A simplified mathematical approach to model and analyze magnet defects fault signatures in permanent magnet synchronous motors

This paper deals with modeling and analysis of broken magnet fault signatures in permanent magnet surface mounted (PMSM) motor variables. A detailed mathematical analysis based on the linear model of PMSM motor is developed to predict the behavior of different fault signatures in stator current and back-emf for various motor operation points. In order to verify the results, a three phase, 8-pole PMSM motor is modeled using finite element analysis (FEA) and 7% of one magnet is cut using a fine cutter on the rotor to model the broken magnet fault. This paper also presents a comprehensive fault severity analysis and its impacts on the current and voltage fault signatures. For this purpose, the fault intensity imposed to the motor is increased in four steps by removing 25% of one magnet at each step. Throughout each fault level, the changes in the spectrum are analyzed which provides an essential information to design threshold fault detection.