To prevent severe flux distortion from armature reaction in D.C. machines, field mmf must be designed to be____________?
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Answer: C. large in comparison with the armature mmf
Explanation
Armature reaction creates cross-magnetizing magnetic fields that distort main flux distributions and cause severe neutral shift. Designing the main field magnetomotive force to be much larger than the armature magnetomotive force overpowers this distortion. This strong field mmf ensures stable flux patterns and maintains good commutation performance in DC machines. Armature mmf refers to the magnetic field generated by current flowing through the armature winding conductors. Field mmf is produced by the main field poles, establishing the primary magnetic flux required for energy conversion. Flux distortion can lead to dangerous sparking at the brushes and reduce the output voltage of loaded generators.
Equal to that of armature mmf provides insufficient magnetic dominance, allowing severe flux distortion to disrupt commutation. Less in comparison with the armature mmf would worsen armature reaction effects, causing massive voltage drops and heavy sparking. The none of the above option is wrong because making field mmf large is the correct engineering solution.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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