| 摘要 |
PURPOSE:To early detect a malfunction by composing a detector by serially connecting one or more diodes, and employing a signal from the detector as a malfunction signal through a time limiting operation circuit. CONSTITUTION:When an operation command contact 1 is first closed, a current I flows to the operation coil 4 of a keep relay 3, a self-switching contact 6 is reversed to a reset coil 5, a terminal (b) by the keep relay operation. Here, if it remains at a terminal (a) due to its switching malfunction, the current I continuously flows. In this case, the forward voltage drop VF of diodes D1-D4 occurs between the terminals A and B of an excitation monitoring unit 7, a current If flows to the light emitting side of a photodiode PC1 through a resistor R1, and the diode PC1 is operated. A time limiting operation circuit 8 connected to the photodetector side is operated by the operation of the photodiode PC1 after a predetermined time thereby to operate 1 relay driver 9 of next stage, and a contact output is produced between terminals C and D and between terminals E and F. |
