As an example, the basic ferroresonance circuit of Figure 1 is analyzed using the dual-state inductance approach. Firstly, the system under study should be represented by two circuits with the saturated and unsaturated core inductances.
When the core operates in its linear region, the nonlinear transformer core is replaced by the linear unsaturated inductance Lunsat, Figure 19(a). However, as the transformer core enters the saturation region, the core is represented by the saturation inductance Lsat, Fig 19(b). To investigate the sys-tem ferroresonance behavior in time-domain, the
solution is repetitively switched between the two circuits of Figures 19(a) and 19(b), depending on the core flux magnitude.