An important indicator of whether a dry-type transformer is good or not depends on its insulation structure and its insulating materials. Because the structure of the transformer is different, its insulating materials are also different. As for other parts, such as the grain oriented cold-rolled silicon steel sheet used in the core, the steel and aluminum wires used in the winding are the same as those of the oil immersed transformer. The following is a brief introduction to the insulation materials used in the transformer.
The first aspect: aromatic polyamide fiber paper
Aromatic polyamide fiber paper is the main insulating material used for conductor insulation and lead wire binding insulation of impregnated dry-type transformer. It is a high-temperature resistant synthetic fiber material. It is a linear polymer. Its molecular chain has hundreds of aromatic nuclei and a molecular weight of 60000-120000. Aromatic core is an important part of the main chain of molecular chain. Benzene ring is connected with nitrogen atom, not aliphatic hydrocarbon. Because aromatic polyamide paper has high heat resistance and amide chain is still kept in molecular chain, it has good physical and mechanical properties of aliphatic amide, which is why polymer has good dielectric stability.
If the heat resistance grade of dry-type transformer is not H-class, other insulation materials should be considered.
The second is impregnating varnish
There are two types of impregnating varnish: solvent and solvent-free. The winding of dry-type transformer is mainly impregnated with impregnating varnish, which is to fill the gaps and micropores between the insulation. After baking and curing the impregnating varnish, the flat paint film is formed continuously on the insulation surface. At the same time, the winding is bonded into a solid whole, which improves the moisture resistance, thermal conductivity, mechanical properties and electrical strength of the insulation structure.
Generally, there are several requirements for impregnating varnish: thick layer curing fast, good drying, strong adhesion, thermal elasticity. It can withstand short-circuit mechanical force after curing; it has low viscosity and high solid content, which is convenient for penetration and filling of impregnants; it has high electrical performance, moisture resistance, heat resistance, oil resistance and chemical stability, and has good compatibility with conductor materials and other materials.
The third aspect is insulation glue
It can be divided into three categories: winding insulation dry-type transformer insulation and casting insulation. In China, epoxy resin is usually used as the base, and curing agent is used to make F-class insulation system for accelerator. The difference between casting insulation and winding insulation is that the process is different.
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