A small air-gap in a three-phase induction motor helps in
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Answer & Explanation
Correct AnswerD. reducing the magnetizing current
Quick Explanation
A smaller air gap reduces magnetic reluctance, so less magnetizing current is required to establish the working flux. This improves power factor and reduces magnetizing reactive demand, although the gap cannot be made arbitrarily small because of mechanical clearance and harmonic/unbalanced-pull considerations. The listed benefit corresponds to option D.
Formula / Key Relation
Reluctance Rm=l/(μA); smaller air gap → lower magnetizing mmf/current
Detailed Explanation
Correct Answer
D — reducing the magnetizing current
Concept and Reasoning
A smaller air gap reduces magnetic reluctance, so less magnetizing current is required to establish the working flux. This improves power factor and reduces magnetizing reactive demand, although the gap cannot be made arbitrarily small because of mechanical clearance and harmonic/unbalanced-pull considerations. The listed benefit corresponds to option D.
Calculation / Key Relation
Reluctance Rm=l/(μA)
smaller air gap → lower magnetizing mmf/current
Exam Takeaway
Small gap mainly reduces magnetizing current.
Common Mistake
Do not ignore required mechanical clearance between stator and rotor.
Quick Trick
Small gap mainly reduces magnetizing current.
Common Mistake
Do not ignore required mechanical clearance between stator and rotor.
Exam Tip
Small gap mainly reduces magnetizing current.
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