Finite-Element Simulation of Homogenised Field Models for Foil Windings

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Foil windings are increasingly applied in electrical energy converter because of their high fill factor, low DC resistance and advantageous thermal properties. They, however, feature a specific eddy-current effect related to the uni-directional redistribution of the currents towards the foil tips, and a comparably large interturn capacitance, related due to the thin insulation layers. Today, a sufficiently accurate simulation of these effects is only possible with three-dimensional finite-element models in which all geometric details in the foil-winding parts are resolved. The unmanageable size of the overall models impedes a further improvement of foil windings in contemporary electrotechnical designs. The outcome of this research project will be a finite-element foil-winding model which is capable of simulating eddy-current, capacitive and thermal effects in foil windings at a computational cost which is comparable to the one for standard wire windings. This goal will be achieved by an appropriate combination of analytical and computational homogenisation methods, a dedicated hybrid finite-element, spectral-element discretisation, error-controlled mesh adaptation, field-circuit coupling and multi-rate time integration. The performance and reliability of the developed numerical schemes will be demonstrated for machine foil windings, for a high-frequency foil-winding transformer and for a metallic film capacitor.