Three-phase AC voltage monitoring circuit - checks deviations from amplitude tolerance limits and generates DC voltage

摘要

The circuit generate a d.c. voltage compared with a six-pulse rectified three-phase a.c. voltage. The reference voltage is a pulsating d.c. voltage whose peak values lie within the tolerance limits of the six-phase rectified a.c. voltage, and shape sufficiently simulates it. It is generated by the circuit from a constant d.c. voltage and a superposed trapezoidal pulsating d.c. voltage. The circuit arrangement comprises a transformer with a primary coil (31R, 31S, 31T) between one of the phase lines and neutral (mp) and the secondary connected with a bridge circuit which has a resistor (33) connected across the diagonal of the bridge. Each diagonal has also a diode (34), and a Zener diode (35) is in the common line connection to the three bridge lines.