During the short-circuit test of a synchronous machine, which of the following are accounted for in the short-circuit test loss?

During the short-circuit test of a synchronous machine, which of the following are accounted for in the short-circuit test loss? (i) I2R loss in the armature winding due to the flow of short-circuit (AC) current (ii) Local core loss caused by armature leakage flux (iii) Core loss due to resultant air-gap flux. (iv) Windage and friction loss

Right Answer is:

(i), (ii), (iii) and (iv)

SOLUTION

The short circuit current is flowing in the synchronous machine due to the following reason:

  • I2R loss in the armature winding due to the flow of short-circuiting (AC) current
  • Local core loss caused by armature leakage flux
  • Core loss due to resultant air-gap flux.
  • Windage and friction loss.

Short Circuit test:

  • The machine is driven at rated synchronous speed and armature terminals are short-circuited through an ammeter.
  • Now, field current gradually increased from zero, until the short-circuit armature current reached its safe maximum value, equal to about 125 to 150% of the rated current.
  • Latter readings may be taken in a short time to avoid armature overheating.
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