Journal articles: 'Rotor Static Eccentricity'

1

Karami, Mahdi, Norman Mariun, Mohammad Rezazadeh Mehrjou, Mohd Zainal Abidin Ab Kadir, Norhisam Misron, and Mohd Amran Mohd Radzi. "Static Eccentricity Fault Recognition in Three-Phase Line Start Permanent Magnet Synchronous Motor Using Finite Element Method." Mathematical Problems in Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/132647.

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This paper is dedicated to investigating static eccentricity in a three-phase LSPMSM. The modeling of LSPMSM with static eccentricity between stator and rotor is developed using finite element method (FEM). The analytical expression for the permeance and flux components of nonuniform air-gap due to static eccentricity fault is discussed. Various indexes for static eccentricity detection using stator current signal of IM and permanent magnet synchronous motor (PMSM) are presented. Since LSPMSM is composed of a rotor which is a combination of these two motors, the ability of these features is evaluated for static eccentricity diagnosis in LSPMSM. The simulated stator current signal of LSPMSM in the presence of static eccentricity is analyzed in frequency domain using power spectral density (PSD). It is demonstrated that static eccentricity fault generates a series of low frequency harmonic components in the form of sidebands around the fundamental frequency. Moreover, the amplitudes of these components increase in proportion to the fault severity. According to the mentioned observations, an accurate frequency pattern is specified for static eccentricity detection in three-phase LSPMSM.

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WERNER, ULRICH. "THEORETICAL VIBRATION ANALYSIS OF SOFT MOUNTED TWO-POLE INDUCTION MOTORS WITH STATIC ROTOR ECCENTRICITY." International Journal of Applied Mechanics 03, no. 01 (March 2011): 131–59. http://dx.doi.org/10.1142/s1758825111000919.

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The paper shows a mathematical model for vibration analysis of soft mounted two-pole induction motors regarding electromagnetic excitation due to static rotor eccentricity. A static rotor eccentricity causes an electromagnetic force, acting on the rotor and on the stator and oscillating with the double supply frequency. This magnetic force is implemented into a simplified analytical machine dynamic model and the correlations between the rotor dynamics, electromagnetic, oil film characteristics of the sleeve bearings, and the stiffness and damping of a soft foundation are mathematically described. The derived results are clarified using an example that shows the influence of the rotor speed and the direction of the magnetic force on the vibration behavior. On one hand the aim of the paper is to show the mathematical correlations, based on a simplified model. On the other hand, the aim is to derive a method for calculating the forced vibrations — as a worst case — caused by a static rotor eccentricity. Therefore, the paper shall prepare the basis for implementing this method in more detailed numerical programs, e.g., finite element programs.

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Lasjerdi, H., Z. Nasiri-Gheidari, and F. Tootoonchian. "Static Eccentricity Fault Diagnosis in Wound-Rotor Resolvers." IEEE Sensors Journal 21, no. 2 (January 15, 2021): 1424–32. http://dx.doi.org/10.1109/jsen.2020.3019260.

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Wang, Wenbo, Pengyun Song, Hechun Yu, and Guoqing Zhang. "Study on Static Characteristics of Ultra-Precision Aerostatic Motorized Spindle under Gas–Magnetic Field Coupling." Electronics 11, no. 9 (April 29, 2022): 1434. http://dx.doi.org/10.3390/electronics11091434.

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In the working process of ultra-precision aerostatic motorized spindles, the journal and the rotor must have a certain eccentricity to have a certain bearing capacity and stiffness, which will induce the unbalanced magnetic pull (UMP). The intercoupling of the UMP and the gas film force will affect the motion state of the rotor and the accuracy of spindles. In order to deeply study the influence of the UMP caused by the rotor eccentricity on the equilibrium position of aerostatic spindles, a physical model of an aerostatic spindle based on slit throttling gas bearing is established and the coupling effect between the rotor and the motor rotor is studied and analyzed as a whole. The equilibrium position of the rotor under the combined action of gravity, the gas film force and the UMP is deduced, and a gas–magnetic field coupling calculation program based on the finite difference method is proposed. The calculation results show that with the increase in rotational speed, the equilibrium position of the rotor will move to the center of the journal in the micron scale, and the moving amplitude will gradually slow down. The UMP caused by rotor eccentricity can offset the rotor equilibrium position in nanometer scale, and the influence degree decreases sharply as the rotor moves to the journal center. With the increase in rotational speed, the direct stiffness and the cross stiffness will increase, and the amplitude of the cross stiffness is greater than the direct stiffness. This study is of great significance for further studying the influence of the rotor eccentricity on the equilibrium position and the accuracy of the rotor.

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Wan, Shuting, and Yuling He. "INVESTIGATION ON STATOR AND ROTOR VIBRATION CHARACTERISTICS OF TURBO-GENERATOR UNDER AIR GAP ECCENTRICITY FAULT." Transactions of the Canadian Society for Mechanical Engineering 35, no. 2 (June 2011): 161–76. http://dx.doi.org/10.1139/tcsme-2011-0010.

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This paper investigates the stator and the rotor vibration characteristics of turbo-generator under the air gap eccentricity fault. Firstly the air gap magnetic flux density of the fault is deduced, and the formula of the magnetic pull per unit area acting on the stator and the unbalanced magnetic pulls of x-axis and y-axis acting on the rotor are respectively gotten. Then the static eccentricity, the dynamic eccentricity and the mixed eccentricity are respectively studied to analyze the stator and the rotor vibration characteristics. Finally experiments are done on a SDF-9 non-salient fault simulating generator to verify the theoretical results. The investigation results of this paper will be beneficial to the air gap eccentricity fault diagnosis of turbo-generator.

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Karami, Mahdi, Norman Mariun, Kadir Ab, Radzi Mohd, and Norhisam Misron. "Analysis of rotor asymmetry fault in three-phase line start permanent magnet synchronous motor." Facta universitatis - series: Electronics and Energetics 34, no. 4 (2021): 483–98. http://dx.doi.org/10.2298/fuee2104483k.

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This article proposed a detection scheme for three-phase Line start permanent magnet synchronous motor (LSPMSM) under different levels of static eccentricity fault. Finite element method is used to simulate the healthy and faulty LSPMSM with different percentages of static eccentricity. An accurate laboratory test experiment is performed to evaluate the proposed index. Effects of loading condition on LSPMSM are also investigated. The fault related signatures in the stator current are identified and an effective index for LSPMSM is proposed. The simulation and experimental results indicate that the low frequency components are an effective index for detection of the static eccentricity in LSPMSM.

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Shuraiji, Ahlam Luaibi. "The effect of static and dynamic eccentricities on the performance of flux reversal permanent magnet machine." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 2 (June 1, 2020): 634. http://dx.doi.org/10.11591/ijpeds.v11.i2.pp634-640.

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This study investigates the effect of static and dynamic eccentricities on the performances of flux reversal permanent magnet (FRPM) machine with even rotor pole number, i.e. FRPM machine with 12/10 stator/rotor combination. No-load and load performances of the machine are investigated under three rotor operating conditions including centricity, static eccentricity and dynamic eccentricity. The investigation has been carried out using 2D-FEA. It has been revealed that the 12/10 FRPM machine under normal operating condition has no unbalanced magnetic force, due to the even pole number of the rotor. On the other hand, such undesirable feature would be presented in the 12/10 FRPM machine as a result of the existing of static and dynamic eccentricities. Both static and dynamic eccentric machines exhibit unbalanced three-phase flux linkage as well as back-EMF. Moreover, three operating conditions of the investigated machine have the same fundamental cogging torque harmonic. However, low order harmonics are existed in the static and dynamic centric machines and are not found in the centric machine. Furthermore, about 16% less torque ripple delivered by the centric machine compared with both static and dynamic counterparts.

