Effects of Negative Sequence Voltage Subharmonics on Cage Induction Motors

Abstract

In some power systems, voltage waveforms contain, apart from harmonics, interharmonics and subharmonics that are components of frequency less than or not an integer multiple of the fundamental frequency. Voltage subharmonics and interharmonics may be of both a positive and negative sequence, independently of their frequency. Previous papers on induction motors under subharmonics have been generally limited to the components of a positive sequence. This study deals with the effect of negative sequence subharmonics on the work of induction motors. Investigations were performed using the 2D finite element method and an experimental method. Differences between the impact of positive and negative sequence subharmonics are discussed. It was found that negative sequence voltage subharmonics can result in significant current subharmonics, torque pulsations and vibration. Further, because of possible resonance, motors that are comparatively resistant to positive sequence subharmonics might be especially sensitive to negative sequence subharmonics of the same frequency and vice versa.

Analysis of Interharmonics Generation in Induction Motors Driven by Variable Frequency Drives and AC Choppers

“…However, it has been demonstrated that the inertia properties of the machine and the load do influence the generation of undesired disturbances, including torque pulsations, currents and vibrations, especially in the positive sequence, under the influence of interharmonic and subharmonic voltage effects in induction motors [32,33,63,64]. In this scenario, a load with a negligible moment of inertia (NMI) that is lower than the motor's moment of inertia generates larger disturbances [33].…”