An induction motor with a star-connected rotor produces a 50V induced emf between its slip rings when at standstill. The rotor has a per-phase resistance of 0.5Ω and reactance of 4.5Ω. The document asks to calculate the current per phase and power factor under two conditions: when the slip rings are short-circuited and when connected to a star-connected rheostat set for maximum starting torque.

1. The 3-phase induction motor having star-connected rotor has an induced
e.m.f. of 50 V between the slip rings at standstill on open-circuit. The rotor
has a resistance and reactance per phase of 0.5 Ω and 4.5 Ω respectively. Find
the current per phase and the power factor at starting when (i) the slip rings
are short-circuited, (ii) the slip rings are connected to a star-connected
rheostat of a value which gives the maximum starting torque condition.
Ans. [6.38 A; 0.11 lag; 4.54 A; 0.707 lag]