Various Characteristics of Induction Motor by Harmonic Equivalent Circuit with LC Resonance

This paper proposes a new equivalent circuit for induction motors having the harmonic components. The proposed circuit consists of T-type equivalent circuit and LC resonant circuit, which is connected in parallel with load resistance. Various features of the induction motors including harmonics can be easily obtained by the proposed circuit. The fundamental component is expressed by the conventional output resistance, and the ripple elements of the mechanical output are represented by the current flowing in the LC parallel resonant circuit. In the proposed equivalent circuit, the current flowing into the load resistance becomes sinusoidal, so that we can separate ripple components from fundamental one. It is necessary to decide the appropriate values of L and C as the resonant frequency that gives the fundamental frequency. Strictly speaking, the resonant frequency is denoted by rotor speed. By means of this circuit, various harmonic torque characteristics can be easily obtained.