With the continuous development of network technology, network technology can be driven directly into the field of instruments, combined with instrument technology, and can be connected to intranets through intranets using OLE and DDE technologies to communicate data with the outside world and transfer real-time measured data to the network. Intranet has become an inevitable trend. IP is a network layer protocol. It implements unreliable, connectionless data packet services. TCP is based on a reliable connection service. Ethernet+TCP/IP-based solutions for factory automation have been put into place. Practical application and more and more attention.
Its main features are: First, the implementation of the TCP / IP protocol embedded in the field of smart devices (mainly sensor) ROM, so that the signal is sent and received in TCP / IP mode. The second is that the measurement and control system is based on the company's internal network (Intranet) and Ethernet as the field bus in terms of data collection, information release, and system integration. The third is to implement a networked virtual instrument on the Internet, free and flexible data collection system and data analysis and management system. The fourth is to interconnect the measurement and control network and the enterprise network with the Internet, realize the unification of the measurement and control network and the information network, and establish a unified system for testing and management. With its low investment and high-performance communication methods, it realizes a completely free topology of instrument networking, and completely realizes a single, open and total networked virtual instrument for testing and researching drive systems along with computer technology. With the rapid development of network technology, networked virtual instruments have emerged. The emergence of networked virtual instruments has greatly broadened the field of application of the instrument. It has enabled the network to intervene throughout the entire modern measurement process, making use of existing Internet resources and the company's internal network topology, making it very easy to set up. Test the network, realize the interconnection of the enterprise network and Internet, enable people to obtain the measurement information in real time anytime anywhere, can apply to set up the factory automation system, have realized the on-line long-distance measurement and control of the frequency converter.
The software of the instrument is developed and designed by the user. The virtual instrument software consists of two parts, namely the application program and the I/O interface instrument driver. The application program mainly includes two functions: one is a software program that implements a virtual panel function, and the other is a software program that defines a flowchart of a test function. The I/O interface instrument driver completes the expansion and drive of the specific external device. The most popular programming software is the LabVIEW developed by the American VI company. It is an object-oriented visual programming environment. It is currently the only compiled graphical software in the world.
As a kind of stable, high precision speed control system, the frequency converter has been widely used in various types of variable speed transmission devices. The inverter speed control system has become an inevitable trend to replace the DC speed control device. The AC variable frequency speed control system has energy-saving, adjustable Wide speed range, high precision, high efficiency, and high power factor, good reliability, easy operation, and easy to interface with other equipment, etc., are recognized as the most ideal and most promising way of speed control. At present, there is no special research on Intranet-based monitoring technology for inverters at home and abroad. Through this topic, the detection system can be automated, and the stability of the system can be improved, the occurrence of failures can be reduced, and manpower can be reduced. Completely automate production management.
Implementation steps The most popular frequency converter is a universal variable voltage variable frequency (Vvvf) frequency converter. We test the key functional parameters of the general frequency converter to ensure the quality and function of the new frequency converter, and then the key parameters of its operating status. Parameters such as voltage, current and speed are monitored, and the monitored data is analyzed and processed so that the operation of the inverter can be monitored and all monitored data can be transmitted to the Intranet or the Internet for data sharing. It is possible to give advice on the status of the equipment through the Internet or an intranet, to improve the degree of automation of the enterprise and improve the reliability of the equipment.
The first is to measure the key parameters of the inverter as a whole. The first is the rated load characteristic test: calculate the accuracy of the three-phase current and the balance of each phase current and the output average voltage under the rated load; second is the protection function test. : Destructive tests such as overcurrent, overheating, grounding, and short circuit of the inverter. Followed by the realization of a network of virtual instrument testing system, the system is divided into four layers: measured device layer, directly associated with the measured device; instrument layer, to provide distributed instrument resources for the system; network communication layer, for the end-user and field instruments Provides remote communication channels; customer layer, for users to browse data, control remote instruments, we adopt multi-parameter multi-channel test technology to carry out relevant state detection, use Web-based remote sensors for measurement, and then use high-reliability, low-cost Network interconnect devices such as gateways, routers, repeaters, and network interface chips replace high-speed communication networks, but require specific, expensive communication chips to support bus lines, and use existing Internet resources and internal corporate networks. Network topology, which is very convenient to set up a test network, to achieve corporate network and Internet interconnection. Ethernet is used as the communication medium between the instruments and between the instrument and the computer, so that the access of the instrument is no longer limited to the layout of the network. The instrument, as a node on the network, exists completely independently of the computer. The instrument can be freely and freely accessible to any point of Ethernet, and can be accessed at any point of the Ethernet. Ethernet is used at the link layer. TCP/IP and Ethernet standards are used as communication standards for test systems. The use of an open Internet connection as a system detection structure has truly achieved the unification and opening of standards. In the monitoring network, traditional instruments and equipment act as independent contact points in the network. Information can be transmitted across the network to any area where it is located, making the network truly involved in the whole process of modern measurement. In the test system relied on the Internet, the setting of the main control computer does not have to depend on the specific physical location. As long as any computer in the LAN can be configured as the master computer of a certain group of instruments, it is very convenient in the LAN. To achieve decentralization and redundancy of the main control computer, the failure of a certain node greatly reduces the possibility of the system being unable to work, and truly realizes integration of management and control.
The overall measurement of the frequency converter is divided into the following sections: (1) For input voltage, current, and power detection: The power analyzer 8903F can be used because the input voltage and current are 50Hz sine waves, and the 8903F fully meets the requirements. The measured data can be sent to the PC via RS-232 serial communication. For the detection of output voltage, current, and power: The power analyzer WT130 can be used because the inverter's control output voltage is a PSW square wave method and is also implemented using a serial port. Overvoltage test: transformer voltage transformer composite transmission voltage can be used. Over-current test: The inverter is connected to a larger motor. For example, a 1.5 KW inverter is connected to a 2.2 KW motor and the inverter is controlled to start quickly, so that the instantaneous current exceeds 150% of the rated current, and overcurrent detection is realized. For larger power, two large motors can be connected together to the output of the inverter. Rated load test: The "two-motor load method" is adopted. The two motors are mechanically connected. When the 400V voltage is tested, the 400V motor can be connected to the output to control the operation and the output is 50Hz. Then the 200V motor is connected because the frequency and the rotation speed are the same and the output current is the same. Smaller, gradually improved, and so on.
Using E-mail alarm technology: By adding E-mail function to the virtual instrument, you can notify the control personnel at the fastest speed when detecting data overruns or abnormal data, and record the necessary data as reference materials. Send it to the designated person's hands together, thus greatly improving the security of the system monitored by the virtual instrument. Key technical problems (1) Designing the entire circuit, under the economical and reasonable conditions, the various functions of the test system of the entire networked virtual instrument can be well realized, and various signals can be smoothly collected without distortion at the maximum. Next, maintain the accuracy of the data, timely and accurate data transmission to the data analysis system to ensure the stability of the system, the data transmission is to be carried out in different equal amounts, the serial port transmission is used during the test, and the monitoring is based on the TCP/IP standard mode. get on. DateSoket technology is used for real-time browsing of network data. It is a programming technology for real-time data exchange through the network for the field of measurement and control. It can support the simultaneous application of specific data to different applications on the same computer. TCP/IP optimization and management simplify Internet communication and provide a free data transmission format through the internal data self-describing format. You can directly transfer virtual instrument programs and commonly used character formats, boolean forms, and digital quantities in collected data. Form, even waveforms acquired. This simplifies the design of more complex TCP/IP stratum programming and also solves the problem of transmission speed.
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