Study Of Conducted EMI In Arc Welding Converter

The Electromagnetic Interference (EMI) is one of the serious problems in thefield of power electronics. Heavy EMI does not only reduce the performance of thesystem itself, but also pollute the environment. Many countries of the world have paidgreat attention to the Electromagnetic Compatibility (EMC) of equipments, and havebuilt some strict criteria in order to reduce the influence on the environment. Theelectrical welding machine, as one of 132 products in 19 groups, has been rigidlyrestricted on EMC by 3C(China Compulsory Certification), which was published onAugust 1, 2003. As a result, the problem of the research on EMC of electrical weldingmachine must be faced up at present. The arc welding converter is the source of serious EMI. It does not only have abad effect on equipments around it and the power line, but also downgrade itself. Thispaper introduces the powerful tool in signal process—wavelet package into highfrequency interference signal analysis for the first time and discloses the spectrumcharacter of the conducted interference signals in electrical welding machine. As thesame time, by building interference source module and electrical welding machinemodule as well as making use of Matlab simulation software, this paper finds out theprinciples of conducted interference in ZX7—160 arc welding converter. Simulation and measurement data shows that the power switching tubes and fastdiodes are the dominating interference sources in the arc welding converter. Parasiticcapacitance and parasitic inductance are the main high frequency interference sourceswhich lead to the misactions of the switching tubes by control circuit. Simulation results agree well with the measurement data. This approves that themodules of interference sources and system can reappear the true state of arc weldingconverter. This paper establishes the theoretical base of other kinds of arc weldingconverters for further researching on the EMC .