Electrical Machines
The maximum possible speed at which an alternator can be driven to generate 50 Hz and 4000 V is

  1500 rpm.
  3000 rpm.
  3600 rpm.
  4000 rpm.

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Electrical Machines
Short circuit test is performed on a transformer with a certain impressed voltage at rated frequency. If the short circuit test is now performed with the same magnitude of impressed voltage, but at frequency higher than the rated frequency then

 The magnitude will both increase.
 The magnetude of current will increase, but power factor will decrease.
 The magnitude of current will decrease but the power factor will increase.
 The magnitude of circuit as well as the power factor will decrease.

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

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