Electric valve is mainly used for liquid, gas and air flow of the wind system. Electric valve structure is divided into two parts, the upper half of the electric actuator, the lower part of the valve.
Operation with an electric actuator control valve action, to achieve the valve open and close, so as to achieve the medium in the tube switch or the purpose of regulation. The electric actuator of the electric valve is generally composed of three phase asynchronous motor, gear reduction box, torque limiting mechanism, manual automatic switching mechanism, opening indicator and electrical component. Valve motor power is generally 0.37 ~ 5.5kW.
In order to ensure the safety and reliability of the electric valve switch, for overload protection requirements are strict, often used in the protection of electrical and mechanical two. Protection by using DL type current relay for overload protection. Mechanical protection using torque limiting mechanism for overload protection.
1. Control requirements
Electric control valve requirements: press the button to open the valve, the valve opens, press off valve button, the valve closed. When the valve is fully open or fully closed, the stroke control mechanism to automatically cut off the AC contactor control circuit, and connect the valve fully open or fully closed signal lamp. Circuit in the process of opening or closing blocked stuck in the overload occurs, the use of DL type current relay protection. There is an electric interlocking between the open and close contactor.
In addition, the control circuit is provided with a mechanical bidirectional over torque protection and a valve opening degree measuring device.
2. Working principle
Switch on the power, the power indicator light.
Press the button to open the valve, the AC contactor coil is energized, the main contact is closed, the motor is transferred, the valve is opened, and intermediate relay and time relay is energized, the intermediate relay normally open contacts, normally closed contact latching current relay, prevent the large starting current of the interlock current relay misoperation. Time relay delay time, the time delay contact is disconnected, the middle relay power off, by the blocking current relay normally closed and the AC contactor normally open contact to play the role of self lock. When the valve reaches the fully open state, the pressure limit switch, AC contactor power off, the motor stops, while the valve fully open indicator light.
The button press off valve, AC contactor coil is energized, the main contact is closed, the motor reversing, the valve closed. Intermediate relay and time relay function same as open valve. When the valve reaches the fully closed state, the pressure limiting switch, AC contactor power, the motor stops, the valve is fully closed indicator lights. Note: the time relay of the delay time is generally 3 ~ 5S, such as no time relay, you must extend the time by pressing the button.
