Analytical Model of Melting Phenomena for Breaking Relay Contacts

Noboru WAKATSUKI  Nobuo TAKATSU  Toshiteru MAEDA  Takayuki KUDO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E92-C   No.8   pp.1003-1007
Publication Date: 2009/08/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E92.C.1003
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Development of Electro-Mechanical Devices (IS-EMD2008))
Category: Arc Discharge & Contact Phenomena
Keyword: 
transient current switch circuit,  melting contact voltage,  electromagnetic relay,  arc ignition,  

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Summary: 
Using the transient current switch circuit in parallel with the energizing contacts, the slow decay of the contact current due to thermal fusion of metal was observed just after the contact voltage exceeded the melting contact voltage Um. At that time, the contact voltage was higher than the boiling contact voltage Ub. These results contradict Holm's θ theory. A new melting model of breaking mechanical contact is proposed. The area surrounding a cluster of contacting a-spots melts, the melt metal diffuses, and the contact spot thermally shrinks. Including the metal phase transition from solid to liquid, the increase of contact resistance is introduced to the electric circuit analysis. The numerical analysis agrees qualitatively with measured V-I characteristics.