Impact of Irreversible Demagnetization on Electromagnetic Noise and Vibrations of Electric Vehicle Traction Motors on Wide Speed Range Operation

This work evaluates the impact of irreversible demagnetization on the electromagnetic noise and vibrations of a permanent magnet synchronous machine (PMSM) embedded small amount of permanent magnet (PM) to apply to electric vehicles (EV). When a PM motor operates, the demagnetization risk can easily happen to the PMs due to the effect of many factors such as temperature distribution, magnetic flux density distribution, and PM operational points in the motor. Thus, it would impact the waveform of air-gap flux density and distribution of electromagnetic force, which is the cause of noise and vibration in the motor. To make these effects clear, the performance of the PMSM under a wide-speed range operation is first analyzed. Then, the PM demagnetization of the PMSM happened in the region of field-weakening (FW) under the impact of the above operational factors. Next, the impact of the PM demagnetization on the motor torque and electromagnetic forces on the stator frame is classified based on the 'demagnetization ratio' index. Then, acoustic noise and vibration characteristics are evaluated through this index on wide-speed range operation. Finally, the study results would be validated through the finite element analysis (FEA) method.