Abstract : The application of frequency converter technology is becoming increasingly widespread, but electromagnetic interference (EMI) in frequency converter systems is quite serious. This paper mainly introduces the sources, propagation paths, and specific measures to suppress EMI in frequency converter application systems. Keywords : Frequency converter; Electromagnetic interference; Anti-interference measures 1. Introduction AC variable frequency speed control technology for motors is a major means of saving electricity, improving process flow to enhance product quality, improving the environment, and promoting technological progress. Variable frequency speed control is recognized domestically and internationally as the most promising speed control method due to its excellent speed control, starting, and braking performance, high efficiency, high power factor, energy-saving effect, wide applicability, and many other advantages. However, EMI in frequency converter systems is quite serious, making corresponding anti-interference technology even more important. Interference in frequency converter systems can sometimes directly cause hardware damage or cause microprocessor program malfunction, leading to equipment and production accidents. How to improve the anti-interference capability and reliability of the system is an important aspect that cannot be ignored in frequency converter application systems. 2. Main Sources of Electromagnetic Interference Electromagnetic interference (EMI) is electromagnetic interference caused by external noise and unwanted signals during reception, usually propagated through circuit conduction and in the form of fields. The rectifier circuit of a frequency converter is a non-linear load for the power grid, and the harmonics it generates can cause harmonic interference to other electronic and electrical equipment on the same power grid. Furthermore, most frequency converter inverters use PWM technology, which generates a large amount of common noise when operating in switching mode and making high-speed switching. Therefore, the frequency converter is an electromagnetic interference source for other electronic and electrical equipment in the system. On the other hand, harmonic interference from the power grid mainly interferes with the frequency converter through its power supply. The power grid contains numerous harmonic sources, such as various rectifiers, AC/DC converters, electronic voltage regulators, non-linear loads, and lighting equipment. These loads cause waveform distortion in the voltage and current of the power grid, thus causing harmful interference to other equipment on the power grid. If the power supply of the frequency converter is interfered with by a polluted AC power grid, and this interference is not addressed, the grid noise will interfere with the frequency converter through the power supply circuit. Secondly, common-mode interference can also interfere with the normal operation of the frequency converter through its control signal lines. [b][align=center]For more details, please click: Measures to Combat Electromagnetic Interference in Frequency Converter Applications[/align][/b]