Typographical Errors in 10 CFR Part 431 Energy Conservation Program: Test

Procedures for Distribution Transformers

NEMA has determined that there are two typographical errors in the April 27, 2006 Final

Rule that have a profound impact on the distribution transformer efficiency and must

therefore be corrected in the implemented rule. These errors existed in the July 29, 2004

proposed rule and were inadvertently carried forward in the NEMA Standards Document

TP-2-2005, and the April 27, 2006 final rule. We regret any inconvenience in the lateness

of our identifying these error, however, they must be resolved. Perhaps an errata to the

Final Rule would be an approach

The error detected in the Federal Register (FR) originates in equation 5-1, FR page 25007

with the formula for Pos, the specified energy efficiency load level.

Please refer to pg 29 of TP2-2005, April 27, 2006 FR pg 25007, and July 29, 2004 FR

page 45532 equation 5-1:

Plc = P1c2 [Pos/Por] = P1c2L2

And the explanation that follows:

POS is the specified energy efficiency load level, where Pos = PorL2

Although, mathematically correct, the concept is not. The superscript "2" should be

added the bracket quantity [Pos/Por] and removed from the explanatory note on Pos

So that it reads Pos = PO1L

Pos is the 'specified energy efficiency load level', which means it is the rated transformer

output power times the load level, not times the load level squared. This is properly

shown in TP 1-2002 page 3, Pos is shown to be = P x kVA x 1000 where P = per unit load.

So, equation 5-1 is to be corrected to:

Plc = Plc2 [Pos/Por]2 = P1c2L 2

and Pos = PorL

It is our belief that this error was not detected sooner because many of the manufacturers

began calculating the efficiency based on the formula specified in TP- 1. For those who

did not, by using the Federal Register and the formula for Pos, the resulting efficiency will

be much lower than what it truly is (see TP2 p30 equation 5-3).

If you have further questions, please let us know.

EE-TP-98-550 COMMENT 66

#6 

Typographical Errors in 10 CFR Part 431 Energy Conservation Program: Test 

Procedures for Distribution Transformers 

NEMA has determined that there are two typographical errors in the April 27, 2006 Final 

Rule that have a profound impact on the distribution transformer efficiency and must 

therefore be corrected in the implemented rule. These errors existed in the July 29,2004 

proposed rule and were inadvertently carried forward in the NEMA Standards Document 

TP-2-2005, and the April 27, 2006 final rule. We regret any inconvenience in the lateness 

of our identifying these error, however, they must be resolved. Perhaps an errata to the 

Final Rule would be an approach 

The error detected in the Federal Register (FR) originates in equation 5-1, FR page 25007 

with the formula for P os, the specified energy efficiency load level. 

Please refer to pg 29 ofTP2-2005, April 27, 2006 FR pg 25007, and July 29, 2004 FR 

page 45532 equation 5-1: 

And the explanation that follows: 

P os is the specified energy efficiency load level, where P os = P orL 2 

Although, mathematically correct, the concept is not. The superscript "2" should be 

added the bracket quantity [P osiP or] and removed from the explanatory note on P os 

So that it reads P os = P orL 

P os is the 'specified energy efficiency load level', which means it is the rated transformer 

output power times the load level, not times the load level squared. This is properly 

shown in TP 1-2002 page 3, P os is shown to be = P x kV A x 1000 where P = per unit load. 

So, equation 5-1 is to be corrected to: 

and Pos = PorL 

It is our belief that this error was not detected sooner because many of the manufacturers 

began calculating the efficiency based on the formula specified in TP-l. For those who 

did not, by using the Federal Register and the formula for P os, the resulting efficiency will 

be much lower than what it truly is (see TP2 p30 equation 5-3). 

If you have further questions, please let us know.