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

ANALOG AND DIGITAL ANTENNA EQUIPMENTS AND CONVERTORS

A television antenna (TV aerial) is an antenna specifically designed for use with a television receiver (TV) to receive over-the-air broadcast television signals from a television station. Television reception is dependent upon the antenna as well as the transmitter. Terrestrial television is broadcast on frequencies from about 47 to 250 MHz in the very high frequency (VHF) band, and 470 to 960 MHz in the ultra high frequency (UHF) band in different countries. Television antennas are manufactured in two different types: “indoor” antennas, to be located on top of or next to the television set, and “outdoor” antennas, mounted on a mast on top of the owner’s house. They can also be mounted in a loft or attic, where the dry conditions and increased elevation are advantageous for reception and antenna longevity. Outdoor antennas are more expensive and difficult to install, but are necessary for adequate reception in fringe areas far from television stations. The most common types of indoor antennas are the dipole and loop antennas, and for outdoor antennas the YAGI and for UHF channel the multi-bay reflective array antenna. 1. Safety Standards for Antenna and Convertors (IEC 60950-1 and IS 13252 part 1

Scope of Standard: Equipment, including electrical business equipment and associated equipment, with a rated voltage not exceeding 660 V. This standard is also applicable to such information technology equipment: a) designed for use as telecommunication terminal equipment and TELECOMMUNICATION NETWORK infrastructure equipment, regardless of the source of power; b) designed and intended to be connected directly to, or used as infrastructure equipment in, a CABLE DISTRIBUTION SYSTEM, regardless of the source of power; c) Designed to use the AC MAINS SUPPLY as a communication transmission medium (see Clause 6, Note 4 and 7.1, Note 4). This standard is also applicable to components and subassemblies intended for incorporation in information technology equipment. It is not expected that such components and subassemblies comply with every aspect of the standard, provided that the complete information technology equipment, incorporating such components and subassemblies, does comply. 2. Critical Tests as per IEC 60950-1 and IS 13252 part 1: Main Tests a) Power Interface b) Heating under Normal Operating Condition c) Constructional Requirements d) Protection from Electric Shock e) Earth Provision f) Stability g) Mechanical Strength h) Protection Against Hazards i) Resistance to Fire j) Touch Current and Protective Conductor Current k) Electric Strength Courtesy - Institute of Testing & Certification India Pvt. Ltd