Flicker Attenuation—Part I: Response of Three-Phase Induction Motors to Regular Voltage Fluctuations

Voltage fluctuations leading to lamp flicker that originate in one place in a power system tend to propagate to other parts of the network with some level of attenuation depending on the network impedances and the loads connected. Numerous subsynchronous-type frequency components exist in these voltage fluctuations that are responsible for lamp flicker. The rudimentary theory and the experimental measurements support the idea that industrial load bases, which contain a large percentage of mains-connected induction motors, tend to attenuate flicker better compared to residential load bases having mainly passive loads. This paper reports on the response of three-phase induction motors of several sizes when subjected to low-frequency voltage fluctuations: 1) the case where a balanced single-frequency component is superimposed on the mains voltage and 2) the case where the mains voltage is sinusoidally amplitude modulated, a scheme that is frequently used in the flicker-related work. Small-signal models are presented that will enable systematic understanding of the behavior which is verified using large signal models.