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; 

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

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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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