Gate pulse requirements for a single-phase full-wave AC regulator (R–L load) In a single-phase full-wave AC voltage controller feeding an R–L load with firing angle α, what is an appropriate gate-pulse strategy?

Introduction / Context:
With inductive loads, current can persist after the source voltage crosses zero. Adequate gate drive ensures reliable triggering throughout the intended conduction interval.

Given Data / Assumptions:

• Single-phase full-wave AC regulator (anti-parallel SCRs).
• R–L load; significant inductive behavior.
• Firing angle α defined from each half-cycle zero crossing.

Concept / Approach:
For inductive loads, short gate pulses at only the initial firing instant may be insufficient due to commutation uncertainty and device turn-on dynamics. A common practice is to apply rectangular gate pulses extending from the firing instant to near the natural turn-off, i.e., with width approximately (π − α) in each half-cycle.

Step-by-Step Solution:
Begin each half-cycle at ωt = 0.Trigger from ωt = α to near ωt = π to ensure robust conduction.This corresponds to rectangular pulses of width (π − α) per half-cycle.

Verification / Alternative check:
Practical controllers often use pulse trains or wide pulses across the expected conduction interval for R–L loads to avoid misfires.

Why Other Options Are Wrong:
Always short duration: Risk of mis-triggering with inductive loads.
Cannot be rectangular: Incorrect; rectangular gating is common and effective.

Common Pitfalls:
Using ultra-short pulses suitable for R loads on R–L loads; neglecting device turn-on time and source disturbances.

Final Answer:
gate pulses should be rectangular with width (π − α) each half-cycle