2. Simplifying separations

2.1 Separation of the electrostatic part

• Transformers used in power electronics are often wound around ferrite cores and, under normal operating conditions, are operated below saturation. This allows us to focus on linear models. Having adopted this simplifying assumption, it remains, for predictions to be reliable when signals are loaded with harmonics, to develop accurate models over a wide range of frequencies, up to at least ten times the working frequency of the assembly. This is not easy when the components have three, four, five or more windings.

• When we observe the behavior of a transformer in harmonic operation, we notice that capacitive effects are negligible up to quite high frequencies relative...