Studies of Mechanical Vibrations and Current Harmonics in Induction Motors Using Finite Element Method

摘要

This paper illustrates a numerical approach to magnetic field modeling for a squirrel-cage induction motor fed by various voltage sources: i) an ideal sinusoidal source, ii) a PWM voltage-source-inverter (VSI), and iii) a six-step VSI. A two-dimensional nonlinear time-stepping finite element method (FEM) is used for electromagnetic field approximation when the motor is under a full-load steady-state revolution. To solve this time-dependent problem, the numerical backward-difference integration is applied. Due to the saturation characteristic of the magnetic materials, the combined Newton-Raphson (N-R) with bi-conjugate gradient (BCG) method is employed to handle the nonlinearity and to solve the linearized equations. The approach has been applied to evaluate the mechanical vibrations of the motors in associate with the geometry of the rotor slots. Also, the effects of nonsinusoidal supply voltages on the current harmonics have been investigated.