Calculation of Parasitic Elements in Toroidal Core Transformers

This paper presents the design formulas for the calculation of the leakage inductance and stray capacitance of a toroidal core transformer. An analytical approach is utilized to calculate the leakage inductance and the turn-to-turn stray capacitance based on stored magnetic energy and electric energy, respectively. In addition, the effect of frequency on the leakage inductance is studied and some modifications are applied to the calculation method to consider the skin effect. The obtained results are validated by 3-D finite element simulations. In addition, the measurements for a prototype transformer are presented as a comparison with the calculated and simulated results. The results show that the presented formulas for the toroidal core transformers have a good accuracy.