Analysis of Vibration of a Dual-stator Hybrid Excitation Permanent Magnet Motor for Electric Vehicles

The Permanent magnet synchronous motor (PMSM) has been broadly applied in electric vehicles due to its high efficiency, high power/torque density, low cogging torque and the ability of fault tolerance [1]. However, both in the integral-slot and fractional-slot motors, the electromagnetic vibration and noise issue, as one of the parasitic effects, has been paid much attention in low noise applications [2]. Furthermore, the vibration and noise levels have been the indexes to evaluate the performance of PMSM for electric vehicles. The conventional permanent magnet motor has the disadvantage that the excitation magnetic field can't be adjusted. Generally, the field weakening operation can be achieved by applying a flux-weakening current in the d-axis. While, the capacity of flux-weakening is limited and there is a risk of demagnetization of permanent magnets. Thus, a dual-stator hybrid excitation permanent magnet (DSHEPM) motor is proposed to realize the field regulation. The vibration of motor is attributed to the electromagnetic forces acting upon the stator and rotor, which are induced by the air-gap magnetic field [3]. Compared with the conventional permanent magnet motor, the DSHEPM motor can operate in a variety of working states, such as increasing magnetization, weakening magnetization and no excitation. Therefore, the air gap magnetic field is relatively complex. Both the electromagnetic force generated under different working states and the electromagnetic vibration characteristics caused by the electromagnetic force are different. Thus, it is necessary to analyze the vibration characteristics produced by the motor, which can provide guidance for the effective suppression of the vibration of the motor.