Harmonic Model and Remedy Strategy of Multiphase PM Motor Under Open-Circuit Fault

Modular multiphase (MMP) PM motors have the ability to work continuously under a faulty mode. However, ripples in the spin torque of the motor and unbalanced forces incur rotor vibrations in postfault operations, which seriously degrade the performance of the PM motors. This paper presents a computationally efficient method to derive harmonic models for characterizing the pulsating torque and unbalanced forces of an MMP-PM motor under an open-circuit fault, and the corresponding optimal solutions to its inverse current model to remedy the fault. The model formulation, current harmonic identification, and remedial strategy for suppressing torque ripples and unbalanced forces are illustrated with an MMP-PM motor under an open-circuit fault; both odd and even number of phases are considered. The effectiveness of the harmonic models and remedy strategies are numerically validated with two typical (5- and 6-phase) MMP-PM motors under a one-phase/open- circuit fault and evaluated experimentally on a custom-designed 6-phase duplex motor .