IGBT Module Rupture Categorization and Testing

The isolated base, plastic molded, power semiconductor module assembly has been available for various devices for over twenty years. During this time the power bipolar junction transistor, the BJT, has given way to the Insulated Gate Bipolar Junction Transistor, the IGBT, as the self commutatible device of choice especially for voltage source inverter topologies. As part of the power structure design process, careful consideration should be given to possible power device failure. Obviously every power structure designer strives to remain well within the operating limits of the power device as specified by the IGBT manufacturer. However, there are component failures either of the power switching device or of supporting components that result in one or more IGBT power device failures. When the IGBT power devices fail, under certain circumstances, the failure can result in the rupture of the power module and extensive damage to the surrounding power components. The topic under investigation in this paper is IGBT module rupture. The IGBT module rupture phenomenon will be characterized through testing and categorized into two separate ratings for each device investigated. A DC link inverter bus fuse is being implemented in most designs as a protective device to minimize extremely high overcurrent faults and power module rupture. The power semiconductor fuses available are optimized for lowest It let though energy, low forward drop and low insertion impedance. As a foundation of the establishment of selected IGBT module rupture ratings the paper contains the testing of several selected fuses and their It values under specific conditions of 600 volts DC applied to an inverter grade capacitor bank. The selected fuses are tested together with the IGBT being evaluated for its rupture ratings. The power circuit is by design a low loss, low inductance structure which will result in the delivery of extremely high currents and energy transmission. The IGBT rupture testing is presented into two categories of overcurrent failure and of unclamped voltage failure. The two failure modes result in different values of rupture energy and It. In conclusion the rupture testing is compared with appropriately sized semiconductor protecting fuses.