Dynamic Eccentricity Research Articles

Vibro-acoustic behavior of a permanent magnet synchronous electrical machine: Influence of rotor displacement on Maxwell's pressures

Electric machines are often perceived as silent, yet the noise they produce has become a significant issue. This paper presents a focused approach to understanding the source of this noise, aiming to enhance machine design. Our study centers on the vibratory model of a permanent magnet synchronous electric machine. The stator and rotor components (shaft, laminations, magnets, and flexible bearings) are modeled using finite element analysis. We calculate the magnetic forces from Maxwell's pressures, which are analytically determined using the subdomain method. A key aspect of our study is the consideration of dynamic eccentricity. The paper explores how the vibratory responses of the rotor affect theses stress and how to address the complexity of magneto-mechanical coupling. Our findings reveal that the magneto-mechanical coupling of the rotor directly and significantly impacts Maxwell's pressures, and has to be taken into account to characterize the dynamics of rotor and stator.

A study on radial oil seal leakage failure due to viscoelasticity under dynamic eccentricity

Purpose This study aims to investigate the causes of leakage in radial oil seals under dynamic eccentricity, elucidate the influence of operating parameters on leakage failure and develop methods for predicting and preventing such leakage. Design/methodology/approach Based on the principle of cam motion and considering viscoelasticity, develops a motion model of the compression and release of the shaft seal and proposes a method to determine its failure. In addition, this study quantifies the leakage gap and formulates a quantitative calculation model to accurately determine the location and shape parameters of the leakage gap. Findings Leakage gaps predominantly occur during the release phase of the shaft seal. Their presence can be identified by comparing the descending times of the seal and the shaft during this phase. An increase in rotation speed and eccentricity heightens the likelihood of gap formation, with both the dimensions and leakage rate of the gap increasing as these factors escalate. Eccentricity, in particular, has a more pronounced effect on gap formation. Originality/value This study clarifies the failure mechanisms of radial oil seals under dynamic eccentricity and introduces a criterion for identifying leakage gaps, providing valuable theoretical guidance for the design and optimization of radial oil seals. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0192/.

Analytical Investigation of Electromagnetic Vibration in Interior Permanent Magnet Synchronous Motors With Dynamic Eccentricity Fault

Analytical Investigation of Electromagnetic Vibration in Interior Permanent Magnet Synchronous Motors With Dynamic Eccentricity Fault

Effects of air gap eccentricity on different rotor structures for PMSM in electric vehicles

In addition to research related to static eccentricity and dynamic eccentricity examining fault and diagnostic methods in various types of motors, there are also studies conducted for motors with non-uniform air gaps similar to the condition. In these studies, improvements and changes in motor performance for such types of motors can be observed. In this study, the effects of the rotor structures determined in the study and the air gap shape, which is effective by changing the eccentricity ratio, on the motor performance of the interior permanent magnet synchronous motor designed for electric vehicle applications are examined. Besides the elliptical rotor structure, which is widely researched in dynamic eccentricity studies, these eccentric motor structures also include novel rectangular and polygonal eccentric rotor structures. Motor models with non-uniform air gap structures are designed in two dimensions and subjected to simulation and analysis studies using the finite element method. At the end of the study, along with the parameters identified for motor performance, the harmonic components of the stator current, radial air gap flux density and the output torque obtained through Fast Fourier Transform analysis have been provided.

Simulation study on the effect of eccentricity on the performance of a reciprocating seal

This article establishes a three-dimensional fluid-structure interaction (FSI) model for reciprocating rod seals. Based on this model, a novel method using a two-dimensional FSI model to solve the average sealing performance across multiple sections is proposed for the first time. This method allows for the dimensional reduction of solid mechanics, contact mechanics, and fluid mechanics analysis. The performance of the sealing system was calculated and analyzed under static eccentricity (which does not change with piston rod motion) and dynamic eccentricity (which changes with piston rod motion) using the aforementioned models. The results indicate that the sealing performance calculated by both models is highly consistent, demonstrating that, within the permissible engineering limits, the two-dimensional FSI model can replace the three-dimensional model, thereby reducing computational costs and improving convergence. Additionally, the results show that eccentricity increases the friction and leakage rates of the sealing system, with dynamic eccentricity having a greater impact on sealing performance than static eccentricity due to the viscoelasticity of the rubber.

