Operating quadrants of a single-phase semiconverter feeding an R–L–E (RLE) load: identify the correct set of quadrants in the v–i plane.

Introduction / Context:
Quadrant operation describes signs of voltage and current at the load. A semiconverter (half-controlled bridge) supplies a unidirectional current with positive average voltage—typical of rectification. For an RLE load (with back EMF), the topology still restricts operation primarily to the first quadrant.

Given Data / Assumptions:

• Semiconverter = two thyristors + two diodes (half-controlled bridge).
• Freewheeling path available ensures current remains positive.
• RLE load implies possible current continuity but not reversal of polarity in standard operation.

Concept / Approach:

Semiconverters cannot force negative current through the load; they deliver positive current with positive average load voltage, placing operation in the first quadrant. Regeneration (second or fourth quadrants) requires fully controlled bridges or dedicated inversion modes not available in a basic semiconverter.

Step-by-Step Reasoning:

Verification / Alternative check:

Converter quadrant charts show semiconverters as one-quadrant converters (rectifiers) unlike full bridges which can be two-quadrant or four-quadrant with control schemes.

Why Other Options Are Wrong:

• Quadrants II, III, IV imply negative voltage and/or negative current not supported by basic semiconverter hardware.
• Mixed quadrants require bidirectional current control absent here.

Common Pitfalls:

• Assuming RLE back EMF enables inversion without proper switching devices.
• Confusing semiconverter with fully controlled converter.

Final Answer:

first quadrant only