HV Exit Exam • Set 4 Question 22 of 30
In an AC synchronous alternator, when the load operates at unity power factor, the effect of armature reaction is:
✓
Direct Answer
Option B: Purely cross-magnetising
At unity power factor, armature current is in phase with induced EMF, producing a cross-magnetising effect that distorts the main magnetic flux distribution across the pole shoes without net demagnetization.
All Options
A
Purely demagnetising
B
Purely cross-magnetising
(Correct Answer)
C
Purely magnetising
D
Zero effect on main field flux
Detailed Explanation & Context
At unity power factor, armature current is in phase with induced EMF, producing a cross-magnetising effect that distorts the main magnetic flux distribution across the pole shoes without net demagnetization.
Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • High Voltage Safety Officer & Switchgear Operations (HV).
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