Meltric Features

Silver-Nickel Contact Materials

Meltric plugs & receptacles feature solid silver-nickel (85/15) butt contacts that are similar to those used in contactors and switchgear. The combination of the outstanding electrical properties of silver and the excellent mechanical properties of nickel provide many advantages relative to common brass contacts or silver-plated brass contacts. •      The hardness of nickel makes the contacts wear resistant and helps provide good mechanical endurance and long operating lives. •      The low contact resistance of silver and its resistance to oxidation provide excellent contact performance that does not deteriorate significantly over time or with heat and oxidation. •      Silver-nickel only welds at extremely high pressure and temperature and thus can withstand arcs very well. •      The strong post-arc dielectric strength of silver-nickel helps reduce the duration of arcs and the good mobility of arcs on the material helps to prevent arc-induced erosion of the material. By contrast, the brass material commonly used for contacts in pin and sleeve devices is a relatively poor conductor, has high contact resistance that increases significantly with oxidation, and is not arc resistant. In addition, brass is a soft material that wears rapidly under friction.     The chart to the left shows the dramatic difference in contact resistance between silver-nickel and brass in both new and typical oxidized conditions. Even in an oxidized state, the contact resistance of silver-nickel is more than 6 times less than the contact resistance of brass in its most favorable (new) condition. Alternatively, when oxidized, the contact resistance of brass is more than 20 times higher than oxidized silver-nickel. The high contact resistance of brass creates additional heat. The heat causes more oxidation, the oxidation further increases contact resistance, the increased contact resistance causes more heat, and so forth. This vicious cycle of degradation accelerates over time and is exacerbated by the reduction in contact force caused by the frictional wear of the material. The net result is diminished electrical performance, reduced safety and shorter operational lives. This is why Meltric does not use brass contacts.