Following are some of the properties of rotating electrical machines
P. Stator winding current is dc, rotor-winding current is ac
Q. Stator winding current is ac, rotor-winding current is dc
R. Stator winding current is ac, rotor-winding current is ac
S. Stator has salient poles and rotor has commutator
T. Rotor has salient poles and sliprings and stator is cylindrical
U. Both stator and rotor have poly-phase windings

DC machines. Synchronous machines and Induction machines exhibit some of the above properties as given in the following table. Indicate the correct combination from this table

A 3-phase, 4-pole squirrel cage induction motor has 36 stator and 28 rotor slots. The number of phases in the rotor is:

The power input to a 415 V, 50 Hz, 6 pole, 3-phase induction motor running at 975 rpm is 40 kW. The stator losses are 1kW and friction and windage losses total 2 kW. The efficiency of the motor is

A three phase, wound rotor induction motor is to be operated with slip energy recovery in the constant torque mode, when it delivers an output power P₀ at slop 's'. then theoretically, the maximum power that is available for recovery at the rotor terminals, is equal to