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He, Yu-Ling, Meng-Qiang Ke, Fa-Lin Wang, Gui-Ji Tang, and Shu-Ting Wan. "EFFECT OF STATIC ECCENTRICITY AND STATOR INTER-TURN SHORT CIRCUIT COMPOSITE FAULT ON ROTOR VIBRATION CHARACTERISTICS OF GENERATOR." Transactions of the Canadian Society for Mechanical Engineering 39, no. 4 (December 2015): 767–81. http://dx.doi.org/10.1139/tcsme-2015-0061.

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This paper investigates the radial rotor vibration characteristics under static air-gap eccentricity and stator inter-turn short circuit composite faults. The air-gap magnetic flux density is firstly deduced to obtain the unbalanced magnetic pull (UMP) on rotor. Then the rotor vibration characters, as well as the developing trend between the faulty parameters and the vibration amplitudes, are analyzed. Finally, the experiments are taken on a SDF-9 type simulating generator. It is shown that the radial deformation possibility, the 2nd, 4th, and 6th harmonic vibrations will be caused by the composite faults. Besides, the development of the inter-turn short circuit, the increment of the static eccentricity, and the rise of the exciting current will all get the deformation trend and the vibration amplitudes increased.

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9

Qian, Kun Xi, and Teng Jing. "Route Chart to Stabilizing Permanent Maglev Rotator." Advanced Materials Research 785-786 (September 2013): 1586–89. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.1586.

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Permanent maglev has been since long recognized to be unstable because of Earnshaw's theory, which theoretically proved that permanent maglev can not achieve stable equilibrium in static state. How about that in dynamic state, for example, about a rotator, nobody has given an answer until now actually. A permanent maglev pump and a permanent maglev turbine have been developed, by using a patented permanent magnetic bearing developed by the author. Experiments demonstrated, there is a critic speed either in the pump or in the turbine, under which the rotors in the pump and the turbine have a maximal eccentricity being possible to reach the gap between the rotor and the stator. That means the rotors have contact with the stators occasionally, and thus the rotor is not suspended. In case the rotating speed is higher than this critic speed, the rotors' eccentricity will be remarkably smaller than the gap between the rotor and the stator, that is to say the rotor is stably levitated. Further investigation exhibtes that at the critic speed a so-called gyro-effect is generated which stabilizes the rotor, just like a gyro standing over a ball, if the rotating speed is large enough it can be stable over the ball. The critic speed, essentially to be minimal stable speed of the rotor, depends on the rotating inertia of the rotor and the bearing force, the larger the inertia and the larger the force, the lower the critic speed. Conclusively, a route chart to stabilization of permanent maglev rotator has been clear: in static state, permanent maglev is unstable (Earnshaw's theory); as the rotating speed gradually increases but not up to a critic speed, the permanent maglev rotator is also unstable; in case that the speed equals or is larger than this critic speed, the permanent maglev rotator is suspended stably because of gyro-effect; the critic speed is affected by rotating inertia of the rotor and the bearing force, by larger inertia and larger bearing force, the critic speed will be smaller.

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10

Lee, Hoon Ki, Tae Kyoung Bang, Jong Hyeon Woo, Hyo Seob Shin, and Jang Young Choi. "Electromagnetic Characteristic Analysis of Permanent Magnet Synchronous Machine Considering Current Waveform According to Static Rotor Eccentricity." Applied Sciences 10, no. 23 (November 27, 2020): 8453. http://dx.doi.org/10.3390/app10238453.

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In this study, we performed an electromagnetic characteristic analysis of a permanent magnet synchronous machine considering the current waveform based on static rotor eccentricity. First, the characteristics of the back electromotive force were analyzed through the no-load analysis of the analysis model according to static rotor eccentricity. Next, a dynamic analysis was performed through mathematical modeling of a permanent magnet synchronous motor and PWM method. The input current during operation was derived through the dynamic analysis, and the core loss analysis was performed using derived input current. The core loss analysis was performed using the case where the fundamental wave current was applied and the input current derived through the dynamic analysis, and the results were compared.

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11

Nässelqvist, Mattias, Rolf Gustavsson, and Jan-Olov Aidanpää. "Experimental and Numerical Simulation of Unbalance Response in Vertical Test Rig with Tilting-Pad Bearings." International Journal of Rotating Machinery 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/309767.

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In vertically oriented machines with journal bearing, there are no predefined static radial loads, such as dead weight for horizontal rotor. Most of the commercial software is designed to calculate rotordynamic and bearing properties based on machines with a horizontally oriented rotor; that is, the bearing properties are calculated at a static eccentricity. For tilting-pad bearings, there are no existing analytical expressions for bearing parameters and the bearing parameters are dependent on eccentricity and load angle. The objective of this paper is to present a simplified method to perform numerical simulations on vertical rotors including bearing parameters. Instead of recalculating the bearing parameters in each time step polynomials are used to represent the bearing parameters for present eccentricities and load angles. Numerical results are compared with results from tests performed in a test rig. The test rig consists of two guide bearings and a midspan rotor. The guide bearings are 4-pad tilting-pad bearings. Shaft displacement and strains in the bearing bracket are measured to determine the test rig’s properties. The comparison between measurements and simulated results shows small deviations in absolute displacement and load levels, which can be expected due to difficulties in calculating exact bearing parameters.

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12

Du, Jianmin, and Yan Li. "Analysis on the Variation Laws of Electromagnetic Force Wave and Vibration Response of Squirrel-Cage Induction Motor under Rotor Eccentricity." Electronics 12, no. 6 (March 8, 2023): 1295. http://dx.doi.org/10.3390/electronics12061295.

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Aiming to address the rotor eccentricity problem caused by various factors, such as manufacturing, operation and the mass imbalance of the induction motor, the variation law of electromagnetic force wave and vibration response under rotor eccentricity during no-load operation is investigated. To begin with, on the basis of the air-gap permeability, the air-gap magnetic density components under static and dynamic eccentricity are analyzed by using the analytical method. The order and amplitude expressions of the radial electromagnetic force generated by the interaction of harmonics are obtained. Subsequently, a finite element model of the electromagnetic field was developed, and the space-time spectrum of the electromagnetic force was obtained by combining the 2D Fourier analysis. Finally, the electromagnetic force wave is used as a load to investigate the electromagnetic vibration response under different rotor eccentric forms. The effect of rotor eccentricity on the vibration response of the motor is quantitatively analyzed by using the spectral analysis method. The method of analyzing electromagnetic force wave and vibration response can also provide a reference for the same type of motor.

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13

Mahdiuon-Rad, S., S. R. Mousavi-Aghdam, M. Reza Feyzi, and M. B. B. Sharifian. "Analysis of PM Magnetization Field Effects on the Unbalanced Magnetic Forces due to Rotor Eccentricity in BLDC Motors." Engineering, Technology & Applied Science Research 3, no. 4 (August 11, 2013): 461–66. http://dx.doi.org/10.48084/etasr.296.

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This paper investigates both static and dynamic eccentricities in single phase brushless DC (BLDC) motors and analyzes the effect of the PM magnetization field on unbalanced magnetic forces acting on the rotor. Three common types of PM magnetization field patterns including radial, parallel and sinusoidal magnetizations are considered. In both static and dynamic eccentricities, harmonic components of the unbalanced magnetic forces on the rotor are extracted and analyzed. Based on simulation results, the magnetization fields that produce the lowest and highest unbalanced magnetic forces are determined in rotor eccentricity conditions.

