Reducing Inverter Losses by Obtaining Optimal Switching Frequency in IPMSM Drives

Interior mounted permanent magnet synchronous machines (IPMSMs), which seem to be more attractive among electric machines in terms of high efficiency and high power/torque densities, are widely used in the industry. Therefore, IPMSM design and their drives are popular topics in both academia and industry. In this study, the trade-off between IGBT driver losses and current quality has been investigated by obtaining the optimal switching frequency applying the Field-Oriented Control (FOC) technique, which is widely used in IPMSM drives. In experimental studies, current waveforms have been compared at switching frequencies of about 1.5, ~5, 12, and 15 times the maximum electrical frequency of a 4.1kW prototype machine under study. It has been validated that the current harmonics increase with reduced switching frequency, while the inverter losses increase and become more severe with increased switching frequency. While the improvement in the current waveforms with increasing switching frequency is significant to some extent, the improvement become relatively low with further increased switching frequency where inverter losses become more severe. Thus, the optimal switching frequency can be obtained based on the trade-off between the current quality and the inverter losses.