From: Phil Hopkinson [mailto:phopkinson@hvolt.com] 

Sent: Sunday, October 16, 2011 12:42 PM 

To: Robert Berman; Hirsch, Bruce R 

Cc: 'Richard Parker'; Alex Hofmann; Andrew Delaski; Aris Marantan; Art Rosenfeld; Bob Saint; Brian 

Coffey; Bruce Smith; Caitlin Johnson; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; 

Chris Bolduc; Clark Silcox; Creevy, Jim; Dan Cohen; Daniel Young; Eric Peterson; Freeman, Jeremiah; 

Gary Fernstrom; Greg Coulter; Greg Rosenquist; James Lass; Jennifer Tiedeman; Jerry Corkran; Jerry 

Hodge; Jerry Schoen; Joanna Mauer; John Cymbalsky; John Rossetti; Katie Coughlin; Ken Winder; 

Mahesh P. Sampat; Matt Miller; Matthew Nardotti; Meg Waltner; Meyers, Aaron; Michael Hyland; Michael 

Rivest; Millure, Dave; Phil Harter; Polinski, Raymond; Puesh Kumar; Rick Anderson; Rob Greeson; Robert 

van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Tim 

Ballo; Tom Eckman; Wes Patterson; Zhimei Luo 

Subject: RE: Amorphous Core Experience at BGE 

Good afternoon all:

A few constructive comments:

1. The last time I collected statistics, winding failures for Distribution Transformers in the early

years were normally <0.25%/yr.   

2. After 20 years in service the winding failures would accelerate for transformers having stringent

duty.

3. I used to worry when winding failures exceeded 0.5%/yr.

On the personal side, please note that HVOLT Inc. is a power transformer consulting company and not a

manufacturer.  HVOLT does do design and design reviews and conducts frequent forensic investigations

of transformer failures of many types of constructions and sizes from small transformers to large power

transformers of high or even extra high voltage classes.  I have been involved with amorphous core

development and design application starting in the 1970’s and find the material fascinating and

definitely useful for many transformer applications.  I also have been involved with many types of silicon

iron cores and find many of those materials to be of high value.  I suspect that there may be a

misinterpretation of my concerns.  Here is something that I worry about:

1. kVA rating for a transformer is defined as the maximum power that can be drawn from the

transformer without exceeding a specified temperature rise.

2. kVA rating also is associated with a impedance which is normally constrained to address

acceptable voltage drop at full rated kVA as well as at normal load and to limit through fault

currents.

3. The kVA rating of a transformer that is specified for an application is normally selected to

provide the following missions:

a. Required output power for normal and peak load conditions.

b. Acceptable voltage regulation.

c. High reliability.

d. Long term robustness.

e. Economy.

f. Efficiency.

4. Most distribution transformers see widely varying load cycles that may dip to a few percent of

rated kVA at night and rise to 60‐80% of nameplate load several times during the day.  Cold load

pickup following storms often reaches to well beyond nameplate rating.
5. The most appropriate transformer for general use has a good balance between low core loss

and low winding loss.

6. If a transformer is only optimized for peak efficiency at a small load like 18% of nameplate then

the inherent ratio of load loss at full load to no load loss will become (1/0.18)^2 or 42:1.  

Presently we optimize peak efficiency to the 50% of nameplate load where the transformers are

tested and get a loss ratio of 4 parts of load loss to 1 part of no load loss or a loss ratio of 4:1.

7. Transformers on the system with a 4:1 loss ratio have been proven to be robust for well over 50

years of history.  We need to be sure that we do not compromise this robustness.

8. For most load cycles, light load occurs at night on all parts of the US power grid.  Generation

costs at night are very inexpensive.  With the light loading comes low winding loss.  This tells me

that the no load loss value of a watt saved is very low.

9. During the day the load peaks on all parts of the US System and energy cost is high.  This tells

me that low load loss is most important to minimizing the need for expensive peaking power.

10. The US Electric Utilities have maintained TOC evaluations mostly in a 3:1‐4:1 ratio for decades.  

Only a few TOC ratios reach 5:1.  This relationship allows many types of core materials to be

investigated and or selected but it never drops the importance of robust windings.

11. In this last week’s meetings I asked if impedance and regulation were to be considered and

heard that they were not to be considered.  However they need to be.

12. My advice to the team is to maintain the tested efficiency to 50% load.  In general we should

assume that manufacturers will produce transformers that are cost optimized to the tested

efficiency.  However if this is the case then an amorphous core transformer will always have

lower core loss than a silicon steel transformer and higher winding loss.  The result of this is that

the amorphous core transformer will save energy at night when the energy cost is low and

dissipate more energy during the day when the energy cost is very high.  This does not seem to

be a convincing argument for making the minimum National Standard an amorphous based

document.  

13. I have personal good and bad experience with amorphous material, am not antagonistic to it,

and continue to recommend it for many applications.