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14

He, Yu-Ling, Wei-Qi Deng, Gui-Ji Tang, Xiao-Ling Sheng, and Shu-Ting Wan. "Impact of Different Static Air-Gap Eccentricity Forms on Rotor UMP of Turbogenerator." Mathematical Problems in Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/5284815.

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Theoretical analysis and numerical FEM calculations, together with segmental experiment studies, are used to study the impact of the static air-gap eccentricity forms on the rotor unbalanced magnetic pull (UMP) of turbogenerator. The universal expression of the magnetic flux density under different forms of SAGE is firstly deduced, based on which the detailed UMP formulas for the normal condition and three SAGE cases are obtained, respectively. Then the exciting characteristics of the UMP for each SAGE form to generate vibrations are analyzed. Finally, numerical FEM calculations and segmental experiments are carried out to investigate the effect of SAGE forms on the rotor UMP, taking the SDF-9 type non-salient-pole fault simulating generator as the object. It is shown that, no matter what kind of SAGE occurs, amplitude increments at each even harmonic component of the UMP and the rotor vibration, especially the 2nd harmonic component, will be brought in. Meanwhile, the UMP keeps directing to the very position where the minimum radial air-gap is. Among the different SAGE forms, the rotor offset has the most sensitive effect on the rotor UMP and vibration, while the stator ellipse deformation has the weakest impact.

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15

ZARETSKIY, R. K. "COMPARATIVE ANALYSIS OF DIFFERENT ROTARY CONTROL SYSTEMS." Fundamental and Applied Problems of Engineering and Technology 6 (2020): 86–93. http://dx.doi.org/10.33979/2073-7408-2020-344-6-86-93.

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This article provides a comparative analysis of various control systems for a rotor system on fluid friction bearings. The control was carried out on the basis of the criterion of the minimum friction moment, the controlled parameter was the bearing stiffness coefficients. The following control methods were compared in terms of friction torque and rotor eccentricity: STATIC, PID, DQN, DDPG, Q-Learning and SARSA. The control systems were guided by the following observed parameters: the values of coordinates and velocities along the x, y axes, as well as the frictional moment and relative eccentricity.

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Abderrahim, Touil, Babaa Fatima, Bennis Ouafae, and Kratz Frederic. "Analytical Model for Separated Frequency Signature of Outer Race Bearing Fault From Static Eccentricity." International Journal of Circuits, Systems and Signal Processing 15 (January 11, 2022): 1821–27. http://dx.doi.org/10.46300/9106.2021.15.196.

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The present paper addresses a precise and an accurate mathematical model for three-phase squirrel cage induction motors, based on winding function theory. Through an analytical development, a comparative way is presented to separate the signature between the existence of the outer race bearing fault and the static eccentricity concerning the asymmetry of the air gap between the stator and the rotor. This analytical model proposes an effective signature of outer race defect separately from other signatures of static eccentricity. Simulation and experimental results are presented to validate the proposed analytical model.

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Belyaev, P. V., A. P. Golovskii, and D. S. Sadaev. "THE MATHEMATICAL MODEL OF ASYNCHRONOUS MACHINE WITH THE ROTOR STATIC ECCENTRICITY." Dynamics of Systems, Mechanisms and Machines 7, no. 2 (2019): 010–18. http://dx.doi.org/10.25206/2310-9793-7-2-10-18.

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Shakouhi, Mohammad, Mustafa Mohamadian, and Ebrahim Afjei. "Fault-Tolerant Control of Brushless DC Motors Under Static Rotor Eccentricity." IEEE Transactions on Industrial Electronics 62, no. 3 (March 2015): 1400–1409. http://dx.doi.org/10.1109/tie.2014.2365439.

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Vaskovskiy, Yuriy, Alexandr Geraskin, and Konstantin Tatarinov. "Research of dampher system damage physical processes of synchronous machines rotor." Bulletin of NTU "KhPI". Series: Problems of Electrical Machines and Apparatus Perfection. The Theory and Practice, no. 2 (6) (December 9, 2021): 19–24. http://dx.doi.org/10.20998/2079-3944.2021.2.04.

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The physical processes in the damper system of the rotor with the appearance of a static eccentricity of the rotor for two types of salient-pole synchronous machines - a capsule hydrogenator SGK 538/160-70M with a capacity of 22 MW and a synchronous generator with a capacity of 500 kW were investigated by means of mathematical modeling. A field mathematical model has been developed that takes into account the combined action of three physical fields of different nature: electromagnetic, temperature and field of thermomechanical stresses, and makes it possible to evaluate the heating and three-dimensional distribution of thermomechanical stresses in the structural elements of the rotor damper system of a salient-pole synchronous machine. These physical processes cause gradual destruction of the structure of the rotor damper system. It is proved that the primary cause of degradation and damage of the damping system of the rotor of an open-pole synchronous machine is the uneven distribution of induced currents in the rods at the poles of the rotor, which occurs when the machine works asynchronously or with the appearance of rotor static eccentricity. The largest induced currents and heat occur in the rods located at the edges of the pole pieces, while the central rods at the pole are heated significantly less. This asymmetric heating of the damping system of the rotor leads to significant thermomechanical stresses in the elements of the damping system of the rotor, which significantly depend on the magnitude of the eccentricity and slippery of the rotor in asynchronous mode. The magnitude of the total thermomechanical stresses in the rods is influenced not only by axially directed forces but also by transverse forces in the end short-circuiting elements. At considerable slippery and eccentricities there are inadmissibly big breaking forces which break cores and face short-circuiting elements of a damping system of a rotor. According to the results of the analysis, the heating and thermomechanical stresses of the structural elements were determined and recommendations for its structural improvement were given.

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Sun, Dan, Sheng-Yuan Li, Huan Zhao, and Cheng-Wei Fei. "Numerical Investigation on Static and Rotor-Dynamic Characteristics of Convergent-Tapered and Divergent-Tapered Hole-Pattern Gas Damper Seals." Materials 12, no. 14 (July 21, 2019): 2324. http://dx.doi.org/10.3390/ma12142324.

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To study the influence of taper seal clearance on the static and rotor-dynamic characteristics of hole-pattern damper seals, this paper develops three-dimensional transient computational fluid dynamic methods, which comprise single-frequency and multi-frequency elliptical orbit whirl model, by the transient solution combined with a mesh deformation technique. Through the investigations, it is illustrated that: (1) In the present paper, the leakage rates of convergent-tapered hole-pattern damper seals are less than divergent-tapered hole-pattern damper seals for the same average seal clearance, and the maximum relative variation reaches 16%; (2) Compared with a constant clearance hole-pattern damper seal, the maximum relative variation of the rotor-dynamic coefficients is 1,865% for nine taper degrees in this paper; (3) Convergent-tapered hole-pattern damper seals have smaller reaction forces and effective damping coefficient, larger cross-over frequency, and direct stiffness coefficient, while divergent-tapered damper seals have the opposite effects; (4) Divergent-tapered hole-pattern damper seals alleviate the rotor whirl because of a larger effective damping coefficient when the rotor system has large natural frequency and small eccentricity. Convergent-tapered damper seals provide both sealing and journal bearing capabilities at the same time, and are more advantageous to the stability of the rotor system when rotor eccentricity is the main cause of rotor instability.

