This paper deals with the effect of simultaneous voltage unbalance and over- or undervoltage on windings temperature and thermal loss of life of an induction cage machine. The presented results of investigations are based on the experiment and thermal modeling. The influence of an angle of the complex voltage unbalance factor (CVUF) on machine heating is considered. The effect of synergy of voltage unbalance and voltage rms value deviation is presented. Two induction machines of different properties are compared. One of them has a comparatively weakly saturated magnetic circuit, and the other a comparatively strongly saturated circuit. The former is especially exposed to overheating in the conditions of undervoltage, and the latter in the conditions of overvoltage.

In some power systems, voltage subharmonics and interharmonics of significant value may occur. They exert a harmful effect on various energy receivers, including induction motors. Previous works on an induction machine supplied with voltage containing subharmonics and interharmonics generally concern currents, power losses, rotational speed, electromagnetic torque and windings temperature. This paper reveals additional detrimental effect of voltage subharmonics and interharmonics: namely, excessive vibration of induction motors. It was found that voltage subharmonics of values a few times less than reported in real power systems may cause unacceptable levels of vibration.

Ship power systems are characterised by a comparatively high level of various power quality disturbances, such as voltage deviations, frequency deviations, voltage waveform distortions and sometimes voltage unbalance, which exert a detrimental effect on energy receivers. Among other things, power quality disturbances may cause an extraordinary increase in power losses occurring in on-board induction motors as well as ineffective utilisation of their mechanical output power. In this study, the results of empirical research which demonstrates how power quality disturbances in real ship microgrids affect induction motors are shown. The results of power quality monitoring in ship power systems from the point of view of the energy-efficient operation of induction motors are presented for various vessels and operating conditions. Recommendations concerning the revision of power quality standards and rules are elaborated to provide more energy-efficient ship operation.