Electrical Machines
If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

 Pe will increase but Ph will decrease
 Ph will increase but Pe will decrease
 Ph will decrease but Pe will remain same
 both hysteresis loss(Ph) and eddy current loss(Pe) will increase

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Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  they are capable of operation under range of leading and lagging pf.
  they have maximum efficiency and maximum starting torque.
  they have very good speed regulation.
  these are cheaper in cost, simple and rugged in construction.

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