| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a voltage drop detecting circuit for three-phase line capable of quickly, surely, and highly accurately detecting a sign of an instantaneous drop and instantaneous stopping of system voltage. <P>SOLUTION: This voltage drop detecting circuit 1 for three-phase line which detects a voltage drop in three-phase system voltage, has first full-wave rectification means 12u, 12v, and 12w for rectifying a full wave on respective-phase voltages on the basis of the three-phase system voltage, a three-phase reference sine wave generating circuit 13 for generating a three-phase reference sine wave synchronized with the three-phase system voltage, second full-wave rectification means 14u, 14v, and 14w for rectifying a full wave on a reference sine wave of respective phases from the three-phase reference sine wave generating circuit 13, waveform comparing means 15u, 15v, 15w, 16u, 16v, and 16w for detecting a voltage drop in the respective phases on the basis of a comparison of a full-wave rectification waveform of mutual corresponding phases in the first full-wave rectification means and the second full-wave rectification means, and a logical circuit 4 for outputting a voltage drop detecting signal of the three-phase system voltage on the basis of the output of the waveform comparing means. <P>COPYRIGHT: (C)2004,JPO |
