Abstract: Frequency converters, which control the speed of AC motors by changing their frequency, are increasingly widely used. These converters can arbitrarily change their operating state via serial communication according to a certain protocol. To improve the reliability and intelligence of the frequency converter control system, this paper develops a motor control scheme tailored to specific needs using the rich hardware and software resources of a computer in the Visual C++ programming environment. This scheme achieves dynamic parameter control and real-time status monitoring of the Dongyuan frequency converter. The entire system is flexible, convenient, and highly practical. Keywords: Serial communication, Frequency converter, VC++ KEYWORDS : Serial communication, Frequency converter, VC++ Frequency converter control is usually accomplished through the operation panel, but manual control panels cannot achieve automatic and intelligent control of the frequency converter's speed, stop, and running status. To address this, most frequency converters have an RS485 communication interface, allowing users to easily and flexibly utilize the powerful functions of the frequency converter to design a frequency converter control system that meets their specific requirements. Developing industrial control software under Windows is feasible due to the abundant hardware and software resources available in computers. Under Win98, VC++ can be used to create control software with a user-friendly interface and strong control management capabilities. However, in the Windows environment, the system completely takes over various hardware resources and does not allow users to directly control the serial port interrupt management. How to develop the low-level resources of a microcomputer under Windows has become a hot topic in industrial control software development. This paper utilizes the VC++ ActiveX control—MSComm communication control—to successfully implement communication control between a computer and a Teco 7200M frequency converter under Windows, developing a frequency converter computer control system that meets specific requirements. 1 Interface Conversion Figure 1 shows the schematic diagram of the single-machine communication between the frequency converter and the computer. In this system, the computer and the frequency converter communicate bidirectionally via an RS485 serial port. Because RS485 data signals use differential transmission, they have advantages such as long transmission distance (approximately 1219m) and strong anti-interference capabilities, making them widely used in serial communication. However, most personal computers currently only have RS232 serial ports; therefore, an adapter must be used between the computer's serial port and the frequency converter to achieve data communication. [b][align=center]For more details, please click: Design of a Computer Control System for Teco Frequency Converters Based on VC++[/align][/b]