Abstract : Imported machine tools suffer from a lack of spare parts, leading to long repair cycles and impacting production. This paper briefly introduces the principle and application of frequency converters through the localization of the U80 frequency converter in imported equipment, and proposes a new approach to the maintenance of imported equipment: the overall localization of faulty units. Keywords : Frequency converter; Localization; AC motor Introduction Imported CNC machine tools are widely used in the machining industry, especially in the oil pump and nozzle industry, due to their significant high precision and efficiency in machining. However, the use of imported machine tools faces a serious shortage of spare parts, resulting in long repair cycles, disrupting normal production, reducing production efficiency, and failing to achieve the original purpose of choosing imported machine tools. To change this situation and restore the high precision and efficiency of imported machine tools, localization is a very effective, practical, and sustainable approach. 1 Problem Statement YTO Company is a manufacturer of oil pumps and nozzles. With the development of production, it increasingly uses CNC machine tools and high-efficiency precision equipment. In the early 1990s, YTO Group Corporation imported three U80 grinding machines from UVA GmbH of Sweden to process the center hole and seat surface of the PB86J needle valve body for fuel injectors. The process requirements were extremely stringent: roundness within 0.5 μm, cylindricity within 0.8 μm, and surface roughness below 0.4 μm, with the ground parts ready for direct insertion. The grinding rod of this machine tool was directly mounted on the electric spindle. Therefore, the operating accuracy of the electric spindle was extremely high, with a required speed of 100,000 r/min, driven by a frequency converter. This machine tool was highly efficient, with a single-piece processing time of 50 seconds, making it a key piece of equipment for ensuring production. However, due to years of use, malfunctions have increased significantly recently, especially with the frequency converter driving the electric spindle, which has become extremely unstable and is now experiencing frequent failures. Due to various objective limitations, the frequency converter cannot be repaired. The original frequency converter is obsolete, and spare parts are not available. Purchasing replacements is expensive, costing approximately RMB 200,000 per unit, and the delivery cycle is long, severely hindering smooth production. Therefore, a modification is necessary. 2. Introduction to Frequency Converter Technology Frequency converters are a high-tech product with high efficiency, good performance, and wide application internationally. They utilize single-chip microcomputer control, power electronic components, and motor drive technology to achieve stepless speed regulation of industrial AC motors. [b][align=center]For details, please click: U80 Frequency Converter Localization Modification[/align][/b]