Analytical method for contact characteristics of rubber shaft seals under dynamic eccentricity considering viscous effect

This study introduces a methodology for analyzing the viscous effect on rubber shaft seals under dynamic eccentricity. It models the radial motion of the shaft seal and quantifies the viscous force arising from the viscous effect. A 3-D FEM with a noncircular shaft is established, equating viscous force to the interference distribution equation. Then, simulated mounting yield contact characteristics. Findings indicate increased interference with the viscous effect and heightened sensitivity of contact characteristics to eccentricity and rotational speed variations. This approach enhances precision in calculating rubber shaft seal contact characteristics under dynamic eccentricity.

Analysis of Vibration and Noise in Electric Drive System Under Resolver and Motor Rotor Coupling Eccentricity

Eccentricity in a permanent magnet synchronous motor (PMSM) can cause additional electromagnetic forces and resolver error, which in turn can lead to an aggravation of vibration and noise in the electric drive system. In this paper, the additional electromagnetic forces and the resulting vibration and noise under the conditions of the three-dimensional (3-D) static and dynamic motor eccentricities, the resolve error, and the coupling between these faults, are analytically derived and analyzed, with special emphasis on the coupling effect of the motor eccentricity and resolver error. The results of the present theoretical analyses agree well with those from the finite element simulations and the experimental measurements. It can be concluded from the results that the coupling between the 3-D motor eccentricity and the resolver error will induce additional electromagnetic forces with much more diverse spatial orders and frequencies.

Study of the Effect of Static Eccentricity on Vibration Damping Properties of Squeeze Film Dampers Considering the Two-Phase Flow Case

To analyze the effect of static eccentricity on the air ingestion distribution and vibration damping properties of the SFD, a numerical simulation study of SFDs considering two-phase flow was carried out based on CFD using a transient solution method and dynamic mesh technique. The results show that the angle between the static eccentricity direction and the circumferential direction of the oil supply hole increases and the air ingestion area in the oil film expands. In contrast, the oil film damping decreases, and the larger the static eccentricity distance, the greater its effect on the air ingestion area in the oil film. When the circumferential angle is small, the oil film damping increases with the increase of static eccentricity distance, and when the circumferential angle is large, the oil film damping decreases with the increase of static eccentricity distance and then increases. With the increase of static eccentricity distance, the air ingestion area at both ends of the oil film increases. At the same time, studying the effect of dynamic eccentricity shows that as the dynamic eccentricity increases, the oil film damping first decreases and then increases, and the air ingestion area increases. Comparing the 1 hole, the 2 hole, and the 3 hole oil supplies, the air ingestion area is significantly larger in the 1 hole oil supply than in the 2 hole or the 3 hole oil supplies, and the oil film damping of the 1 hole oil supply is smaller than the oil film damping of the 2 hole or the 3 hole oil supplies. It can be seen from the present study that in the actual installation of the SFD, when the circumferential angle is less than 60°, the static eccentricity can be increased appropriately. When the circumferential angle is greater than 60°, the static eccentricity can be appropriately reduced.

An Expeditious Algorithm for Identification and Classification of Rotor Faults in Salient Pole Synchronous Generators

Providing secure electricity depends on the reliable operation of the synchronous generators in power plants. Inter-turn short circuit (ITSC) and dynamic eccentricity (DE) faults are among the most prevalent fault types in wound field synchronous generators (WFSGs). Among the various signals used to detect faults such as current, voltage, and vibration, the stray magnetic field provides higher sensitivity for early-stage ITSC and DE detection. The introduced detection methods rely on comparison of various signals frequency spectrum's from fault and healthy generators. However, obtaining a frequency spectrum of a healthy synchronous generator that has been operating for decades in a power plant is almost impossible. A unique pattern is introduced using fast Fourier transform that can be implemented on a low-end microcontroller and ideal for IoT solutions. The efficacy of the proposed pattern is examined by finite element modeling and validated on a 100 kVA WFSG setup in the laboratory and field test in a power plant with a power rating of 22 MVA.

