Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current

Interior permanent magnet synchronous motor (IPMSM) is widely used for many industrial applications such as power train, compressor and home appliances due to its high power density and wide speed range. However, IPMSM have relatively high torque ripple in comparison with surface mounted permanent magnet motor. In case of IPMSM, d-axis current should be fed to use reluctance torque, and the more d-axis current is needed as the motor speed goes up. Therefore, back electromotive force (EMF) of IPMSM contains much harmonics and torque ripple tend to increase as the motor speed increase. This paper proposes a method to reduce torque ripple using harmonic injected current. Firstly dominant harmonic order of back EMF is investigated then under the consideration of harmonics, torque ripple using harmonic injected current will be compared with that of sinusoidal current by finite element analysis.