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Transformer Efficiency Requirements in the USA

Low Voltage Dry type transformers excluded from the NEMA TP-1 Energy Efficiency requirements are special purpose transformers, such as an Auto-transformer, Drive (Isolation) transformer, Grounding transformer, Machine-Tool (control) transformer, Non-ventilated Transformer, Rectifier transformer, Regulating transformer, Sealed transformer, Special-Impedance transformer, Testing Transformer, Transformers with tap ranges of 20% or more, Uninterruptible Power Supply transformer or welding transformer.

DOE (USA Department of Energy) officials advise that this act is now law and will be in effect for all transformers built in the USA or imported into the USA as of January 1, 2007.

The DOE officials also advise that efficiency standards for Medium Voltage Dry Type Distribution Transformers (Input voltage of 601 Volts to 34.5 kilovolts) are expected to come into effect around the year 2010.

REX Power Magnetics is fully prepared to produce these higher efficiency units with optimized designs, higher grade silicon steel and specialized core cutting equipment. In fact REX has produced High efficiency transformers for the past 3 years to meet various State level requirements in the USA and Canada . REX high efficiency units are approved to carry the ENERGY STAR® label and will carry the appropriate performance certification mark.

With the recent dramatic increases in the cost of copper and grain oriented silicon steel, manufacturers with optimized designs and specialized core cutting equipment will be the only ones able to offer quality and value at competitive prices.

Starting in September 2006 our responses to requests for quotations for units likely to be produced after January 1, 2007 will also be quoted as NEMA TP-1 compliant. The price of higher efficiency units are normally 10% to 15% higher than standard efficiency units.

For more information go to:

We ask that you notify our customers of this efficiency requirement that becomes effective on January 1, 2007 and ensure that they are aware of its implications and are prepared for it.

It appears that many transformer manufactures are not as yet prepared (with designs and equipment) to effectively meet this efficiency requirement. Please forward any feedback you receive from customers or other relevant information from the marketplace regarding this upcoming efficiency standard.

Please contact the REX Sales Team, Rory or myself for any questions or concerns. 


Levon Hasserjian 
Vice President, REX Power Magnetics