Determine the control mode of the electric actuator according to the production process control requirements
1.Switch type (open-loop control)
generally achieve the valve on or off control, the valve is either in a fully open position, or in a full-off position, such valves do not need to accurately control the media flow. In particular, it is worth mentioning that the switch type electric actuator can be divided into split structure and integrated structure because of the different structure form.This must be explained when selecting, otherwise it will often occur in the field installation and control system conflicts, such as the mismatch of the present image.
A) split structure (commonly referred to as ordinary type): the control unit and the electric actuator separation, the electric actuator can not achieve the control of the valve alone, the need for additional control unit to achieve control, the general external use of the controller or control cabinet form for matching.The disadvantage of this structure is that it is not convenient for the overall installation of the system, increase wiring and installation costs, and prone to failure, when the failure occurs is not easy to diagnose and repair, the price is not ideal.
b) Integrated structure (often referred to as integral type): the control unit and the electric actuator package into one, without the need for the external control unit can be realistic in-place operation, remote only need to output the relevant control information can be operated on it. The advantage of this structure is that it facilitates the overall installation of the system, reduces wiring and installation costs, and makes it easy to diagnose and troubleshoot.
But the traditional integrated structure of the product also has a lot of imperfections, so the emergence of intelligent electric actuator.
2.Modulating type (closed-loop control)
Not only has the function of switched-type integrated structure, but also can control the valve precisely and adjust the dielectric flow.
A) control signal type (current, voltage), adjustable electric actuator control signal generally has current signal (4~20Ma, 0~10Ma) or voltage signal (0~5V, 1~5V), selection needs to clarify its control signal type and parameters.
b) Working form (electric open type, electric type), adjustable electric actuator Working mode is generally electric open type (taking 4~20Ma control as an example, the electric opening type refers to the 4mA signal corresponding to the valve off, 20mA corresponds to the valve opening), the other is the electric shutdown (with the control of 4-20mA as an example,The electric opening type refers to the 4mA signal corresponding to the valve opening, 20mA corresponds to the valve off).
c) Loss of signal protection, loss of signal protection refers to the loss of control signal due to line and other faults, the electric actuator will control the valve opening and closing to the set protection value, the common protection value is fully open, full off, maintain in situ three cases.