Electrical Machines
If iron loss and full load copper loss of any transformer are denoted by Pi and Pc, then the load corresponding to maximum efficiency is given by

 (Pi / Pc) × full Load.
 (Pi / Pc)1.6 × full Load.
 (Pi / Pc)2 × full Load.
  (Pi / Pc)0.5 × Full Load.

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Electrical Machines
The damper windings also called the squirrel cage windings or damper grids

  are provided on the stator for improving power factor.
  both (A) and (B).
  consists of short-circuited copper bars embedded in the field pole faces.
  are provided in a synchronous motor to make it self starting.

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Electrical Machines
The results of a slip test for determining direct axis (Xd) and quadrature axis (Xq) reactances of a star connected salient pole alternator are given below Phase values: Vmax = 108 V ; Vmin = 96 V Imax = 12 A ; Imin = 10 A Hence the two reactances will be

 Xd = 9.6Ω and Xq = 9Ω
 Xd = 8Ω and Xq = 10.8Ω
 Xd = 9Ω and Xq = 9.6Ω
 Xd = 10.8Ω and Xq = 8Ω

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Electrical Machines
In a stepper motor the detente torque means

  maximum of the static torque with the phase winding excited.
  minimum of the static torque with the phase winding unexcited.
  minimum of the static torque with the phase winding excited.
  maximum of the static torque with the phase winding unexcited.

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