The ferroresonant circuit

A circuit which consists of capacitance in series with an iron-core reactor, with or without other circuit elements, may be a ferroresonant circuit. Ferroresonance, as the term indicates, is resonance associated with circuits in which at least one of the circuit elements contains iron and which is a nonlinear inductive element. Resonance in any series circuit occurs where the inductive and capacitive reactances are equal. In a given series circuit of linear resistance, inductance, and capacitance, there is only one frequency of applied sinusoidal voltage at which resonance will occur; but at this frequency, resonance occurs at all values of applied sinusoidal voltage.