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Feng, Hui-Hui, Chun-Dong Xu, and Jie Wan. "Mathematical Model and Analysis of the Water-Lubricated Hydrostatic Journal Bearings considering the Translational and Tilting Motions." Mathematical Problems in Engineering 2014 (2014): 1–15. http://dx.doi.org/10.1155/2014/353769.

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The water-lubricated bearings have been paid attention for their advantages to reduce the power loss and temperature rise and increase load capacity at high speed. To fully study the complete dynamic coefficients of two water-lubricated, hydrostatic journal bearings used to support a rigid rotor, a four-degree-of-freedom model considering the translational and tilting motion is presented. The effects of tilting ratio, rotary speed, and eccentricity ratio on the static and dynamic performances of the bearings are investigated. The bulk turbulent Reynolds equation is adopted. The finite difference method and a linear perturbation method are used to calculate the zeroth- and first-order pressure fields to obtain the static and dynamic coefficients. The results suggest that when the tilting ratio is smaller than 0.4 or the eccentricity ratio is smaller than 0.1, the static and dynamic characteristics are relatively insensitive to the tilting and eccentricity ratios; however, for larger tilting or eccentricity ratios, the tilting and eccentric effects should be fully considered. Meanwhile, the rotary speed significantly affects the performance of the hydrostatic, water-lubricated bearings.

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Li, Shanle, Feng Liu, Hongyan Wang, Haijun Song, and Kuilong Yu. "Nonlinear Vibration Analysis of Rotor considering Cogging and Harmonic Effects." Shock and Vibration 2021 (March 4, 2021): 1–16. http://dx.doi.org/10.1155/2021/6685588.

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This paper aims to investigate nonlinear vibration characteristics of rotor system considering cogging and harmonic effects. Firstly, relative permeance with eccentric was established and then corrected by correction factor caused by the cogging effect. Based on the new formula of relative permeance, the expression of unbalanced magnetic force was obtained, and the coefficient of cogging effect was defined. Motion equations of rotor system were established, and Runge–Kutta method was used to solve the equations. Results showed that errors between finite and analytical results were smaller considering cogging and harmonic effects. When the harmonics were taken into consideration, the vibration of rotor increases sharply. When the cogging and harmonics were taken into consideration simultaneously, the vibration of rotor decreased instead, which means that stator slots have the effect of reducing vibration in rotor system. Rotor vibration was axis symmetry with static eccentricity rather than central symmetry with no eccentricity, and double, four times, and six times supply frequency always existed in the components of main frequency with eccentric.

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Petryna, Janusz, Arkadiusz Duda, and Maciej Sułowicz. "Eccentricity in Induction Machines—A Useful Tool for Assessing Its Level." Energies 14, no. 7 (April 2, 2021): 1976. http://dx.doi.org/10.3390/en14071976.

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In the condition monitoring of induction machines operating in various industry sectors, the assessment of eccentricity is as important as the assessment of the condition of windings, bearings, mechanical vibrations or noise. The reasons for the eccentricity can be various; for example, rotor imbalance, damage or wear of the bearings, improper alignment of the rotor and the load machine and finally, assembly errors after overhaul. Disregard of this phenomenon during routine tests may result in the development of vibrations transmitted to the stator windings, faster wear of the bearings and even, in extreme cases, rubbing of the rotor against the stator surface and damage to the windings and local overheating of the machine core. On the basis of years of experience in the diagnosis of large induction machines operating in various industries, the article deals with the problem of developing reliable indicators for assessing the levels of commonly accepted types of eccentricity. Starting from field calculations and analyzing various cases of eccentricity, the methodology for determining the indicators for evaluation from the stator current spectrum is shown. The changes in the values of these indices for various cases of simultaneous occurrence of static and dynamic eccentricity are shown. The calculation results were verified in the laboratory. Also shown are three interesting cases from diagnostic practice in the evaluation of high-power machines in the industry. It has been shown that the proposed indicators are useful and enable an accurate diagnosis of levels of eccentricity.

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Jiang, Hong-Chun, Gui-Ji Tang, Yu-Ling He, Kai Sun, Wei-Jun Li, and Lun Cheng. "Effect of Static Rotor Eccentricity on End Winding Forces and Vibration Wearing." International Journal of Rotating Machinery 2021 (March 29, 2021): 1–14. http://dx.doi.org/10.1155/2021/5554914.

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In order to study the vibration wearing regularity and the strength failure point of stator end windings before and after static rotor eccentricity, the three-dimensional electromagnetic forces and the subsequent mechanical responses are studied in this paper. The electromagnetic force, stress, and deformation on the end winding of the QFSN-600-2YHG turbo-generator are calculated by the finite element method (FEM) through an electromagnetic-structure coupling. The radial vibration characteristics of the winding are verified by experiments. It shows that the vibration wearing in the same layer is more serious than that between two neighboring layers. For different layers, the interphase coils endure a larger wearing risk than the innerphase coils. Inside the same phase, the last coil along the rotating direction has the highest risk of insulation wearing. The occurrence of static rotor eccentricity will significantly increase the electromagnetic forces and the vibration amplitudes on some coils. The end-phase coil which is close to the minimum air-gap point is the most dangerous one due to the lasting overstresses and the intensified deformations.

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Kruchinina, Irina Yu, Yuvenaliy Khozikov, Alexandr Liubimtsev, and Valentina Paltceva. "Harmonic losses in high-speed PM synchronous machines." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 36, no. 3 (May 2, 2017): 683–91. http://dx.doi.org/10.1108/compel-09-2016-0401.

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Purpose The purpose of this paper is the development of a new numerical method for the calculation of the air-gap magnetic flux harmonics in synchronous machines with permanent magnet (PM) excitation. The harmonic analysis results are used as input data for the eddy-current loss calculation and for the rotor heating evaluation. Design/methodology/approach The method is based on the finite element analysis (FEA). The model takes into account toothed stator design, rotor asymmetrical magnetic reluctance and saturation. At first, a series of static DC magnetic (magnetostatic) simulations is run. Each problem corresponds to specific rotor position and the momentary stator winding currents. The Fourier analysis performed for each problem yields the harmonic spectrum variation in time. Then, a series of AC magnetic (time-harmonic) simulations is run. Each problem corresponds to a specific harmonic. The result is the eddy-current losses distribution. After total loss is calculated, the heat transfer analysis is conducted. Findings The analysis reveals that 90 per cent of losses are located in the sleeve that holds PMs together. Rotor eccentricity brings even harmonics of low magnitude that have little impact on heating. Originality/value In general, the study requires transient electromagnetic analysis with motion. The purposed method allows to simplify the problem. The method is based on static and quasi-static (time-harmonic) problems simulation. It is fast and highly automated. The method allows simultaneous taking into account of tooth-order harmonics, stator winding harmonics and eccentricity for heating calculation.

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Zhang, Chao, Chuang-Jin He, Shuai Li, Yu-Ling He, Xiao-Long Wang, Xiang-Yu Liu, and Lun Cheng. "A Hybrid Method to Diagnose 3D Rotor Eccentricity Faults in Synchronous Generators Based on ALIF_PE and KFCM." Mathematical Problems in Engineering 2021 (May 31, 2021): 1–14. http://dx.doi.org/10.1155/2021/5513881.

