Vibration Of Electrical Machines Research Articles

WIRELESS SENSOR SYNCHRONIZATION METHOD FOR MONITORING SHORT-TERM EVENTS

Topicality. The key part of experimental research is obtaining the most accurate data about the studied object or event. Often, it is necessary to record parameters of processes that are c hallenging to precisely localize in space and time. The process or event under consideration can occur very rapidly, within fractions of a second, making it difficult for the researcher to deploy and configure recording equipment. This necessitates the creation of a network consisting of numerous recording devices to not miss critical events related to the studied process and obtain a sufficient volume of experimental data. Another issue is the synchronization of data obtained from different measurement devices. Spatially distributed recording devices must operate with a high degree of autonomy, leading to discrepancies in timekeeping and the need for synchronization. In processes with sub-millisecond durations, imperfections in timekeeping at each node have a significant impact: undetected and unaccounted discrepancies can lead to distortion or a misunderstanding of the overall picture of the studied process or event, even after acquiring all the necessary data. This is why the development and improvement of methods for synchronizing data recording nodes in distributed wireless sensor networks is important and urgent task. Task statement. One practical application of the proposed solution is the study of injuries caused by the penetration of foreign objects with high kinetic energy into the human body. These studies are conducted using artificial simulators of the human body made from composite materials and ballistic gelatin, with implanted electronic devices for recording changes in physical parameters. Results and conclusions. The article presents a hardware and software method, along with the technical implementation of the process for synchronizing the local clocks of wireless nodes, integrated into a unified information-measurement system located on the simulator. The proposed method allows achieving synchronization accuracy of no more than 12 μs/second using low-cost commercial off-the-shelf components. The practical part of the research discusses microprocessors from the ESP family, which, in general, provide sufficient time synchronization accuracy when using the proposed method, allowing for cost-effective node development within the system. The proposed method can also be applied in other fields, such as measuring vibrations in electrical machines and engines, as well as structural health monitoring.

Influence of magnetic saturation on the noise and vibration of electrical machines

Influence of magnetic saturation on the noise and vibration of electrical machines

Discontinuous PWM Strategy with Frequency Modulation for Vibration Reduction in Asynchronous Machines

The aim of this paper is to present our research into the reduction of vibrations in induction motors. The use of power inverters results in the generation of electrical harmonics, which increase the level of the mechanical vibrations of electrical machines. To reduce these harmonics, we present a discontinuous pulse-width modulation (PWM) control strategy based on carrier-wave modulation applied to multilevel inverters. Using the proposed modulation technique, the amplitude of the electrical harmonics is reduced, as compared to other conventional techniques. These current harmonics produce the MMF (magnetomotive force) harmonics in the air gap, which are one of the main sources of vibrations. The control strategy makes it possible to vary the electrical spectrum at the output of a multilevel inverter by modifying a control parameter of the carrier wave in the PWM, thus avoiding the natural frequencies of mechanical resonance. The proposed technique also has the feature of attenuating the total harmonics distortion of the voltage of the multilevel inverters, as well as the achievement of a higher RMS value of the output voltage for the same DC level. Laboratory results for an induction motor with different modulation strategies, applied in a multilevel inverter and compared to the strategy presented, are attached.

Calculation of Stator Natural Frequencies of Electrical Machines Considering Complex Boundary Conditions

The accurate calculation of the natural frequencies of the stator is an important prerequisite for predicting and improving electromagnetic vibration in electrical machines. In this article, the stator core and the enclosure are regarded as cylindrical shells with axial ribs attached inside and outside the shells, respectively. Considering the moment of inertia and the shear deformation of the cylindrical shell, the displacement functions of the mid-surface in cylindrical shell are expressed as a superposition of orthogonal polynomials, the natural frequencies including axial, and circumferential modal shapes under different boundary conditions are obtained by combining the energy method and the Gram–Schmidt orthogonalization method, and the accuracy of the calculation results is verified by the finite element method and modal test. Considering the orthogonality of the stator material and specific slot structure, the natural frequencies of the stator including the stator core, windings, and enclosure are accurately obtained, the actual constraints of the end covers on the enclosure are accurately simulated by the simply supported boundary conditions.

