Transient thermal analysis of thyristors using finite element method

The finite element method (FEM) was used to obtain spatial and temporal distribution of temperatures in high-power SCRs (silicon-controlled rectifiers) used for switching high di/dt current pulses. The meshing strategy heat source model and boundary conditions used for the analysis are presented. The failure temperature of the device was computed to be 1100 degrees C from the analysis. Additionally, the results indicate that thermal failure does not occur at the peak power, as has been suggested, but at a time greater than 10 mu s after the anode current begins to flow, in agreement with experimentally observed time to failure. The instantaneous cooling cycle of the device and, therefore, the cooling and time constant of the device obtained from the simulations are also presented. From the parameters, the operating frequency of the device can be predicted. The results and analysis illustrate the potential of FEM for performing thermal analysis on solid-state devices under various operating conditions.<>