Volume Comparison of Passive Components for Hard-Switching Current- and Voltage-Source-Inverters

By utilizing high switching speeds, wide-bandgap (WBG) semiconductor switches based on silicon-carbide (SiC) and gallium-nitride (GaN) are a key technology to further reduce the volume and therefore increase the power density of inverters for drive applications. These devices not only make volume reduction possible by increasing the electric breakdown field but by reducing the size of the inverters’ passive components due to high switching frequencies. For hard switched converter topologies like the voltage-source-inverter (VSI) this increase in switching frequency also presents it’s own challenges. This is due in part to the necessary fast rise and fall times of the output voltage. This in turn can cause overvoltages at the terminals and stress the insulation system of the driven machine and lead to additional losses because of stray capacitances in the cable connection between machine and inverter. These problems may be addressed either by placing an LC-filter between the VSI and the electric machine or by the use of the increasingly popular current-source-inverter (CSI) topology. Both possibilities come at the cost of additional passive components. This paper compares the volumes of these components for a VSI with an LC-filter and a CSI for a three-phase 400 V, 10.6 A, application.