The communication of frequency converter is disturbed. What method can be used to reduce the interference?
Answer: the communication interference of frequency converter mainly comes from electromagnetic interference and harmonic interference of other thyristor and DC rectifier electrical equipment in low-voltage power supply line.
The frequency converter itself is also an interference source. Therefore, in order to overcome the electromagnetic interference caused by the above two aspects, we can consider adding “AC input reactor”, “input AC filter” and “AC output reactor” when using the upper computer to communicate with the inverter. See the figure below.
The power input terminal is equipped with EMC input filter, which can effectively prevent the interference of electromagnetic interference on communication facilities.
The grounding terminal PE must be reliably grounded, and the grounding resistance value must be less than 0.1 Ω. Otherwise, the inverter will work abnormally or even be damaged. See the figure below.
The installation of an external EMC input filter between the inverter and the power supply (as shown in the above figure) can not only suppress the interference of electromagnetic noise in the surrounding environment on the frequency converter, but also prevent the interference of the frequency converter on the surrounding equipment. It is necessary to connect a filter at the input end to make the frequency converter meet the C2 level in installation. Attention should be paid to the installation of EMC input filter:
1) When using the filter, please use it in strict accordance with the rated value: as the filter belongs to class I electrical appliances, the metal shell ground of the filter should be in good contact with the metal ground of the installation cabinet in large area, and it is required to have good conductive continuity, otherwise there will be electric shock hazard and seriously affect the effect of EMC filtering.
2) The filter ground must be connected to the same common ground as the PE terminal of frequency converter, otherwise the EMC effect will be seriously affected.
3) The filter shall be installed as close as possible to the power input of frequency converter.
Whether the input side signal of frequency converter is analog voltage input or digital input mode, they are particularly sensitive to external electromagnetic interference, so shielding cables are generally required, and the wiring distance shall be as short as possible, not exceeding 20 meters. In addition, in the field with strong electromagnetic interference, filter capacitor or ferrite core shall be installed at the analog signal source side, as shown in the figure below.
Through the above processing, the interference of electromagnetic induction on communication signal can be greatly reduced in general.
Editor in charge: CT