Design optimization methodology for high-frequency rotary transformers for contactless power transfer systems

This paper describes a novel and all-encompassing optimum design technique for high-frequency radial-type rotary transformers used in contactless power transfer applications. The magnetic, electrical, and thermal properties of the rotary transformer are analytically modelled, and the results are compared to 2-D axis-symmetric FEM simulations. In contrast to the state-of-the-art, which uses standard geometries and assumes important parameters to be constant without investigating their variations and effects, this work employs generic analytical models for design optimization of the radial-type rotary transformer. The transformer is constrained by a given space envelope and a coolant air temperature. This method first determines the significant system parameters, which include the frequency range of 10 kHz to 100 kHz and sets of all realistic system parameters' combinations, which results in the realization of all practical transformer designs, which are then evaluated in terms of loss and mass. This method is used to optimize the design of a 40 kW rotary transformer for a Dual Active Bridge DC-DC converter presented in this paper, highlighting design peculiarities as well as the effect of optimization design factors.