Thyristor Devices for Electric Power Systems

Thyristors of higher voltage and current ratings containing new gate and self-protective features are being developed at General Electric with EPRI (Electric Power Research Institute) support. Some of the more important of these are described in this paper. Devices include light triggered thyristors (LTT\´s), now at the 5 and 6KV level, and asymr metric light triggered thyristors (ALTT\´s) with 50% higher surge capability and 50% faster turn-off times than a regular thyristor. New features include "controlled turn-on", which protects thyristors from destructive di/dt during turn-on, and " voltage breakover" (VBO) protection, which prevents destructive avalanche current turn-on.