Potentials and Limits of Reducing Switching Losses in Motor Drive Power Converters by using fast switching SiC Bipolar Junction Transistors

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The purpose of this project is to investigate what extent the switching losses in a power converter for motor drive by using fast switching silicon carbide bipolar junction transistors without damaging the inverter or the connected electrical machine. At first a driver configuration for the lowest possible converter losses needs to be found. Besides the conventional voltage source based driver a new current source is supposed to be used. In any case, passive switching actions that could lead to converter destruction have to be prevented by appropriate driver and commutation circuit design. Secondly, the sharpest tolerable voltage rise across the transistors is to be found, in order to connect an electrical motor via motor cable directly to the inverter without endangering the winding insulation. A major focus of this project is the precise measurement of switching losses of fast switching semiconductor devices by double pulse test in buck converter setting as well as the measurement of the overall converter losses by using power analyzer and calorimeter. For the determination of the inverter and overall converter losses the induction motor connected to the inverter is loaded by another machine that is torque controlled. Additionally the on-state losses are supposed to be measured, too. Especially the uncertainty of measurement of each measuring technique needs to be determined to evaluate the measuring results. Based on these investigations the measuring set-ups with the most precise measurement results are to be selected. Thus, the lowest converter losses with and without an output filter can be determined. If a sine-wave filter is applied, the correlation between pulse frequency and filter-space needs to be explored. In case there is not any output filter, the effect of voltage rise times under 50 ns on critical cable length should be examined. Furthermore switching losses, that have been calculated based on double pulse measurements are supposed to be set in correlation with measured switching losses of the converter.