| 摘要 |
<p>PROBLEM TO BE SOLVED: To maintain opened and closed states of contacts, which are inserted between a commercial power supply and a load, and are driven with a control power supply, the same as before the control power supply is failed, even if the control power supply is failed. SOLUTION: A serial contact circuit 11 is constituted by serially connecting a first contact 12 driven by the control power supply 18, which supplies power for control to an unterruptible power supply device and is normally closed with a second contact 13, which is normally opened by an electromagnetic relay. The serial contact circuit 11 is inserted between the commercial power supply 1 and the load 10, and the load 10 is connected with a backup power supply 9 in parallel. A changeover contact 14 which selects the load side of the serial contact circuit 11 when the output of the control power supply 18 is nil, and selects the commercial power supply side of the serial contact circuit 11 when driven by the control power supply 18, and a serial connected circuit of a diode 15 and a capacitor 17, which is inserted between the changeover contact 14 and the other end of the commercial power supply 1, are inserted; and the a coil 16 of the electromagnetic relay is connected with the capacitor 17 in parallel.</p> |
