Voltage disturbances occur frequently in power systems. The most important voltage disturbances are voltage unbalance, voltage deviation, and voltage waveform distortions. Voltage waveform distortions are usually considered harmonics, but subharmonics and interharmonics may also occur. Voltage subharmonics are components with frequencies lower than the fundamental frequency. In contrast, voltage interharmonics are components of the frequency spectrum that are higher than the fundamental frequency and are not integer multiples of it. Voltage fluctuations are the superposition of the first voltage harmonic and subharmonic components. This work analysed the shaft torque pulses of an induction motor under single-subharmonic action or under periodic voltage fluctuations combined with voltage unbalance. The experimental results were compared with results from previous work. We also analysed the influence of voltage disturbances on the selection of the coupling connecting the induction motor to the working machine.

Voltage fluctuations can be regarded as the superposition of voltage subharmonics and interharmonics of various frequencies – that is, the frequency components are less than, or not integer multiples of, the fundamental frequency. In practice, under voltage modulation each subharmonic or interharmonic corresponds to a particular harmonic of the modulating function. This work addresses currents in single-phase induction motors under conditions of asymmetric rectangular voltage fluctuations. Empirical results are presented for a motor with a permanently connected capacitor.

In addition to fundamental harmonics, the voltage waveform may contain various undesirable components, including subharmonics (subsynchronous interharmonics) and interharmonics (SaIs), which are components with frequencies less than or not an integer multiple of the fundamental frequency. Voltage SaIs are considered especially detrimental power quality disturbances, exerting negative impacts on rotating machinery. They are generated by various electrical equipment, including single-phase equipment. This work addresses the effects of the occurrence of subharmonics in one phase of the supply voltage on three-phase cage induction motors. The results of 2D finite element computations and experimental investigations show that subharmonics occurring in one phase cause high torque pulsations and unacceptable vibrations. For the investigated motor, the minimal value of the voltage subharmonic causing excessive vibration is more than twice that in the case of balanced three-phase subharmonics. It is concluded that power quality standards should contain separate limits for SaIs averaged for three line voltages and for SaIs occurring in each phase voltage.

In some power systems, the voltage waveform contains frequency components less than fundamental, called subharmonics or subsynchronous interharmonics. Voltage subharmonics can be both positive- and negative-sequence, independent of their frequency (order). Subharmonics exert harmful effects on sundry electrical equipment, especially on rotating machinery; they cause various noxious phenomena, such as a local saturation of the magnetic circuit, increases in power losses and windings temperature, and torque pulsations leading to vibration of unacceptable severity. Notably, previous works reported excessive vibration of rotating machinery only under no-load, while under full load, rather moderate vibration occurred. This study deals with vibration analysis of a line-start permanent magnet synchronous motor (LSPMSM) supplied with the voltage containing negative-sentence subharmonics. Experimental investigations were conducted for a 3 kW, four-pole production LSPMSM for subharmonics of various values and frequencies. Voltage subharmonics of values significantly less than reported in real power systems were found to cause unacceptable vibration, especially under full load.

In power systems, various power quality disturbances are present, including voltage deviation, voltage unbalance, and voltage waveform distortions. Voltage waveform distortions are usually identified with harmonics, but in some systems, subharmonics (subsynchronous interharmonics) and interharmonics may also occur—that is, components of frequency less than the fundamental frequency, or not an integer multiple of it. This study examines torque pulsations of an induction motor under voltage subharmonics combined with voltage unbalance. The motor and the driven DC generator vibrations were analysed under the power quality disturbances. Investigations were carried out using finite element and empirical methods. Experimental tests were performed for the maximal levels of the power quality disturbances specified or proposed in the relevant standards. For the investigated motor, under voltage subharmonics or voltage unbalance occurring as a single power quality disturbance, the vibration level was within the prescribed limit. However, under unbalance combined with subharmonics, the level could be accepted for only a limited time. Consequently, the permissible level of voltage subharmonics in non-generation installations should be interconnected with the voltage unbalance in the power system.

This study deals with currents of a line start permanent magnet synchronous motor (LSPMSM), supplied with voltage containing subharmonics and interharmonics – components of the frequency less than the fundamental frequency or not being equal to its integer multiple, respectively. The results of experimental investigation are presented for a factory-made four-pole LSPMSM of the rated power 3 kW. Voltage interharmonics result in the flow of current components of various frequencies and comparatively small values. Their presence could lead to resonance phenomena, but is not expected to cause the motor overheating. Contrastingly, voltages subharmonics cause the flow of significant current subharmonics, which may considerably increase power losses, and consequently – the thermal loads of the LSPMS.

One of the types of power quality disturbances met in a power system is voltage fluctuations. Cyclic voltage fluctuations are interconnected with the presence of subharmonics and interharmonics – that is components of frequency less than the fundamental frequency or not being its integer multiple. Voltage fluctuations can be considered as practical examples of the simultaneous presence of subharmonics and interharmonics of various frequencies. This study deals with the preliminary investigations on an induction motor under voltage fluctuations of frequency greater than the supply voltage frequency. The results of the empirical investigations on currents under rectangular modulation of voltage amplitude are presented for a four-pole cage induction motor of a rated power of 4 kW.

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.

