EasyAssistant Engineer (Electrical), Class-2, Road and Building Department2025✓ Editorially verified

Efficient LCC HVDC converters generally use __________

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Answer & Explanation

Correct AnswerA. thyristor

Quick Explanation

Modern efficient line-commutated HVDC converters use series-connected high-power thyristor valves. Thyristors can be triggered at a controlled firing angle and naturally commutate off using the AC system voltage.

Formula / Key Relation

LCC switching device: thyristor

Turn-on: gate controlled

Turn-off: line/natural commutation

Detailed Explanation

Concept & Reasoning

Early HVDC schemes used mercury-arc valves, but semiconductor thyristor valves became the standard LCC technology because of improved reliability, controllability and maintainability. Diodes cannot provide firing-angle control, while mechanical switches are far too slow for power-frequency conversion.

How to Solve It in the Exam

LCC literally points to line-commutated thyristors.

Important Exam Point

Distinguish LCC thyristors from self-commutated IGBT-based VSC technology.

Related Revision Path

This question sits in the revision path Power System → HVDC Transmission → Line-Commutated Converters .

Thyristor Valves in LCC HVDC explanatory diagram

Quick Trick

LCC literally points to line-commutated thyristors.

Common Mistake

Choosing mercury valves because they were historically used in early HVDC links.

Exam Tip

Distinguish LCC thyristors from self-commutated IGBT-based VSC technology.

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Exam Path

Knowledge Path

Study concept · Thyristor Valves in LCC HVDC →Practice concept Practice topic

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