Test: Three Phase Induction Machine of Electrical Machines - Electrical Engineering (EE) MCQ

A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?

A 10 kW, 400 V, 3-phase induction motor draw a current of 5 times its full-load current at rated voltage and at standstill developing a starting toque of 1.5 times its full-load torque. An autotransformer is installed to reduce the starting current and to give full-load torque at starting. Neglecting exciting current of auto-transformer, the voltage applied to the motor terminals at the time of starting with auto transformer is

A 3-phase, 20 kW, 400 V, 1470 rpm, 50 Hz squirrel cage induction motor develops a torque of 100 N-m at a speed of 1400 rpm. if the motor is connected to a 30 Hz supply; for keeping the same air-gap flux, the supply voltage and the speed for the same load torque would respectively be

In a 3-phase squirrel cage induction motor, applied voltage is reduced to x times its rated value. Then, its starting line current from mains and starting torque by auto-transformer starting would reduce respectively from their corresponding direct switching values by a factor of

A 3-phase IM with stator in delta draws a line current of 10 A. When connected in star, it would draw a line current of

The power factor of a delta-connected 3-phase, 50 kW, IM is 0.4 when delivering 35% of its rated load. If the stator is reconnected in star, then its

A 3-phase, star-connected SRIM is fed from 400 V, 50 Hz source. Stator to rotor effective turns ratio is 2. At a rotor speed of 1440 rpm, the rotor induced emf per phase would be