Assertion–Reason on inverter commutation and operating modes Assertion (A): The McMurray–Bedford half-bridge inverter uses complementary commutation. Reason (R): A three-phase inverter can have two modes of operation.

Introduction / Context:
Assertion–Reason questions test conceptual links. The McMurray–Bedford inverter family uses auxiliary components for forced commutation, and three-phase inverters can operate in different conduction modes (e.g., 120° and 180°). We must judge correctness and explanatory linkage.

Given Data / Assumptions:

• McMurray–Bedford half-bridge: a classic forced-commutated thyristor inverter.
• Three-phase inverter modes: 120° (two devices on) and 180° (three devices on).

Concept / Approach:

Assertion: True. The McMurray–Bedford topology employs complementary (auxiliary) commutation where charged capacitors and coupling inductors transfer current and reverse-bias a conducting SCR to turn it off. Reason: True. Three-phase inverters indeed have different conduction schemes (operating modes). However, the reason does not logically explain why the McMurray–Bedford inverter uses complementary commutation; they are separate facts.

Step-by-Step Solution:

Verification / Alternative check:

Topology descriptions and timing diagrams show auxiliary commutation pairs in McMurray–Bedford and separate discussion for 120° vs 180° conduction in bridge inverters.

Why Other Options Are Wrong:

Options claiming wrong statements or causal linkage are inconsistent with standard inverter theory.

Common Pitfalls:

Assuming any true statement about inverters automatically explains another; causality must be explicit.

Final Answer:

Both A and R correct but R is not correct explanation of A