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This paper proposed a new hybrid diagnosis method for the generator’s 3D static eccentricity faults which include the axial eccentricity, the radial eccentricity, and the mixed eccentricity composed of the former two. Firstly, adaptive local iterative filtering (ALIF) method was used to decompose the vibration signals of the generator under eccentricity faults. Then, in order to figure out the intrinsic mode function (IMF) components with the upmost feature information, the correlation coefficient was calculated. Finally, the components’ permutation entropy (PE) is extracted to construct the eigenvector matrix which can be used to input the kernel fuzzy C-means (KFCM) algorithm to obtain the result of clustering. The result indicates that the classification coefficient based on ALIF and KFCM behaves closer to 1, while the average fuzzy entropy (FE) is closer to 0, showing that this method is able to detect different eccentricity faults more accurately.

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Liu, Yi, Heng Liu, and BoWen Fan. "Nonlinear dynamic properties of disk-bolt rotor with interfacial cutting faults on assembly surfaces." Journal of Vibration and Control 24, no. 19 (August 10, 2017): 4369–82. http://dx.doi.org/10.1177/1077546317724602.

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Interfacial cutting faults on assembly surfaces are considered in a three-dimensional (3D) disk-bolt rotor system. The traditional finite element method is used to establish the 3D model of faulted disk-bolt rotor. A contact algorithm is applied to calculate the static features of this combined rotor. It is revealed that interfacial cutting faults produce rotor bending which is gradually strengthened as rotational speed increases besides disk’s mass eccentricity. The 3D dynamic equations of a faulted disk-bolt rotor system include these cutting faults’ static influences. The nonlinear dynamic properties are investigated by Poincaré mapping, Newton iteration and a prediction-correction algorithm. As a result, the rotor bending due to cutting faults reduces the global stability of the complicated rotor and enlarges the vibration amplitude obviously. This speed-variant bending also decides the feature that rotor vibration increases again after critical speed no matter whether dynamic balance is carried out. The maximum allowable fault depth is obtained and it gives an explanation as to why the machining precision of assembly surfaces should be strictly controlled in the disk-bolt rotor. Generally, this paper originally tries to provide a feasible approach to consider a 3D interfacial cutting fault with specific shape and to analyze the static–dynamic coupling characteristics for a disk-bolt rotor.

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Werner, Ulrich. "Theoretical rotor dynamic analysis of two-pole induction motors regarding excitation due to static rotor eccentricity." Archive of Applied Mechanics 81, no. 2 (February 4, 2010): 241–62. http://dx.doi.org/10.1007/s00419-010-0413-z.

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Wei, Kaijun, Shuguang Zuo, Huijuan He, and Zhe Wang. "Study on the aerodynamic noise of centrifugal compressors with rotor static eccentricity." Journal of the Acoustical Society of America 135, no. 4 (April 2014): 2406. http://dx.doi.org/10.1121/1.4877967.

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Li, Fengqin, Lulu Zhai, Baoling Cui, Jia Guo, and Guoyou Chen. "Investigation of the Dynamic Characteristics of an Eccentric Annular Seal on the Basis of a Transient CFD Method with Three Whirl Models." Journal of Marine Science and Engineering 9, no. 11 (November 19, 2021): 1290. http://dx.doi.org/10.3390/jmse9111290.

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Many annular seals suffer eccentricity because of rotor–stator misalignment or the deflection of a flexible rotor, which has a strong influence on the vibration characteristics and stability of rotating machines. In this article, a transient CFD method based on three whirl models is employed to research the dynamic characteristics of annular seals at various static eccentricities. The influence of the whirl amplitude on the dynamic characteristics of eccentric annular seals are also explored. The results of the transient CFD method are compared with the bulk flow model results and the experimental results. It is shown that the transient CFD method possesses high prediction precision for direct damping, with a maximum error of 25%. Negative kyx increases by 166% when the static eccentricity ratio is increased from 0 to 0.5. The dynamic characteristics of the annular seal operating at high static eccentric ratio are sensitive to whirl amplitude, and the model with an amplitude of 1% Cr has great advantages for the prediction of direct virtual-mass, while the model with an amplitude of 10% Cr has great advantages for the prediction of cross-coupled damping.

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Siew, C. C., M. Hill, R. Holmes, and M. J. Brennan. "Reduced-order modelling methods to assess the overall vibration response of a flexible rotor-squeeze film damper bearing assembly." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 216, no. 11 (November 1, 2002): 1081–97. http://dx.doi.org/10.1243/095440602761609452.

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This paper uses two reduced-order methods to calculate the overall non-linear vibration response of a multi-mode rotor-squeeze film damper (SFD) bearing assembly. Good agreement has been found between their computed results and those calculated by the conventional Runge-Kutta-Merson method (RKMM), yet they require less than 5 per cent of the computing time consumed by the RKMM. They are applied to compute the vibration response, three-dimensional deflection shape and the overall vibrational kinetic energy of the rotor-bearing assembly. The assembly is simulated under various operating conditions including different unbalances, oil viscosities, static misalignments and damper factors. It is concluded that effective vibration control of a flexible rotor-SFD bearing assembly can be achieved when the vertical static eccentricity ratio of the SFD is set to a certain limit.

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Soulas, Thomas, and Luis San Andres. "A Bulk Flow Model for Off-Centered Honeycomb Gas Seals." Journal of Engineering for Gas Turbines and Power 129, no. 1 (March 1, 2002): 185–94. http://dx.doi.org/10.1115/1.2227031.

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A computational analysis for prediction of the static and dynamic forced performance of gas honeycomb seals at off-centered rotor conditions follows. The bulk-flow analysis, similar to the two-control volume flow model of Kleynhans and Childs (1997, “The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals,” ASME J. Eng. Gas Turbines Power, 119, pp. 949–957), is brought without loss of generality into a single-control volume model, thus simplifying the computational process. The formulation accommodates the honeycomb effective cell depth, and existing software for annular pressure seals and is easily upgraded for damper seal analysis. An analytical perturbation method for derivation of zeroth- and first-order flow fields renders the seal equilibrium response and frequency-dependent dynamic force impedances, respectively. Numerical predictions for a centered straight-bore honeycomb gas seal shows good agreement with experimentally identified impedances, hence validating the model and confirming the paramount influence of excitation frequency on the rotordynamic force coefficients of honeycomb seals. The effect of rotor eccentricity on the static and dynamic forced response of a smooth annular seal and a honeycomb seal is evaluated for characteristic pressure differentials and rotor speeds. Leakage for the two seal types increases slightly as the rotor eccentricity increases. Rotor off-centering has a pronounced nonlinear effect on the predicted (and experimentally verified) dynamic force coefficients for smooth seals. However, in honeycomb gas seals, even large rotor center excursions do not sensibly affect the effective local film thickness, maintaining the flow azimuthal symmetry. The current model and predictions thus increase confidence in honeycomb seal design, operating performance, and reliability in actual applications.

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Ruf, Andreas, Michael Schröder, Aryanti Kusuma Putri, Roman Konrad, David Franck, and Kay Hameyer. "Analysis and determination of mechanical bearing load caused by unbalanced magnetic pull." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 35, no. 2 (March 7, 2016): 728–43. http://dx.doi.org/10.1108/compel-03-2015-0111.

