Thyristor circuit breaker for overcurrent protection of industrial d.c. power installations

The paper describes a d.c. thyristor circuit breaker (t.c.b.) used for high-speed overcurrent protection in low-voltage industrial power installations. The forced-commutation t.c.b. principle of operation, and an industrial model (rated at 600 V d.c., 800 A continuous current) that was subjected to tests under various duty conditions, are discussed. In conclusion, the presented contactless c.b. gives lower peak let-through currents, lower let-through I2t values, and clears faults at least ten times faster than its electromechanical equivalent. It may be advantageously used in networks with a fault-current rise rate up to 107 A/s. Therefore the t.c.b. may be considered an effective overcurrent protector for solid-state power devices in industrial applications.