Coating of Electrical Contactor

APPLICATION OF CONTRACTOR-

An electrical ‘contactor’ is the name given to a relay that is used to switch large amounts of electrical power through its ‘contacts’. Contactors typically have multiple contacts to share out the load. Silver is a good conductor of electricity and its use in plating the contacts is mainly to reduce the contact resistance at the point where the tips makes contact with the source of power. Electrical contractors are normally made from electrically conductive, lower cost copper or copper alloys. However, copper and copper alloys are prone to corrosion and oxidation. This can lead to problems such as fretting including fretting wear, fretting fatigue and fretting corrosion. These in turn lead to further formation of insulating oxide layers, increasing the electrical resistance of the contacts. It is essential to keep the electrical resistance at minimum. Silver is corrosion and oxidation resistant so coating the contact points of electrical contractors overcomes these problems which provides cost-effective solution. Silver also has the highest electrical conductivity of all metals. It is even higher than the copper or copper alloys from which the contactors are made. Courtesy- ATF Table of Resistivity and Conductivity at 20°C Material ρ (Ω•m) at 20 °C Resistivity σ (S/m) at 20 °C Conductivity Silver 1.59×10−8 6.30×107 Copper 1.68×10−8 5.96×107 Annealed copper 1.72×10−8 5.80×107 Gold 2.44×10−8 4.10×107