Especially when a three-phase or single-phase circuit contains at least one capacitor and one saturable inductance, the waveform of the periodic voltages and currents in this circuit can reach several different values (depending on the initial conditions) for the same applied voltages, according to the particular values of the parameters involved (capacitances, shape of the magnetic curves) and the impressed voltages level. The authors point out that the so-called `resonant' state is characterized by current peaks far above the peak values in the `non-resonant' state, and by a distortion and greater amplitude of the voltage waveform, too