A single-phase semi-converter (half-controlled bridge) operates in how many quadrants of the voltage–current plane?

Introduction / Context:
Semi-converters (half-controlled bridges) are widely used in DC drives and power supplies. Understanding their quadrant operation is crucial for predicting whether they can handle regenerative braking or reverse power flow.

Given Data / Assumptions:

• Converter type: Single-phase semi-converter (half-controlled bridge).
• Standard operation with passive DC load (e.g., R–L).
• No active power reversal path is provided.

Concept / Approach:
A semi-converter has two thyristors and two diodes. Output voltage remains nonnegative for normal operation, and current direction is typically one way due to the diode structure. This means the converter can operate only in the first quadrant (positive voltage, positive current). Two-quadrant operation requires full control of current polarity or voltage polarity that a semi-converter does not inherently provide.

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