Induction Motor Supplied with Voltage Containing Symmetrical Subharmonics and Interharmonics

Abstract

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.

Line-Start Permanent Magnet Synchronous Motor Supplied with Voltage Containing Negative-Sequence Subharmonics

“…In addition, previous research [5,[35][36][37][38] indicated high transverse vibration of the rotating machinery for no-load, while in other load conditions, the observed vibration was generally moderate. At the same time, at least temporarily, many motors carry a load much less than rated [42,43], but this is not typical.…”

“…A prominent source of SaIs includes time-varying loads, which can be divided into regularly fluctuating loads, e.g., welder machines, laser printers, and devices with integral cycle control, and irregularly fluctuating loads, such as arc furnaces [16]. The work of timevarying loads causes current modulation [7,16], resulting in voltage fluctuations [7,25,26,35]. At the same time, sinusoidal voltage fluctuations can be analysed as a superposition of the fundamental voltage component, a subharmonic component, and an interharmonic component of the following frequencies [7,27,31,35]:…”

“…Subharmonics and, interconnected with them, voltage fluctuations cause various noxious phenomena in transformers, light sources, control systems, and power electronic and measurement equipment [4,7,16,24,27,29,30]. Especially sensitive to subharmonics is rotating machinery (based on [5,14,23,27,[31][32][33][34][35][36][37][38][39]). Subharmonics have been reported to cause excessive transverse and torsional vibrations, increases in power losses and windings temperatures, local saturations of magnetic circuits, and speed fluctuations.…”

“…Rotating machinery supplied with voltage containing SaIs is the subject of numerous research works. They usually concern either multi-megawatt powertrains [10,14] or induction motors [5,23,28,[31][32][33][34][35]. Furthermore, the effect of SaIs on the line-start permanent magnet synchronous motor (LSPMSM) [40,41] was only preliminarily analysed in the authors' works [36,37].…”

Monitoring Single-Phase LV Charging of Electric Vehicles

“…Disturbances in the power quality have negative impacts on particular elements of the power system, including electric machines [ 2 , 3 ], causing, e.g., their overheating [ 4 ], excessive vibrations [ 5 ], torsional vibrations [ 6 ], reduced efficiency [ 7 ], loss of reliability, and durability [ 8 , 9 , 10 ]. Power quality disturbances that occur in the power grid and affect the reliability of electrical machines include, among others, voltage fluctuations [ 11 , 12 ], voltage distortions caused by higher harmonics [ 13 ] or inter-harmonics [ 14 , 15 ]. At the same time, in some cases, the operation of electric machines or devices associated with them can also cause disturbances of power quality [ 16 , 17 , 18 ], for example, the electric machine control or the charging of an electric vehicle (EV) [ 19 , 20 ].…”