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Stator Teeth Tips Shape Influence in Permanent Magnet Synchronous Motors on a Test Bench
... The optimization of the design of electric machines is a highly challenging topic, as it involves performing a multiphysics analysis [6]. In the literature, many different approaches have been proposed in recent years to optimize the design of PMSMs regarding their vibration behaviour [7]. ...
The use of electric motors, and particularly, Permanent Magnet Synchronous Motors, is increasing in recent years, and their vibration response is one of the most crucial aspects regarding their behaviour. Thus, the reduction in vibrations is one of the key objectives when optimizing electric motors. In an initial design state, the influence of the main design parameters on the behaviour of the machines is not always clear. For that reason, this work presents a global sensitivity analysis procedure that allows identifying the most influential design parameters and determining guidelines to optimize the design of Permanent Magnet Synchronous Motors. First, the analytical calculations employed to estimate the electromagnetic torque and the vibration response of the machine are described. Then, the sensitivity analysis procedure, based on the Monte Carlo method, is presented, and the conditions to apply the method successfully and accurately are analysed. Finally, the sensitivity analysis is performed for a particular electric motor design, and some general design guidelines are deduced, which can be extrapolated to similar machines.
This paper presents the loss-oriented performance analysis of a radial highspeed permanent magnet (PM) machine with concentrated windings for automotive application. The PM synchronous machine was designed for an operating frequency up to 800 Hz. The main aim of this paper is to analyse the selected methods for magnet eddycurrent loss reduction. The first approach to rotor modification regards magnet segmentation in circumferential and axial directions. The second approach is based on changes in tooth-tips shape of the stator. The best variants of tooth-tip shapes are determined for further investigation, and adopted with a rotor having magnet segmentation. It is found that the machine with a segmented magnet leads to magnet loss reduction by 81%. Further loss reduction by 45% can be realized with the proposed tooth-tip shape. Additionally, owing to the stator and rotor modifications, the main machine parameters are investigated, such as back-EMF, electromagnetic torque, torque ripple and cogging torque. The 2-D and 3-D finite element analysis (FEA) is used for electromagnetic analysis. An experimental approach based on a partially wound stator is employed to verify the 3-D FEA.
Audible noise of electric machines has become an important criterion in their design. In this paper we used a multi-physics numerical model (electromagnetic-dynamic) in order to predict mechanical vibration caused by magnetic pressure in a wound rotor synchronous machine. The final objective is to reduce this mechanical vibration. The novelty of this paper is to use an optimization method with this multi-physics numerical model in order to reduce important vibration peaks thanks to magnetic pressure harmonics.
Because of their numerous advantages but also of some undesirable effects, permanent-magnet synchronous machines (PMSMs) with non-overlapping concentrated windings have recently been widely investigated. In this paper, the design features specific to 3-phase PMSMs with non-overlapping concentrated windings are presented. Especially, it is shown that the selections of the stator core manufacturing method, the number of winding layers, the combination of pole and slot numbers, and the geometry of the tooth tips are crucial during the design stage of the machine.
This paper deals with the core loss reduction according to the change of stator shape in an interior permanent magnet synchronous motor (IPMSM). The number of slots per pole per phase of the IPMSM is 0.5, and the tooth width and yoke thickness are chosen as design factors. According to the ratio of tooth width and yoke thickness, the core loss is analyzed under considering the rotating and alternating magnetic field at the main operation. Base on the functional core loss data obtained by the Steinmetz equation, the core loss is calculated by using finite element method (FEM). In this study, the determination of ratio of tooth width and yoke thickness to minimize the core loss in the IPMSM is presented. In additional, the torque characteristics according to the ratio are also investigated.
Cogging torque in permanent-magnet motors is one of the most important problems to be considered in high performance applications especially in low speed and direct drive applications. In this paper, the analytical expression for cogging torque in permanent-magnet synchronous motors (PMSM) with auxiliary teeth is derived by the energy method and the Fourier series analysis, based on the air gap permeance and the flux density distribution in an equivalent slotless machine. Analytical method was proposed to determine an appropriate scope of auxiliary tooth width. In order to reduce cogging torque to the maximum extent, cogging torque corresponding to different slot openings was analyzed. To determine the auxiliary teeth width accurately, finite element method (FEM) which considered the effects of flux leakage and saturation was proposed. And then on this basis auxiliary teeth height was determined by analyzing the distribution of the radial component of the flux density in the air gap. Finally, calculation results of cogging torque corresponding to different distributions of the auxiliary teeth, the auxiliary teeth width as well as the auxiliary height were discussed.
