A holistic approach to optimise the power density of a silicon carbide (SiC) MOSFET based three-phase inverter

Conventional multi-kW three-phase power converters (e.g. 380 V output) based on silicon (Si) devices (e.g. IGBTs) typically operate at switching frequencies of 50 kHz or less. By contrast, silicon carbide (SiC) MOSFETs are capable of switching at frequencies of up to several hundreds of kHz while still maintaining high efficiency operation. This opens up opportunities for greater system design optimisation, such as determining the smallest possible power converter volume and weight. Of particular interest is how the switching frequency affects the size of the passive components (e.g. heatsink, line filter, dc-link capacitor and EMI filter) which account for around 70-80% of the power converter's volume and weight. This paper presents a set of models that outline the effect that changing the switching frequency has on the design of a 2-level, 3-phase inverter using silicon carbide (SiC) MOSFETs as the active switches. In particular it will focus on the effect of the switching frequency on the design of the passive components.