Pre-Conditioning Automotive Relay Contacts to Increase Their Resistance to Dynamic Welding

Thomas J. SCHOEPF  Abdellah BOUDINA  Robert D. ROWLANDS  Brent T. REPP  

IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.7    pp.1441-1447
Publication Date: 2007/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.7.1441
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Development of Electromechanical Devices (Selected Papers from ICEC2006))
Category: Relays & Switches
automotive relay,  silver tin oxide,  inrush current,  dynamic welding,  pre-conditioning,  DC,  

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Electromechanical switching devices such as relays may be surprisingly forgiving to occasional, but temporary, electrical stress beyond specification. Consequently delayed openings due to welded contacts on the order of milliseconds usually have been unnoticed and hence have not been reason for concern. However, as electrical systems of vehicles are getting "smarter" and more and more diagnostic routines are being implemented, even such short delay times may be translated as errors. Pre-conditioning contact surfaces has been explored as a measure to increase the welding resistance and eliminate contact opening delays. The 20-A-class relay investigated has been optimized to break occasional current peaks up to 80 ADC.