Electrical Machines
The direction of rotation of a 3 - Φ induction motor can be reversed by

  transposing all the three leads from the supply.
  transposing any two leads from supply.
  transposing any two leads from slip rings.
  disconnecting any one phase.

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Electrical Machines
DC Motor

  dc shunt with armature resistance control.
  dc shunt motor with field weakening.
  dc compound motor.
  dc series motor.

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

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