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Safe, Reliable Operation, Easy Maintenance
- Sep 04, 2017 -

Epoxy resin cast dry-type transformers because of the flame retardant, safe, reliable operation, easy maintenance, small size and other characteristics, has been in the city's high-rise buildings and power stations and other places have been widely used. In recent years, China's dry-type transformer production has been a greater development of the manufacturers from the early 1990s, seven or eight rapidly increased to nearly 100, the production capacity from 3000 ~ 4000MVA increased to more than 20000MVA. Product performance and appearance have a greater improvement.

Epoxy resin cast dry-type transformer winding is the vast majority of the use of epoxy resin casting molding (many manufacturers of low-voltage winding with copper foil), the inner performance of the formation of the winding is also determined, once the shape of the winding performance Fail to meet the required standards, had to scrapped. Therefore, in order to ensure the casting quality of the winding, the structure of the pre-cast winding must be reliable. At the same time, the requirements of winding casting material formula to be reasonable, and the pouring process to advanced. In this paper, the selection and formulation design of casting material without filler winding are put forward, the selection of process parameters and some matters that should be paid attention to in pouring process.

Epoxy resin casting process characteristics

Epoxy resin casting process is a molding molding technology, dry-type transformers are more mature in a casting process, many countries have been widely used in the world. Its main features are:

(1) the winding is fixed in the metal mold, the injected epoxy resin mixture penetrates into the layers of the winding, and is cured and molded so as to be firmly integrated with the wire and the insulating material, and the winding after curing High mechanical strength.

(2) As the winding and resin mixture are degassed in a high vacuum state, so after curing, the partial discharge of the winding (the measured results are generally below 10pC) is very low.

(3) in the gel process, to maintain a certain pressure, so that the resin within the compensation tank into the mold cavity to compensate for the resin shrinkage caused by shrinkage, to prevent casting defects.

(4) in the curing process, the use of ladder curing process, so that the winding to minimize the internal stress, to avoid winding cracking.

The choice of epoxy resin mixture should be considered from the performance requirements of the product and the casting process.

For dry-type transformers, due to the large volume of the winding, the electrical performance, mechanical strength requirements, so the selected casting material must meet all aspects of transformer performance requirements, and the insulation level generally required to achieve more than three.

In terms of process, it is mainly required that the mixture has high fluidity, easy immersion and the suitability of the mixture under certain conditions, that is, the pouring time of the mixture can be controlled under certain conditions.

At present, dry-type transformer winding casting mix (no filler type) components: epoxy resin, curing agent, plasticizer, accelerator and color paste and other materials.