Load Commutation Mode in Single-Phase Full Bridge Inverter

Load commutation mode is a technique used in single-phase full bridge inverters to achieve energy transfer from DC to AC in a load. In this mode, the load current is commutated to a different load branch by turning off the thyristor in the original load branch. The single-phase full bridge inverter can operate in load-commutation mode only if the load is RLC underdamped.

RLC Underdamped Load

An RLC circuit consists of a resistor (R), an inductor (L), and a capacitor (C). The RLC circuit can be critically damped, overdamped, or underdamped based on the values of R, L, and C. In an underdamped RLC circuit, the energy stored in the inductor and capacitor oscillates between the two components, resulting in an oscillatory response.

Single-Phase Full Bridge Inverter

A single-phase full bridge inverter converts DC to AC by switching the DC voltage across the load in a controlled manner. The load is connected between two AC output terminals of the inverter. The inverter consists of four thyristors, two on the positive side and two on the negative side of the DC supply.

Load Commutation Mode in Single-Phase Full Bridge Inverter with RLC Underdamped Load

In a single-phase full bridge inverter, load commutation mode can be achieved only if the load is RLC underdamped. In this case, the load current oscillates between two branches of the load circuit, and the inverter can control the energy transfer by turning off one thyristor and turning on the other thyristor in the other branch.

Conclusion

Therefore, the single-phase full bridge inverter can operate in load commutation mode only if the load is RLC underdamped, and the load current can be commutated between two branches of the load circuit.