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

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

A cable has the following characteristics. $$L = 0.201\,\,\mu H/m\,\,$$ and $$\,C = 196.2\,pF/m.\,$$ The velocity of wave propagation through the cable is

An alternator is connected to an infinite bus as shown in figure. It delivers 1.0 p.u. current at 0.8 p.f lagging at V = 1.0 p.u.. The reactance X_d of the alternator is 1.2 p.u. Determine the active power output and the steady state power limit. Keeping the active power fixed, if the excitation is reduced, find the critical excitation corresponding to operation at stability limit.