What is enameled wire
2020-11-30
Enamelled wire, a category of electromagnetic wire, generally refers to insulated wire used to manufacture coils or windings in electrical products. Also known as winding wire. Electromagnetic wire meets various requirements for use and manufacturing processes. The former includes its shape, specifications, the ability to work at high temperatures for short and long periods, and withstand strong vibrations and centrifugal forces at high speeds, as well as resistance to corona discharge and breakdown at high voltages, and chemical corrosion in certain atmospheres; the latter includes requirements for stretching, bending, and wear during winding and embedding, as well as swelling and erosion during impregnation and drying processes. Electromagnetic wire can be classified according to its basic composition, conductive core, and electrical insulation layer. Typically, it is divided into enamelled wire, wrapped wire, enamelled wrapped wire, and inorganic insulated wire based on the insulation materials and manufacturing methods used for the insulation layer. Enamelled wire is made by coating the conductor with a corresponding varnish solution, followed by solvent evaporation, varnish film curing, and cooling. Enamelled wire can be categorized based on the insulation varnish used into polyester enamelled wire, polyester-imide enamelled wire, polyamide-imide enamelled wire, polyimide enamelled wire, polyester-imide/polyamide-imide enamelled wire, corona-resistant enamelled wire, as well as oil-based varnish, phenolic varnish, polyurethane enamelled wire, etc.
Sometimes classified by their applications, such as self-adhesive enamelled wire, freeze-resistant enamelled wire, etc. The early enamelled wire was oil-based enamelled wire made from tung oil and other materials. Its varnish film had poor wear resistance and could not be directly used to manufacture motor coils and windings, requiring a cotton yarn wrapping layer during use. Later, polyvinyl alcohol formaldehyde enamelled wire was introduced, significantly improving mechanical properties, allowing direct use in motor windings, and was referred to as high-strength enamelled wire. In recent years, thin film wrapped wire has developed rapidly, mainly including polyester film and polyimide film wrapped wire. Recently, there has also been mica tape wrapped polyester-imide film wrapped copper flat wire for wind power generation. Inorganic insulated wire is typically used when the heat resistance requirements exceed the limits of organic materials, usually coated with inorganic insulation varnish. Existing inorganic insulated wires can be further divided into glass film wire, oxide film wire, and ceramic wire, among others. There are also composite conductors and switching conductors. With the development of weak current technology, self-adhesive enamelled wire has emerged, which can achieve better integrity without impregnation or baking. However, its mechanical strength is relatively poor, suitable only for micro motors and small motors. Additionally, to avoid the hassle of removing the varnish film before soldering, direct solderable enamelled wire has been developed, which allows the coating to fall off in a high-temperature tinning bath, making it easier to solder the copper wire. Due to the increasing application of enamelled wire and the growing strict requirements, composite enamelled wire has also been developed. Its inner and outer varnish films are made of different polymer materials, such as polyester-imide/polyamide-imide enamelled wire. Wrapped wire is an important variety of winding wire. Early versions used cotton yarn and silk, known as yarn-wrapped wire and silk-wrapped wire, which were used in motors and electrical appliances. Due to the large insulation thickness and low heat resistance, most have been replaced by enamelled wire. Currently, it is only used as high-frequency winding wire. In large and medium-sized specifications of winding wire, when the heat resistance level is high and mechanical strength is large, glass fiber wrapped wire is also used, with appropriate adhesive varnish added during manufacturing. Among wrapped wires, paper-wrapped wire still holds a significant position, mainly used in oil-immersed transformers. The oil-paper insulation formed at this time has excellent dielectric properties, is cost-effective, and has a long lifespan.
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2020-11-30
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