Permanent magnet synchronous motors PMSM are widely used in industry due to their higher torque and higher power to volume ratio. Moreover they have a better dynamic performance compared to the motors with electromagnetic excitation. Despite its robustness electrical, mechanical and magnetic faults has been described. It has led to the development of specific diagnostic systems for such machines. These systems are constantly evolving according to the literature. In this situation of increasing use of PMSM it is necessary to teach and train professionals in diagnostic techniques. This paper describes the design process of an experimental bench on which can be studied all types of faults associated with the PMSM operation. The design of a PMSM prototype, which is the most important equipment of this bench, is described in more detail.
Torque ripple has been a major problem for the permanent magnet (PM) machine. It is discussed focusing on the magnetic circuit of the PM machine. Since it is known the relationship between the torque ripple and the magnetic energy that is stored in the magnetic field along the air gap of the PM machine, fluctuation in the magnetic energy was initially revealed. New tooth geometry was obtained by drilling holes into stator tooth to modify this variation in the magnetic energy and the fluctuation in torque. Thus, a new stator tooth design in outer rotor surface-mounted permanent magnet (ORSPM) machine was proposed to minimizing the torque ripple in this study. Improvement in torque ripple value was performed in excess of 50% thanks to new stator tooth design. In addition, improvements have been carried out at the average torque and total harmonic distortions (THD) of back EMF (electromotive force).
This paper presents the method on the stator teeth shape design in Surface-Mounted Permanent Magnet Synchronous Motor (SPMSM) for reducing torque ripple. In order to examine the effect of the stator teeth shape to torque ripple, three models of the SPM motor which have the different stator teeth shapes are selected, and then FEM analysis is carried out to compare their characteristics. Then, a method about specifying a design parameter to be able to effectively reduce torque ripple is developed. By use of this method, the optimized model can be achieved rapidly and reliably. The torque ripple is reduced by cogging torque which can decrease torque value of maximum points and increase that of minimum points.
The electrical machine (EM) is a key component in plug-in electric and hybrid vehicle (PEV) propulsion systems. It must be designed for high torque/power densities, wide speed range, over load capability, high efficiency at all speeds, low cost and weight, fast acceleration and deceleration, while meeting performance and reliability expectations. This paper overviews various EM technologies that are the best candidates for use in PEVs. Their basic operational characteristics, design features and relative advantages and disadvantages are discussed and compared for PEV propulsion systems. The latest and future research directions of EMs for PEVs are identified and discussed. Literature concerned with limitations and capabilities of finite element analysis and magnetic equivalent circuit analysis for EM design and analysis in PEVs is presented. Unfortunately, few papers give thorough comparisons between experimental measurements and simulation tools for EMs; even fewer compare torque. Those that report on torque show errors of 10% or more between tests and simulations. Saturation and losses appear to be the likely culprits. When nonlinear magnetic effects are taken into account, including magnetic saturation, eddy currents losses, and modeled with care, differences between simulations and tests typically are on the order of 5%.
A detailed analysis of electromagnetic noise in external rotor permanent-magnet synchronous motors is presented in this paper. First, the spatial distribution and frequency characteristics of the electromagnetic force acting on the surface of the permanent magnet are discussed. Then, calculation models for electromagnetic force, structural vibration, and acoustic radiation are developed to predict noise by taking an external rotor in-wheel motor as example. The uneven distribution of electromagnetic force on the surface of the permanent magnet is taken into account by means of loading nodal force into the structural model which is verified by modal test. Through the mode superposition method, the vibration on the surface of the outer rotor is calculated, and the acoustic boundary element method is used to predict the acoustic radiation. Noise test is conducted to validate the simulated noise. It is shown in both simulation results and noise test that the electromagnetic force due to slotting effects contributes the most remarkable component to the overall noise. Finally, slot opening width is optimized to reduce the amplitude of magnetic force close to resonance frequencies, and the overall sound pressure level decreases by 6 dB(A) after optimization.
The noise and vibration of the motor has been a very important factor in the performance of the motors. Particularly for permanent magnet synchronous motor, noise and vibration characteristics also have a lot of particularities. In this paper, Firstly, the author analyzes the air-gap flux density expression of fractional slot permanent magnet motor stator in slotted condition from the magnetic field. Secondly, the author analyzes the influence of vibration and noise on the motor including the length of Permanent magnet in polarization direction, the shape and size of teeth notch in the stator, the size of stator notch width. At last, the comparative results show that, the proposed method can effectively weaken electromagnetic vibration and noise of permanent magnet synchronous motor.
