- 95 kV BIL 15

- 833 kVA

8 Dry

- Type Three Medium 46

- 95 kV BIL 15

- 2500 kVA

9 Dry

- Type Single Medium > 96 kV BIL 75

- 833 kVA

10 Dry

- Type Three Medium > 96 kV BIL 225

- 2500 kVA35 | Building Technologies Program eere.energy.gov 

# Distribution Transformers 2009 Industry Shipments

Equipment Class Grouping Units Shipped MVA Capacity Shipped 1. Liquid

- immersed, medium

- voltage, single

- phase 683,726 21,994
2. Liquid

- immersed, medium

- voltage, three

- phase 49,739 32,266
3. Dry

- type, low

- voltage, single

- phase 17,740 647
4. Dry

- type, low

- voltage, three

- phase 206,929 15,778
5. Dry

- type, medium

- voltage, single

- phase, 20

- 45 kV BIL 709 23
6. Dry

- type, medium

- voltage, three

- phase, 20

- 45 kV BIL 522 257
7. Dry

- type, medium

- voltage, single

- phase, 46

- 95 kV BIL 546 23

8. Dry

- type, medium

- voltage, three

- phase, 46

- 95 kV BIL 2,074 3,655
9. Dry

- type, medium

- voltage, single

- phase, ≥ 96 kV BIL 202 9
10. Dry

- type, medium

- voltage, three

- phase, ≥ 96 kV BIL 1,286 2,206

TOTAL 963,473 76,85836 | Building Technologies Program eere.energy.gov 

# Technology Options

Technology Option Material / Concept

Conductor Materials for Coils Aluminum (wire and sheet)

Copper (wire and sheet)

Core Materials Cold

- Rolled High Silicon (CRHiSi) Steel

CRHiSi Domain

- Refined Steels

Amorphous Materials in Wound Core

Geometry Modifications Adjust the cross

- sectional area of the core/conductor, or adjust volts per turn
Symmetric Core Designs Continuously wound cores with 120 degree radial symmetry for three

- phase designs

Core Deactivation Technology A transformer is replaced by three smaller transformers that are (de)activated in response to changes in load demand.37 | Building Technologies Program eere.energy.gov 

## • “Symmetric Core” designs are three

- phase designs that use a continuously wound core with 120 ° radial symmetry.

• Advantages include lowered: weight, volume, no

- load losses, noise, vibration, stray magnetic fields, inrush current, and power in the third harmonic.

• Best suited for delta

- delta or delta

- wye connections, though zero

- sequence fluxes associated with wye

- wye connections can be mitigated by a delta

- connected tertiary winding. 

# Technology Assessment: Symmetric Core Designs

Source: Lundmark, Sonja. “Computer Model of Electromagnetic Phenomena in Hexaformer.” 2007. http://www.hexaformer.com/ExternaDokument/chalmers_re port1.pdf.38 | Building Technologies Program eere.energy.gov 

## • Reduces core losses by using a system of smaller transformers to replace a single, larger transformer.

– Example: Three 25 kVA transformers in parallel replace a 75 kVA transformer.



## • Control unit can activate and deactivate component transformers depending on the loading demands.

– Optimizes combination of transformers at given load.



## • DOE is only aware of this technology in LVDT distribution transformers.

– Medium

- voltage core deactivation systems have not been produced commercially, and pose difficulties for switching within the primary and secondary connections.



## • Best suited for applications with low loading demands. 

# Technology Assessment: Core Deactivation Technology39 | Building Technologies Program eere.energy.gov 

# Core Deactivation Technology Load vs. Efficiency

This figure is for illustrative purposes only, and is not based on actual DOE research 93 94 95 96 97 98 99

5 15 25 35 45 55 65 75 85 95Efficiency %

Percentage of Full Rated Load Core Deactivation System

Traditional Transformer Design

Test Procedure Loading40 | Building Technologies Program eere.energy.gov 

## • While core deactivation technology could save energy over a load cycle, these energy savings may not be captured by the current test procedure specifying a single load factor.

• A weighted

- average loss calculation using various loadings could better capture this technology’s energy savings potential.

Example: 

# Technology Assessment: Core Deactivation Technology

Loading (%) Losses (W) Single Loading Point, Load Frequency (%) Weighted Average, Load Frequency (%)
0 200.0 0 31
15 222.5 0 22
35 322.5 100 20
50 450.0 0 18
75 762.5 0 9
Average Losses 322.5 322.541 | Building Technologies Program eere.energy.gov 

## • DOE is not considering core deactivation technology in the context of setting standards, but may explore doing so in the future.

– Scale each design to 1/3 its kVA and group them in sets of three.

– Account for additional cost and weight of the core deactivation technology.

– Analyze each core deactivation system using various loading scenarios.



## • Core deactivation systems using non

- identical component transformers.

– Each component transformer requires a similar winding design to maintain impedance at each loading.



## • Based on conversations with manufacturers, core deactivation with MVDT has additional challenges. 

# Technology Assessment: Core Deactivation Technology42 | Building Technologies Program eere.energy.gov 

# Screening Analysis

Impacts on health or safety Adverse impacts on equipment utility or availability to

consumers Practicability to manufacture, install, and service Technological feasibility 

## Purpose

• Screen out technology options that DOE will not consider in the engineering analysis for distribution transformers.



## Approach

• DOE will evaluate each technology option based on the following criteria:43 | Building Technologies Program eere.energy.gov 

# Technology Options Screened Out of the Analysis

Technology Option Excluded Screening Criteria

Silver as a Conductor Material Practicability to manufacture, install, and service

High

- Temperature Superconductors Technological feasibility; Practicability to manufacture, install, and service

Amorphous Core Material in Stacked Core Configuration Technological feasibility; Practicability to manufacture, install, and service
Carbon Composite Materials for Heat Removal Technological feasibility High

- Temperature Insulating Material Technological feasibility

Solid

- State (Power Electronics) Technology Technological feasibility; Practicability to manufacture, install, and service. Nanotechnology Composites Technological feasibility44 | Building Technologies Program eere.energy.gov 

## • DOE may make available detailed design information for certain design lines and efficiency levels to allow manufacturers to compare with designs of their own.

• DOE may invite manufacturers to submit similar design information for their own designs. Such information, if submitted to a Department contractor, would be kept in confidence. 

# Engineering Validation