Design of High-Precision Thyristor Trigger Unit for CRAFT Magnet Power Converter

The high-power converter for the comprehensive research facility for fusion technology (CRAFT) magnet power supply has a dc output current of 30 kA and a voltage of 250 V. The multidevice parallel converter requires synchronized turn-on of the parallel semiconductor devices in microseconds, so the driver circuit must synchronize the semiconductor devices to provide a large gate-triggering current and an extremely fast current rise rate to increase the turn-on speed of the thyristor. Therefore, to design a suitable gate drive circuit, this article first theoretically analyzes the characteristic line of the thyristor and determines that the intersection of the thyristor load characteristic line and the gate cathode characteristic curve is the effective operating point. On this basis, a new trigger unit is deliberately designed to improve the reliability and consistency of the drive circuit. To verify the design, the designed driver circuit is simulated in this article. The simulation results show that the driving circuit is able to complete the triggering of the thyristor with good thyristor triggering speed, and the circuit structure is simple, which has good cost-effectiveness and application value and improves the safety of rectifier operation.