Electrical Mach...

A 6 pole slip ring induction motor operating on 50 Hz supply is driven by a variable speed prime mover as a frequency changer. If it is operated at 1500 rpm in opposite direction then the supply frequency generated is – (in Hz)

A three phase squirrel cage induction motor has a starting current of eight times the full load current and full load slip of 4%. If an autotransformer is used for reduced voltage starting to provide 150% of full load torque as starting torque. The autotransformer ratio will be – (in %)

A centre-zero Galvanometer is properly connected in the rotor of 4 Pole 60 Hz wound-rotor induction motor. When the galvanometer makes 144 complete oscillations in one minute, calculate the rotor speed in rpm.

A 3000 V, 24 pole, 50 Hz, 3-phase, star connected induction motor has a slip ring rotor of resistance 0.016 Ω and stand still reactance 0.265 Ω per phase.

Full load torque is obtained at a speed of 247 rev per minute. Neglect rotor impedance.

Estimate the ratio of maximum to full load torque.

A 6-pole, 50 Hz, 3 – phase induction motor running on full load with 4% slip develops a torque of 149.3 N-m at its pulley rim. The friction and windage losses are 200 W and the stator cu and iron losses equal to 1620 W. The efficiency at full load is ____

A 150 kW, 3000 V, 50 Hz, 6 – pole star connected induction motor has a star-connected slip ring rotor with a transformation ratio of 3.6 (stator/rotor).

The rotor resistance is 0.1 Ω/phase and its per phase leakage reactance is 3.61 mH. The stator impedance may be neglected. The starting torque on rated voltage with short-circuited slip rings is ______ (in N-m)

A 3-phase, 50 Hz, 12 pole induction motor has star connected rotor and the resistance measured across any two slip ring is 0.04 Ω. Its full load slip is 0.02 the torque required by the load varies as the speed squared. The torque slip curve to be a straight line. In the normal operating region. The resistance to be inserted in the rotor circuit to reduce the full load speed 350 RPM is ______

For a 3-phase slip ring induction motor, the maximum torque is 2.5 times the full load torque and the starting torque is 1.5 times the full load torque. The percentage reduction in rotor circuit resistance to get a full load slip of 3% is _______

Neglect stator impedance.