Wiring and componentsQuestion 1008 of 1506

How is a 120/240 V split-phase supply usually made from a utility transformer?

  1. The primary winding has a centre tap
  2. Two separate transformers are connected 120 degrees apart
  3. The secondary winding has a centre tap
  4. A capacitor shifts the phase of one half
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Correct answer: The secondary winding has a centre tap

The centre tap gives two equal in-phase voltages, and the tap is the neutral.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 7.1: Single-Phase Power Systems

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Questions last reviewed: 18 October 2026