Modeling of The Transformer Windings under VFTO based on Transfer Function

A systematic methodology is presented for establishing the high frequency circuit model of transformer windings under VFTO based on transfer functions in this paper. Firstly, the voltage transfer functions are deduced from the S parameters which are measured by network analyzer. Secondly, the voltage transfer functions are fitted with rational functions by vector fitting and then order-reduced by modified Routh approximation method. Lastly, the resultant voltage transfer functions are synthesized by lumped elements. The simulation results from the circuit are in good agreement with the measured. This shows that the method is correct.