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Purpose – The purpose of this paper is to focus on the mechanical bearing load caused by the unbalanced magnetic pull (UMP), which is studied in detail. The applied approach is based on an analysis of static and dynamic eccentricities at different positions and different amplitudes. The influence of the operating points is calculated to show the effective bearing load for machines operating at different speeds. The decreasing lifetime of the applied bearings is examined and evaluated in detail. Design/methodology/approach – To evaluate the proposed methodology a permanent magnet synchronous machine (PMSM) with buried magnets is used. To consider effects of slotting and saturation, a finite element (FE) model is employed. The Monte Carlo method is used to determine the most likely amplitudes of the eccentricities. Calculating the UMP for all possible operating points using a control strategy for the machine and coupling this results with a drive cycle, determines the effective force acting on the bearing. Findings – It has been shown that the position of the eccentricity has a not significant influence on the behavior of the UMP and may therefore be neglected. The amplitude of the eccentricity vector influences the amplitude of the UMP including all harmonic force components. For technical relevant eccentricities, the influence is approximately linear for the average and the dominant harmonics of the UMP. In most cases, it is sufficient to displace the rotor at an arbitrary position and amplitude. It is sufficient to simulate one type of eccentricity (static or dynamic) with an arbitrary value of displacement (rotor or stator) to evaluate all possible airgap unbalances. Using stochastic simulations of the eccentricity amplitudes enables an a priori design and lifetime estimation of bearings. Originality/value – This paper gives a close insight on the effect of mechanical bearing load caused by rotor eccentricities. The effect of the position of the eccentricity vector, the operational range and a drive cycle are considered. A stochastic simulation and an empirical lifetime model of one bearing gives an example of using this methodological approach.

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Jiang, Hong-Chun, Yu-Ling He, Gui-Ji Tang, and Xing-Hua Yuan. "Electromagnetic Force and Mechanical Response of Turbo-Generator End Winding under Electromechanical Faults." Mathematical Problems in Engineering 2021 (December 23, 2021): 1–19. http://dx.doi.org/10.1155/2021/9064254.

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This paper comparatively studies the electromagnetic force and mechanical response of the end winding before and after 3 kinds of typical electromechanical faults in turbo-generator. The analytical expression of electromagnetic force of end winding is derived under the composite fault of static eccentricity and rotor interturn short circuit. Meanwhile, the three-dimensional transient finite element simulation is carried on, and the frequency composition and amplitude variation characteristics of the radial, axial, and tangential electromagnetic force are analyzed for the end windings under static eccentricity, rotor interturn short circuit, and composite fault. Therefore, it provides a reference for the vibration wear detection and electromagnetic force control of the end winding. Moreover, the maximum stress and deformation of different positions on the end involute are obtained. And the three-directional vibration acceleration characteristics of the end winding are further analyzed. Finally, the distribution law of winding fatigue failure and vibration wear is acquired, which lays a foundation for the reverse suppression of end winding fatigue failure and insulation wear.

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Grinek, AV, IP Boychuk, A. M. Fishenko, NV Savosteenko, and O. N. Gerasimenko. "Investigation of the operation of a ship’s synchronous generator based on a numerical model." Journal of Physics: Conference Series 2061, no. 1 (October 1, 2021): 012004. http://dx.doi.org/10.1088/1742-6596/2061/1/012004.

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Abstract The article presents the results of modeling a ship’s synchronous generator. Based on preliminary design calculations, a geometric model of the generator was built. The static and overclocking processes of the generator are investigated. For static modes, the frequency response of the process is obtained. A numerical model was used to identify a mechanical defect. On the example of a simulated defect of an electrical machine - the eccentricity of the generator rotor, the signature of the defect signal is obtained. The study revealed that the presence of rotor eccentricity leads to the appearance of a harmonic component in the spectrum of the force of large amplitude with a maximum value at a low frequency. Transient analysis was carried out using wavelet transformations. The results of the study of dynamics show how the rotor speed increases. The simulation revealed three frequency regions of the signal under study: the region of the increase in speed, the achievement of the critical speed (between the second and third seconds), and the exit to the steady-state. A diagram of a system for diagnosing defects in an electrical machine using a digital twin - a numerical model is proposed. Generator defects (mechanical and electromechanical) can be identified based on model data. Databases of defect signatures in a static mode and a diagnostic model, which contains algorithms for deciding on the presence of a defect, can serve as the basis of information for an operator to decide.

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Alexander, C. R., D. W. Childs, and Z. Yang. "Theory Versus Experiment for the Rotordynamic Characteristics of a Smooth Annular Gas Seal at Eccentric Positions." Journal of Tribology 117, no. 1 (January 1, 1995): 148–52. http://dx.doi.org/10.1115/1.2830591.

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Experimental results are presented for the rotordynamic coefficients of a smooth gas seal at eccentricity ratios out to 0.5. The effects of speed, inlet pressure, pressure ratio, fluid prerotation, and eccentricity are investigated. The experimental results show that direct stiffness KXX decreases significantly, while direct damping and cross-coupled stiffness increase with increasing eccentricity. The whirl-frequency ratio, which is a measure of rotordynamic instability, increases with increasing eccentricity at 5000 rpm with fluid prerotation. At 16,000 rpm, the whirl-frequency ratio is insensitive to changes in the eccentricity. Hence, the results show that eccentric operation of a gas seal tends to destabilize a rotor operating at low speeds with preswirled flow. At higher speeds, eccentric operation has no significant impact on rotordynamic stability. The test results show that the customary, eccentricity-independent, model for rotordynamic coefficients is only valid out to an eccentricity ratio of 0.2~0.3. For larger eccentricity ratios, the dependency of rotordynamic coefficients on the static eccentricity ratio needs to be accounted for. Experimental results are compared to predictions for static and dynamic characteristics based on an analysis by Yang (1993). In general, the theoretical results reasonably predict these results; however, theory overpredicts direct stiffness, fails to indicate the decrease in KXX that occurs with increasing eccentricity, and incorrectly predicts the direction of change in KXX with changing pressure ratio. Also, direct damping is substantially underpredicted for low preswirl values and low supply pressures, but the predictions improve as either of these parameters increase.

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Shengtong, ZHOU, ZHU Jingwei, XIAO Qian, GUO Weinian, and ZHOU Xinjian. "Initial Static Eccentricity and Gravity Load on Rotor Orbit of EMU Traction Motor." Journal of Mechanical Engineering 56, no. 17 (2020): 145. http://dx.doi.org/10.3901/jme.2020.17.145.

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38

Crâştiu, Ion, Liviu Bereteu, and Dorin Simoiu. "Determination of the Eccentricity of a Rotor by Impulse Excitation Technique of Vibration." Applied Mechanics and Materials 801 (October 2015): 176–81. http://dx.doi.org/10.4028/www.scientific.net/amm.801.176.

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The aim of this paper is the development and validation of an impulse excitation technique to determine static imbalance of a rotor. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone. In determining the center of mass three measurements are needed: one in plane flexure, and other out of the plane flexure, to which is added a measurement for a balanced rotor. By the means of Finite Element Method (FEM), the natural frequencies and shape modes of two rotor specimens are determined. The analysis is carried out in balanced condition as well as unbalanced one, after artificially induced imbalance. The vibration responses of the specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform (FFT). To validate the results of the modal parameters estimated using Finite Element Analysis (FEA) these are compared with experimental ones.

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Riquelme, Danilo, Carlos Madariaga, Werner Jara, Gerd Bramerdorfer, Juan A. Tapia, and Javier Riedemann. "Study on Stator-Rotor Misalignment in Modular Permanent Magnet Synchronous Machines with Different Slot/Pole Combinations." Applied Sciences 13, no. 5 (February 21, 2023): 2777. http://dx.doi.org/10.3390/app13052777.