Analytical Model to Calculate Radial Forces in Permanent-Magnet Synchronous Machines

There are three principal sources of noise and vibration in electrical machines: electromagnetic sources, mechanical sources, and aerodynamic sources. Nowadays, one of the major advantages of permanent-magnet synchronous machines is their torque density. This density is achieved through a high magnetic flux density in the air gap, which is achieved through hard magnets. Unfortunately, in these machines, electromagnetic forces have been identified as the main source of vibration and noise, and high magnetic flux densities make these vibrations and noises more significant. With the aim of better understanding the relationship between electromagnetic forces and design variables, this article, which is the continuation of previous work, firstly describes a study of the sources of magnetic forces in permanent-magnet synchronous machines. Subsequently, an analytical model for the computation of the radial forces originating from electromagnetic sources in permanent-magnet synchronous machines is stated. This model analyzes the forces on both the rotor surface and the base of the stator tooth. The analytical results were corroborated through simulations using the finite element method (FEM) and also by experimental tests performed over two prototypes. The results achieved by the analytical model show good agreement with both FEM results and experimental measurements.

New elements within finite element modeling of magnetostriction phenomenon in BLDC motor

AbstractReluctance forces are the main cause of vibration in electrical machines. The influence of magnetostriction is still the matter of controversy. In the article, program Ansys (typical for finite element method) was used to analyze stator deformation due to magnetic forces (Maxwell and magnetostriction) for the different boundaries and different methods by taking into account the windings in the mechanical model. Different parameters of numerical model are important factors affecting the level of magnetostriction deformation.

Mechanical and Magnetic Pivot Roles of Tooth in Vibration of Electrical Machines

The magnetic field including tooth effect can be calculated by the tooth harmonic permeance. However, the mechanical pivot role of tooth is always neglected in vibration analysis and the slotted stator is considered as a simple cylinder. In this article, the mechanical pivot role that the tooth plays in vibration analysis is illustrated, where the transfer function of force is proposed to represent the process of force from the top of tooth to the yoke. First, the magnetic pivot role of tooth in magnetic field analysis is described by the tooth harmonic permeance. Then the force on the top of tooth is transferred to the yoke by the transfer function of force, after that the yoke can be considered as a cylinder. Based on the pivot role of tooth, the phenomenon that the high order force can cause the low mode vibration is explained and clarified straightforwardly. Not only the fractional slot permanent magnet synchronous motor (PMSM), but also the integer slot PMSM, are analyzed to demonstrate the universality of these methods. Finally, the finite element method simulation, and the experiments on one fractional slot PM motor and one integer slot PM motor, are applied to validate the theory.

Research on weakening measure of radial electromagnetic force waves in permanent magnet synchronous motors by inserting auxiliary slots

The accurate calculation and analysis of electromagnetic force waves are especially crucial for comprehensively predicting and weakening the electromagnetic vibration of electrical machines. In this study, a fast and accurate calculation method of radial electromagnetic force density of surface-mounted permanent magnet synchronous motor (PMSM) is presented, the radial electromagnetic force density including amplitude, frequency and order is obtained and the accuracy is verified. Comprehensively considering that the effects of the auxiliary slots on cogging torque and torque ripple, the weakening measure of radial electromagnetic force waves by inserting auxiliary slots is research, and the optimal determinations of the number and the structural parameters of auxiliary slots in PMSMs with different slot–pole combinations are summarised, and six PMSMs with 6-pole/36-slot (6p36s), 4p36s, 6p9s, 8p9s, 8p12s and 10p12s are analysed to verify the universality of the conclusions.

Multiple Multiphase Combined Star–Polygon Winding Analysis

In order to improve the efficiency and to reduce the field amplitudes of spatial harmonics influencing noise and vibration of electrical machines, three- and five-phase combined star-polygon windings have been suggested in the literature. Besides, the efficiency of an electrical machine is dependent on the fundamental winding factor and the noise/vibration level is related to the winding factors of some higher/lower harmonics. However, there is no systematic method to calculate the winding factor of each spatial harmonic for a multiple topology. This paper deals with proposing different topologies of multiple series multiphase combined star-polygon windings and accordingly with the calculation methods of winding factors for all spatial harmonics and the harmonic leakage factor. The results of winding function approach and symmetrical components of electromotive forces (EMFs) are perfectly in compliance with each other, provided that the fast Fourier transform (FFT) analysis is sufficiently accurate. The results obtained from measurements on an unskewed electrically excited synchronous machine are applied for validating the results given by the sum of EMFs and the proposed calculation formula. The sum of EMFs, considering just one set of a multiple topology, can give the same results as the proposed winding analysis methods for the fundamental or the slot harmonic winding factors.

