Abstract
When a thyristor junction is heated above its rated temperature, many electrical characteristics of the thyristor are changed and eventually the high temperature may damage or break down the thyristor. Therefore, we have to be vigilant at keeping track of the junction temperature of the conducting thyristor. To estimate the junction temperature of the thyristor, we may apply the forward voltage drop method, or we may calculate the heat resistance, the heat losses and measure the temperature of the case. But, these methods are difficult to apply under an A. C. conduction. The gate triggering method by H. Q. Tserng is hardly applicable except for an A. C. phase control circuit. We use the gate triggering method by the saw-tooth wave voltage to measure the junction temperature and indicate its temperature digitally.
Applying a saw-tooth voltage to the gate of the thyristor of the parallel inverter, the junction temperature Tj is obtained as the function of the gate triggering voltage Vgt and the voltage between the anode and the cathode Vak By G. M. D. H., we can determine the equation to calculate Tj. And, we can indicate Tj of the thyristor in the running state by the microcomputer.
In this paper, we report the method of observing the junction temperature of the conducting thyristor of the parallel inverter using the microcomputer.
