In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
Correct answer: C. 25% of the previous value
- A. 100% of the previous value
- B. 50% of the previous value
- C. 25% of the previous value
- D. 10% of the previous value
- E. none of the above
Explanation
Before magnetic saturation, a series motor has flux proportional to armature current, so T ∝ φIa ∝ Ia². Reducing current to half therefore reduces torque to one-fourth, or 25%, of its former value.
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