Efficiency Improvement of Induction Motors using Novel Magnetic Slot Wedges

Abstract

This paper introduces novel magnetic slot wedges made of a newly developed resin-free magnetic composite material. The novel magnetic slot wedges exhibit superior permeability and strength compared with conventional magnetic slot wedges made of iron powder and resin. Finite Element Method (FEM) analysis indicated that the efficiency improvement of a 7.5 kW 2-pole induction motor with the novel magnetic slot wedges was expected to be approximately 1.5 times higher compared to that with the conventional magnetic wedges. Installing those magnetic slot wedges into the originally vacant slot openings of commercially available 7.5 kW 2-pole, 7.5 kW 4-pole, and 0.75 kW 6-pole induction motors resulted in efficiency improvements of 1.6%, 1.1%, and 2.8%, respectively, at each rated output. Noticeable decreased in temperature rise were also observed. Consequently, the novel magnetic slot wedges proved to be effective in improving the efficiency of induction motors without requiring significant design changes, such as increasing the motor size.