**Single Phase Dual Converter – Circuit Diagram and Four Quadrant of Operation:**

We have seen that Single Phase Dual Converter with inductive loads allow only a two-quadrant operation. If two of these full converters are connected back to back, as depicted in Fig. 27.20 (a) , both the output voltage and the load current flow can be reversed. This system provides a four-quadrant operation as shown in Fig. 27.20 (b) and is called a **dual converter**. Dual converters are normally used in high-power variable speed drives. If α_{1} and α_{2} are the delay angles of converters 1 and 2 respectively, the average output voltages are V_{dc1} and V_{dc2}.

The delay angles are controlled such that one converter operates as a rectifier and the other operates as an inverter; but both converters generate the same output voltage.

The average output voltage of converter 1 is given by

The firing angle α_{2} of converter 2 will be equal to (π – α_{1}) and when converter 2 is operating as an inverter