NSEL Rectifiers India Thyristors may also be necessary to act in the opening switch mode as well. Such applications may contain those where voltage is reapplied to the pulse power switch shortly after closing and the switch needs to have improved blocking capability or the transfer energy needs to be controlled. In these applications, the switch needs to have turn-off capability to decrease the natural turn-off time (tq) of the device. The device is operated in GTO mode with the suitable commutating gate drive.