IGBT and diode loss measurements in pulsed power operating conditions

High voltage IGBTs and series diodes are used in Cymer´s solid-state pulsed power commutator module. The IGBTs and series diode losses in the module affect the cooling system design and the energy transfer efficiency. It is difficult to estimate the IGBT and diode losses in the pulsed power operating condition. We have previously tried to measure the IGBT losses by measuring the voltage across the IGBT (using a high voltage differential probe) and the current through the IGBT. Since the voltage across the IGBT changes from the kilo-volt level to several volts, it is very difficult to measure the small on-state voltage accurately. Also very small internal package inductance can obscure the voltage measurement due to the high dl/dt level in the circuit. In this work, the IGBT and series diode losses were measured with a commutator module directly by measuring the water flow rate going through a cold-plate attached to the IGBT or diode and the temperature difference of the inlet and outlet water. Heat transfer through other means, such as free convection, was minimized by sealing the IGBT/diode inside a thermal isolation blanket and polyurethane foam. The loss measurement results on the dual package IGBT and dual package diode are presented in the paper