The power circuit diagram for a four-quadrant chopper is shown in Fig.1.a. It consist of four semiconductor switches $\mathrm{CH} 1$ to $\mathrm{CH} 4$ and four diodes $\mathrm{D} 1$ to $\mathrm{D} 4$ in antiparallel. Working of this chopper in the four quadrants is explained as under,

First quadrant: For first-quadrant operation …