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New copper nickel graphite composites for low voltage electrical contacts

The research covered the development of silver free electrical contacts for low voltage circuit breakers and minimisation of production costs of electrical contacts by increasing the effectiveness of composites which could replace silver in low voltage circuit breakers.

There are, in theory, 6 alternative ways of obtaining a satisfactory composite by combining 2 alternative ways of presenting graphite (particles or fibres) and 3 alternative consolidation methods (pressureless sintering, hot unaxial pressing and a third, alternative method developed by the researchers). In practice, only 3 out of the 6 combinations were practicable. The first step in carrying out the project used copper-nickel/graphite composites after preliminary microstructural studies indicated their promising possibilities to replace silver in electrical contacts for low voltage circuit breakers. Although partners expected to extend the results to composites of similar characteristics, information obtained was hardly extendable to other composites. As a consequence, the second step of the research focussed on the study of only copper-nickel/graphite composites; good performances were obtained for low voltage breakers used in consumer terminal distributions. For such devices, the breaking and life demands are not too heavy. For higher voltage industrial breakers, however, further work is necessary and, moreover, their electrical performance is not yet satisfactory.

Reported by

Institut National Polytechnique de Grenoble
38402 St Martin d'Heres
France
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