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

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Electrical Machines
Commutation in a DC machine may be explained as a process

 how alternate flux affects the main field flux.
  in which magnetic field is set up.
 by virtue of which emf is induced in the armature conductors.
  by which electric current in a coil is reversed.

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Electrical Machines
The speed of a DC series motor is

 Proportional to field current.
 Proportional to the square of the armature current.
 Inversely proportional to the armature current.
 Proportional to the armature current.

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