Research of the hardness of the varnish layer of the insulation fingers of the locomotive traction electric motor with the convective and thermo-radiation drying methods

The article describes the study of the mechanical characteristics of polymer insulation, in particular the hardness of the insulating lacquer layer with a different methods of drying it. The influence of the hardness and elasticity of the dried impregnating material on the reliability of the insulating structures during the operation of electrical equipment of the traction rolling stock is analyzed. A device has been created and presented that allows for a simple measurement of the hardness of the varnish film on a pre-selected object of study, which was the insulating finger of the bracket of the brush holder of an electric locomotive traction motor. The process of measuring hardness and results for three groups of insulating fingers are presented: insulating fingers without coating by an impregnating compound (press material); impregnating material, sealed by convective method; impregnating material baked by thermoradiation method. On the basis of the obtained practical results, the effect of the energy supply on the curing process when performing drying by the convective and thermoradiation methods is explained. Also presented are photographs of an electrically insulating lacquer layer from an electron microscope, which allow the microstructure to be evaluated for the presence of gas inclusions, which have a negative effect on both mechanical and electrical indicators of polymeric insulation. A study was made of the relationship between the parameter of electrical and mechanical strength. On the basis of experimental data, the dependence of the breakdown voltage on the hardness of the insulating lacquer layer was constructed.