The programmable controller has the characteristics of strong anti-interference, easy maintenance and transformation, strong practicability and simple operation. Its application in electrical control makes full use of the important advantages of the programmable controller and effectively improves the accuracy and control efficiency of electrical control. This paper briefly introduces the application characteristics of programmable controller in electrical control, analyses the working flow of programmable controller in electrical control, and expounds the practical application of programmable controller in electrical control.
In recent years, with the rapid development of automation control technology, programmable controllers are becoming more and more mature and widely used in many fields. The application of programmable controller in the field of electrical control greatly meets the requirements of automation and intellectualization of electrical control, and enriches the use function of electrical control system. In the future development process, we should further strengthen the research of programmable controllers and promote the wider application of programmable controllers in electrical control. Electrical control system is also known as secondary control circuit of electrical equipment, which includes a variety of control equipment, locking and self-locking circuit, braking and parking circuit, manual and automatic circuit, signal circuit, protection circuit and power supply circuit, etc. In order to improve the safety and reliability of primary equipment, a variety of auxiliary electrical equipment is set up to achieve electrical control function. Programmable Logic Controller (PLC) is a kind of micro-computer, which is widely used in the industrial field. It mainly consists of communication module, functional module, I/O interface circuit, memory, CPU, power supply and so on. According to the operation requirements of the electric control system, compile the PLC program code, scan the input area of the electric control system in real time according to the control instructions, collect information, and compare with the requirements of the PLC instructions to judge the operation status of the electric control system. In the application of PLC in the electric control system, the system scans in real time according to the control instructions of the PLC program, compares the operation status of the control instructions with that of the electric control system, and executes according to the instructions to realize the logical operation and real-time analysis of the electric control system. According to the data results of the PLC program control instructions, the electrical control system carries out logical operations, and then sends the data results to the output devices to perform the corresponding actions. Usually, the data results are sent to the host computer of the electrical control system, then the data analysis and processing are carried out, thermostatic element and then the host computer of the control system sends execution instructions to different module devices to realize the PLC control.
Switching control is a widely used method of PLC in electrical control, and it is also the most basic control mode of programmable controller. PLC switching control in electrical control can realize sequential control and logical control. It can completely replace electromagnetic relay, and can be applied to one or several devices in electrical control system. It is flexible and convenient to operate. There are many chemical or physical quantities in the operation of electrical control system, such as pressure, speed, temperature, concentration, humidity, etc. Many of them change with the operation of electrical control system. The application of PLC in the electrical control system can simulate the change of parameters, and then use D/A and A/D converters to realize the mutual conversion of digital and analog values [4], realize real-time tracking and recording, and effectively monitor the operation status of the entire electrical control system. The application of PLC in electric control can realize the centralized control design. It uses a complete monitoring system to automatically monitor the computers and various electrical equipment in the electric control system to realize the centralized management control.
In the electrical control system, the PLC unified configuration monitoring relationship and the connection of various electrical equipment, the PLC centralized control design has the advantages of low cost, easy to use, but its application in the electrical control system is also prone to some problems, for example, the cascading stop caused by equipment failure is the need of process and equipment operation safety, and will not affect the stability of the system, while the PLC centralized control design has the advantages of low cost and easy to use. Hardware failure will affect the stability of the electrical control system for the normal operation of the whole system. Distributed control of programmable control in electrical control system is mainly through setting up a PLC on each electrical equipment. In practical application, PLC decentralized control is mostly used in pipeline production in the field of electrical control. Different PLC programs control various equipment with different functions on the pipeline. Decentralized control avoids the defects of centralized control design and the hardware of a single PLC. Obstacles affect the normal operation of the whole system, but the investment cost of this control method is higher. The application of PLC in electrical control system can not only realize linear motion control, but also control circular motion. It is suitable for machine tools, mechanical equipment, elevator and other control systems. Based on the motion control of PLC, the motion module of electric control system, such as the axial control of servo motor, is reasonably configured, and then the execution instruction and sensor of the motion module are automatically controlled. The application of PLC in electric control system can realize data processing functions such as statistics, conversion, mathematical operation and transmission. By collecting the operation data of electric control system, the data are first summarized and sorted out, then the data are processed, and finally the execution instructions are sent to the electric control equipment. Large-scale integrated circuit is used in PLC. This kind of integrated circuit requires high processing technology and circuit design. Anti-interference measures are often used in the design process. And the automatic detection and alarm module is configured in PLC, which makes the whole PLC have strong anti-interference ability. Compared with ordinary relays, the application of PLC in electrical control system is not easily disturbed by external factors, and can adapt to complex and changeable industrial environment and electrical control conditions. At the same time, according to the operation requirements of the electrical control system, the designer can write the automatic fault detection and diagnosis procedures, protect the circuit and equipment around the PLC, and ensure the safe and stable operation of the electrical control system. PLC programmable controller uses modern logic control storage technology, which not only effectively improves the utilization rate of the design space of the electrical control system, but also reduces the peripheral wiring of the electrical control system and occupies less space, which provides great convenience for the later maintenance and transformation. In the application of PLC in electrical control, the designer can compile the program according to the actual requirements of the system, and modify it at any time, which is very convenient and fast. Moreover, PLC can adapt to various complex operating environments of electrical control system, and has good stability and reliability. Once the electrical control system fails, the PLC indicator will give an alarm reminder [2].
According to the operation of the PLC indicator and monitoring equipment, the staff can timely carry out maintenance and repair, which greatly improves the efficiency of fault detection of the electrical control system and ensures the safe and stable operation of the electrical control system. There are many similarities between the expressions, language symbols and ladder diagrams of programmable controller and traditional relays, so the PLC interface in electrical control system is easy to distinguish. As long as the staff have a general understanding of the logic control program and related operation instructions of the PLC, they can quickly start and understand and accept the electrical control. They can compile trapezoidal diagrams according to the actual requirements of the electrical control system, which can effectively reduce the difficulty of circuit design. The later maintenance of the electrical control system is relatively simple. PLC has good adaptability. It can transform complex logic control into efficient and simple control loop. This simple and practical characteristic can be widely used in electrical control system.
In recent years, China’s industrial field has developed rapidly, especially the electrical control system for automation, stability control put forward higher requirements. The application of programmable controller in electric control makes the operation and maintenance of electric control system more convenient, the function more abundant and perfect, and greatly improves the reliability of control system. In the future development process, we should actively promote the rapid, intelligent and standardized development of PLC.