Whats the control model of electric valve actuators?
1. ON/OFF type electric motor operated valve actuator (open loop control)
The ON/OFF type actuator only control the valve either 100% open or 100% close, for valves which do not need to accurately control the medium flow. In addition,due to the different structural forms, the ON/OFF type actuator also have 2 types: one is split structure and another is integrated structure, . This must be explained clearlt when selecting actuators, otherwise the actuator will conflicts with the control system during field installations.
Split structure,which usually called ordinary type: The electric actuator cannot control the valve alone,because the control unit is separated from the actuator. Controller or control cabinet must be added to achieve valve control.
Integrated structure,which usually called integral type: The actuator intergrated the control unit and actuator body, with the output control signal remotely, the actuator valve can operated on the spot without external control unit.
But this structure also have many disadvatages, so intelligent electric valve actuators have been produced.
2. Modulating type electric motor operated valve actuator (closed loop control)
type electric motor operated valve actuator not only has the function of a ON/OFF-type integrated structure, it can also precisely control the valve, so as to adjust the medium flow precisely.
Control signal types (current or voltage signal). The control signals are generally current signals (4-20mA input, or 0-10mA input ) or voltage signals (0-5V input or 1-5V input).
The type and parameters of the input control signals must be specified when selecting actuator valves.
Modulating signal loss protection means that when the control signal is lost due to a fault such as a line, the electric valve actuator will open or close the control valve to a set protection value. The common protection values are fully open, fully closed, and maintained in a certain position.
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