The problem of improving the operational reliability of insulation of traction motors (TM) of locomotives has been given constant attention. In accordance with the State Program for Strategic Development of Railways of Ukraine, prepared by the State Research Centre of Rail Transport of Ukraine together with the specialists from Ukrainian Railways, a sectoral Programme for Renewal of Traction Rolling Stock of Railways for the period up to 2020 was developed, which indicated the need to implement the next generation systems for maintenance and repair of traction rolling stock (TRS) and development of relevant regulatory documents. The development of theoretical and methodological foundations that will ensure effective decision making regarding the selection and improvement of systems for maintenance of TRS and its components is currently an urgent science issue, which is nowadays of great importance for the rail transport of Ukraine. The scientific novelty of the obtained results lies in the improved system for diagnostics of frame insulation of TM of locomotives for the purpose of predicting its residual life and improving the system for repair of TM frame insulation, taking into account the restoration technology: − for the first time, the equivalence of the maximum value of reverse voltage and the value of integrated estimation of frame insulation performance was established; − for the first time, an integrated indicator of the reverse voltage curve was suggested for classifying the conditions of TM frame insulation in order to further predict the residual life of frame insulation before its restoration or replacement; − for the first time, the conditions of TM frame insulation performance were suggested based on the classification of the degree of insulation wear; − the mathematical model for determining rational periods for repair of frame insulation of ЕД-118А traction motor was improved, taking into account a restoring 10 technology, initial state of insulation performance and limits on the critical value of reverse voltage. Practical importance. The research results obtained in the thesis are used: • by the Service of Locomotive Facilities of the Regional Branch of Cisdnieper Railways (Certificate of Implementation of Research Work Results No. 0118U005059 dated 05.02.2019); • by Metalurhtransremont PJSC (Certificate of Implementation of Research Work Results No. 0119U000430 dated 23.04.2020); • Materials of the thesis and results obtained upon the completion of research work (state registration numbers No. 0118U005059, No. 0119U000430) are used by the Department of Locomotives of the university in the educational process and advanced training courses for employees of Ukrainian Railways. When analysing the research regarding the main methods for monitoring the TM insulation performance, it was observed that in most cases the destructive testing methods were used for monitoring the current condition of insulation, which, as a rule, did not give an adequate assessment of the condition of electric motor insulation. The researchers point out that the parameters associated with the processes of absorption and resorption in dynamics have the highest informative value concerning the aging of insulation. The models of repair suggested in modern publications often do not take into account the current condition of TM, which is repaired and the degree of repair (restoration technology). The models related to predicting the residual life of TM insulation have not been unambiguously defined by the researchers.
The characteristics of inhomogeneous insulation considered in the work were conditioned by the presence of absorption charge and had parameters firmly related to the specific electrical properties of insulation. Therefore, the measurement and analysis of such characteristics can provide useful information about the condition of insulation, number of layers with different properties and specific parameters of these layers. Formally, all absorption characteristics contain almost identical information about insulation. The failures of TM of locomotives and factors of insulation failures due to malfunctions of other TM elements were analysed. A common cause of TM malfunction is insulation breakdown and turn-to-turn short circuits, which account for about 20% and 24% of the total number of failures for electric and diesel locomotives, respectively. Measurements were performed and the change in the insulation resistance of the excitation windings of TM main poles, depending on the operating time in summer and winter, were studied. It turned out that the insulation resistance, which was measured with a megohmmeter, had a uniform distribution law and did not depend on the season. That is, this parameter (insulation resistance) was not informative in terms of diagnostics and prediction of the condition of insulation of the main pole coils.