Review of Electromagnetic Vibration in Electrical Machines

Electrical machines are important devices that convert electric energy into mechanical work and are widely used in industry and people’s life. Undesired vibrations are harmful to their safe operation. Reviews from the viewpoint of fault diagnosis have been conducted, while summaries from the perspective of dynamics is rare. This review provides systematic research outlines of this field, which can help a majority of scholars grasp the ongoing progress and conduct further investigations. This review mainly generalizes publications in the past decades about the dynamics and vibration of electrical machines. First the sources of electromagnetic vibration in electrical machines are presented, which include mechanical and electromagnetic factors. Different types of air gap eccentricity are introduced and modeled. The analytical methods and numerical methods for calculating the electromagnetic force are summarized and explained in detail. The exact subdomain analysis, magnetic equivalent circuit, Maxwell stress tensor, winding function approach, conformal mapping method, virtual work principle and finite element analysis are presented. The effects of magnetic saturation, slot and pole combination and load are discussed. Then typical characteristics of electromagnetic vibration are illustrated. Finally, the experimental studies are summarized and the authors give their thoughts about the research trends.

A general electromagnetic excitation model for electrical machines considering the magnetic saturation and rub impact

The electromagnetic vibration of electrical machines with an eccentric rotor has been extensively investigated. However, magnetic saturation was often neglected. Moreover, the rub impact between the rotor and stator is inevitable when the amplitude of the rotor vibration exceeds the air-gap. This paper aims to propose a general electromagnetic excitation model for electrical machines. First, a general model which takes the magnetic saturation and rub impact into consideration is proposed and validated by the finite element method and reference. The dynamic equations of a Jeffcott rotor system with electromagnetic excitation and mass imbalance are presented. Then, the effects of pole-pair number and rubbing parameters on vibration amplitude are studied and approaches restraining the amplitude are put forward. Finally, the influences of mass eccentricity, resultant magnetomotive force (MMF), stiffness coefficient, damping coefficient, contact stiffness and friction coefficient on the stability of the rotor system are investigated through the Floquet theory, respectively. The amplitude jumping phenomenon is observed in a synchronous generator for different pole-pair numbers. The changes of design parameters can alter the stability states of the rotor system and the range of parameter values forms the zone of stability, which lays helpful suggestions for the design and application of the electrical machines.

Analysis of electromagnetically-induced vibrations of electrical machines based on spatiogram technique

Analysis of electromagnetically-induced vibrations of electrical machines based on spatiogram technique

Numerical representation of two-dimensional magnetostriction in electrical machines

Abstract. In order to reduce acoustic noises and vibrations of electrical machines caused by magnetostriction, it is necessary to make clear the distribution of magnetostriction on magnetic core. The distribution of magnetostriction has been visualized by measured two-dimensional magnetostriction of electrical steel sheet and vector magnetic characteristics analysis technique. The distributions of vector magnetic characteristics and magnetostriction and the relationship between the magnetic flux density vector and two-dimensional magnetostriction have been made clear in the method.

Water Pump Mechanical Faults Display at Various Frequency Resolutions

When an electrical machine suffered a mechanical fault, it generally emits certain sounds. These sounds came from the vibration. Therefore, based on the vibration, it could be detected if there was a mechanical fault in an electrical machine. This paper discussed the graphical display of the vibration of electrical machines in the form of household water pumps which were in good condition, faulty bearing, faulty impeller, or faulty foot valve. Vibration could be displayed in the time domain, or in the frequency domain, by using the three axes, i.e. X, Y, and Z. In the frequency domain, the vibration could be displayed at various frequency resolutions. Based on the observations, the higher frequency resolution, the lower detail in the graphical display of frequency domain would be shown. Although there was lower detail in the graphical display of frequency domain, at frequency resolution of 11.7 Hz in the X axis, showed that it could be visually distinguished among water pumps which were in good condition, faulty bearing, faulty impeller, or faulty foot valve.

