Research on transient junction temperature rise of pulse thyristor

Thyristor has been widely used in HVDC transmission system and pulsed power system. The thyristor will be damaged if transient temperature rise of valve plate is too high. It will result in the system failure if thyristors are damaged. The relationship between peak value of pulse current through the circuit and maximum transient temperature rise of thyristor in pulsed power system was investigated in this paper. Firstly, equivalent thermal impedance model was built. The thermal resistance and thermal capacitance can be obtained by transient thermal impedance curve fitting, and parameters of equivalent current source can be calculated from the power curve. The curve which reflected the change of temperature would be calculated by the thermal impedance simulation model as the pulse current through thyristor. Then one circuit used to measure junction temperature rise of thyristor was designed, which was based on the theory that there is a linear relationship between the conducting voltage drop of thyristor and junction temperature rise of thyristor. The thyristor was kept on during the measuring process in the designed circuit. The junction temperature rise of thyristor was calculated through the thermal sensitive curve and the change of the conducting voltage drop of thyristor. The maximum junction temperature rise of thyristor was obtained after one heavy pulse current through. The junction temperature rise of thyristor obtained from the simulation result was almost the same as temperature rise obtained from experiment data. A method to evaluate the temperature rise of thyristor was obtained through the research.