Frequency spectra of the arc current due to opening electric contacts in air

Opening electric contacts generate electromagnetic noise due to are phenomena and the transients. Frequency spectra of the arc current caused by Ag contacts upon opening in air at atmospheric pressure are described. A distributed constant model was introduced, and it consisted of relay contacts and a coaxial distributed constant line. The experiment was made under conditions of low circuit current (3.84 A) and low source voltage (48 V). From the experimental results, it became clear that the frequency spectra of the are current depended on the length and terminal conditions of the line connected to the contacts.