Novel Salient Stator Pole-Shoe Structure for Reducing Shaft-to-Frame Voltage of the PMSM

Abstract

The permanent magnet synchronous motors (PMSMs) are exposed to harmful bearing currents and shaft voltage, which affect their lifetime. This study suggests a novel salient stator pole-shoe (SSPS) structure to suppress the shaft voltage and bearing current. The SSPS interferes with the effect of the electric field between the winding and the rotor, thereby reducing winding-rotor capacitance $C_{\text {wr}}$ , which is a major factor for the shaft voltage. An analytical method is proposed to simply account for the fringing effect (FE) and charge sharing effect (CSE) of the electric field to verify the reduction effect of $C_{\text {wr}}$ in SSPS. The electrostatic finite element analysis (FEAs) is performed to calculate the parasitic capacitance and compare the difference between the SSPS and the classical pole-shoe model. To validate the effectiveness of the SSPS, the magnetic field transient FEA is performed compared with classical model. Finally, the shaft voltage of two prototypes (SSPS and classical model) is verified by experiment. The SSPS enhances the manufacturability through minimal modifies in geometry, unlike the conventional method of using additional shielding parts. In other words, this study offers a compromise between manufacturability and shaft voltage reduction issue for many researchers and engineers.