In this paper, the influence of slot harmonics on magnetic forces and vibration is studied in a 120-slot/116-pole low-speed PM machine at no-load. It is shown how the lowest mode of vibration is produced at no-load due to slotting. Comparing the cases of open slots, semi-closed slots and magnetic wedges, the effect of slot closure on radial forces and torque production capability is discussed. Magnetic flux distribution in the airgap is computed using finite element analysis. Spatial harmonics due to slotting are investigated in different cases. Maxwell’s stress tensor is employed to calculate radial and tangential components of the force density in the airgap. Spatial distribution of the total forces on the teeth and also timedependent force waveform on one tooth are analyzed and discussed for different cases. It is shown how the magnitude of the lowest mode of vibration is reduced in the case of using semiclosed slots and magnetic wedges. Tangential force density distribution and torque production capability are also discussed. Structural analysis is presented to compute the maximum amplitude of the stator deformations due to the radial forces. Experimental results of the prototype generator are presented verifying the existence of the lowest mode of vibration at no-load because of the slot harmonics.
This paper describes important design considerations for a bearingless brushless motor (permanent magnet synchronous motor, PMSM) in exterior rotor construction. In order to come up with a compact energy-dense setup which can provide both bearing forces and high torque, several parameters have to be accounted for while considering mutual dependences. Moreover, the magnetic bearing and the drive are interlinked for this disk-shaped bearingless motor (with combined concentrated windings). A detailed analysis about the design of the stator teeth has been undertaken, and the influence on torque and active and passive radial forces has been investigated.
This paper deals with how to obtain the optimal shape of a permanent magnet of surface mounted permanent magnet brushless synchronous machine using the level set based topology optimization method. Two types of the flux linkage calculation method are formulated; one is a modified method based on traditional flux linkage calculation through transient analysis and the other is the mono-tooth method newly introduced in this study. The mono-tooth method makes it possible to avoid time-consuming transient analysis because it requires only magnetostatic field analysis and may deal with infinite design points. The level set based topology optimization method is combined with both types of flux linkage calculation method. The optimization problem for shape design of a surface mounted permanent magnet synchronous machine is defined focused on the permanent magnet shape design and optimization results by two different approaches are compared. The performance of the optimal model is also compared with that of a conventional magnet shape model.
In an electric motor in which permanent magnets are used, the magnetic flux is caused by the magneto-motive force of the permanent magnets of the rotor and the stator winding wire, and the performance of the electric motor is determined by the scale of the magnetic flux and the magnetic circuit. This thesis is aimed at introducing electric motors in which permanent magnets are used and focuses on a performance analysis of said electric motors according to the scale of the magnetic flux and changes in the magnetic circuit. The analysis was carried out by separating the magnetic flux occurring at the stator winding wire into the magnetic flux of axis d and that of q axis, so that the impact of the magnetic flux on the performance of the electric motor could be analyzed. In addition, the impact of changes in the magnetic circuit, which were caused by the magnetic flux at the permanent magnet of the rotator, on the electric motor was analyzed. Finally, the results of the analysis were verified by performing experiments on a model made by using selected analysis results.
This paper presents a tooth shape optimization method based on a generic algorithm to reduce the torque ripple of brushless permanent magnet motors under two different magnetization directions. The analysis of this design method mainly focuses on magnetic saturation and cogging torque and the computation of the optimization process is based on an equivalent magnetic network circuit. The simulation results, obtained from the finite element analysis, are used to confirm the accuracy and performance. Finite element analysis results from different tooth shapes are compared to show the effectiveness of the proposed method.
For the reduction of the cogging torque of permanent-magnet synchronous machines several approaches are known. But cogging torque predictions for arbitrary types of machines using the same approach are still troublesome and imprecise. Therefore, a fast optimization process is developed and presented in this paper. Here, the combination of both numerical and analytical simulation results in such a fast method
This paper focuses on the experimental investigation for incipient fault detection and fault detection methods suitably adapted for use in permanent-magnet motors for direct-drive elevator systems. The proposed system diagnoses permanent-magnet motors having two types of faults such as short circuit of stator windings and bearing fault. After processing current data the classical fast Fourier transform is applied to detect characteristics under the healthy and various faulted conditions with MCSA.
