Transformer requirement for 180° phase difference to a rectifier: Which transformer configuration supplies two equal-magnitude secondary voltages that are 180° out of phase for full-wave rectification?

Introduction / Context:
One classic full-wave rectifier topology uses a center-tapped transformer secondary and two diodes. The center tap provides a reference, and the two half-windings produce equal voltages that are 180° out of phase, steering both halves of the AC cycle in the same direction through the load.

Given Data / Assumptions:

• Desire is to obtain two anti-phase secondary voltages for a two-diode full-wave rectifier.
• Transformer considered ideal for phase discussion.
• Load is connected from the diode junction to the center tap.

Concept / Approach:
A center-tapped secondary comprises two identical half-windings about a common midpoint. The voltages at the ends are equal in magnitude but opposite in instantaneous polarity with respect to the center tap. Each half-cycle forward-biases exactly one diode, producing full-wave rectification with only two diodes. Alternatives like ”step-down” or ”stepped-up” describe magnitude changes, not phase relationships; ”split winding primary” pertains to primary connections, not the secondary phase requirement for this rectifier style.

Step-by-Step Solution:

Verification / Alternative check:
Phasor diagrams show V_s1 = +V/2 and V_s2 = −V/2 relative to the center tap, confirming the 180° phase difference. Lab measurements of each end versus the center confirm opposite polarity at any instant.

Why Other Options Are Wrong:

• Step-down/stepped-up: Only specify turns ratio; no guarantee of phase-split outputs.
• Split winding primary: Concerns primary-side flexibility; does not directly yield the required secondary phase relationship.

Common Pitfalls:
Confusing the bridge rectifier (which needs no center tap) with the two-diode full-wave rectifier that requires one.

Final Answer:
center-tapped secondary