Silicon rectifier overvoltage protection - incorporates two mutually coupled air cored coils as inductors

摘要

A circuit to protect silicon rectifiers against harmonic overvoltages superimposed on the supply employs cancellation of the voltage spike instead of a bypassing arrangement. The required result is achieved by putting an air cored choke (1) in series with each a.c. supply line to the rectifier (4). These chokes are closely coupled magnetically but electrically isolated from each other. A suitably rated capacitor (2) is connected across the a.c. lines on the rectifier side of the chokes. Non-linear resistors (3) or similar devices may still be used to limit slower rising peaks. The circuit also prevents the feed back of commutation spikes into the supply system.