A brief introduction to the characteristics and principles of the electric valve control mechanism
1. On-off type (open-loop control) On-off type electric actuators generally realize the opening or closing control of the valve. The valve is either in the fully open position or in the fully closed position. Such valves do not need to accurately control the flow of the medium. It is particularly worth mentioning that the switch-type electric actuator can be divided into split structure and integrated structure due to different structural forms. This must be explained when selecting models, otherwise there will often be mismatches such as conflicts with the control system during on-site installation. 1-1. Split structure (usually called ordinary type): the control unit is separated from the electric actuator, and the electric actuator cannot control the valve alone, and an external control unit is required to realize the control. Generally, a controller or a control cabinet is used externally. form matching. The disadvantage of this structure is that it is inconvenient for the overall installation of the system, increases wiring and installation costs, and is prone to failures. 1-2. Integrated structure (usually called integral type): the control unit and the electric actuator are packaged into one body, which can be operated on the spot without external control unit, and can be operated remotely only by outputting relevant control information . The advantage of this structure is that it is convenient for the overall installation of the system, reduces wiring and installation costs, and is easy to diagnose and troubleshoot. However, the traditional integrated structure products also have many imperfections, so intelligent electric actuators have been produced. 2. Adjustment type (closed-loop control) The adjustment type electric actuator not only has the function of a switch-type integrated structure, but it can also precisely control the valve, so as to precisely adjust the flow of the medium. 2-1. Type of control signal (current, voltage) The control signal of regulated electric actuator generally has current signal (4~20mA, 0~10mA) or voltage signal (0~5V, 1~5V), which needs to be clearly selected when selecting the type. Its control signal type and parameters. 2-2. Working form (electric open type, electric close type) The working mode of the regulating electric actuator is generally the electric open type (taking the control of 4-20mA as an example, the electric open type means that the 4mA signal corresponds to the valve closing, 20mA corresponds to the valve opening), and the other is the electric close type (taking 4-20mA control as an example, the electric open type means that the 4mA signal corresponds to the valve open, and 0mA corresponds to the valve close). In general, the selection requires a clear working form. 2-3. Loss of signal protection Loss of signal protection means that when the control signal is lost due to line failures, the electric actuator will control the valve to open and close to the set protection value. The common protection values u200bu200bare fully open, fully closed, and keep the original value. There are three cases, and it is not easy to modify after leaving the factory.