Abstract : This article introduces the application of large aluminum electrolytic capacitors in frequency converters, focusing on the selection and usage precautions of filter capacitors in frequency converters. Keywords : Capacitor, Frequency converter 1 Introduction As is well known, the main function of large aluminum electrolytic capacitors in frequency converters is filtering. It seems like a very simple component, but it plays a crucial role in the frequency converter. The failure of the filter capacitor leads to the frequency converter stopping operation and failing, showing that the quality of the filter capacitor plays a decisive role in the lifespan of the frequency converter. 2 Capacitor Quality Assessment How to assess whether a large aluminum electrolytic capacitor is operating well in a frequency converter? Capacitor manufacturers and frequency converter manufacturers, especially some well-known foreign frequency converter manufacturers, have jointly discussed and summarized a relatively simple and practical method. We install a thermocouple in the middle of the capacitor (as shown in the attached diagram). A detection device is installed at the other end of the thermocouple, allowing us to directly understand the internal temperature rise of the capacitor. The most basic failure condition of a capacitor is that with prolonged use, heat causes the electrolyte to dry out, resulting in reduced capacity and increased losses, leading to failure. Determining the quality of a capacitor involves checking if its center temperature rise meets requirements. Center temperature rise is related to the capacitor's heat generation and heat dissipation. Traditionally, capacitor quality was judged by testing three parameters: capacitance, leakage current, and loss tangent. However, considering products from various brands and manufacturers, it's difficult to determine a capacitor's quality solely based on these three parameters. Furthermore, inverter circuits are complex, and it's difficult to simulate the same circuit configuration used in actual inverter operation in a laboratory. By installing thermocouples and monitoring the capacitor's temperature rise during actual inverter operation, the author can essentially determine its quality. [b][align=center]For more details, please click: Application of Large Aluminum Electrolytic Capacitors in Inverters[/align][/b]