Which of the following method of speed control of D.C. machine will offer minimum efficiency ?
Correct answer: C. Armature control method
- A. Voltage control method
- B. Field control method
- C. Armature control method
- D. All above methods
Explanation
Armature-control speed regulation uses a series resistance, which wastes substantial power as heat and therefore has low efficiency. Field control is comparatively efficient because the field current is small.
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