Abstract : Speed-regulating motors using frequency converters are widely used due to their excellent control performance, speed control range, efficiency, and maintainability, as well as their advantages of energy saving and high productivity. As power electronic devices, frequency converters mainly contain electronic components and computer chips, making them susceptible to external electrical interference. Furthermore, the input side of the frequency converter is a non-linear rectifier circuit, which distorts the power supply waveform and introduces high-order harmonics. The output voltage and current of the frequency converter are also non-sinusoidal or not perfectly sinusoidal, containing abundant harmonics, which also affect the output circuit. This means that frequency converters generate high-order harmonics after being put into operation, which can interfere with the connected power grid and electrical equipment, a phenomenon commonly referred to as electromagnetic compatibility (EMC). [b]Inverter Input Side Interference (1) Inverter Interference to Power Grid[/b] For inverters, since they have a rectifier circuit on the power supply side, they will inevitably generate harmonics due to their nonlinearity, causing the total input harmonic current distortion to exceed 5% (IEEE 519-1992 standard stipulates that the grid harmonic current should be less than 20 times the load current, and the current distortion should be less than 5%). The harmonic current generated by the inverter is input to the power grid, which can cause the inductors and capacitors of the power distribution system to resonate and present minimum impedance, causing the power distribution system to present maximum current, and both the inverter and the capacitor will be damaged. Thus, there is a problem of inverter harmonic pollution to the power grid. (2) Inverter Interference to Electrical Equipment If the power system connected to the inverter also has loads such as power capacitors, generators, and motors connected in parallel, the harmonic current generated by the inverter is distributed to the power system and the parallel loads according to their respective impedances. For power capacitors, due to the parallel resonance caused by harmonics, abnormal current flows into the capacitor, which often leads to overheating and insulation damage of the capacitor. For generators, harmonics can induce currents in the braking and excitation windings of synchronous generators, potentially leading to overheating and shortened lifespan. For transformers, current harmonics increase copper losses, and voltage harmonics increase iron losses, causing transformer temperature to rise and affecting its insulation capacity. Harmonics can also cause resonance between transformer windings and inter-line capacitances, and lead to core flux saturation or misalignment, generating noise. [b][align=center]For more details, please click: Inverter Harmonic Interference and Solutions[/align][/b]