Question

If the internal power factor angle of synchronous motor is 30 degree. Then the direct-axis component of the armature current will be __________

(a) 0.5 pu

(b) 0.866 pu

(c) 1.73 pu

(d) 0

The question was asked in a job interview.

I'm obligated to ask this question of Two Reaction Theory of Salient Pole Machines topic in section Synchronous Machines of Electrical Machines

Answer 1

Right answer is (a) 0.5 pu

Explanation: Id = Ia*sinψ = 1*sin30

               = 0.5 pu.