Thyristor (diode) transient thermal impedance modeling including the spatial temperature distribution during surge and overload conditions

Circuit modeling is an essential tool in the design of power electronic applications. The widespread use of these models, however depends upon the availability of parametric data for devices and the proper trade-off of accuracy and simplicity of the model. This paper addresses these two areas as well as describing another modeling subject, the spatial temperature distribution during serge and overloads of thyristors and diodes. The conversion from the physical ladder thyristor (diode) thermal model to the much simpler series equivalent thermal circuit model was described previously. This paper describes a unique multiple regression method to automate the calculation of the parameters for the simplified model. This permits the manufacturer to provide the necessary parameter values for the power electronic design engineer to hard code and/or use SPICE circuit modeling to obtain the waveform of virtual junction temperature verses time in a proposed or existing application. An important characteristic of thyristors is the ability to withstand surge and overloads significantly above their steady state ratings. When considering this ability of the device to absorb and remove heat we are forced to extend our analysis to another dimension, namely, the physical or spatial distance through the device. The spatial temperature-time distribution provides a millisecond by millisecond account of the temperature in each of the device components during surge and overload conditions