How frequency conversion circuits deal with electromagnetic interference
Variable frequency drives bring significant economic benefits but also many negative impacts. Electromagnetic radiation generated by variable frequency circuits can cause interference with other communication and electronic devices.
1. Electromagnetic radiation propagation mode: In frequency conversion circuits, high frequency harmonic current components have the ability to radiate into the air, causing interference to other equipment. Especially communication equipment interference is more severe.
2. Methods for resolving interference
(1) Input reactor: ①. Input reactor: Input reactor can greatly improve the waveform of input current. It significantly improves the power factor and effectively weakens the interference of high-order harmonic components in the input current on other devices Output reactor: Generally, the output side of the frequency converter is not connected to a reactor, but connecting an output reactor can effectively weaken the harmonic components in the output current.
(2) Correct connection: The main purpose of connection is safety, but for some equipment with high-frequency interference signals, it also has the function of introducing high-frequency interference signals. When connecting, attention should be paid to the following points: ①. The wiring should be as thick as possible, and the contacts should be as close to the frequency converter as possible. ② Try to keep the wiring away from the power cord as much as possible All wiring of the frequency converter must be separated from other equipment, as shown in Figure 1-b above. Avoid connecting all equipment wires together before reconnecting The frequency converter terminal cannot be connected to the neutral line of the power supply.
(3) Access filter: The filter is mainly used to suppress high-frequency harmonic currents with radiation capability in the input and output circuits of series frequency converters, as shown in Figure 2. The filter consists of high-frequency coils and capacitors. It must be noted that in the output side filter of the frequency converter, the capacitor can only be connected to the motor side and a resistor should be connected in series to prevent the inverter tube from being impacted due to capacitor charging and discharging.
