Electromagnetic vibration analysis in full frequency band of multi-unit PMSMs under fault tolerance state by magnetic field-structure coupling model

Multi-unit permanent magnet synchronous motors (PMSMs) have the advantages of good fault tolerance and low driving power. Therefore, they are widely used in high power and high torque propulsion fields. Based on the electromagnetic field-structure coupling model, the electromagnetic vibration of multi-unit PMSMs in the full frequency band under normal operation and fault-tolerant operation is studied in this paper. Firstly, an electromagnetic field analytical model was established to explore the space–time characteristics of air gap flux density and electromagnetic force. Then, a mechanical structure model was established by the finite element method (FEM). An electromagnetic field-structure coupling model was established to explore the full-band electromagnetic vibration characteristics. Finally, the full-band electromagnetic force and electromagnetic vibration under fault-tolerant operation were studied. The results show that the coupling model can quickly and accurately calculate electromagnetic vibrations. When a multi-unit PMSM is operating normally, the electromagnetic vibration contains a large number of full-band harmonics. When a multi-unit PMSM is operating in fault-tolerant, modulation frequencies with a distribution of 2hfe±iωr are generated at low frequency band, and modulation frequencies with a distribution of afs±cfe±iωr are generated in high-frequency band. This greatly increases the possibility and intensity of resonance. This study provides a reference for electromagnetic and mechanical fault diagnosis of multi-unit PMSMs.