In the impact load such as electric welding machine, electric arc furnace, rolling mill and other occasions, the voltage often flickers; in a workshop, there are several frequency converters and other capacitive rectifier loads working, the harmonic generated by them has a very serious pollution to the quality of the power grid, also has a considerable damage to the equipment itself, light can not be able to run normally, heavy will cause damage to the input circuit of the equipment. The following measures can be taken.

In the case of impact load such as electric welding machine, electric arc furnace and rolling mill, it is suggested that users should add reactive static compensation device to improve power factor and quality of power grid.

In the workshop with concentrated frequency converters, centralized rectification and DC common bus power supply mode are recommended. It is suggested that users adopt 12 pulse rectification mode. The advantages are small harmonic, energy saving, especially suitable for frequent starting, braking, motor in both electric operation and power generation operation.

A passive LC filter is installed at the input side of the inverter to reduce the input harmonics and improve the power factor. It has high reliability and good effect.

It is the best to install active PFC device at the input side of frequency converter, but the cost is high.