1. Acetal Enameled Wire
Acetal enameled wire is one of the earliest varieties developed in the world. It was put on the market by Germany and the United States respectively in 1930. The Soviet Union also developed rapidly. There are two kinds of polyvinyl formal and polyvinyl acetal. China also successfully studied them in the 1960s. Although the enameled wire has a low-temperature resistance grade (105 C, 120 C), it is widely used in oil-immersed transformers due to its excellent high-temperature hydrolysis resistance. This characteristic has been notarized by various countries in the world. At present, there is still a small amount of production in China, especially acetal enameled flat wire is used to make transposed conductors for large transformers.
2. Polyester enameled wire
Polyester enameled wire paint based on dimethyl terephthalate was first developed by West Germany in the mid-50s. Due to its good heat resistance and mechanical strength, a wide range of painting technology and low price, it has become the main product dominating the enameled wire market since the 50s.
3. Polyurethane enameled wire
Polyurethane enameled wire paint was developed by Bayer in 1937. It is widely used in the fields of electronics and electrical appliances due to its direct weldability, high-frequency resistance and dyeability. At present, foreign countries pay great attention to improving the heat resistance of polyurethane enameled wire without affecting its direct welding performance. The development of polyurethane enameled wire in China is slow. Although common polyurethane paint is produced by some factories, it is mainly imported due to poor manufacturability and surface quality.
4. Polyesterimide Enameled Wire
Due to the improvement of heat resistance through modification of polyester imine, the amount of polyester imine enameled wire has risen sharply in the world since the 1970s. In Europe and the United States, the enameled wire has completely replaced polyester enameled wire with a single coating. At present, the world's representative products are Terebe FH series products in Germany and Isomid series products in the United States. Domestic polyesterimide paints have successively imported manufacturing technology from Germany and Italy, and have been successfully developed by themselves. However, due to the instability of raw materials and other reasons, a large number of polyesterimide paints used as a primer for cryogen-resistant composite enameled wire still rely on imports. Only a small number of single-coated polyesterimide enameled wires are applied with domestic paint, but voltage instability is still a problem that the manufacturers are worried about. Direct-weldable polyesterimide paint has been successfully developed by the Cable Research Institute.