Damian Hallmann

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.

Voltage fluctuations are a common occurrence in power systems. They can be regarded as a superposition of the fundamental voltage component, subharmonics and interharmonics – components at frequencies below the fundamental one or not being its integer multiple, respectively. This paper focuses on the effect of the moment of inertia of a driven unit on the subharmonics and interharmonics present in the supply current of a cage induction motor under rectangular voltage modulation. The results of a 2D finite element analysis are presented for a cage induction motor with a rated power of 3 kW. W systemie elektroenergetycznym powszechnie występują wahania napięcia. Można je traktować jako superpozycję składowej podstawowej napięcia, subharmonicznych i interharmonicznych – składowych o częstotliwości mniejszej od podstawowej lub niebędących jej całkowitą wielokrotnością. Niniejszy artykuł poświęcony jest wpływowi momentu bezwładności napędzanego urządzenia na subharmoniczne i interharmoniczne występujące w prądzie zasilania silnika indukcyjnego klatkowego przy prostokątnej modulacji napięcia. Przedstawiono wyniki analizy elementów skończonych 2D dla silnika indukcyjnego klatkowego o mocy znamionowej 3 kW.

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.

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W artykule przedstawiono wyniki badań ultraszybkiego napędu indukcyjno-dynamicznego o dużej energii początkowej baterii kondensatorów. Celem badań było symulacyjne określenie właściwości dynamicznych i termicznych, na podstawie których można wyznaczyć parametry krytyczne zasilania i wymiary cewki miedzianej oraz dysku dwuwarstwowego gwarantujące powtarzalną pracę napędu. Wyznaczone parametry muszą zapewniać oczekiwaną dynamikę poruszającego się dysku nie przekraczając przy tym dopuszczalnej temperatury cewki i dysku.

Cyclic voltage fluctuations can be considered as a superposition of the fundamental voltage component, subharmonic and interharmonic components – that is the components of frequency less than the fundamental one or not being its integer multiple. A commonly occurring case of voltage fluctuations is square voltage modulation. This paper deals with the effect of square voltage modulation on the rotational speed of an induction motor. The results of the FEM computations are presented for a cage induction motor with a rated power 3 kW and various parameters describing the voltage modulation.

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.

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.