Red Seal Electrician Practice
Power factor and three-phaseQuestion 216 of 1506

How does a power factor corrector save energy on a single-phase induction motor that is lightly loaded?

  1. It speeds the motor up past synchronous speed
  2. It adds a large capacitor across the motor terminals
  3. It raises the motor voltage above its rating
  4. It lowers motor voltage to restore power factor
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Correct answer: It lowers motor voltage to restore power factor

At light load the fixed magnetizing current is too large. A lower voltage reduces it and improves power factor.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 13.9: Single-phase Induction Motors

Practice power factor and three-phase

Questions last reviewed: 18 October 2026