Efficiency Optimization and Modeling of the Air Gap Permeance of Low-Voltage Induction Motors Using Soft Magnetic Slot Closing Material

Increasing global efficiency requirements for directly line-operated motors necessitate innovative solutions. This document evaluates the potential of soft magnetic slot closing materials to improve the efficiency of low-voltage induction motors. In the first step, a tailored measurement setup was developed and applied to investigate the soft magnetic properties of various slot closing materials. In the second step, an analytical machine model of the induction motor was built, focusing on the influence of the slot closing material on the motor's operational behavior. The measured properties of the slot closing materials were also implemented in this model. In the third step, several motors were designed, built, and measured before and after the application of slot closing materials to verify the analytical modeling approach. Thus, by carefully dimensioning the slot closing material, a reduction of motor losses of up to 12 % is achievable. The key focus of this paper is on modeling the air gap permeance function, given its significant impact on the modeling of magnetization behavior and additional no-load losses.