The spectral analysis of stator interharmonic currents of induction and synchronous motors with oscillating mechanical loads

Motors are widely utilized in industry. When the mechanical load oscillates, a motor injects interharmonic currents to the grid and becomes an interharmonic source. The interharmonic currents have an important impact on power quality. This paper, respectively, presents the spectrum of the stator interharmonic currents of the induction and synchronous motors. The mathematical models of both motors, which are nonlinear when the load torque oscillates, are linearized. Then, the spectrum expressions of the interharmonic currents of the two types of motors are derived, respectively. On this basis, the relationship between load torque oscillations and the spectrum of the stator interharmonic currents is analyzed. The effect of the various induction motor steady output powers on the spectrum of the interharmonics is investigated. Simulation results validate the theoretical analysis. Copyright (C) 2013 John Wiley & Sons, Ltd.