Analytical study of pulsating torque and harmonic components in rotor current of six-phase induction motor under healthy and faulty conditions

In literature, open phase faults in multi-phase induction motor have been investigated. However rotor faults and their impact on the performance of multi-phase induction motor aren´t widely discussed. An analytical study of the pulsating torque and harmonic components in rotor current of six-phase induction machine as a function of displacement between sub-windings in healthy and faulty cases (the rotor broken bar) is developed. The novel formula of pulsation torques of six-phase induction motor presented in this paper can be used as a fault indicator for broken rotor bars. The used model is based on multiple coupled circuits and takes into account the geometry and winding layout, including the calculation of pulsating torques. The simulation results show the disappearance of some higher rotor slot harmonics in torque spectrums as well as a significant improvement in the rotor current harmonics for a specific displacement between sub-windings.