The control mode of the electric actuator is determined according to the control requirements of production process.
(Open-loop control) Switch-type electric actuators generally control the opening or closing of the forged valve. The forged valve is either in the fully open position or in the fully closed position. Such forged valves do not require precise control of the medium flow. It is particularly worth mentioning that switch-type electric actuators can be divided into separable structures and integrated structures due to different structural forms. This must be explained when selecting the type, otherwise mismatching will often occur in the field installation such as control system conflicts.
1. Separable structure (commonly referred to as common type): The control unit is separated from the electric actuator. The electric actuator cannot realize the control of the forged valve by itself. It is necessary to add the control unit to realize the control. Generally, the external device is equipped with a controller or a control cabinet. The disadvantage of this structure is that it is not easy to install the whole system, increases wiring and installation costs, and is prone to malfunction. When the fault occurs, it is not easy to diagnose and repair, and the cost performance is not satisfactory.
2. Integrated structure (commonly referred to as the integral type): The control unit is integrated with the electric actuator, which can be operated locally without external control unit. The remote control can be operated only by outputting relevant control information. The advantage of this structure is that it facilitates 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 the intelligent electric actuators are produced.
(Closed-loop control) The regulating electric actuator not only has the function of a switch-type integrated structure, but also precisely controls the forged valve to regulate the medium flow.
First, the types of control signal (electric current, voltage). The control signals of regulating type electric actuator generally involve current signal (4~20mA, 0~10mA) and voltage signal (0~5V, 1~5V). The type and parameter of the control signal must be specified when selecting the type.
Second, the operation modes (electric opening type, electric closing type). The working mode of the regulating electric actuator is generally electric opening type (taking 4~20mA control as an example, the electric opening type means that the 4mA signal corresponds to the forged valve closing, the 20mA corresponds to the forged valve opening), and the other is the electric closing type. (for 4~20mA control, the electric closing type means that the 4mA signal corresponds to the forged valve opening, and the 20mA corresponds to the forged valve closing)
Third, signal loss protection. Signal loss protection means that the electric actuator will control the forged valve to open and close to the set protection value when the control signal is lost due to faults such as line fault. The common protection values are full open, full off, and in-situ.
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