Striving for the Highest Efficiency Class With Minimal Impact for Induction Motor Manufacturers

In the recent past, several successful experiences to modify standard efficiency induction motors in premium efficiency class (IE3) machines have been presented, considering simple and low-cost changes in the design and production processes. However, this approach-also known as no-tooling-cost process-seems to have reached its limit without offering appreciable margins above the IE3 efficiency levels. In order to avoid the electromagnetic redesign of entire machine series for an IE4 efficiency class, the authors investigated how to obtain further efficiency gains in the same volumes of IE3 induction motors. The study looked at unconventional modifications in the production process/design procedure that can still be considered to have minimal impact on manufacturers. In particular, stator winding layouts targeted at very low spatial harmonic content, rotor bar skew removal, and rotor slot insulation prior to aluminum cage die casting are investigated as potential low-cost solutions.