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Drying transformer casting
Classification:
Industry News
Release time:
2025-03-05
There is a process for dry transformers in the production process: pouring. Simply put, it is to fill in insulating materials such as epoxy resin into the coil of the transformer. The casting process is very important for dry transformers. It realizes the insulation and heat dissipation functions of dry transformers. The excellent casting process will ensure the performance of the finished dry transformer in the future.
The pouring process of dry transformer
Preparation Work
Before the dry transformer is poured, there will be some preparation work, including pretreatment of the coil, such as cleaning, drying, preheating, etc., which can improve the adhesion ability of the casting material.
Material Configuration
The configuration of the material is mainly the configuration of epoxy resin, in which some curing agents, plasticizers, accelerators, color pastes and other materials should be added, and the mixture is mixed evenly.
Vacuum casting
This operation will be carried out under vacuum, injecting the mixed epoxy resin into the mold to ensure that the epoxy resin fully penetrates each layer of the winding. This operating vacuum condition is the key to the pouring process. It can effectively remove bubbles generated during the pouring process and ensure that there are no voids inside the insulation layer, thereby improving the electrical performance and mechanical strength of the product.
Curing and demolding
After the pouring is completed, the product needs to be removed from the vacuum environment, placed in a curing furnace, and cured by high temperature. After curing is completed, demolding can be performed and can be used after a slight adjustment.
Epoxy
In the casting process, there are many types of epoxy resins that can be used, but since dry transformers are limited by technical conditions and process conditions, the material performance requirements of epoxy resins are very strict. If the organic chlorine and inorganic chlorine content are required, the content of organic chlorine in the epoxy resin is high, the electrical properties of the cured epoxy resin will be reduced at high temperature; if the inorganic chlorine is present in the epoxy resin, the electrical properties of the cured epoxy resin will be deteriorated at room temperature or the cured cleave. At the same time, due to the presence of impurities such as chloride ions in the epoxy resin, the gel time of the epoxy resin mixture is shortened during the casting process, making the casting process unable to proceed smoothly, resulting in premature gelation of the mixture and scrapping.
Curing agent
Solid anhydrides are mostly used in early curing agents, such as polyazelaic anhydride, phthalic anhydride, etc. However, due to the poor casting process performance, it is no longer used. Nowadays, methyl tetrahydrophenyl anhydride (MTHPA) and hexahydrophenyl anhydride (HHPA) are usually used. This material has better performance and more friendly operating conditions.
In epoxy resin mixture, the type and quality of the curing agent are directly related to the main performance of the product. The impurities, volatile components and main components in different curing agents are different. Incorrect choices will lead to abnormal pouring, so you must be careful when choosing a curing agent.
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