Multiphysics-based design optimization of medium frequency transformer with experimental validation

In resonant converters, medium frequency transformers (MFTs) are used to provide galvanic isolation between the primary and secondary converters. The overall power transfer efficiency of the converter topology largely depends on the efficiency of the MFTs. Existing methods in literature often estimated the MFT's parameters analytically and also do not optimize the MFTs using all the physics models that describe the practical behaviour of the MFT during operation. These approaches introduces some errors consequently increasing the discrepancies between the simulation and experimental results. Also many optimization algorithms often neglect the material cost of the MFT during optimization. This paper proposes a FEA-based multi-physics (time-harmonic electromagnetic, thermal and fluid models) coupled design optimization for MFT. The proposed optimization minimizes the total transformer power loss, and cost while maximizing its power density. The core dimensions, number of turns and the switching frequency are obtained from the Pareto optimal solutions. A case study of a 5kW, 110/110V transformer is investigated. The optimization results is compared with experimental measurements. The experimental results are in very good agreement with the optimization results which shows that a higher level of accuracy can be achieved using this approach.