One method for the remote management of electrical equipment is ripple control (RC), based on the injection of voltage interharmonics into the power network to transmit information. The disadvantage of this method is its negative impact on energy consumers, such as light sources, speakers, and devices counting zero crossings. This study investigates the effect of RC on low-voltage induction motors through the use of experimental and finite element methods. The results show that the provisions concerning RC included in the European Standard EN 50160 Voltage Characteristics of Electricity Supplied by Public Distribution Network are imprecise, failing to protect induction motors against excessive vibration.

Sinusoidal voltage fluctuations can be considered a specific result of the occurrence of voltage subharmonics and interharmonics, which are components of low frequency or not being an integer multiple of the frequency of the fundamental voltage harmonic. These components—symmetrical subharmonics and interharmonics—are of the same magnitude, while their frequencies are symmetrical with respect to the fundamental frequency. Depending on their phase angles, various kinds of voltage fluctuations can be distinguished: amplitude modulation, phase modulation and intermediate modulation. In this study, the effect of phase angles on noxious phenomena in induction motors was analyzed. Additionally, torque pulsations and vibrations of an induction motor under sinusoidal voltage fluctuation and a single voltage subharmonic or interharmonic were compared. The investigations were performed with the finite element method and an experimental method. Among other findings, it was found that for some phase angles torque pulsations could be about ten times higher than for other angles, roughly corresponding to the amplitude modulation.

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.

Some of the most common power quality disturbances are voltage fluctuations. They are interconnected with the presence of voltage subharmonics and interharmonics. Voltage fluctuations, subharmonics and interharmonics exert a negative effect on various elements of a power system, including cage induction motors. This work is devoted to the impact of voltage fluctuations on the current of a one-phase induction motor. The results of empirical investigations are presented for sinusoidal amplitude modulations of various frequencies and are compared with the effects of voltage subharmonics occurring as a single power quality disturbance.

In a power system, the voltage waveform usually contains harmonics and sometimes interharmonics, often defined as components of frequency greater than the fundamental voltage component but not of its integer multiple. Previous studies have reported a minor effect of voltage interharmonics on a cage induction machine. This paper reveals their extraordinary harmfulness for induction motors. Namely, voltage interharmonics may cause high vibration, which can result in machine damage. In addition, interharmonics can lead to torque pulsations corresponding to the natural frequency of the first elastic mode. Consequently, possible torsional resonance may cause destruction of a power train. In this study, the results of investigations on undesirable phenomena due to interharmonics are presented for seven motors with a rated power 3 kW–5.6 MW.

In very low power drives, a single-phase induction motor is used. This motor, like the 3-phase induction squirrel-cage motor, requires a voltage supply with suitable parameters – of suitable quality, in practice. In energy systems, voltage quality distortions may occur in connection with the deviation of the RMS voltage and the occurrence of harmonics, subharmonics and interharmonics in its waveforms. Subharmonics and interharmonics in the voltage waveforms are particularly detrimental to induction motors. They cause, for example, additional power losses, electromagnetic torque pulsation and motor vibrations. It should be stressed that the existing publications on the impact of the considered distortions on the induction squirrel-cage motor are almost only applicable to 3-phase machines. The article presents the results of research on the influence of subharmonic and interharmonic voltage components on the single-phase induction squirrel-cage motor.

A particularly promising industrial prime mover is a line start permanent magnet synchronous motor (LSPMSM). LSPMSMs, just as other energy receivers, are exposed to the noxious impact of various power quality disturbances. Previous works on this issue have been limited to the effect of voltage harmonics, voltage unbalance and voltage deviation on the motor. This study initiates novel research on the LSPMSM supplied with the voltage containing subharmonics, which involve components with frequencies less than that of the fundamental component. The results of experimental investigations are presented for a factory-made 3-kW LSPMSM. Voltage subharmonics were found to exert an extraordinarily harmful influence on motor under consideration. Subharmonics of values similar to those reported in real power systems were determined to cause unacceptable vibration.

Power quality disturbances related to voltage waveform distortions and effective value deviation are common in power systems. Apart from higher harmonics, subharmonics and interharmonics may also appear in voltage waveforms. The presence of the above-mentioned disturbances causes additional power losses and an increase in thermal loads on induction motors. In this paper, the results of the study of the influence of subharmonics present in voltage waveform on the currents in the investigated induction motors of standard efficiency class – IE1 and high efficiency class – IE3, are presented.

The reduction of greenhouse gas emissions is a major contemporary challenge. This has prompted the requirements concerning energy efficiency for ships, among other things. Improvement in efficiency of ship operations could be achieved by reducing unnecessary power consumption by induction motors. Specifically, the occurrence of power quality disturbances, such as frequency and voltage deviations, voltage unbalances, and voltage harmonics, can cause an extraordinary increase in the power losses occurring in induction motors, as well as an unnecessary increase in the output power. Furthermore, excessive power quality disturbances are often interconnected with failures of on-board equipment, and in extreme cases, these may even pose a threat to safety at sea. Consequently, strict power quality monitoring of on-board microgrids can also contribute to improving safety while afloat. In this study, a dedicated tool for power quality monitoring is proposed, namely the coefficient of voltage energy efficiency, which has a value proportional to the power losses occurring in induction motors under power quality disturbances.

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.

This paper deals with the effect of voltage subharmonics on power losses and heating of an induction motor. An increase in power losses in stator and rotor windings and their impact on windings temperature is presented for subharmonics of various frequencies. The results of this study's investigations are provided for subharmonics occurring as a single power quality disturbance and combined with voltage deviation. The appropriate electromagnetic computations were performed with the finite element method, and thermal ones - with an analytical method.