Views: 266 Author: Site Editor Publish Time: 2021-05-27 Origin: Site
There are two types of electric actuators, generally divided into part turn electric valve actuator and multi turn electric valve actuator.
The former mainly controls valves that require partial rotation, such as actuated ball valve, PVC shut off valve and automatic butterfly valve, etc., while the latter requires valves with multiple rotations, such as plug gate valves.
With the rapid development of microelectronics, computers, communication network technology and mechatronics technology, after the 1990s, intelligent electric actuators appeared in the world. It is a new type of intelligent terminal actuator with microprocessor. Since then, intelligence has formed the general trend of actuator development, and it is very necessary to understand the development status of intelligent electric actuators as soon as possible.
In recent years, electric rotary actuator and electric rod actuator have achieved rapid development. Some domestic and foreign manufacturers have successively introduced intelligent electric actuators with fieldbus communication protocols. The new intelligent electric actuator uses microcomputer and fieldbus communication technology to integrate the servo amplifier and the actuator. This move not only realizes the functions required by multiple control technologies such as two-way communication, PID adjustment, online automatic calibration, self-correction and self-diagnosis, etc, but also adds functions such as stroke protection, over-torque protection, motor overheating protection, power-off signal protection, output on-site valve position indication and fault alarm. It can perform on-site operation or remote operation, complete manual operation and switch between manual and automatic without disturbance.
The intelligent electric actuator adopts novel structural components. A microprocessor system is used in the servo amplifier. All control functions can be realized by editing, and it also has a digital communication interface, which has the HART protocol or fieldbus communication function, and becomes a node in the fieldbus control system. In some servo amplifiers, inverter technology is also used, which can more effectively control the action of the servo motor. The reducer adopts a novel transmission structure, stable operation, high transmission efficiency, no crawling, and low friction. The position transmitter adopts new technology and new method, and some adopts Hall effect sensor, which directly senses the longitudinal or rotational movement of the valve stem, realizing non-contact positioning detection. Some use special potentiometers, which are equipped with ball bearings and resistor sheets made of special conductive materials. Some non-contact rotation angle sensors using magnetoresistive effect.
Intelligent electric actuators usually have liquid crystal displays and manual operation buttons, which are used to display various status information and input configuration data and manual operations.
Compared with traditional electric actuators, smart electric actuators mainly have the following characteristics.
The main parameters and technical indicators are advanced, such as working dead zone, basic error, return difference and other indicators have reached or approached the world's advanced level.
It adopts advanced microcomputer and digital display technology, replaces traditional servo amplifiers with intelligent servo amplifiers, and replaces the original analog pointer operators with digital operators, which solves the problem of eye fatigue caused by frequent digital display beating.
Its function is strong, easy to use, with self-diagnosis, self-adjustment and PI adjustment functions, especially the PI adjustment function can save the previous stage regulator, directly accept the transmitter signal.
Added software revision of flow characteristics. After adopting the microprocessor, it can flexibly set and change the flow characteristics and improve the control performance of the regulating valve. A control valve with inherent characteristics can have multiple output characteristics. It is possible to change the flow characteristics of valves that cannot be corrected for the spool shape (butterfly valve). It is possible to correct non-standard features to standard features. This function will change the long-term status quo of correcting flow characteristics by spool processing.
Electric brake and intermittent adjustment technology are used in the adjustment, and the mechanical friction brake can be cancelled for the actuator with self-locking function, which improves the reliability of the whole machine.
The design of the three-phase amplifier adopts the combined scheme of a single-phase intelligent servo amplifier with an external three-phase power converter, which facilitates production and material preparation, and provides the possibility for the control room without three-phase power supply.