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Addressing stator-rotor misalignment, usually called eccentricity, is critical in permanent magnet (PM) machines since significantly high radial forces can be developed on the bearings, which can trigger a major fault and compromise the structural integrity of the machine. In this regard, this paper aims to provide insight into the unaddressed identification and analysis of the impact of eccentric tolerances on relevant performance indices of permanent magnet synchronous machines (PMSMs) with modular stator core. Static and dynamic eccentricity are assessed for different slot/pole combinations through the finite element method (FEM), and the results are compared with those of PMSMs with a conventional stator core. The unbalanced magnetic forces (UMF), cogging torque, back-emf, and mean torque variations are described and related to the eccentricity magnitude and classification. The main findings indicate that severe radial forces and significant additional cogging torque harmonics are generated because of eccentricity. Additionally, it is found that the main differences between modular PMSMs and conventional PMSMs rely on the value of slots per pole per phase.

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40

Qiu, Z. L., and A. K. Tieu. "Misalignment Effect on the Static and Dynamic Characteristics of Hydrodynamic Journal Bearings." Journal of Tribology 117, no. 4 (October 1, 1995): 717–23. http://dx.doi.org/10.1115/1.2831542.

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This paper solves the Reynolds equation by the finite difference method in a fixed coordinate system with the static load acted in the vertical direction. All static and dynamic characteristics (including load capacity, attitude angle, side flow, friction force, misaligned moments, and eight linear force coefficients) of a horizontally grooved bearing under different eccentricity and misalignment conditions are presented and compared with available experimental data. The effects of misalignment on all these bearing characteristics and on the stability of the rotor-bearing system are analyzed.

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Zhao, J. Y., and E. J. Hahn. "Subharmonic, Quasi-Periodic and Chaotic Motions of a Rigid Rotor Supported by an Eccentric Squeeze Film Damper." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 207, no. 6 (November 1993): 383–92. http://dx.doi.org/10.1243/pime_proc_1993_207_145_02.

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This paper analyses the complexity of the unbalance response possible with a simple rigid rotor supported by an eccentric squeeze film damper. The damper forces are obtained from the ‘π’ film short bearing approximation to the Reynolds equation and a fourth-order Runge-Kutta integration is used to evaluate the rotor response. Poincaré maps, rotor trajectories, bifurcation diagrams and power spectra are used to elucidate and to illustrate the diversity of the system behaviour. It is shown that for a large unbalance and static eccentricity ratio, the system can exhibit undesirable jump phenomenon and subharmonic, quasi-periodic and even chaotic motions, which limit the operating conditions at which dampers should be used.

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42

Natesan, Sivaramakrishnan, Karuna Kalita, and Venkatesu Samala. "Numerical and Experimental Investigation of Bridge Currents of an Induction Machine Equipped with Bridge Conﬁgured Winding." International Journal of Electrical and Computer Engineering (IJECE) 5, no. 6 (December 1, 2015): 1262. http://dx.doi.org/10.11591/ijece.v5i6.pp1262-1274.

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<p class="CM1">An eccentric rotor motion imbalances the magnetic ﬁeld distribution in the air-gap region. Due to this uneven ﬂux density distribution, a net radial force called Unbalanced Magnetic Pull (UMP) is in action towards the shortest air-gap. This UMP can degrade the machine’s performance. UMP can be controlled by a special kind of winding called Bridge Conﬁgured Winding (BCW). The BCW winding is a single set of winding which is used to produce the torque as well as the controllable force. The main contribution of this paper is to inspect the ﬂow of bridge currents in the bridges when the machine is having rotor eccentricity or unbalance. The bridge currents in the presence of rotor eccentricity with the stator of an Induction machine model has been analyzed by using an Electromagnetic Finite Element (FE) solver called Opera 2D/RM solver (Rotation Motion Analysis). The bridge currents have been measured for two different cases., (i) Induction machine model with zero eccentricity, (ii) Induction machine model with 10% static eccentricity of the air gap. Experimental results are presented for the validation of Opera 2D/RM results. A modiﬁed 37kW Induction machine has been used for this study. A known mass unbalance is introduced in the perforated disc in order to create the unbalance in the system purposefully. The bridge currents have been measured and compared with and without unbalance present in the system. The comparison of measured bridge currents for all the cases are given in the frequency domain.</p>

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Tvorić, Stjepan, Miroslav Petrinić, Ante Elez, and Mario Brčić. "STATIC ECCENTRICITY FAULT DETECTION METHOD FOR ELECTRICAL ROTATING MACHINES BASED ON THE MAGNETIC FIELD ANALYSIS IN THE AIR GAP BY MEASURING COILS." Journal of Energy - Energija 69, no. 4 (December 30, 2020): 3–7. http://dx.doi.org/10.37798/202069451.

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Electrical rotating machines have a great economic significance as they enable conversion of energy between mechanical and electrical state. Reliability and operation safety of these machines can be greatly improved by implementation of continuous condition monitoring and supervisory systems. Especially important feature of such systems is the ability of early fault detection. For this reason, several methods for detection and diagnosis of the machine faults have been developed and designed. As fault detection methods can largely differ in the types of detectable faults, machine adoptability and price of the system, a novel method was developed that can be used for cost-effective detection of various faults of electrical machine. Machine fault detection technique presented in this paper is based on the measurement of magnetic field in the air gap. Numerous studies have proven that crucial information about the machine condition can be determined based on measurement and analysis of the magnetic field in the air gap. It has also been confirmed that analysis of the air gap magnetic field can be used to detect, diagnose and recognize various electrical faults in their very early stage. Proposed method of positioning and installation of the measuring coils on ferromagnetic core parts within the air gap region of the machine enables differentiation of various faults. Furthermore, different faults can be detected if measuring coils are placed on the stator teeth then when placed on the rotor side. The paper presents method on how to analyse and process the measured voltages acquired from measuring coils placed within the machine, especially in the case of rotor static eccentricity detection. The methodology is explained by means of finite element method (FEM) calculations and verified by measurements that were performed on the induction machine. FEM calculation model was used to predict measurement coil output of the induction motor for healthy and various faulty states (at different amounts of static eccentricity). These results were then confirmed by measurements performed in the laboratory on the induction traction motor that was specially modified to enable measurements of faulty operation states of the machine. Measurements comprised of several machine fault conditions broken one rotor bar, broken multiple rotor bars, broken rotor end ring and various levels of rotor static eccentricity. Other methods used for faults detection are primarily based on the monitoring of quantities such as current and vibration and their harmonic analysis. This new system is based on the tracing the changes of induced voltage of the measuring coils installed on the stator teeth. Faults can be detected and differentiated based on RMS value of these voltages and the number of voltage spikes of voltage waveform i.e. without the need of harmonic analyses. If these coils are installed on the rotor it is possible to detect the stator winding faults in a similar manner.

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Cao, Hao, Jian Gang Yang, Wan Fu Zhang, and Rui Guo. "Experimental Identification for Seals Rotordynamic Coefficients Based on Double Plane Balance Method." Advanced Materials Research 291-294 (July 2011): 1965–69. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1965.

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This paper presents a new rotordynamic measurements conducted on a test rig for evaluation of multiple rings of labyrinth seals. Considering the tilting motion of cylinder occurs in experiments, the impedance matrix of cylinder system is obtained first. An equivalent seal force identification model is set up for multiple seals based on double plane balance theory of rotor dynamics. The resultant seal forces are calculated on two end planes of the cylinder, and resolved to multiple sections that seals located. A frequency domain identification method delivers the test seals stiffness and damping coefficients. Compressed air inlet tests were run from 1000 rpm-2200rpm, 0.1-0.6Mpa supply pressures were used. For each ΔP test condition, the static eccentricity ratio ε=e/Cr is range from zero to approximately 0.6. Results show that 8 rotordynamic coefficients increase almost linearly with inlet/outlet pressure ratio. Increasing eccentricity ratio weakens the stability of seal-rotor system obviously.

