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?
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A2 diodes and 2 thyristors
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B2 thyristors
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C1 diode and 1 thyristor
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D2 diodes
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E—
Answer
Correct Answer: 1 diode and 1 thyristor
Explanation
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:
Choose a thyristor for controlled conduction on, say, the positive half-cycle.Use a diode for the negative half-cycle path or to block it according to the topology.Hence, the typical device pair is 1 diode + 1 thyristor.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