Leakage Inductance and Interwinding Capacitance in Toroidal Ratio Transformers

The small, but often significant, voltage ratio error of a ratio transformer is caused by leakage of magnetic flux and the flow of displacement currents around the windings. A model of the flux leakage pattern within a toroidal transformer is used in conjunction with an analysis of the effect of interwinding capacitances to predict the change of voltage ratio with frequency. Reasonably close agreement between this prediction and measured values of voltage ratio suggest that the theory is essentially correct.