Half-bridge inverter feeding an R–L load A single-phase half-bridge inverter must feed an R–L load (current continuity required). What minimum set of power devices is needed in the inverter leg(s)?

Introduction / Context:
Inductive loads store energy and force current to continue flowing when the applied voltage reverses or devices turn off. Inverters for R–L loads therefore require freewheeling paths to maintain current continuity and avoid overvoltage across switches. This is fundamental to safe commutation and waveform quality.

Given Data / Assumptions:

• Topology: single-phase half-bridge.
• Load: R–L, so current lags voltage and must freewheel when switches commutate.
• Switches are thyristors; diodes can provide antiparallel freewheeling paths.

Concept / Approach:

Each active device needs an antiparallel diode to allow reverse or freewheel current when the device is off. In a half-bridge with two controlled devices, two antiparallel diodes are sufficient to provide current paths during the opposite half-cycle or device turn-off, ensuring current continuity and limiting overvoltage.

Step-by-Step Solution:

Verification / Alternative check:

Standard inverter schematics for inductive loads show antiparallel diodes across each controlled device (also inherent body diodes in MOSFETs/IGBTs provide this in other technologies).

Why Other Options Are Wrong:

Only thyristors (no diodes) leave no path for inductive current → dangerous; using four thyristors is full-bridge, not half-bridge; omitting diodes with MOSFETs is unrealistic because body diodes exist and are required.

Common Pitfalls:

Confusing half-bridge with full-bridge; ignoring the need for freewheel diodes for inductive loads.

Final Answer:

2 thyristors and two diodes