An efficiency rule was issued by the US Department of Energy on March 9, 2010, covering 1/3- through 3-HP Open Drip-Proof general-purpose single and three-phase motors with two-digit NEMA frames (and equivalent IEC frames). Minimum average efficiency levels were issued for single-phase capacitor start, induction run and capacitor start, capacitor run designs, and three-phase induction two-, four-, and six-pole AC motors.
NEMA has written a guide to the Small Motor Rule. The organization received comments from the DOE stating that it doesn't agree with NEMA’s interpretation of the rule. We are awaiting clarification on these comments.
The Small Motor Rule will set fairly high efficiency levels for motors that are currently unregulated in the US. The physical size of redesigned compliant open motors may change, particularly on single-phase designs where much larger capacitor housings may be used on higher output ratings. OEMs may require redesign of their equipment to accommodate these new designs and they should check with their motor supplier soon. Manufacturers importing machinery that includes small motors embedded must also comply with the new rule.
Another new DOE Rule is expected in May of this year covering 1-HP to 500-HP three-phase motors. This comprehensive rule will be discussed in future blogs.
John Malinowski is the general product manager for general-purpose and severe duty AC motors at Baldor Electric Company.