Rotor Notching for Electromagnetic Noise Reduction of Induction Motors

This paper presents a new technique, notching the induction motor rotor core, so as to reduce the electromagnetic noise by suppressing the vibration due to the rotor slot permeance harmonics. First, the principle of such technique is presented along with theoretical analysis. Then, finite element method is used to calculate the Maxwell force harmonics and the vibration spectra of a 5.5 kW 3000 r/m commercial induction motor and a modified motor. Finally, experimental results are given to validate the proposed technique by testing the vibration and acoustic noise spectra of the two induction motors. It is shown that the modified motor has about 5 dB(A) reduction of the overall sound pressure level compared with the commercial one.