Single-phase fully controlled bridge with source inductance During the commutation (overlap) interval caused by source inductance, the instantaneous output voltage of the rectifier equals:

Introduction / Context:
Source inductance in line-commutated rectifiers creates commutation overlap, during which outgoing and incoming thyristor pairs conduct simultaneously. Understanding the effect on output voltage is important for predicting performance, especially at high load current and low firing angles.

Given Data / Assumptions:

• Single-phase fully controlled bridge (four SCRs).
• Finite source inductance causing overlap.
• Ideal devices aside from commutation overlap.

Concept / Approach:

During overlap, both thyristor pairs are on. The AC source effectively short-circuits through the two conducting legs, and the instantaneous output voltage becomes the difference of the two phase voltages applied by each leg. In a single-phase bridge, these two are equal and opposite in sign at the commutation instant, yielding a net of approximately zero at the DC terminals during the overlap interval.

Step-by-Step Solution:

Verification / Alternative check:

Classical expressions show v_o is reduced by overlap such that the average output voltage V_dc is decreased by a term proportional to overlap angle and source inductance; instantaneously, v_o ≈ 0 while both pairs share current.

Why Other Options Are Wrong:

Options (a), (b), and (e) assume single-pair conduction. Option (d) is not the correct instantaneous relation for a full bridge during overlap.

Common Pitfalls:

Confusing average voltage reduction over a cycle with instantaneous voltage during the overlap interval; mixing half-controlled and full-controlled behavior.

Final Answer:

Zero