“…which proves that the magnitudes of U(x) and I(x) also follow elliptic formula. Note that, ω is the excitation frequency and parameters of a, b, and Z c are all dependent on ω, so the elliptic formula, that is Equation (18), is not only applicable for fundamental frequency, but also for harmonic frequencies. Key parameters of ellipses (focus points, semi-major axis, semi-minor axis and eccentricity) shown in Equations ( 12), ( 13), (18) are illustrated in Table 1.…”