Electrical Machines
In a 3 - Φ IM with line frequency f1 and winding factor kw1 and kw2 for stator and rotor respectively the ratio of per phase stator winding emf E1 to per phase rotor winding emf E2 at standstill is given by

  E1 / E2 = N1 / N2.
  E1 / E2 = N1kw1 / N2kw2.
  E1 / E2 = f1kw1 / f2kw2.
  E1 / E2 = 1.

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Electrical Machines
No load primary current in a transformer

 leads the applied voltage somewhat less than 90Ã&
 lags behind applied voltage somewhat less than 90Ã
 lags behind applied voltage by exactly 90Â&am
 leads the applied voltage by exactly 90Â&

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