Commutation classes and “two-lead” terminology Which commutation method is commonly referred to as using two leads (two main thyristors commutating each other)?

Introduction / Context:
Textbook thyristor commutation methods are labeled Class A through Class F. The term “two-lead” or “complementary commutation” typically refers to arrangements where two main SCRs aid in commutating each other via a shared commutation network.

Given Data / Assumptions:

• Naming follows standard power electronics literature.
• Focus on single-quadrant choppers/inverters nomenclature.

Concept / Approach:
In Class C (complementary) commutation, two main thyristors are engaged so that turning one on helps reverse-bias and turn the other off. This pairing is the typical basis for the “two-lead” descriptor.

Step-by-Step Solution:
Identify complementary action: each device provides the path to remove charge from the other.Network elements are arranged so conduction of one device assists the forced turn-off of its complement.Therefore, the method aligned with the “two-lead” naming is Class C.

Verification / Alternative check:
Many references list Class C as complementary/two-thyristor commutation used in choppers and inverters.

Why Other Options Are Wrong:

• Class A is load (resonant) commutation.
• Class B is self (resonant-pulse) commutation.
• Class D is auxiliary-pulse commutation; Class E/F are specialized.

Common Pitfalls:

• Mixing “two-lead commutation” with “two-quadrant choppers”; they are related but not identical terms.

Final Answer:
Class C