Numerical simulation study of high-speed lip seal considering eccentricity

PurposeThis paper aims to focus on the high-speed rotary lip seal in aircraft engines, combining its service parameters, its own structure and application conditions, to study the influence of different eccentric forms, eccentricity, rotational speed and other factors on the performance of the rotary lip seal.Design/methodology/approachA numerical simulation model for high-speed eccentric rotary lip seals has been developed based on the theory of elastic hydrodynamic lubrication. This model comprehensively considers the coupling of multiple physical fields, including interface hydrodynamics, macroscopic solid mechanics and surface microscopic contact mechanics, under the operating conditions of rotary lip seals. The model takes into account eccentricity and uses the hazardous cross-sectional method to quantitatively predict sealing performance parameters, such as leakage rate and friction force.FindingsEccentricity has a large impact on lip seal performance; lips are more susceptible to wear failure under static eccentricity and to leakage failure under dynamic eccentricity.Originality/valueThis study provides a new idea for the design of rotary lip seal considering eccentricity, which is of guiding significance for the engineering application of rotary lip seal.

Diagnosis of Mixed Eccentricity in 400 kW Induction Machine Based on Inspection of Stator Current Spectrums

This paper dealing with diagnosis of induction machines affected by combined eccentricity via analyzing the sator curents, inspection of the current spectrums and predict the harmonics that present in the spectrums and represent an indication for this ailment . The machine under invistigation is a 400 kW, four pole-pair, squarelcage induction machine. The current spectrums were calculated for the cases of full symmetry and mixed eccentricity. The calculations presented in this paper, are based on the poly-harmonic model that accounting for static and dynamic eccentricity, stator and rotor slotting, parallel branches as well as cage asymmetry. The calculations were followed by Fourier analysis of the stator currents in steady state operation. The inspection of the current spectrums focusing on two main zones these are the 50 Hz fundamental harmonic zone and the main slot harmonic zone. The paper will include the zooms of the above mentioned zones to demonstrate the harmonics presented in each zone. The calculated spectrums will be compared with the spectrums of the real measured currents.

Spectrum of Induction Machine Stator Currents, Affected By Clutch Wobbling and Mixed Eccentricity

Current spectrum of a four pole-pairs, 550 kW, induction machine were calculated for the cases of full symmetry, clutch wobbling, static and mixed (static + dynamic) eccentricity. The calculations involve integration of 93 electrical plus four mechanical ordinary differential equations. Electrical equations account for variable inductances affected by slotting and eccentricities. The calculations were followed by Fourier analysis of the stator currents in steady state operation. Zooms of the current spectrums, around the 50 Hz fundamental harmonic as well as of the main slot harmonic zone, of both calculated and measured currents are included.

Induction Motor Vibrations Caused by Mechanical and Magnetic Rotor Eccentricity

Vibration reduction of induction motors is a significant problem that requires effective models for the effects of mechanical and electromagnetic unbalanced forces. This article presents a mathematical model of dynamics for induction motors with rotor mass eccentricity and static and dynamic magnetic eccentricity. The model allows for the influence of the gyroscopic torque of the rotor and considers the elastic-damping characteristics of each of the stator supports and their location. The model has eight degrees of freedom, which makes it possible to simulate transverse and axial vibrations of various designs’ rotors and housings of induction motors. The results of modeling the dynamics for a three-phase squirrel cage induction motor with 11 kW capacity agreed with those obtained by other authors. Simultaneously, new results were also obtained within the research. The simulation results showed that the static magnetic eccentricity causes the appearance of additional critical speed of the motor, and its value decreases in proportion to the growth of the number of pole pairs. The change of the moment of inertia of the motor at a mismatch of the main axis of symmetry of the stator and the rotor axis of rotation allowed for obtaining an actual frequency spectrum of free oscillations, including the rotational motion of the stator. Since the actual static magnetic eccentricity can additionally increase at operating frequencies due to the increase of bearing clearance caused by dynamic unbalanced load, it should be considered in the analysis of unbalanced magnetic pull. The angle of static magnetic eccentricity significantly affects the magnitude of radial vibrations. This feature should also be considered when selecting the locations of balancing weights during the rotor balancing procedure.

