Electrical Machines
In a DC generator the actual flux distribution depends upon

  clearance between tips of the adjacent pole shoes.
  shape of the pole shoe.
  all of above.
 size of air gap.

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Electrical Machines
Ward-Leonard system for controlling the speed of a DC motor is used where

 All of above.
 The speed in both the direction is required.
 The accuracy in speed control is required.
 Very fine speed control over the whole range from zero to normal speed is required.

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Electrical Machines
Consider the following statements regarding dc machines : 1. possible resistance of shunt-field winding is 1 Ω 2. possible resistance of series-field winding is 1 Ω 3. electrographite brushes are used for 230 V, 10 A machines 4. Copper-graphite brushes are used for 230 V, 10 A machines 5. Possible armature-circuit resistance is 1 Ω From these, the correct statements are

 2, 3 , 5
 2, 4 ,5
 1, 4
 1, 3, 5

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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,

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

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