Introduction / Context:
Controlled rectifiers with highly inductive loads exhibit nearly continuous current, which alters the conduction interval of the devices. Understanding the interplay between firing angle and load inductance is central to power electronics and converter design.
Given Data / Assumptions:
- Topology: Single-phase full-wave converter (M-2 connection, two devices).
- Load: Highly inductive (large L makes current continuous or nearly continuous).
- Each thyristor is fired at angle α in its respective half-cycle.
Concept / Approach:
With a highly inductive load, current does not fall to zero quickly. In a full-wave controlled rectifier, each thyristor conducts for approximately π radians because the inductor maintains current flow into the next half-cycle until the complementary device naturally commutates the current. Thus, the conduction interval becomes independent of α (for continuous current conditions) and equals π radians per device.
Step-by-Step Solution:
Assume continuous current due to large L.When a thyristor is triggered at α, the inductor forces current to continue through it until the line voltage reverses and the complementary thyristor can take over.This results in a conduction span of π radians for each device in steady state.Therefore, conduction period per thyristor = π radians.
Verification / Alternative check:
In the discontinuous current case (small L), the conduction angle could shrink; however, the question specifies a highly inductive load, implying continuous conduction, validating π radians.
Why Other Options Are Wrong:
π − α, π − 2α: These apply to discontinuous or different conditions, not highly inductive continuous current operation.π + α: Exceeds half-cycle; not correct for standard continuous conduction in a single-phase full-wave rectifier.α: This is merely the delay angle, not the conduction interval.
Common Pitfalls:
Confusing firing delay angle α with conduction duration; ignoring the role of inductance in sustaining current.
Final Answer:
π radians
Discussion & Comments