Influence of short circuit conditions on IGBT short circuit current in motor drives

Protecting the IGBTs against short circuit conditions is a critical aspect of the Industrial motor drive design. The SC (short circuit) conditions can occur in a variety of ways in an industrial environment. The SC applied across the motor drive terminals result in a different fault current profile than a SC that happens at the motor terminals or between inter winding coils. The packaging parameters such as number of wire bond contacts, thermal impedance of the package also have significant impact on the short circuit current profile and the robustness of the system. The voltage spike suppression methods and gate driver response to the over current shut down conditions influence the robustness of the system. This paper studies the influence of the inductance of the short circuit on the saturation current of the IGBT and its effects on the device robustness. The paper also briefly discusses the transient suppression methods and soft shut down methods for the gate drive circuit to improve the robustness.