Improving the reliability of the TD802 direct-current traction generator of the ChME3 shunting diesel locomotive through insulation replacement

Abstract

This paper presents an analysis of the design and insulation system of the TD802 (TO802) direct-current traction generator installed on ChME3 shunting diesel locomotives operated on the railways of Uzbekistan, and substantiates a technology for improving its reliability through the replacement of that insulation. The study was carried out in three stages: an assembly-by-assembly analysis of the factory insulation system (armature winding, main and commutating pole coils, commutator, brush apparatus); identification of the physical mechanisms of insulation ageing and of their cumulative interaction; and development of a technological regulation for insulation replacement using modern heat-resistant materials. The proposed solution comprises vacuum-pressure impregnation (VPI) of the armature winding, replacement of asbestos gaskets with glass-mica and aramid-fibre materials, renewal of the commutator insulation, transition to a monolithic insulation system for the pole coils, and an upgrade of the insulation thermal class to H (180 °C). A quality-control procedure based on insulation resistance, absorption coefficient, polarization index, high-voltage testing, partial discharge monitoring and infrared thermography is proposed, together with a methodology for quantitative evaluation of the effect through the mean time between failures. It is shown that the proposed measures do not alter the design scheme of the machine and modernize only the insulating materials and the technology of their application, which makes them practically feasible at depot level.