Three-phase bridge inverter operating modes The two standard conduction modes of a three-phase bridge inverter are commonly referred to as:

Introduction / Context:
Three-phase bridge inverters can be operated with different device conduction intervals to shape line-to-line voltages and control harmonic content. Two standard patterns are widely taught and applied in motor drives and power conversion: the 120° and 180° conduction modes.

Given Data / Assumptions:

• Six-switch (six-pulse) three-phase bridge inverter.
• Ideal switches, balanced DC link and loads assumed for conceptual explanation.
• Focus on conduction intervals per device per electrical cycle.

Concept / Approach:

In 180° mode, each device conducts for 180° electrical; three devices conduct at any instant (one per leg), creating quasi-square three-phase line voltages. In 120° mode, each device conducts for 120°; only two devices conduct at any instant, producing a different line voltage pattern and harmonic spectrum, often with reduced switching losses in certain applications.

Step-by-Step Solution:

Verification / Alternative check:

Drive handbooks and power-electronics texts tabulate device conduction tables for both 120° and 180° modes and compare resulting phase and line voltages and dominant harmonics.

Why Other Options Are Wrong:

Pairs including 60°, 90°, or 240° do not represent standard full-bridge three-phase conduction modes.

Common Pitfalls:

Confusing the number of conducting devices: 180° mode has three devices on; 120° mode has two devices on at a time.

Final Answer:

120° mode and 180° mode