In recent years, China's telecommunications industry is also gradually on the power harmonic currents have a certain understanding, the latest standard in the telecommunications industry, has also been added for UPS equipment input current harmonic content requirements, what is the harmonic control provisions depending on the circumstances of the size and importance of the use of UPS capacity and other places of harmonic content index is divided into three levels, namely 5%, 15% and 25% power (due to frequent use of a communication larger capacity UPS systems, system requirements and high reliability, it should be in accordance with the requirements of 5% of the index). In the communication field, in order to try not to run harmonic oil interfere with other equipment, in order to make the whole system more secure and reliable power supply, the current harmonic content at various points in the system are controlled within 5 percent is the best option . Therefore, in the new system, to deal with a variety of equipment specially made harmonics metrics related requirements to ensure the system harmonics in the building would be controlled. For existing system, because it is running, the transformation of the difficulty and investment are relatively larger, harmonic control, therefore, can be considered to ensure that the basic safety of the entire system under the premise of harmonic control costs, due to lower harmonic control requirements. There is a certain asymmetry waveform arc current. It is because of a non-sinusoidal arc current, arc heating equipment causing harmonic pollution is relatively large, but mostly for low harmonic pollution 18 times less. In fact, in the last century welding forties and fifties have been widely used. At that time, less arc heating equipment, while the rate of welding applications even smaller impact on the power grid is relatively small, but found in the burning welding, voltage and current changes in local low-voltage grid is large, there is a greater harmonic wave effect. Harmonic sales, 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.