OT: For the motor gurus

I ran across this item in a spec for a "green screen" to be installed in the front lobby of a building, illustrating the green features currently being utilized by the building to reduce carbon footprint.

"Premium efficiency electric motors versus high efficiency EPACT Motors"

I hadn't previously heard of premium efficiency motors, and always thought Design E motors were the most efficient. Can anyone explain premium efficiency in simple terms, and where it rates in the energy efficiency hierarchy?

High efficiency EPACT motors are the law of the land and have been for over 10 years. Some manufacturers have chosen to build motors that exceed the EPACT rules. These are generally labelled "Premium Efficiency". I know of no standards other than "better than EPACT" that governs that terminology.

Dick,

Thanks for the response.

Ok, so EPACT is the law of the land and has been, is it correct to say that a Design B motor is EPACT compliant? Also, if I have a design E motor, is it correct to say that motor is of "Premium efficiency?" Is it possible to have a Design E motor that is EPACT compliant, and not a premium efficiency motor?

As you might guess, I've always been concerned about the "Design" rating on the motor for overcurrent protection purposes. Since EPACT was the law of the land, I've never had to make a decision to use a EPACT or non-EPACT motor.(I'm a young engineer, for a little while yet) Anytime I wanted to use high efficiency motors, Design E was the qualifier. I'm just trying to get a solid grasp on where Nema designs lie in relation to the EPACT and premium efficiency map.

Russ:
This link has a complete explanation:
http://www.automationnotebook.com/2009-Issue-14/cover-story-issue14-2009.html

The NEMA Design Letter can be A, B, C, D, or E and defines the torque-speed characteristic curve. Efficiency is completely independent of the Design Letter. With the exception of NEMA D, you could have high or premium efficiency in any of the Design types.

I would suggest getting a Pocket Electrical Engineering Handbook. It has the motor data in it with some explanation of the purposes and differences. The handbook is often a free handout item from distributors or motor shops.

Thanks guys

Thanks for clarifying. I actually have a handbook as you mentioned, and it sounds like I assumed too much. I had noticed that across the board, the Design E motors efficiencies listed were higher than that of the A,B, and C types. As such, I have for the past couple of years assumed that the E stood for "high efficiency", which I now understand is incorrect. I'll have to do some more reading to fully know how the speed/torque curves are different for the different types, but this conversation has definitely cleared up the picture for me. Thanks again.

I believe you will find that design E motors are LESS efficient at lower loads than design C or B... They are optimized to run fans (typically).