Calculation of inductances of high frequency air-core transformers with superconductor windings for DC-DC converters

A simplified Neumann´s formula to calculate the inductance of a transformer with spiral shape is proposed. The advantage of using the proposed method is to avoid the cumbersome and tedious integration in Neumann´s formula; the solution usually includes elliptic functions that are complicated and long power series. The stray capacitance of the transformer is also calculated. The experimental measurement agrees well with the calculation.