Voltage monitoring circuit for three=phase network - has rectifier bridge whose positive and negative DC output voltages and compared with threshold values with result being combined and pulse blocked

摘要

The circuit monitors the d.c. voltage of a rectifier bridge (16) for a fall below a defined threshold value. The 3-pulse d.c. voltages occurring at the positive (17) and negative (18) bridge outputs w.r.t. the secondary star point (6) are fed to threshold switches (21, 22) with positive and negative thresholds respectively. The outputs of the two threshold switches are combined and connected to a pulse blocking stage. Resistors (27-29) inserted in each bridge supply line form potential dividers cyclically and alternately with resistors (19, 20) connected between the bridge d.c. outputs and the secondary star point. USE/ADVANTAGE - For voltage monitoring of three-phase networks with real or synthetic midpoints. Maximum dead time between occurrence of fault and indication is reduced.