Purpose -The purpose of this paper is to contribute toward the modelling of the microscopic interaction between high-frequency discharge bearing currents and rolling element bearings in the contact zone. It also aims to develop a reduced model that can serve as a starting point for further developments. Design/methodology/approach -The complexity of an ideal comprehensive model is identified and analysed. Based thereon, a reduced model is developed. Findings -The true system is highly complex and cannot be solved in a single-step approach. The proposed reduced model allows the explanation of the melting of the bearing surfaces under the influence of the high-frequency currents. It also provides a starting point for the development of an extended model. Research limitations/implications -The model excludes the dynamic rolling movement of the bearing. The development of the frosting and fluting observed on the bearing running surfaces can only be explained in parts. Practical implications -The melting of the bearing race surface can be modelled and thereby explained. The proposed model forms a good basis for further work toward an extended model to explain the high-frequency bearing current bearing damage mechanism. Originality/value -The paper offers a method to model the microscopic interaction between high-frequency discharge bearing currents and rolling element bearings in the contact zone. This phenomenon has not yet been modelled to this extent. Such a model -and the understanding brought forth from it -allows the reduction in the cost for safe operation of modern variable speed drive systems.

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We present a method for fast identification of the thermal behavior of vehicle integrated electric drives to propose a better understanding of electric machine design tailored to driving cycles. A simple, but satisfactorily accurate calculation method for the estimation of machine losses, which is an input for the analytic thermal network, in the early design stage is introduced. The analytic models, which are verified using measurement data, are used for parameter and case studies for consideration of the thermal environment with focus on the gearbox. An improvement of machine performance using an alternative cooling approach which cools down the end windings is shown in the final section of the paper.

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