Electrical Machines
At what power factor, the voltage regulation of a transformer can be zero ?

 Unity power factor.
  Leading power factor.
 Lagging power factor.
 Zero power factor.

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

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