Thermal modelling of high power GTO thyristors

The advent of high power gate turn-off thyristors, has led to high current and voltage capabilities at moderate switching speeds. Their potential use is limited by their inherent limiting junction temperature of typically 125°C. This major limitation often leads to the derating of the device. The thermal modelling of the device heatsink system is required to predict the junction temperature under various operating conditions. The concepts of thermal resistance and thermal capacitance are no longer valid due to the complexity of the physical characteristics as well as the system geometry. A 3D finite element thermal model is developed to deal with steady-state and transient problems. The latter can be used to predict the temperature distribution under fault operating conditions