Abstract : Addressing the difficulty engineers face in selecting and designing input and output filters for frequency inverters, this paper analyzes the role of input and output filtering, and provides the basis for whether to use input and output filters and how to calculate and design them, so that designers can design more conveniently and effectively. Keywords : frequency inverter; filter; protection [b][align=center]Input and Output Filters for Frequencey Inverters HUANG Jin-feng, DONG Feng-bin (Department of Electrical Engineering and Automation, Shaanxi University of Technology, Hanzhong 723003, China)[/align][/b] Abstract : The input and output filters for frequency inverters are analyzed in this paper. The design guidelines for these filters are also outlined and introduced. Key words: frequency inverter; filter; protection 1 Introduction In AC motor speed control, frequency inverter speed control can achieve stepless speed regulation and energy saving, and is widely used in industrial production. However, frequency converters often operate in a relatively "complex" environment. Their input side is a non-linear rectifier circuit, the external power grid contains harmonics, and there are also high-order harmonics from other equipment. Therefore, even with a high-performance frequency converter, the performance of the assembled system may not be satisfactory. Extensive engineering practice has proven that to prevent interference from the power grid and other sources, and to reduce the frequency converter's impact on other equipment and the power grid, filters and AC reactors, among other anti-interference devices, are often configured at the frequency converter's input and output terminals. Therefore, the proper selection of anti-interference peripheral equipment is a prerequisite for ensuring the normal operation of the frequency converter. However, due to differences in power supply capacity, input voltage, cable length between the frequency converter and the motor, and the frequency converter's output frequency, the selection of input and output filters cannot be generalized, inevitably posing certain difficulties for engineering designers. Therefore, the relevant selection methods and calculation basis are given below. [b]2 Input Reactor 2.1 Function of Input Reactor[/b] [b][align=center]For details, please click: Input and Output Filtering Protection of Frequency Converters[/align][/b]