DC reactor can increase the power factor to more than 0.9. Because of its small size, many frequency converters have installed DC reactors directly in the frequency converter. In addition to improving the power factor, the DC reactor can also weaken the impact at the moment when the power supply is just connected. If AC reactor and DC reactor are equipped at the same time, the power factor of variable frequency speed regulation system can be increased to more than 0.95. Structural design The DC smoothing reactor is used for the filter circuit at the output side of the rectifier circuit. Because there is a DC current component, the magnetic flux of the iron core works in the first quadrant, resulting in magnetic bias. In order to increase the inductance and prevent magnetic flux saturation, DC smoothing reactors adopt cut iron core and add air gap to lengthen their hysteresis loop laterally, which is a bit like the case of single ended flyback transformer in principle. In this way, when there is a current of the same size, B is small and not easy to be saturated.