Radial Force Harmonics Reduction of IPM Motor by Injection of Zero-Sequence Harmonic Current

This paper addresses reduction of 6f (6 times of electrical frequency, f-radial force harmonics with zero-order mode in an interior permanent magnet synchronous motor by injection of the zero-sequence third-harmonic current, which has only little influence on the motor performance. The injection frequency for reduction of 6f-radial force harmonics in the proposed method is half of that for conventional dq-harmonic current injection. Thus, the control of current injection can be easier. Furthermore, the proposed system with a three-phase four-wire inverter enables providing the zero-sequence current without additional power electronics circuit. To demonstrate the effectiveness of the proposed method, three-dimensional FEM analysis was performed using an IPM motor with 8-pole/48slots distributed winding. The analysis results indicated that the 6f radial force harmonics and sound pressure were reduced by injection of the zero-sequence third-harmonic current while the torque ripple is largely not changed.