Electrical Machines
A 400 V, 50 Hz, 30 Hp, three phase IM is drawing 50 A current at 0.8 p.f lagging. The stator and rotor copper losses are 1.5 KW and 900 W respectively. The friction and windage losses are 1050 W and core losses are 1200 W. The air gap power of the motor will be

 25 kW.
 26.21 kW.
 23.06 kW.
 24.11 kW.

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Electrical Machines
Consider the following statements about commutating poles which are fitted on most large dc Shunt motors: 1. The commutating poles are placed in the geometric neutral plane and their number is usually Equal to the number of main poles 2. The winding on the commutating poles is connected in series with the shunt-field winding on the main poles 3. The polarity of the commutating pole must be that of the next pole further ahead 4. The commutating poles neutralize the reactance voltage produced in the coil undergoing Commutation. Of these statements,

 1 and 4 are correct
 1, 2 and 3 are correct
 2, 3 and 4 are correct
 1, 2 and 4 are correct

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Electrical Machines
When the supply terminal of a DC shunt motor are interchanged

  The motor will run at its normal speed in the same direction as before.
 The direction of rotation will reverse.
 The motor will run much faster in the same direction.
 The motor will stop.

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