Chopper quadrants: Which class operates in quadrants I and IV of the V–I plane (forward voltage with bidirectional current)?

Introduction / Context:
DC choppers are categorized by the quadrants of operation on the voltage–current (V–I) plane. Knowing which class supports motoring and regenerative modes is essential in electric drives and power conversion.

Given Data / Assumptions:

• Quadrant I: V > 0, I > 0 (forward motoring).
• Quadrant IV: V > 0, I < 0 (regeneration to the source at positive voltage).
• Ideal switching and proper freewheeling/feedback paths.

Concept / Approach:

Class A operates only in Quadrant I (step-down). Class B operates in Quadrant II (regenerative). Class C (composite of A and B) covers Quadrants I and II. Class D uses two diagonal choppers enabling current reversal while keeping output voltage positive, thus covering Quadrants I and IV. Class E spans all four quadrants with a full bridge arrangement.

Step-by-Step Solution:

Verification / Alternative check:

Standard drive texts show Class D with two choppers and diodes arranged to allow reversal of current through the load while maintaining positive voltage at the load terminals.

Why Other Options Are Wrong:

Class A and B are single-quadrant; Class C is I and II; Class E is four-quadrant (I, II, III, IV), more than required.

Common Pitfalls:

Mixing up Class C (I & II) with Class D (I & IV); assuming all bridges are four-quadrant.

Final Answer:

Class D chopper