The main disadvantage of Hopkinson's test is that

  • AIt needs large power
  • BIt needs two identical machines
  • CNo account is taken for change in iron losses due to flux distortion on full load conditions 
  • DAll of the above 
Correct Answer : (B)

It needs two identical machines

Hints :

The current drawn by a 120 V dc motor with back emf of 110 V and armature resistance of 0.4 ohm is


With the increase in speed of a dc motor

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