Electrical Machines
If Pi and Pc represent core and full load copper loss respectively, the maximum KVA delivered to load corresponding to maximum efficiency is equal to rated KVA is

 Pc/Pi
 √(Pi/Pc)
 (Pi/Pc)2
 Pi/Pc

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Electrical Machines
In large sized DC machines the compensating windings are provided to

 reduce eddy current losses by providing local short circuits.
  neutralize voltage induced in coil due to fluctuation of l
None of these
 compensate for the decrease in speed due to increase of load.

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

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