Experimental Results on Operating Characteristics of Ag, Pd and Cu Contacts in Nitrogen Atmosphere

Makoto HASEGAWA  Jiro MAKIMOTO  Naoki MINOURA  Koichiro SAWA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E83-C   No.9   pp.1385-1394
Publication Date: 2000/09/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Current Electromechanical Devices and Their Materials with Recent Innovations)
Category: 
Keyword: 
contact resistance,  arc,  nitrogen atmosphere,  

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Summary: 
Some experimental results on the contact phenomena that have been observed with electrical contacts operated to break an inductive DC load current in nitrogen atmosphere and in air (laboratory atmosphere) are presented. When Ag, Pd and Cu contacts were operated to break an inductive DC load current in the range of 1.0 A to 3.0 A in nitrogen atmosphere, more stable contact resistance characteristics were obtained, as compared to the case where operated in air, or at least the occurrence of unstableness and increase in contact resistance was delayed. The arc duration in nitrogen atmosphere became shorter in general than in air, especially with the Pd and Cu contacts. Voltage waveforms of arc discharges in the Ag and Pd contacts operated in nitrogen atmosphere showed a relatively clear step-like transition from the metallic phase to the gaseous phase as compared to the case where operated in air, while the Cu arcs did not show such significant differences due to the surrounding atmosphere. Although any apparent differences on the contact surface conditions in connection with the surrounding atmosphere were not clearly observed after the switching operations, the anode mass change characteristics were found to be more significantly affected by the difference of surrounding atmospheres than the cathode mass changes. The obtained experimental results suggest that the difference in the surrounding atmosphere introduce some difference in the anode surface morphology, possibly through the deposition of arc products in different deposition patterns, which will then result in differences in the contact resistance characteristics.