Research has found that an alloyed aluminum wire can represent a very cost-effective replacement for copper in enamelled wires. Enamelled wires have long been used for electrical windings for electric motors, transformers and coils, but increasingly they have also been used for electronics (e.g. computer hard disk drives or headphones) and for power supplies (e.g. inverters or switch elements and electric current supply sources). Enamelled winding wires have an electric-conducting core with an external insulation layer made from materials such as polyvinyl formal, polyurethane, polyester, polyesterimide, poly-amideimide and polyimide enamels. Enamelled wire requirements can be divided into five main groups: thermal, electrical, chemical, physical and economic properties. Thermal properties describe insulation behavior at high temperatures, the "thermal shock" effect. Electrical properties relate to the dielectric strength of, insulation. Chemical resistance to transformer oils or refrigerant mediums is needed for some uses. Physical properties relate to flexibility, elongation or abrasion of insulation layers. Specified parameters result from operating conditions whereas physical properties - like adhesion to metal, curing temperature or viscosity of varnish at the application temperature - are very important technological factors. Also, economic aspects, such as varnish price, production efficiency or final properties of wire, should be considered. Detailed analysis of different kinds of enamel has been presented. After silver, copper is the best material for electrical use for conductivity. Aluminum has been tried in winding applications but was not economically viable, and copper enamelled wire dominates for both economics as well as some critical technological advantages. Conventional electrolytic tough-pitch copper is the most popular conductor material for winding wires but oxygen-free, electrolytic copper has been used quite often, especially for thin-wire applications. Fundamental analysis about the influence of copper quality on enamelled wire properties has been performed. Depending on operating conditions, enamelled wire is distinguished by its high thermal class, high mechanical strength, solderability and self-bonding capability. Many laboratory tests have been performed on the final enamelled wires.
展开▼
