Influencing Factors Of Temperature Field In Transformer Coil Curing Process

Shanghai Ghang Vacuum Technology Co., Ltd. explores the mutual influence factors between the temperature field and the stress field in the process of dry transformer pouring, curing and setting cycle.Because the temperature field is not uniform, thermal stress is generated, and part of the thermal stress and deformation will be converted into heat, which in turn affects the distribution of temperature field.Therefore, strictly speaking, the heat-structure problem of the whole process is a coupling problem.However, considering that the coil deformation belongs to static deformation and the deformation rate is very small, the thermal effect caused by stress deformation work can be ignored compared with the thermal effect caused by temperature change and latent heat release in the curing process, so the thermal process and stress process analysis can be carried out separately.

In the process of casting and curing the coil, the heat transfer is mainly conduction and convection, and the thermal radiation is very little.There are also changes in heat resulting from chemical reactions and phase transitions.The numerical simulation of the temperature field in the process of casting, curing and cooling of the coil must first establish a reasonable mathematical model.The success and accuracy of the numerical simulation depend on the degree of generalization of the simulated object expressed by the mathematical model.There are many complex factors in the process of casting, curing and cooling, and the main contradiction must be grasped in the analysis process. In the initial stage of analysis, the influence of the main factors in the process of casting, curing and cooling of the coil is considered, and the following factors are proposed according to the actual situation .

(1) There is only heat conduction between the coils, without convection and radiation heat transfer;
(2) Convection exists in the air between the coil and the outside of the coil as well as between the molds. At this time, the air is free air without forcing
Heat transfer.
(3) In a certain temperature range, the thermal properties of the material do not change with temperature.
(4) The whole process is divided into casting, gel, and curing process to analyze.

The winding materials of yu type transformer mainly include wire, foil, epoxy resin, curing agent, toughening agent, glass fiber, glass felt, etc.Epoxy resin is mainly bisphenol A glycidyl ether type epoxy resin, through the polar group hydroxyl -CH-OH, ether bond -C-O-C, epoxy group and wire, copper foil, glass fiber polar surface to produce strong intermolecular force, the important parameter is epoxy equivalent.The most important curing agent is the anhydride value of the curing agent.The property parameters of winding in casting, curing and cooling mainly include density, thermal conductivity, heat transfer coefficient, thermal expansion coefficient, stiffness coefficient, specific heat capacity, Poisson’s ratio, Yang’s modulus and so on.

Editing by Frank Lee
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