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Fast switching behavior of IGBTs with high inductive and capacitive loads

Fast switching behavior of IGBTs is investigated at up to four times the nominal current with an inductive load connected using a 200 m motor cable. A power integrated module (PIM) with a blocking voltage of 1200 V was used for the measurements. In the module, fast IGBTs with increased channel width and reduced short-circuit withstand time were integrated as switches. The experimental waveforms manifest the expected reflection on the collector emitter voltage and the collector current with considerable duration due to the long cable. It is shown that in spite of these significant parasitic effects, very fast short-circuit detection is still possible, which is required for fast switching IGBTs. In power drive systems, a common way to reduce the emission of electromagnetic interference (EMI) is to use shielded motor cables. Due to its shielding, the motor cable lowers radiated EMI but, on the other hand, adds parasitics, such as stray inductance and capacitance to the system. As the characteristic impedance of a shielded motor cable is relatively low, a significant additional charging current flows from the inverter into the cable when a switching operation takes place.

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• Feb 11, 2014