A half-wave thyristor converter supplies a purely inductive load, as shown in figure. If the triggering angle of the thyristor is $${120^ \circ }$$, the extinction angle will be

A $$3$$-phsae, fully controlled, converter is feeding power into a $$d.c.$$ load at a constant current of $$150A.$$ The $$r.m.s$$ current through each thyristor of the converter is

When the firing angle $$\alpha $$ of a single phase, fully controlled rectifier feeding constant $$d.c.$$ current into a load is $${30^ \circ }$$ , the displacement power factor of the rectifier is