120 degrees and 180 degrees Conduction Mode for controlling three phase inverter

Three-phase inverters are commonly used in high power applications and they can be controlled using different conduction modes. The two most common conduction modes are 120-degree mode and 180-degree mode.

1. 120-Degree Conduction Mode: In the 120-degree conduction mode, each switch conducts for 120 degrees. During each 60-degree interval, two switches in the upper half and one switch in the lower half are turned on. This mode is also known as six-step mode or 120-degree mode. The advantage of this mode is that it is simple and easy to implement. However, the output waveform is not sinusoidal and contains harmonics.

2. 180-Degree Conduction Mode: In the 180-degree conduction mode, each switch conducts for 180 degrees. During each 60-degree interval, three switches in the upper half and one switch in the lower half are turned on. This mode is also known as sinusoidal PWM mode or 180-degree mode. The advantage of this mode is that it produces a nearly sinusoidal output waveform with less harmonics. However, it requires more complex control circuitry.

In summary, the choice between 120-degree and 180-degree conduction mode depends on the specific requirements of the application. The 120-degree mode is simpler but produces more harmonics, while the 180-degree mode produces a cleaner output waveform but requires more complex control.