Static Eccentricity Fault Diagnosis in an Accelerating No-load Three-phase Saturated Squirrel-cage Induction Motor

A no-load induction motor under static eccentricity is modeled using time stepping finite element (TSFE) method; current, torque, and speed signals of the motor are obtained by finite element method (FEM) and used for static eccentricity fault diagnosis and analysis. The frequency spectrum analysis of the stator current around fundamental frequency component is used to predict the static eccentricity. Noise, unbalanced magnetic pull (UMP) and arc occur during the starting of the faulty motor, therefore, performance of the motor over the period of starting up to the steady-state is investigated. It is shown that the rate of obtained signals from the constant permeability based analysis is very larger than that of the real case. It is indicated that in order to obtain accurate results the saturation must be taken into account in the analysis of the motor. Simulation results for a 3 hp, three-phase, 230 V, 36 stator slots induction motor with 28 rotor slots are given in this paper. Experimental results for the motor confirm the simulation results very well.