Interaction between IGBT, diode and parasitic inductances during short-circuit type 3

During short-circuit type 3 which occurs when the freewheeling diode conducts current and the anti-parallel IGBT is switched on the current commutates from the diode to the IGBT and vice versa. This commutation between the semiconductor includes parasitic inductances on the module substrate which are not optimized. During the short-circuit type 3 the avalanche of the diode, the collector-emitter voltage at the beginning of the short-circuit, the voltage stress of the semiconductor and the current mismatch between the IGBTs are influenced by the parasitic inductances. In this paper the inductance on substrate level is measured and the influence on the short-circuit behavior is presented with the help of measurements and simulations. The behavior of the IGBT during the short-circuit especially at the beginning is explained with the help of the parasitic inductances. Moreover an equivalent circuit for the substrate inductances between IGBT and diode is discussed.