Single-phase half-wave AC voltage regulator (controller) Which device combination is typically used to realize a single-phase half-wave regulator for a resistive load?

Introduction / Context:
AC voltage regulators adjust the RMS voltage supplied to a load by phase-controlling conduction. In the single-phase half-wave variant, only one polarity half-cycle is controlled, while the opposite polarity is either blocked or allowed by a passive device to complete the circuit as designed.

Given Data / Assumptions:

• Single-phase supply and a resistive load.
• Half-wave regulation implies one controlled half-cycle.
• Low/medium power implementation.

Concept / Approach:

A common half-wave regulator uses one thyristor to control conduction during one half-cycle and one diode to provide the complementary path during the other half-cycle (when desired). This achieves half-wave control with a minimal parts count and provides a predictable waveform for the load.

Step-by-Step Solution:

Verification / Alternative check:

Standard educational schematics of half-wave AC regulators show a single SCR in anti-parallel with a diode for basic control.

Why Other Options Are Wrong:

• Two thyristors are used for full-wave control (antiparallel), not half-wave.
• Two diodes provide rectification, not controlled regulation.
• “2 diodes and 2 thyristors” corresponds to more complex controllers.

Common Pitfalls:

Confusing half-wave and full-wave AC regulators; mixing rectifier topologies with regulator topologies.

Final Answer:

1 diode and 1 thyristor