In this paper, measurements of the magnetic flux in a permanent magnet synchronous machine (PMSM) with non- overlapping concentrated windings are analyzed. Flux leakage, inductances and stator iron losses are investigated from measurements performed at open-circuit, blocked-rotor, and load conditions, respectively. Comparisons of the measurements with the corresponding 3D finite-element (FE) simulations allow validating thoroughly the FE model. The zigzag leakage flux flowing from one magnet to another through a tooth tip, which is characteristic for PMSMs with concentrated windings, is highlighted and its effect on the stator iron losses is investigated.
The teeth shapes of permanent-magnet motors with concentrated windings are optimized in order to reduce the eddy-current losses of magnets. First, the main factors that cause the magnet eddy-current losses in surface and interior permanent-magnet motors are discussed by analyzing the variation in flux distributions. Next, automatic optimizations are carried out for each motor by using the adaptive finite element method. The validity of the calculation is confirmed by the experiment of prototype motors. It is clarified that the optimized teeth shapes of the surface and interior permanent-magnet motors are significantly different from each other because of the difference in the main factors that cause the magnet eddy-current losses.
This paper proposes a methodology for the acoustic optimization of PMSM applying two steps: hybrid modeling to obtain the magnetic field and forces at comparatively small computational effort and FEM-to-measurement transfer functions to assess the structural behavior and the radiation characteristics of the machine at once. Both steps are explained and applied to a specific PMSM design, which is subject to optimization. The proposed approach relies on a (virtual) protoype. The resulting optimized geometry shows significant reduction potential in terms of total sound pressure level, up to 18dB(A), but at the cost of a larger magnet volume. Limitations of this procedure are discussed.
In external rotor permanent magnet synchronous motors, also the higher frequency harmonics of the radial forces generate considerable resonant vibrations and acoustic noise. Therefore, diversity of spatial and especially frequency harmonic ordinal numbers of representative slot and pole number combinations are derived analytically with open-circuit and under load. Amplitudes of radial force waves are calculated by means of the finite element method and two-dimensional Fourier analysis. The obtained results confirm the analytical investigation. Determining factors on amplitudes are analyzed on a machine having 12 slots, 10 poles and a double-layer winding. Higher frequency harmonics can be significantly affected by pole and tooth shaping. With open-circuit, the calculations are validated by experimental results.
Interior permanent magnet (IPM) synchronous machines can experience large harmonic eddy-current losses in the stator teeth under flux-weakening operation, significantly depressing the efficiency of these machines at high operating speeds. This paper presents a new analytical/finite-element hybrid design approach to reduce the harmonic eddy-current losses in IPM machine stator teeth during flux-weakening operation. The proposed technique achieves this objective by three steps: 1) developing an analytical index for the harmonic eddy-current losses in IPM machine stator teeth; 2) designing the spatial distribution of the rotor MMF to minimize the analytical index; and 3) synthesizing the rotor geometry to implement the desired rotor MMF function while maintaining the basic machine characteristics unchanged. It will be shown that two-layer rotors, if properly optimized, are significantly more effective than one-layer rotors for the purpose of reducing the harmonic eddy-current losses in IPM machine stator teeth during flux-weakening operation at high speeds.
A principal source of vibration in permanent magnet (PM) motors
and generators is the traveling forces on the stator induced by the
rotating permanent magnets. These forces are transmitted through the
stator and to the surrounding system. The magnetic forces were
calculated from the flux density by finite element methods (FEMs). The
dynamic reactions at the motor mounting points, which provide the
forcing function to the base system, were also calculated by FEMs. The
vibration characteristics and the transmissibility of each frequency
component were investigated using Fourier decomposition of the traveling
magnetic force. The results showed that for a radially centered rotor
the frequency components of the magnetic force were integer multiples of
the rotor speed multiplied by the number of magnetic poles. Higher
harmonics were more difficult to transmit, except when stator structure
resonance occurred. The edge shape of the PM determined the shape of the
magnetic force and the magnitude of the frequency components. By proper
shaping of the magnetic edges, the composition of the magnetic force
spectrum can be assigned to higher frequencies, reducing the overall
transmission to the base system
Torque ripple minimization in PM synchronous motors using tooth shape optimization
- A Jabbari
- M Shakeri
- A Nabavi Niaki
A. Jabbari, M. Shakeri, and A. Nabavi Niaki, "Torque ripple
minimization in PM synchronous motors using tooth shape
optimization," Majlesi Journal of Mechanical Engineering, vol. 3,
no. 2, 2010.
Torque ripple minimization in PM synchronous motors using tooth shape optimization
- jabbari