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Sun, Yu, Lichen Gu, Peijin Liu, Jiangcheng Chen, and Donghong Cheng. "Analytical Calculation of Air-Gap Magnetic Field Distribution in IPMSMs with Mixed Eccentricity Accounting for Bridge Saturation." Applied Sciences 12, no. 23 (November 23, 2022): 11956. http://dx.doi.org/10.3390/app122311956.

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This paper presents an analytical model for calculating the detailed air-gap magnetic field distribution in interior permanent magnet synchronous motors (IPMSMs) with mixed eccentricity. In order to improve the efficiency of model solving, a modeling strategy combining the equivalent magnetic circuit network method and the subdomain method was adopted. Specifically, the magnetic field distribution of the rotor was modeled by using the magnetic circuit analysis method, and the magnetic field distributions of the air-gap, slot opening and stator slot along the radial direction were modeled in different regions according to their structure ruler. Then, the influence of bridge saturation was considered. Moreover, based on the analysis of the air-gap geometric structure with mixed eccentricity, a detailed spatiotemporal analytical model of the air-gap magnetic field was established, which provides a more accurate description of the mixed eccentricity composed of static and dynamic rotor eccentricities of different severity. The analytical models were compared with the corresponding models established by the finite element method, which proved the accuracy and validity of the models established in this paper. Finally, some key features related to radial and tangential air-gap flux density were extracted, which can significantly reflect the characteristics of eccentricities. The main findings reported in this paper will be of benefit for developing methods for early identification and diagnosis of eccentricity faults in IPMSMs.

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Del Pizzo, Andrea, Luigi Pio Di Noia, and Emanuele Fedele. "A Simple Analytical Model of Static Eccentricity for PM Brushless Motors and Validation through FEM Analysis." Energies 13, no. 13 (July 2, 2020): 3420. http://dx.doi.org/10.3390/en13133420.

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The paper firstly summarizes a simple analytical model of the air gap flux-density distribution for isotropic permanent magnet (PM) synchronous machines, in the presence of static eccentricity. The model was proposed by the authors in a previous paper and is based on an efficacious analytical expression of the variable length of air gap magnetic field lines which occur in eccentric brushless machines with surface-mounted permanent magnets. The approximate expression of the air gap field makes it possible to achieve a mathematical model with concentrated parameters close to that of a PM machine without eccentricity. The expression of the armature voltages and electromagnetic torque are found, also with reference to steady-state operating conditions at fixed rotor speed and impressed currents. The differences introduced by the considered type of eccentricity are evaluated and highlighted especially with reference to the air gap inductance and to waveforms and frequency spectra of voltages and shaft torque. Numerical results in a case-study of an 8-pole, 110 kW PM motor are compared to those obtained by using finite element analysis.

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Ri, Kwangchol, Junhyok Jang, Cholil Yun, Choljun Pak, and Kwangchol Kim. "Analysis of subharmonic and quasi-periodic vibrations of a Jeffcott rotor supported on a squeeze-film damper by the IHB method." AIP Advances 12, no. 5 (May 1, 2022): 055328. http://dx.doi.org/10.1063/5.0088334.

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In rotors supported on a squeeze-film damper (SFD) with static eccentricity, subharmonic and quasi-periodic vibrations are generated by rotor unbalance. In this paper, subharmonic and quasi-periodic vibrations in a Jeffcott rotor supported on an SFD are analyzed using the modified incremental harmonic balance (IHB) method. Oil film forces in the damper are calculated using π film theory and short bearing approximation. These forces are first calculated in the time domain and then transformed into the frequency domain by Fourier transformation. The oil film forces in the frequency domain are multiplied by a transformation matrix to match the matrices used in the classical IHB method. To apply the continuation technique, the Jacobian matrix of residuals is calculated analytically. The stability analysis of the calculated solutions is analyzed using Floquet theory. Using this theory, saddle-node, symmetry breaking, period-doubling, and secondary Hopf bifurcations are detected. The phase plane, Poincaré sections, and time history at these bifurcation points are calculated using the Runge–Kutta method.

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Zhang, Haibo, Yi Liu, and Xin Huang. "Nonlinear Dynamic Performance of a Bolt-Disc Rotor with the Position Error of Circumferential Bolt-Holes." Shock and Vibration 2021 (May 7, 2021): 1–10. http://dx.doi.org/10.1155/2021/6639375.

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The bolt-holes in the assembly discs are designed to limit the circumferential displacement of bolts for the bolt-disc rotor. The position error of circumferential bolt-holes is created in a three-dimensional model of bolt-disc rotor. The distribution of nonuniform stress and deformation is acquired according to finite element approach. Static results demonstrate that the position error of bolt-holes leads to obvious concomitant unbalances including constant mass eccentricity and speed-variant bending under the influence of large tightening force. When these unbalance factors are taken into consideration, dynamic performance such as instability areas and nonlinear motions are analyzed by Newton iterative process and a prediction-correction calculation method. Dynamic results show that rotor flexure enables the systematic stability decreased obviously because of this position error. There is a special phenomenon compared to monobloc rotor that the vibration amplitude proceeds to rise when rotating speed exceeds the critical speed. Moreover, the allowable position error of bolt-holes is obviously smaller than that of monobloc rotor and uneven tightening is a feasible way to reduce adverse effects on the dynamic properties when position error appears. This work proposes a static-dynamic approach to investigate the dynamics of imprecise bolt-disc rotor and establishes the relationship between machining error and dynamic features.

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Park, Jin-Cheol, Soo-Hwan Park, Jae-Hyun Kim, Soo-Gyung Lee, Geun-Ho Lee, and Myung-Seop Lim. "Diagnosis and Robust Design Optimization of SPMSM Considering Back EMF and Cogging Torque due to Static Eccentricity." Energies 14, no. 10 (May 17, 2021): 2900. http://dx.doi.org/10.3390/en14102900.

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Static eccentricity (SE) is frequently generated by manufacturing processes. As the nonuniformity of the air-gap length is caused by the SE, the torque ripple and cogging torque increase in the motor. This study analyzes the distorted back electromotive force (EMF) and cogging torque due to SE. Further, a motor design considering SE is performed for stable back EMF and low cogging torque. First, the SE was diagnosed and analyzed using the back EMF and cogging torque measured from the test results of the base model. In addition, the rotor position was calculated using the unbalanced back EMF due to the SE. The calculated rotor position is used when analyzing phenomena due to SE and applied to robust design. Subsequently, robust design optimization was performed to improve the unbalanced back EMF and cogging torque due to SE. Using finite element analysis (FEA) considering SE, the shape of the stator was designed based on the base model. The estimated rotor position from the base model was applied to the optimum model to confirm its robustness from SE’s effects. Finally, the base and optimum models were compared through the test results.

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Mirimani, Seyyed Mehdi, Abolfazl Vahedi, Fabrizio Marignetti, and Enzo De Santis. "Static Eccentricity Fault Detection in Single-Stator–Single-Rotor Axial-Flux Permanent-Magnet Machines." IEEE Transactions on Industry Applications 48, no. 6 (November 2012): 1838–45. http://dx.doi.org/10.1109/tia.2012.2221673.

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Journal articles on the topic 'Rotor Static Eccentricity'

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