A 3-φ alternator has negligible stator resistance. A short-circuit test is conducted on this alternator. At a particular speed a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current
A. would be equal to Ifi.
B. would be equal to 2If1.
C. would be equal to If1/2 .
D. cannot be predicted due to insufficient data. [GATE 1993]
Answer:D
A 3-φ alternator has negligible stator resistance. A short-circuit test is conducted on this alternator. At a particular speed a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current
A. would be equal to Ifi. B. would be equal to 2If1. C. would be equal to If1/2 . D. cannot be predicted due to insufficient data. [GATE 1993]