Abstract : Based on the author's practical experience in drainage engineering, this paper carefully analyzes the phenomena and root causes of harmonic, noise, load matching, and overheating problems currently existing in the use of frequency converters, and proposes several practical and effective countermeasures. Keywords : Harmonics; Noise; Load matching; Overheating Variable frequency speed control is one of the fastest-developing motor speed control methods in modern electrical engineering. Its speed equation is: Where: f, and P are the power supply frequency, motor slip, and the logarithm of the motor poles, respectively. As can be seen from the above equation, changing the power supply frequency f can change the speed n, thus easily achieving stepless speed regulation. The frequency converter is the executor of this speed regulation behavior. 1. Application of Frequency Converters The main function of our group's Shaoxing County Drainage Co., Ltd. is to collect industrial and domestic sewage within Shaoxing County, centrally transport it to the Shaoxing Sewage Treatment Plant for treatment, and then discharge it after meeting standards. Since its establishment in 1996, the drainage company has constructed 32 sewage pumping stations of varying sizes within Shaoxing County. Its underground pipeline network covers most of the county, with a total length of 324 kilometers and a daily sewage transport capacity of approximately 550,000 tons. The main power load for these pumping stations is the submersible sewage pumps, which constitute a significant portion of the company's daily operating costs. The starting methods for these pumps have evolved from autotransformer reduced-voltage starting and soft starting to the current variable frequency drive (VFD) starting, making the operation of the pumps more flexible. Currently, all of the company's pumping stations can adjust the flow rate using VFD technology according to the sewage volume. We have found that the energy-saving potential of applying VFD speed control technology is indeed very large, with power savings reaching 20%-50%, resulting in significant benefits. A rough estimate suggests that in 2004 alone, the company saved over 1.7 million yuan in electricity costs by adopting VFD technology. Utilizing frequency converters to drive motors results in low starting current, soft starting, and stepless speed regulation. It also facilitates acceleration and deceleration control, enabling high motor performance and significantly saving energy. Therefore, frequency converters are increasingly widely used in industrial production and daily life. However, with the expansion of frequency converter applications, more and more problems are emerging during operation, requiring careful analysis and effective solutions. [b][align=center]For details, please click: Problems and Countermeasures in Frequency Converter Applications[/align][/b]