| 摘要 |
A motor driven valve control circuit includes an electronic switch element biased to conduct by a resistor connected by diodes to both poles of a switch. A relay controlled by one pole of the switch determines the direction of connection of the motor in series with the element. A thyristor connected to shunt the bias current away from the switch element is gated by a voltage comparator comparing the voltage across a motor current sensing element with a reference voltage, so as to fire the thyristor when the motor current exceeds a set limit. The circuit eliminates the need for latching limit switches usually employed in motor driven valve controls.
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