Torque Equation to Predict Torque Harmonic Characteristic of IPMSM According to Winding Arrangement, Number of Phases, and Pole-Slot Combination

Abstract

This paper presents a novel torque equation to predict the torque harmonic characteristic of an interior permanent-magnet synchronous motor (IPMSM). The procedure for establishing the proposed equation is as follows. First, we classify the origins of torque, phase, and slot harmonics. The harmonics are then analyzed to study the relationship between the harmonic generated in the N and S poles of a magnet. Second, we establish the equation consisting of two terms for phase and slot harmonics. In particular, the phase harmonic part embodies a new concept, namely the number of coil groups per phase wound in the adjacent slots to express the period of the stator magneto-motive force. Based on the analysis results, the proposed equation is applied to an IPMSM to verify whether the equation can consider the three cases: the winding arrangement, slot-pole combination, and number of phases. The equation can aid the initial design focusing on the low torque ripple characteristic.