| 摘要 |
<p>A motor driven valve control circuit includes an electronic switch element (19,13) biased to conduct by a resistor (20) connected by diodes (21,22) to both poles of a switch (23). A relay (10) controlled by pole of the switch determines the direction of connection of the motor (11) in series with the element (19,13). A thyristor (24) connected to shunt the bias current away from the switch element (19,13) is gated by a voltage comparator (30) comparing the voltage across a motor current sensing element (17) 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.</p> |
