THREE PHASE INVERTER 180 Degree Mode

3-phase inverter circuit with star connected load.

Three phase inverters are normally used for high power applications. The advantages of a three phase inverter are:
• The frequency of the output voltage waveform depends on the switching rate of the switches and hence can be varied over a wide range.
• The direction of rotation of the motor can be reversed by changing the output phase sequence of the inverter.
• The ac output voltage can be controlled by varying the dc link voltage.
Two types of control signals can be applied to the switches:
• 180° conduction
• 120° conduction
In 180 degree mode each SCR has a duration of 180°. The SCRs of same arm operate in a complementary manner i.e with a time interval of 180° whereas the inverter arms are operated at a 120° phase difference.