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Frequency converter anti-interference technology The interference problem of frequency converters has been bothering many customers. Here we will introduce some common interference and elimination methods to you.: 1 Common interference pathways (1) Aerial radiation mode. Spread through the air as electromagnetic waves. (2) Line propagation method. Mainly spread through power supply networks. (3) Line-to-line sensing method. The electromagnetic induction generated by an inductor or the electrostatic induction generated by a capacitor propagates through line-to-line induction. 2 Elimination of interference sources (1) High-frequency and high-power DC welding machines should be kept away from the frequency converter. The welding machine itself should be well grounded. (2) The on-off contact of the electromagnet should be equipped with an RC surge absorber. (3) For contactors installed in the same electrical cabinet as the frequency converter, inferior products must be eliminated. Choose products with low switching noise and good arc extinguishing effect. If necessary, an RC surge absorber should also be installed. (4) The impedance of the power supply should be low to prevent the startup and shutdown of hundreds of kilowatts of electrical appliances nearby, causing excessive sudden changes in the input voltage of the inverter. (5) The phase voltage of the power supply must be constant to avoid causing the 220V single-phase input inverter to operate under undervoltage or overvoltage. (6) For the user's factory's self-generated power generation system, it is required that the output power supply voltage does not fluctuate high and low. Mutations must be avoided and stability must be maintained. 3 Common anti-interference measures for frequency converters (1) The E end of the frequency converter must be connected to the control cabinet and motor casing, and must be connected to the security ground. The ground resistance should be less than 100 Ω to absorb surge interference. (2) Install an inductive magnetic ring filter at the input or output end of the frequency converter. Take Delta's KG series inverters as an example (many inverter brands have user manuals with specifications). Winding the inverter flat and winding it 3-4 times will help suppress high-order harmonics (this method is simple, easy and cheap). If you need to further enhance the anti-interference effect, you can choose a filter device specially designed for Delta inverters that complies with EMC standards (the specifications are provided in the Delta inverter user manual). (3) The above-mentioned magnetic ring filter can also be wound on the incoming line of the control signal end of the frequency converter or the analog signal given end according to the site conditions. (4) In the electric control cabinet equipped with the frequency converter, the power lines and signal lines should be routed through separate pipes, and the metal hose should be well grounded. (5) The analog signal line should be shielded, and the single end should be connected to the simulated ground at the inverter. (6) Interference can also be improved by adjusting the carrier frequency of the frequency converter. The lower the frequency, the smaller the interference, but the greater the electromagnetic noise. (7) The RS485 communication port must be connected to the host computer using photoelectric isolation transmission to improve the anti-interference performance of the communication system. (8) The power supply of external computers or instruments should be separated from the power supply of the power device of the inverter, and try to avoid sharing an internal transformer. (9) Instruments and equipment that are subject to interference must also be independently shielded. Instruments such as thermostats, PID regulators, PLCs, sensors or transmitters on the market must be installed with metal shielding shells and connected to the security ground. If necessary, the above-mentioned inductive magnetic ring filter can be installed at the power incoming end of this type of instrument.