Electrical Machines
In which of the following speed control of DC motor the speed obtained is below than the rated speed?

 Field resistance control.
 Armature circuit resistance control.
 Armature voltage control.
 Any of above.

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Electrical Machines
Consider the following statements : Interpoles in dc machines 1. reducearmature reaction effects in the interpolar region 2. have the same dimension as main polls 3. have their windings connected in series with the armature 4. have same number of turns as the armature 5. have the polarity same as that of the main pole ahead in a motor From these, the correct statements are

 1, 2 and 3
 1, 3 and 5
 1, 2, 3 and 5
 1 and 3

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Electrical Machines
In a stepper motor the detente torque means

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

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Electrical Machines
The residual magnetism of a self-excited dc generator is lost. To build up its emf again

 the field winding must be replaced
 the field winding connection must be reversed
 field winding must be excited by low voltage dc supply
 the armature connection must be reversed

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