Rotor notching for electromagnetic noise reduction of induction motors

This paper presents a new method by notching the induction motor (IM) rotor core to reduce the electromagnetic noise. The aim of the proposed strategy is to decrease the vibration caused by the rotor slot permeance harmonics. Firstly, principle of such electromagnetic noise reduction technique is presented. Then, finite element method (FEM) is used to calculate the Maxwell force harmonics and the vibration spectra of a 5.5kW sample induction motor and a corresponding modified motor. Finally, experimental results are given to validate the proposed technique, by testing the vibration and acoustic noise spectra of the two sample induction motors. It is shown that the modified motor has about 4.6 dB(A) reduction of the overall sound pressure level (SPL) comparing with the original one.