Which three-phase connection can be used in a transformer to introduce a phase difference of 30° between its output and corresponding input line voltages

For an induction motor, operating at a slip 's', the ratio of gross power output to air gap power is equal to:

On the torque/speed curve of induction motor shown in Fig, four points of operation are market as W, X, Y and Z. Which one of them represents the operation at a slip greater than 1?

Under no load condition, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value,