14. My analysis for the next US Efficiency Standard is that it be achievable with M3 core material.  

This does not prevent anyone from using amorphous or other core grades.  However, I do not

believe that amorphous is more optimum than M3 for a minimum National Standard.

I hope this helps,

Best regards,

Phil

Philip J Hopkinson, PE 

President & CEO HVOLT Inc. 

3704 High Ridge Rd. 

Charlotte, NC 28270 

phopkinson@hvolt.com

Ph 704-846-3290 

Fx 704-845-2520 

Cell 704-236-3320 

www.hvolt.com
From: Robert Berman [mailto:bermaneconomics@gmail.com] 

Sent: Sunday, October 16, 2011 11:13 AM 

To: Hirsch, Bruce R 

Cc: 'Richard Parker'; Alex Hofmann; Andrew Delaski; Aris Marantan; Art Rosenfeld; Bob Saint; Brian 

Coffey; Bruce Smith; Caitlin Johnson; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; 

Chris Bolduc; Clark Silcox; Creevy, Jim; Dan Cohen; Daniel Young; Eric Peterson; Freeman, Jeremiah; 

Gary Fernstrom; Greg Coulter; Greg Rosenquist; James Lass; Jennifer Tiedeman; Jerry Corkran; Jerry 

Hodge; Jerry Schoen; Joanna Mauer; John Cymbalsky; John Rossetti; Katie Coughlin; Ken Winder; 

Mahesh P. Sampat; Matt Miller; Matthew Nardotti; Meg Waltner; Meyers, Aaron; Michael Hyland; Michael 

Rivest; Millure, Dave; Phil Harter; Phil Hopkinson; Polinski, Raymond; Puesh Kumar; Rick Anderson; Rob 

Greeson; Robert Berman; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve 

Nadel; Steve Rosenstock; Tim Ballo; Tom Eckman; Wes Patterson; Zhimei Luo 

Subject: Re: Amorphous Core Experience at BGE 

Importance: High 

Very strange results. You're talking about two closely related distributions. If the expected life 

for 93% is 30 years, and the average age of the 7% was 11 years, the only statistical inference 

that you could reasonably make is that the 7% appeared to have been drawn from a very different 

population -- a different distribution -- or, perhaps even multiple distributions and populations. 

Clearly the expected value and variance of the distributions are significantly different. Rather 

than an apples-to-apples comparison, the set of numbers provided is anything BUT apples-toapples. The more information you can get on the failed units, the better. Indeed, your experience 

with the amorphous units generally is significantly better than the 88%/78%/47% survival rates 

for DOE compliant transformers generally after 10/20/30 years respectively. As a start, if you 

don't have any information about the failures, I would look at a plot of the ages at failure for the 

7%. Based on the numbers you provide, I would expect to see a "clump" (technical statistical 

term) in the data, probably occurring in the late '80s or early '90s (to make your distributions 

balance out). The statistician in me suspects a single bad batch or other anomalous event. A 

either would both explain the numerical results you obtained as well as reconcile the apparently 

conflicting results and confirming that at lest a portion of the 7% came from a very different 

population. 

On the upside, it's worth noting that its probably a good thing that BG&E didn't get any of the 

HVOT transformers that Mr. Hopkinson reports he unsuccessfully tried to build. Your 

experience, generally, seems to be consistent with the high quality amorphous product lines 

marketed by the 4 manufacturers represented on this committee, and totaling more than 2.3 

million units internationally. Although I confess that I have difficulty seeing any relevance to 

this committee's task of how much the efficiency standard should be increased to Mr. 

Hopkinson's inability to build transformers or his obvious personal distaste for the highly 

efficient amorphous material successfully used for more than 30 years by most or all major 

manufacturers. 

Regards,

Robert A. Berman, Principal

Berman Economics

www.BermanEconomics.com
1915 Grand Court

Vienna, VA 22182

703‐281‐0490

703‐655‐8398 (cell)

BermanEconomics@gmail.com

On Oct 14, 2011, at 12:16 PM, Hirsch, Bruce R wrote: 

This is just a single Company’s experience with amorphous core transformers. Please note that based on

this data we have NOT ruled out using amorphous steel in our transformers, however, the numbers are

troubling.

BGE owns 2,770 transformers with amorphous steel cores. Most are three phase units purchased in the

mid to late 80’s.

Of that number, 201 have failed in service. The cause of failure is not known but to be considered a

failure the probability is that either the core or coil failed. This represents an 7% failure rate.

The average age of the failed amorphous core transformers is 10.97 years.

The average age of failed transformers for BGE’s entire fleet is 29.4 years.

BGE has over 216,000 transformers in the fleet, thus the quantity of amorphous core transformers

represents 1.4% of the total.

While we could debate the cause of failure for any particular class or design of transformer, the average

age to failure date is a good apples to apples comparison of the performance of the transformers since

the exact same criteria was used across the board.  

Hope this information, along with other user responses is helpful in the decision making process.

                                                                                                                                                                Bruce

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