Abstract : This paper analyzes in detail several issues concerning high- and low-voltage frequency converters used in water supply systems, including an overview and the reasons for selecting domestic Jialing frequency converters. It covers the characteristics of high-voltage frequency converters, circuit introduction, series technology of high-speed power devices, sine wave technology, common-mode voltage rejection technology, frequency converter selection, performance comparison of various high-voltage frequency converters, basic specifications, and main parameters. Keywords : High-voltage frequency converter, Low-voltage frequency converter, Performance parameters 1 Introduction Qidong Waterworks is the only waterworks in Qidong City, responsible for the domestic and industrial water needs of nearly 300,000 people. Therefore, the quality, efficiency, and energy saving of the water supply system are of paramount importance to the plant. The plant's leadership and management have long planned to adopt advanced technology and implement variable frequency speed control for both the primary intake pump and the secondary clean water pump. After years of research, interviews, and investigations, they finally decided to select Chengdu Jialing frequency converters. From technical exchanges and solution selection to drafting contracts, equipment manufacturing, installation, commissioning, and trial operation, the process took six months. By mid-January 2005, it had passed acceptance testing and was officially put into operation, delivered to the factory for use. Test results from the Qidong Municipal Power Testing Institute showed an energy saving rate between 20-30%, meeting the client's requirements. Therefore, its successful acceptance on the first attempt represents a significant energy-saving project for Qidong municipal engineering, bringing substantial economic and social benefits, especially under the current power shortage situation, achieving both increased supply and reduced demand. "Fundamental technical measures". [b]2 System Introduction 2.1 Secondary Clean Water Pump[/b] The secondary clean water pump can supply qualified tap water, which is directly sent to users through the pipe after being pressurized by the pump. The plant has 3 10kV pumps, including 2 400kW and 1 280kW. Normally, the 400kW pump is used, and the 280kW pump is used at night. During the peak flow period in summer, the 400kW pump is used, plus the 280kW pump, and the water supply pressure is about 3.2kg. In the past, the flow (or pressure) was adjusted manually by adjusting the outlet valve, which is obviously an uneconomical and untimely operation. After adopting frequency conversion speed regulation, the speed can be automatically adjusted, which can not only stabilize the pressure and save energy and reduce consumption, but also realize automatic closed-loop PID regulation. [b][align=center]For details, please click: Application of Domestic High Voltage Frequency Converter in Waterworks[/align][/b]