Conduction count in a 3-phase bridge inverter (180° mode) In the 180° conduction mode of a three-phase bridge inverter, the statement “two thyristors conduct at one time” is:

Introduction / Context:
Three-phase bridge inverters can be operated in different conduction modes. Recognizing how many devices conduct simultaneously helps derive phase and line voltages and understand current paths and device stresses.

Given Data / Assumptions:

• Six-switch bridge (upper and lower switches in three legs).
• Ideal commutation with 180° conduction per device.

Concept / Approach:

In 180° mode, each device conducts for 180° electrical. At any instant, exactly three devices conduct: one from each leg (two from the top group and one from the bottom, or vice versa), establishing a three-phase set of line voltages. In contrast, in 120° mode only two devices conduct at a time, with the third phase open, altering the waveform set and harmonic content.

Step-by-Step Solution:

Verification / Alternative check:

Standard inverter sequence diagrams show a six-step pattern with three devices on at each step, producing six line-voltage levels per cycle.

Why Other Options Are Wrong:

Options implying conditional truth confuse with the 120° mode or PWM nuances; the base 180° conduction definition remains three devices conducting at once.

Common Pitfalls:

Mixing up 120° and 180° modes; forgetting that device conduction counts are independent of load connection (star/delta) for the ideal model.

Final Answer:

False