Figure shows a chopper operating from a $$100$$ $$V$$ $$dc$$ input. The duty ratio of the main switch $$S$$ is $$0.8.$$ The load is sufficiently inductive so that the load current is ripple free. The average current through the diode $$D$$ under steady state is

Figure shows a chopper. The device $${S_1}$$ is the main switching device. $${S_2}$$ is the auxiliary commutation device. $${S_1}$$ is rated for $$400V, 60A.$$ $${S_2}$$ is rated for $$400V, 30 A.$$ the load current is $$20$$ $$A.$$ The main device operates with a duty ratio of $$0.5.$$ The peak current through $${S_1}$$ is

The triac circuit shown in figure controls the $$ac$$ output power to the resistive load. The peak power dissipation in the load is

The triggering circuit of a thyristor is shown in figure. The thyristor requires a gate current of $$10$$ $$mA,$$ for guaranteed turn-on. The value of $$R$$ required for the thyristor to turn on reliably under all conditions of $${V_b}$$ variation is