Dynamic Eccentricity Impact on Electromagnetic Vibration and Acoustic Noise of Interior Permanent Magnet Synchronous Motors With Different Numbers of Parallel Branches

Dynamic Eccentricity Impact on Electromagnetic Vibration and Acoustic Noise of Interior Permanent Magnet Synchronous Motors With Different Numbers of Parallel Branches

Analysis of power grid operation modes considering the influence of tooth harmonics

A harmonic analysis of the magnetic field of an asynchronous motor was carried out, taking into account bilateral gearing and magnetic asymmetry of the air gap. The spectrum is obtained in the form of infinite series of spatio-temporal harmonic components. Magnetic asymmetry of an asynchronous motor takes into account static and dynamic eccentricity, magnetic asymmetry of steel. 27 different spatial harmonics of the field in the air gap of the induction motor were obtained. The considered spectrum of harmonics of the magnetic field will be induced in the stator windings by the electromotive force with the corresponding frequencies. The fields with γр ± κ pairs of poles rotate asynchronously with the rotor and are damped by the fields created by the currents of the rotor cage. Thus, the magnetic asymmetry affects the spatial harmonics of the magnetic field, changing the angular velocities of their rotation in the air gap. The appearance of magnetic asymmetry causes a redistribution of the spatio-temporal distribution of the harmonics of the magnetic field of the tooth frequency, which leads to a change in the amplitude and phase relationships between the quantities. This leads to the appearance of an asymmetric system of electromotive force of tooth frequency in the stator windings, and, therefore, to a different effect of the asymmetry of the air gap at the level of symmetrical components. In the general case, at the level of symmetric components, the electromotive force of the gear frequency is influenced by two groups of factors that determine asymmetric or different from the nominal operating modes of an asynchronous motor of the same size. An increase in the magnetic asymmetry of the air gap causes a nonlinear, close to parabolic character of the growth of the existing symmetrical components. Symmetric components of the electromotive force of the toothed frequency cause currents of the corresponding components to flow through the closed circuits of the stator windings of the asynchronous motor and the entire power supply system. The calculation scheme for replacing a three-phase network for toothed harmonics of electromotive force is given. The phase resistances of the windings of rotating electric machines for asymmetric three-phase networks are not the same for different sequences. The main method of calculating the considered network is the method of symmetrical components. The calculation is made for one main phase according to the substitution schemes, which corresponds to the symmetrical components of the electromotive force of the tooth frequency. As a result of theoretical studies, functional dependences of the influence of magnetic asymmetry on the level and distribution of phase currents of the toothed frequency were obtained. The nature of the influence at the level of symmetric components is close to parabolic, and the most sensitive to changes in magnetic asymmetry is the minor symmetric component of the zero sequence. The method of calculating the currents and voltages of the toothed frequencies of asynchronous motors in the conditions of power consumption has been developed. Theoretical propositions are confirmed by experimental studies. It has been established that the levels of toothed harmonics in power supply systems, as a rule, do not exceed 10–15 % of the level of the fundamental frequency. This leads to a decrease in the reliability of the operation of electrical networks and a shortening of the service life of the main energy equipment at the enterprise. However, frequency-amplitude resonance at tooth frequencies causes the greatest threat to the power plants of industrial enterprises. This is due to the specific nature of gear harmonics of asynchronous motors (parity, dependence on load and various technological factors). The biggest threat arises when using the same type of asynchronous motors with similar operating modes. Oscillograms of experimental studies are given.

Analysis of the effect of maneuvering overload on the reaction force of the main shaft bearing in aero-engine

In order to study the effects of maneuvering overload on the main shaft bearing (abbreviation: bearing) reaction force in an aero-engine, a bending-torsion coupling dynamic model of the dual rotor system under maneuvering overload was established. Combined with the output parameters of the system model, the bearing reaction force analysis model was established. The maneuvering overload parameters are input into system model. Newmark-β and Newton-raphson methods are used to obtain the bearing reaction force response, and the change laws of bearing reaction force under the different maneuvering overloads are analyzed. The results show that gravity will make the transient response of bearing reaction force offset, and maneuvering overload will make the offset shift. Maneuvering overload will cause bearing to produce a circumferential asymmetric reaction force. For bearing 1, the additional gyroscopic torque in maneuvering overload has a significant effect on the dynamic eccentricity, resulting in a larger offset of reaction force of y direction. For bearings 3 and 4, reaction force of x direction has a larger offset. Under the influence of bent-torsional coupling, the combined frequencies of base frequencies of rotational speed appear in the reaction force spectrum diagram.

