The inverter includes a rectifier circuit and an inverter circuit. The input AC power is converted into a DC voltage through a rectifier circuit and a smoothing circuit, and then the DC voltage is converted into a pulse voltage of different widths through an inverter. This working principle leads to the following three types of electromagnetic interference: harmonic interference, radio frequency conduction interference, and radio frequency radiation interference

To prevent interference, hardware anti-interference and software anti-interference can be used.

1. Use software anti-interference measures

Use the human-machine interface of the inverter to lower the carrier frequency of the inverter to an appropriate range. If this method does not work well, hardware anti-interference measures can be taken.

2. Correct grounding

The main circuit terminal PE (E, G) of the inverter must be grounded. The grounding can be shared with the motor of the inverter, but not with other equipment. A separate grounding pile must be driven, and the grounding point should be as far away from the grounding point of the weak current equipment as possible. The length of the inverter grounding wire should be controlled within 20m.

3. Shielding interference sources

Usually, the inverter itself is shielded with an iron shell to prevent electromagnetic interference leakage, but the output line of the inverter is best shielded with a steel pipe and a shielded twisted pair cable, which is completely separated from the main circuit line (AC380) and the control line (AC220V).

In addition, the electronic sensitive equipment lines in the system are also required to use shielded twisted pair cables, especially pressure signals.

And all signal lines in the system must not be placed in the same pipe or cable trough as the main circuit line and control line.

4. Reasonable wiring

(1) The power line and signal line of the equipment should be as far away from the input and output lines of the inverter as possible.

(2) The power line and signal line of other equipment should not be parallel to the input and output lines of the inverter.

5. Interference isolation

Usually, an isolation transformer is used on the power line between the power supply and the amplifier circuits such as the controller and transmitter to avoid conducted interference. The power isolation transformer can also use a noise isolation transformer.

6. Set up filters in the system line

Filters can be divided into input filters and output filters according to the different locations of use

7. Use reactors

Depending on the different wiring locations, there are mainly two types: AC reactors and DC reactors