Design and Implementation of a Test Circuit of a Repetitive Critical Rate of Rise of ON-State Current for a High-Power Thyristor

A test circuit of a repetitive critical rate of rise of ON-state current (di/dt) for a high-power thyristor is designed and implemented. The operating principle of the test circuit specified in the standard IEC-60747-6 is explained in detail. The design example for the circuit to test repetitive di/dt of 300 A/μs for a thyristor having a mean ON-state current of 2200 A is presented. The value of the charging resistor is chosen by simulations considering the maximum charging current, power consumption of the charging resistor, maximum charging voltage of the capacitor, and the peak pulsed current of the thyristor. The best firing angles of the thyristor are decided based on the simulations focused on the pulsed current of the thyristor, charging diode current, apparent power of the step-up transformer, and reverse voltage of the charging diode. The repetitive di/dt test prototype of 300 A/μs, 60 Hz, and 60 shots is assembled with the Infineon light-triggered thyristor (T1503N). The design results are verified by an experiment.