A pair of Silicon Controlled Rectifiers (SCRs) is used to control the output of a welding power transformer for low-frequency welding control. How are these SCRs connected with respect to each other?

Which parameter primarily determines the maximum voltage a TRIAC can block in both directions without triggering?

A step-up chopper is used to deliver a load voltage of 400 V from a 200 V D.C. source. If the blocking period (off-time) of the thyristor is 80 μs, compute the required pulse width (on-time).