Application of Model Predictive Control for Improving Stability of Rotor and Controlling Active Rotor Vibration

The aim of this paper is to study the application of model predictive controller for improving stability of rotor and rotor vibration. Rotor vibrations in electrical machines are dampen out by model predictive control algorithm. The controlled system is the one dimensional Jeffcott-rotor. Model predictive control algorithm was designed, and the simulation results were obtained by Mat lab software tools. Model Predictive Control (MPC) refers to a class of algorithms that compute a sequence of manipulated variable adjustments in order to optimize the future behavior of a plant. In this paper the controlled output of rotor by MPC is further compared with output of same rotor with PID controller.

Fast Computation of Electromagnetic Vibrations in Electrical Machines via Field Reconstruction Method and Knowledge of Mechanical Impulse Response

The main objective of this paper is to provide an efficient computational model for fast and accurate calculation of electromagnetically induced vibrations in electrical machines. Although a three-phase permanent-magnet synchronous machine has been used in this paper, the same methodology can be extended to other types of electric machinery. A brief comparison between the different methods for structural analysis in electrical machines is introduced. The method proposed in this paper uses finite-element analysis in order to extract the impulse responses that are used in calculating the vibration. A field reconstruction method is used for the electromagnetic field analysis.

Hybrid Swarm Algorithms for Parameter Identification of an Actuator Model in an Electrical Machine

Efficient identification and control algorithms are needed, when active vibration suppression techniques are developed for industrial machines. In the paper a new actuator for reducing rotor vibrations in electrical machines is investigated. Model‐based control is needed in designing the algorithm for voltage input, and therefore proper models for the actuator must be available. In addition to the traditional prediction error method a new knowledge‐based Artificial Fish‐Swarm optimization algorithm (AFA) with crossover, CAFAC, is proposed to identify the parameters in the new model. Then, in order to obtain a fast convergence of the algorithm in the case of a 30 kW two‐pole squirrel cage induction motor, we combine the CAFAC and Particle Swarm Optimization (PSO) to identify parameters of the machine to construct a linear time‐invariant(LTI) state‐space model. Besides that, the prediction error method (PEM) is also employed to identify the induction motor to produce a black box model with correspondence to input‐output measurements.

Vibration Synthesis for Electrical Machines Based on Force Response Superposition

A universal and modular approach for synthesizing electromagnetically excited vibrations in electrical machines is presented. The synthesis process uses force responses, i.e., the normalized structural vibration responses for a machine's generic set of force excitation shapes. The responses are superposed after scaling by the operating point dependent force excitation amplitudes. This leads to a computationally efficient process. It allows to use detailed structural 3-D models and to synthesize the vibrations in the entire operating range of the machine. For validation, measured and synthesized vibration spectrograms of a run-up test of an interior permanent magnet traction motor are presented.

Modelling of flexural rotor vibration and time-periodic system dynamics in a two-pole cage induction machine equipped with a self-bearing force actuator

In this paper, linear time–periodic system dynamics in rotor vibration of electrical machines is examined. We consider a two-pole cage induction machine equipped with a built–in force actuator for active generation of lateral force on the rotor.The main contribution of the work is to identify and model the sources of time-periodic system dynamics in the coupled electromechanical actuator-rotor system. Especially, the effect of higher spatial harmonics of the magnetic field on the generated force is considered. In this work, a linear time–periodic model for the actuator-rotor system is derived. The parameters of the analytical model are estimated by using time-stepping finite-element analysis of the machine.

Attenuation of Harmonic Rotor Vibration in a Cage Rotor Induction Machine by a Self-Bearing Force Actuator

In this paper, attenuation of flexural rotor vibration in electrical machines is considered. In order to generate force on the machine rotor, an electromagnetic actuator based on self-bearing machine working principle is examined. A control method for attenuating harmonic rotor vibration components is applied in a 30 kW two-pole cage induction machine. The machine is equipped with a four-pole supplementary winding for generation of lateral force on the rotor. Experimental results for the two-pole induction motor are presented. The main contribution of this paper is to apply a control method, specially designed for compensating harmonic excitations, by using a built-in electromagnetic actuator in an induction machine.