Basic knowledge of explosion-proof electric actuators
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2018-12-13
With the rapid development of microelectronics, computers, communication network technology, and mechatronics integration technology, intelligent electric actuators have emerged. It is a new type of intelligent terminal execution component with a microprocessor. From then on, intelligence has become the overall trend of actuator development, and it is necessary to understand the development status of intelligent electric actuators as soon as possible.
1、 Intelligent electric actuator and its characteristics In recent years, electric actuators have achieved rapid development, and some domestic and foreign manufacturers have successively launched intelligent electric actuators with fieldbus communication protocols. The new intelligent electric actuator utilizes microcomputer and fieldbus communication technology to integrate the servo amplifier and actuator. It not only achieves various control technology requirements such as bidirectional communication, PID adjustment, online automatic calibration, self correction and self diagnosis, but also adds functions such as stroke protection, over torque protection, motor overheat protection, power outage signal protection, output on-site valve position indication and fault alarm. It can be operated on-site or remotely, achieving undisturbed switching between manual operation and manual/automatic operation.
The intelligent electric actuator adopts novel structural components. The servo amplifier adopts a microprocessor system, and all control functions can be achieved through editing. It also has a digital communication interface, which enables the HART protocol or fieldbus communication function, becoming a node in the fieldbus control system. Some servo amplifiers also use frequency converter technology to more effectively control the action of servo motors. The reducer adopts a novel transmission structure, with smooth operation, high transmission efficiency, no crawling, and low friction. The position transmitter adopts new technologies and methods, some of which use Hall effect sensor to directly sense the longitudinal or rotary movement of the valve stem, realizing non-contact positioning detection; Some use special Potentiometer, and Potentiometer are equipped with ball bearings and resistance sheets made of special conductive materials; Some use non-contact rotary angle sensors with Magnetoresistance effect.
Intelligent electric actuators usually have LCD displays and manual operation buttons, which are used to display various status information, input configuration data, and perform manual operations.
Compared with traditional electric actuators, intelligent electric actuators mainly have the following characteristics.
(1) The main parameters and technical indicators are advanced, such as working dead zone, basic error, backlash and other indicators have reached or approached the Vanguard International Semiconductor Corporation level, exceeding the existing DDZ-II and III electric actuators in China. (2) Adopting advanced microcomputer and digital display technology, intelligent servo amplifiers are used to replace traditional servo amplifiers, and digital operators are used to replace the original analog pointer operators, solving the problem of eye fatigue caused by frequent jumping of digital displays. (3) Strong functionality, easy to use, with functions such as self diagnosis, self adjustment, and PI adjustment. Especially, the PI adjustment function eliminates the need for a front-end regulator and directly accepts transmitter signals. (4) Added software correction for traffic characteristics. After using a microprocessor, the flow characteristics can be flexibly set and changed to improve the control performance of the regulating valve. This allows a regulating valve with inherent characteristics to have multiple output characteristics, and valves that cannot be corrected for valve core shape (butterfly valves) can also change the flow characteristics. This function can correct non-standard characteristics to standard characteristics, and will change the current situation of correcting flow characteristics through valve core processing for a long time. (5) The electric braking and intermittent adjustment technology are used in the adjustment, and the mechanical friction brake can be canceled for the actuator with self-locking function, which improves the reliability of the whole machine. (6) The design of three-phase amplifier adopts a combined scheme with single-phase intelligent servo amplifier and three-phase power converter, which facilitates production and material preparation and makes it possible to control the control room without three-phase power supply.
2、 The Development Trend of Intelligent Electric actuators In summary, the development trend of intelligent electric actuators can be summarized as follows: mechatronics integration structure gradually replaces combination structure, intelligent control technology gradually replaces pure electronic control technology, communication technology function gradually replaces non communication technology, digital control method gradually replaces traditional analog control method, non-contact debugging technology using infrared remote control gradually replaces contact manual debugging technology, and so on.
When the intelligent electric actuator is connected to the fieldbus, it becomes a field instrument in the fieldbus control system (F). At this time, it not only has actuator functions, but also functions such as control, computation, and communication. It can be seen that the new generation of intelligent electric actuator products that comply with the field bus in China is an inevitable trend for the future development of actuators. Its successful research and application have laid a good foundation for the further development of electric actuators and will bring broad market development prospects to intelligent electric actuators.
