I. Trip types and applicable scenarios 

 According to the movement form, the electric actuator can be divided into straight stroke, angular stroke and multi-turn type. Its stroke characteristics and applicable scenarios are as follows: 

 1. Straight stroke (type B) 

 Stroke range: linear displacement, usually a push-pull structure, and the stroke length is customized according to the valve type (for example, the gate valve stroke can reach dozens of centimeters). 

 Applicable scenarios: When the linear position needs to be controlled, such as the flow adjustment of the regulating valve and the globe valve. 

 Typical applications: flow control valves in chemical production, welding line material transportation in the automotive industry. 

 2. Angle stroke (Q-type) 

 Stroke range: rotate around the axis, the output torque range is 0-500N·m, and the common angle is 0°-90° (partial rotation) or more than 360° (multi-turn). 

 Applicable scenarios: occasions where the rotation angle is required, such as the control of ball valve, butterfly valve and shutter valve. 

 Typical application: the valve adjustment of the HVAC system and the rotation operation of the robotic arm. 

 3. Multi-turn type (Z-type) 

 Stroke range: It needs to run more than 360° to open and close the valve, which is suitable for high torque and large stroke scenarios. 

 Applicable scenarios: opening and closing of gate valves, plug valves and diaphragm valves. 

 Typical applications: oilfield wellhead control and truncation operation of large pipelines. 

II. Core control mode 

 The control mode of the electric actuator directly affects its accuracy, response speed and applicable scenarios, and is mainly divided into the following four categories: 

 1. Analog control (4-20mA/0-10V) 

 Principle: Receive 4-20mA analog signal, corresponding to 0%-100% valve opening, to achieve continuous adjustment. 

 Advantages: High adjustment accuracy (±0.5% FS), strong compatibility, and seamless docking with DCS, PLC and other systems. 

 Application scenarios: chemical reactor feed adjustment, boiler water level control and other occasions where accurate flow or pressure control is required. 

 ** Case: A chemical enterprise controls the regulating valve through a 4-20mA signal to achieve a material flow error of ≤ 0.5%. 

 2. Switching control (acive/passive) 

 Active control: The actuator requires external power supply (such as 24VDC) to drive the switch signal, which is suitable for PLC direct control. 

 Passible control: controlled by dry contact (relay contact), no additional power supply, suitable for simple start-stop scenarios. 

 Application scenarios: two-type valves such as fire protection system and emergency cut-off valve (full on/full off). 

 Case: The fire pipe valve is controlled by a passive dry contact to automatically close in case of fire. 

 3. Bus protocol control (Modbus/Profibus/HART) 

 Principle: Digital communication protocol is adopted to support remote parameter setting, condition monitoring and fault diagnosis. 

 Advantages: It supports multi-device networking, is suitable for intelligent factories, Internet of Things (IIoT) systems, and can read torque, temperature and other data in real time. 

 Application scenarios: power plants, sewage treatment plants and other occasions where a large number of actuators need to be centrally managed. 

 Case: A power plant connects 200 electric actuators through the Profibus bus to achieve remote monitoring and fault warning. 

 4. Pulse signal control 

 Principle: The displacement of the actuator is controlled by inputting the pulse signal, and the number, frequency and width of the pulse determine the position, speed and acceleration. 

 Advantages: high-precision positioning and fast response. 

 Application scenarios: feed system of CNC machine tools, robot joint control. 

 Case: The CNC machine tool controls the movement of the workbench through the pulse signal to achieve a machining accuracy of ±0.01mm. 

 III. Intelligent function and protection mechanism 

 Modern electric actuators integrate a variety of intelligent functions to improve the reliability and security of the system: 

 1. Torque protection: monitor the motor load in real time, and automatically shut down when the torque exceeds the set threshold to prevent the valve from getting stuck or the actuator from being damaged. 

 2. Limit protection: 

 Mechanical limit: prevent overpass through physical blocks to ensure that the valve is completely closed or opened. 

 Electronic limit: accurately locate through encoders or potentiometers to avoid mechanical wear. 

 3. Automatic phase sequence correction: identify the phase sequence of the three-phase power supply without manually adjusting the wiring to avoid valve damage caused by motor reversal. 

 4. Delayed execution: automatic delay of 0.5-3 seconds when receiving the reverse operation instruction, reducing mechanical impact and protecting the gearbox and valve stem. 

 5. Power supply monitoring: voltage + current dual detection mechanism is adopted to monitor the power supply status in real time to prevent the lack of phase from burning the motor. 

 IV. Key points of selection and maintenance 

 1. Selection principles: 

 Match the stroke type according to the valve type (for example, choose Z type for gate valve and Q type for butterfly valve). 

 Calculate the required torque (formula: T=K×Q×ΔP/D², K is the safety factor 1.2-1.5). 

 Consider the environmental protection level (IP68 for wet environments and ExdIIBT4 for explosion-proof areas). 

 2. Maintenance specifications: 

 Daily inspection: clean appearance and tight wiring. 

 Weekly inspection: grease supplement (molybdenum disulfide lithium base grease). 

 Quarterly inspection: position calibration (using laser alignment instrument). 

 Annual inspection: bearing replacement, gearbox inspection.