Electrical Machines
The direction of rotation of a 3 - Φ induction motor is clockwise when it is supplied with 3 - Φ sinusoidal voltage having phase sequence A - B - C. For counterclockwise rotation of motor, the phase sequence of the supply should be

 B - C - A.
 C - A - B.
  A - C - B.
 B - C - A or C - A - B.

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Electrical Machines
Flashing the field of DC generator means

  creating residual magnetism by a DC source.
 increasing flux density by adding extra turns of winding.
  making the magnetic losses forces parallel.
  neutralising residual magnetism.

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Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

 changes to three times the original value
 changes to 1.5 times the original value
 changes to 0.5 times the original value
 remain the same as the original

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