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.