Analysis and Reduction of Inherent Shaft Voltage in Interior Permanent Magnet Synchronous Machines

This paper presents the analytical model of inherent shaft voltage in interior permanent magnet synchronous machines (IPMSMs). Based on this model, the influence of stator slotting and saliency-effect on inherent shaft voltage is analyzed. Different combinations of PM pole-arc coefficients are proposed to reduce peak inherent shaft voltage. The optimal combinations of PM pole-arc coefficients are derived analytically. However, the even-order harmonics of inherent shaft voltage are introduced, thus, the reduction effect reduces. To further cancel these even- order harmonics, optimal combinations of PM pole-arc coefficients with two segmented rotors in the axial direction are adopted. Finite element results show that adopting optimal combinations of PM pole-arc coefficients with two segmented rotors can reduce peak inherent shaft voltage by 37.8%. Moreover, inherent shaft voltage flux encircling the shaft is observed for the first time in the finite element models.