Induction Cage Machine Thermal Transients under Lowered Voltage Quality

In many power systems, voltage parameters change over time. Variation of power quality disturbances causes thermal transients in electrical machines. Under volatile power quality disturbances, the windings temperature can reach an extremely high level. This problem might be especially important in the case of low-power motors, as they have comparatively short thermal time constants. In this study, thermal transients of an induction machine are analysed for time-varying power quality disturbances. The machine's thermal response to voltage deviation, voltage unbalance, and voltage waveform distortions is compared. The effect of fluctuating voltage unbalance on the heating of the windings is examined. The results of experimental investigations and numerical calculations are presented for two low-power, totally enclosed fan-cooled induction cage machines. It was found that voltage unbalance causes much faster heating of the windings than do other power quality disturbances and that the current power quality standards require revision.