AC Voltage Controllers MCQs

Practice AC Voltage Controllers MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Power ElectronicsAC Voltage Controllers

An AC voltage controller converts?

AFixed-frequency AC to variable-magnitude AC at the same basic frequency
BDC to AC
CAC directly to pure DC only
DDC to DC

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Correct Answer: A. Fixed-frequency AC to variable-magnitude AC at the same basic frequency

Explanation: An AC voltage controller regulates the RMS AC output, commonly by phase or integral-cycle control, while retaining the supply's fundamental frequency.

Reference: Standard power electronics: ac voltage controllers

Question 2

Power ElectronicsAC Voltage Controllers

A single-phase AC voltage controller with a resistive load commonly uses two antiparallel SCRs or a?

ATRIAC
BPower diode only
CZener diode
DBJT operated as a linear amplifier only

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Correct Answer: A. TRIAC

Explanation: A TRIAC provides bidirectional controlled conduction and can replace two antiparallel SCRs in many single-phase AC controllers.

Reference: Standard power electronics: ac voltage controllers

Question 3

Power ElectronicsAC Voltage Controllers

With a purely resistive load in an AC voltage controller, increasing the firing angle generally causes the RMS load voltage to?

ADecrease
BIncrease above the source RMS without a transformer
CRemain constant
DBecome DC

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Correct Answer: A. Decrease

Explanation: A larger firing delay reduces the conduction interval in each half-cycle, lowering the RMS output voltage.

Reference: Standard power electronics: ac voltage controllers