Effects of the geometry of the rotor slots on the mechanical vibration of three-phase induction motors

This paper presents the development of mathematical models and simulations of magnetic field, and mechanical vibration in a three-phase squirrel-cage induction motor. Its aim is to compare the vibration magnitude when the motor possesses different geometrical rotor-slot shapes. The cross sectional areas of two typical semi-closed slot shapes (rectangular and round shapes) are kept equally constant according to the IEEE standard. Under an assumption of sinusoidal motor excitation, the simulation works employ the finite element method (FEM) and the Newton-Raphson method to solve time varying nonlinear equations. The numerical solutions obtained indicate the electromagnetic force distribution over the motor cross sectional area. Such forces cause mechanical vibration in the motor. To evaluate this vibration, the displacement of stator inner perimeters was observed carefully. As a result, the round rotor slot gives 4.8% less vibration than the rectangular rotor slot does.