Red Seal Electrician Practice
Power factor and three-phaseQuestion 1042 of 1506

A Y-Y three-phase system with no neutral wire loses one source winding. What is the worst effect on the load?

  1. All three loads keep their full voltage and nothing changes
  2. All three loads receive double the normal voltage
  3. Two loads get reduced voltage and the third loses all
  4. Only the neutral wire is affected by the open winding
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Correct answer: Two loads get reduced voltage and the third loses all

The Y source with an open winding is much less fault tolerant than a delta source.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 7.5: Three-phase Y and Delta Configurations

Practice power factor and three-phase

Questions last reviewed: 18 October 2026