Interbar currents and axial fluxes in healthy and faulty induction motors

Nearly 10% of failures in cage induction motors are on the rotor. In previous works, it has been shown that interbar currents exist in healthy and faulty squirrel cage induction motors. On the other hand, the majority of techniques detecting bar failures depend on detecting the twice slip frequency modulation harmonic in speed, torque or stator current by analyzing the appropriate frequency spectrum and neglecting interbar currents. However, interbar currents create axial fluxes through the rotor shaft. In this paper, a three-dimensional magnetic equivalent circuit (MEC) method is presented for the analysis of this phenomenon. Effects on the broken rotor bar currents, and transient behavior of induction motor are also presented. Theoretical findings have been verified through experiments.