Empirical mode decomposition and Hilbert–Huang transform-based eccentricity fault detection and classification with demagnetization in 120 kW interior permanent magnet synchronous motors

Permanent magnet synchronous motors (PMSMs) are extensively used in electric vehicles (EVs) owing to their high power density and efficiency. However, their safety and reliability have not been verified sufficiently. Failure of PMSMs in EVs can cause performance degradation, increased maintenance costs, and catastrophic accidents. Therefore, early detection of faults in PMSMs is necessary for an efficient and safe operation. In this study, static, dynamic, and mixed eccentricity faults in 120 kW interior permanent magnet synchronous motors (IPMSMs) were diagnosed and distinguished from uniform demagnetization fault by monitoring the Hilbert spectrum of the stator current. Experiments were carried out for different speeds, loads, and fault severities to analyze the effect of operating conditions on the proposed fault detection method. The phase current data were decomposed into set of intrinsic mode functions (IMFs) with empirical mode decomposition (EMD) method and Hilbert transform was applied for each IMFs to calculate the instantaneous frequency and energy. The resultant Hilbert spectrum exhibited instantaneous frequency distortions with an instantaneous energy surge under an eccentricity fault. The effect of thresholding in EMD was analyzed to improve the accuracy of the proposed method under high-load and high-speed conditions. Also, the experimental results showed that eccentricity and uniform demagnetization faults can be classified by monitoring the overall instantaneous energy.

Stator current signal crossing for fault diagnosis of self-excited induction generators

This paper presents a novel method for modelling and diagnosis of electrical and mechanical faults in fixed-Speed Self-Excited Induction Generators (SEIGs) operating in autonomous mode in a small-scale wind energy system. The proposed method is validated using the finite element method. After the selection of the magnetising capacitors, the self-excitation process is performed under no-load conditions. Once the stator voltage is established, a symmetrical three-phase load is connected. The fault detection method introduced here is called Stator Current Signal Crossing (SCSC). The SCSC extracts a new signal from the stator currents, that enables the detection of stator inter turn shortcircuits, broken rotor bars, and dynamic eccentricity faults in SEIGs. A spectral analysis of SCSC using the Fast Fourier Transform (FFT) algorithm is used to precisely locate the induced fault components. What sets this fault-tracking method apart from its predecessors is its exceptional ability to detect faults of any magnitude by analysing the modulation of the SCSC signal. These faults are directly identified by the presence of distinct harmonics, each indicative of a specific type of fault. This study also focuses on the SEIG in a wind energy system, whereas previous works have mainly addressed the induction machine in motor mode. In contrast, previous methods involved analysing a single current signal and isolating specific harmonics from a wide frequency range. The effectiveness of the proposed fault detection method and the self-excitation process are illustrated by simulation results and spectral analysis.

Investigation on the Influence of Eccentricity on the AC Copper Loss of High-Speed Slotless Permanent Magnet Motor

The armature winding of slotless motor is directly exposed to the air gap magnetic field. During high speed operation, the effective part of the armature winding cuts the flux lines directly, which would inevitably cause large AC copper loss. Moreover, when the rotor is eccentric, appreciable distortions would be appeared in the air gap flux density. The additional flux density would aggravate the AC copper loss. In this paper, the mechanism of AC copper loss of high speed slotless motors is explained firstly. Then the influence of eccentricity on AC copper loss is evaluated. Finally, the difference in the effect of dynamic and static eccentricity on AC copper loss is compared.

A mathematical analytical modeling method for rotor eccentricity fault of large VSPSU

Aiming at the rotor eccentric fault modeling problem of large VSPSU (VSPSU), a mathematical analytical modeling method based on air gap magnetic field analysis is proposed. This method uses Fourier series decomposition to represent the air gap permeability of static and dynamic eccentricity faults. Then, taking a single coil as a unit, the eccentric self-inductance coefficients between each branch of the windings are derived. Furthermore, the mathematical analytical modeling of the eccentric fault is completed by combining the voltage and flux formulas of each winding branch. The model can reliably reflect the typical fault characteristics of large VSPSUs with eccentric faults, which can provide an analysis basis for subsequent relay protection research.