Induction Motors Under Voltage Fluctuations and Power Quality Standards

Periodic voltage fluctuations are considered superposition of the fundamental harmonic and additional components, namely subharmonics and interharmonics (SaIs) —components of frequencies that are less than or not integer multiples of the fundamental frequency. Therefore, voltage fluctuations (VFs) occurring in real power systems are practical examples of various voltage SaIs. VFs and SaIs interconnected with them exert a harmful effect on rotating machinery, transformers, control systems, and electronic appliances. This study analyzes induction motors under VFs using experimental and finite element methods. The vibration and torque pulsations are compared for a single voltage subharmonic/interharmonic injection and VFs with various shapes of the modulating function. The results show that requirements concerning flicker severity, as well as the proposals to limit SaIs included in the standard IEEE-519:2022, do not protect induction motors against excessive vibration. Recommendations concerning the limitations of SaIs are formulated.