Free-wheeling diode conduction in a rectifier A single-phase half-wave rectifier includes a free-wheeling diode. Under which load condition(s) will the free-wheeling diode conduct?

Introduction / Context:
Free-wheeling (flyback) diodes are added to rectifiers feeding inductive loads to provide a path for the load current when the main rectifying device is reverse-biased. This protects components and smooths current, improving performance in drives and controlled rectifiers.

Given Data / Assumptions:

• Single-phase half-wave rectifier topology.
• One additional diode connected across the load (polarity to conduct when source reverses).
• Load could be R, L, or R–L.

Concept / Approach:
Inductance resists sudden changes in current. When the input source voltage becomes negative (or the rectifier device turns off), the inductive energy forces current to continue in the same direction through an alternative path. The free-wheeling diode provides that low-loss path, clamping the load voltage and allowing current to decay safely.

Step-by-Step Solution:
Pure R load: current is in phase with voltage; when input reverses, current instantly goes to zero → free-wheeling diode has no role.L or R–L load: current lags input and cannot instantly stop at the moment the rectifier is reverse-biased → the free-wheeling diode conducts, circulating current through the load.Therefore, conduction occurs for purely inductive or R–L loads.

Verification / Alternative check:
Waveforms of an R–L rectifier show continuous or quasi-continuous current with a clamp at approximately one diode drop during the free-wheel interval.

Why Other Options Are Wrong:

• Pure R: no energy storage → no need for a free-wheel path.
• Pure C: current leads voltage and free-wheeling diode is not the correct protection mechanism.
• R only or L only answers are incomplete.

Common Pitfalls:

• Assuming free-wheeling reduces average output voltage in all cases; its main role is current continuity and device protection with inductive loads.

Final Answer:
load is purely inductive or combination of R and L