Current Noise up to GHz Band Generated by Slowly Breaking Silver-Compound Contacts with External DC Magnetic Field

摘要

Since electromagnetic (EM) noise resulting from an arc discharge disturbs other electric devices, parameters on electromagnetic compatibility, as well as lifetime and reliability, are important properties for electrical contacts. To clarify the characteristics and the mechanism of the generation of EM noise, the current noise up to GHz band generated by slowly breaking silver-compound contacts with external DC magnetic field, up to 40mT, is investigated experimentally in this paper. Firstly, effect of external DC magnetic field on the duration of the breaking arc is quantified. It was cleared that when the external magnetic field is applied, the duration of gaseous phase becomes shorter. Secondly, short time FFT for time change of frequency spectrum characteristics on current noise are studied by comparison with and without external DC magnetic field. It is measured that larger current noise arises, when the contact voltage is rapidly varied at the arc discharge. The variation of contact voltage in the "B=30Mt" case is higher than that of "without external DC magnetic field" case. These results suggest that although applying external DC magnetic field is effective in reduction of arc duration, higher variation of contact voltage in the gaseous phase which results in high frequency noise is caused. These results are basic and useful finding and consideration to clarify not only the correspondence to noise generation of the contact-breaking phenomena but the material dependency for EMC problems.