AC power supply system, power supply contains a lot of harmonics can be modeled as a linear load and a series of harmonic current sources. It is believed connected to AC power draw non-linear load fundamental current from the AC power supply feedback to the AC harmonic currents of various frequencies. Harmonic current value and greater power resistance, what is harmonic control, harmonic voltage waveform distortion caused by the greater, the greater the harm caused. Ordinary capacitors have amplification of the harmonic series must be a reactor can protect capacitors, and can effectively prevent system harmonics is amplified. According to GB50053-94 "10kV and below substation design specifications," provides that "when a nearby high harmonic content capacitor means exceeds the allowable value should be set harmonic suppression reactors in series in the loop." GB50227-95 "shunt capacitors design specifications," provides that "for suppressing harmonics, when the background of shunt capacitors connected to the grid at the harmonics and when more than 5 times, harmonic control vendors, should take 6%; when shunt capacitors BACKGROUND connected to the grid at three times more harmonics, harmonic control and, should take 12 percent. " In summary, in the construction of communication power supply system, should be based on a detuned circuit, first consider the use of the active filter control. Preferably in the initial stage of construction will be considered resolved. As in the construction of UPS systems, active filters configured directly, it will not only ensure the construction of the system more secure and reliable, and because you can easily achieve the end of treatment, so that the power supply reliability and power efficiency has increased. Harmonic manufacturers, learning Connaught Electrical and Mechanical, harmonic control by learning Connaught Mechanical and Electrical Equipment Co., Ltd., Henan. Henan Xi Connaught Electrical Equipment Co. (www.hnxinuo.com) located in the south China city of Zhengzhou Area 6B 6B-3-342. Scraps and development in the wave of market economy, the current study Connaught Electrical and Mechanical has a high profile in the electronics, electrical products processing, enjoys a good reputation. Xi Connaught Electrical and Mechanical made whole network business alliance certification, marking our service and management level has reached a new height. Xi Connaught Electrical and Mechanical staff is willing to joint development with all people a better future.