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An induction motor drawing rated current at reduced voltage will

  • A.refuse to run at all until rated voltage is restored
  • B.overheat, since it cannot develop rated torque
  • C.run cooler than at rated voltage, since less power is being drawn
  • D.develop more than its rated torque at that current

Answer: B

Reduced voltage means reduced flux, so the same current gives less torque and the machine slips further to carry its load, drawing yet more current. Sustained undervoltage is therefore a thermal hazard as well as a performance one.

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