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Calculation of ohmic losses in litz wires by coupling analytical and numerical methods

: Roßkopf, Andreas; Joffe, Christopher; Bär, Eberhard


Institute of Electrical and Electronics Engineers -IEEE-; Verband Deutscher Maschinen- und Anlagenbau e.V. -VDMA-, Frankfurt/Main:
4th International Electric Drives Production Conference, EDPC 2014 : 30.09. – 01.10.2014, Nuremberg, Germany
Piscataway, NJ: IEEE, 2014
ISBN: 978-1-4799-5008-9
ISBN: 978-1-4799-5009-6
ISBN: 978-1-4799-5010-2
International Electric Drives Production Conference (EDPC) <4, 2014, Nuremberg>
Fraunhofer IISB ()
litz wire; loss calculation; proximity effect; skin effect; electromagnetic simulation

Up to now, litz wires with many (several hundreds) strands are simplified in complex systems such as transformers or coils to make simulations feasible. However, frequency dependent losses of litz wires and solid conductors differ strongly. In this paper, a coupled process of numerical simulation and analytical methods is described which allows efficient simulation of full 3D structures including resolving litz wire sub-structure. To achieve this, 3D simulation with a simplified conductor calculates the magnetic field in the entire system. Based on these data, a new analytical method determines the losses in the litz wire along the conductor for the large number of 2D cross-sections. The error of the analytical method is less than 5% at frequencies up to 1MHz and external magnetic fields u p to 2500kA/m. Because of the significant reduction of calculation time, windings and ferrite structures can be efficiently optimized.