How can I control the frequency converter with a computer?
The commonly used PLC and DCS control system in industrial area are applicable to the conditions of inverter interface control module, can realize the closed-loop converter convenient automatic control in the control system, widely used in large and medium. The control device for some smallexperimental device and embedded processor in inverter control, generally also need to deal with the keyboard input, display, data acquisition and other work such as process control, this control is more suitable for single-chip control system as the core, and uses PLC and operation panel, it can achieve the function but the cost is too high. Should not be used.
The use of single-chip to control the inverter can choose the last two kinds of methods, the use of communication control, the utility model has the advantages of full control function, suitable for inverter through the level conversion circuit form of communication (RS484/RS232/CAN), you can communicate with the inverter hardware is simple, the number of connections between the two less convenient connection. The disadvantage is that we need to understand the communication protocol of frequency converter to control programming, and the software design is complicated. The inverter communication interface and communication protocol of different brands are different, there is no uniform standard, only for a converter for development, narrowing the selection range of the frequency converter varieties, the applicability is limited. As for the analog input control, can support almost all of the inverter is, although the function is relatively simple, but the main function can realize speed, can meet the use requirements of the majority of occasions, universal.
Variable frequency speed control has been applied in the industrial field as the main means of AC motor speed control is very extensive, it has a wide speed range, steady speed and high precision fast dynamic response for a wide range of technical performance and reliable operation, has gradually replaced the DC motor speed control system. There are three main control modes of inverter: 1. through inverter panel operation, that is through the operation panel to change the output frequency and other operating parameters; 2. in the frequency converter analog input 0 ~ 10V or 4 ~ 20mA signal, by changing the size of input analog control of inverter output frequency converter; 3. through communication port (for RS485 control). The first method is generally used for manual adjustment and parameter setting on the spot, and the latter two are mostly used for automatic adjustment and remote control.
RS232 communication can be used to control the frequency converter and other equipment, but there are several problems to be solved:1, frequency converter is generally two wire communication (422/485), so there must be 485/232 or 485/USB conversion.2, software problems, you can use VB, C, and with any of their own familiar with the method of preparation of a control interface, and in accordance with the frequency converter communication protocol written.3, also can buy ready-made configuration software, that saves the trouble of programming and debugging program.4, with computer communication with PLC (currently popular), and then use PLC and frequency converter communication (program is more simple and practical than using VB).
