Efficiency Improvement Analysis of a SiC MOSFET-based PMSM Drive System with Variable Switching Frequency

The widespread deployment of electric vehicles (EVs) requires high efficiency of traction inverters to drive longer distances in one charge. The widely used silicon insulated-gate bipolar transistor (Si IGBT) for EV motor drives is mature and practical; however, it can result in large inverter losses, especially at high switching frequencies. Whereby, silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs) can reduce both conduction and switching losses compared to Si IGBT. Increasing the switching frequency of the traction inverters is proven to be effective in lowering the motor iron losses; however, this will concurrently increase the inverter switching losses. This paper aims to show the effectiveness of operating SiC MOSFETs in a permanent magnet synchronous motor drive using variable switching frequency pulse-width modulation. Optimisation of the switching frequency is therefore demonstrated to maximise the motor drive system efficiency. Results show that the efficiency of the whole system, i.e., motor and motor drive, can be improved through optimally selecting the switching frequency of the motor drive at different driving operating points.