Research on the generation mechanism of EFT interference produced by electromagnetic relay considering the parasitic parameters

In order to research the generation mechanism of the electrical fast transient (EFT) interference produced by the electromagnetic relay, considering the main circuit high frequency parasitic parameters, the method of adding equivalent lumped parasitic parameters has been used to solve the three classical steps during the process of shutting down of the contact. The traditional method only concentrates on the general breakdown characteristic of the relay's EFT interference. The fundamental frequency expression has been discussed. However, the high frequency characteristic of the interference can not be reflected. The transient dynamic electric contact model, which describes the process of relay shutting down the inductive load, has been established by this method. This model can be used to analyze the influence of the parasitic parameters on the EFT interference in wide frequency and a special phenomenon can be explained by this model. At last, a couple of experiments have been done to approve the correctness of the electric contact model.