Investigation on the performance of thyristors for pulsed power applications

In this paper, we investigated the di/dt capability and the turn-on action of conventional thyristors (including common thyristor and GTO) under short pulse conditions. Although the common thyristor is proven to be not adequate for pulse application, the GTO behaves excellently and it exhibits the potential of being operated in the case of much higher di/dt and pulse current than its rated values. Multi-cell PSpice simulation model of GTO was developed to evaluate influence factors of current distribution in thousands units of the GTO. It was found that forward transport time (TF) of excess carriers flowing through base region in each unit mainly determines the current distribution. If some unit has smaller TF, it will bear larger current compared with others in the turn-on process and thus has the risk of overheating. The use of magnetic switch in series with GTO can greatly reduce the power dissipation in the process and guarantee the GTO's safe operation. Our tests have originally resulted in a maximum di/dt of 6 kA/μs for a 10-μs half-sine wave current pulse of 17.3 kA amplitude by using a GTO, whose rated RMS on-state current is 1500 A and di/dt capability is 800 A/μs. The measurements show that turn-on losses and conduction losses are less than 0.5 J.