Effects of novel skewed rotor in squirrel-cage induction motor on electromagnetic force and vibration characteristics

In rotating-field machines, especially in squirrel-cage induction motor, the rotor slots are often assembled in a skew position in order to reduce the influences of permeance harmonics caused by slots [1]; Moreover, induction motor suffers from the vibration and acoustic noise from radial electromagnetic force produced by harmonic field [2]. However, besides the rotary torque, torque of axial component is also generated in rotating machines. Former skewed rotor designs fail to solve those problems. In this paper, a novel skewed rotor is proposed, which can offset the axial component of electromagnetic force. Besides, the ill-effects of the electromagnetic force wave to rotor will be reduced or offset, thus the vibration of the rotor and the noise of the motor will be decreased, which in return further optimizes the air gap flux density. The effects of the novel skewed rotor on air-gap magnetic flux density, torque and radial electromagnetic force characteristics in a squirrel-cage induction motor are investigated.