Towards an IE4 Efficiency Class for Induction Motors with Minimal Manufacturer Impact

In recent times, standard efficiency induction motors have been modified achieving IE3 efficiency requirements simply by adopting simple and low-cost changes in their design and production processes. However, looking at several experiences reported in literature, it seems evident that these approaches are at their present limits and cannot guarantee appreciable margins above the minimum IE3 values. As a consequence, radical re-designs of the machines' electromagnetic structures are usually suggested to achieve the IE4. This is particularly challenging and impacting for small and medium manufacturers. For this reason, the paper investigates alternative solutions to push IE3 induction motors towards the IE4 class, with minimal impact to manufacturers. In the paper, 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 options to increase efficiency.