| 摘要 |
A solenoid control circuit is disclosed for providing the initial pull-in power to a magnetically-held solenoid and thereafter providing a release-pulse upon power loss to the circuit to release the solenoid. The solenoid control circuit has an AC input which is converted to a DC power supply. Power is supplied to an energy storage device after an initial time delay. After the time delay, the magnetic solenoid is tripped to its hold-in position. After being tripped, the magnetic solenoid is held in its hold-in position by the magnetic properties of the solenoid. Upon power interruption to the circuit, the solenoid is held in its tripped position for a desired period of time. After the time delay has expired, the energy storage device is discharged in an opposite direction through the magnetic solenoid, such that the magnetic solenoid is returned to its extended position. The circuit is employed in a biased modulating valve application to control operation of a solenoid which governs engagement and disengagement of a drop-out gear assembly in the valve drive system, to disengage the valve drive system when power is interrupted for a period of time exceeding the time delay.
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