A comparison between A 2-level and 3-level inverter for a permanent magnet synchronous motor drive under different inverter switching frequencies

Abstract

This paper is concerned with the comparison between two motor drives, one driven from a 2 level inverter and the other from a 3-level inverter. The inverters were operated at different switching frequencies, 5kHz, 10kHz and 20kHz. The motor copper losses and torque ripples were parameters of interest. Field oriented space vector Modulation control was used for speed control. The 3-level inverter promised lower torque ripples and copper losses as compared to the 2-level inverter. A maximum difference of approximately 16.82% and 66.1% lower copper losses and torque ripples respectively were reached at particular switching frequencies and motor speeds. On average the 3-level invereter promised a difference of 30% and 9.57% lower torque ripples and copper losses respectively. The results also showed that, the choice of the inverter in terms of lower torque ripples and lower copper losses do not only depend on the switching frequency but also on the motor speed.