FEM modeling of skin and proximity effects for coreless transformers

This paper addresses the evaluation of the high frequency effects for coreless transformers using PCB coils. Especially it is crucial to calculate accurately the resistances of the coils as they are responsible for the Joule losses and therefore have a great influence on the heat generation and the efficiency. First, a numerical model is implemented with a FEM software. The method used to compute the resistance is presented. Measurements are then realized on PCB coils and the results are compared to those of the model.