Radial Electromagnetic Force Research Articles

Numerical Investigation on Vibration Performance of an Improved Switched Reluctance Machine with Double Auxiliary Slots

Considerable vibration and acoustic noise limit the further application of Switched Reluctance Machine (SRM) due to its structural characteristics and working principle. An improved SRM model with double auxiliary slots (DAS) was proposed, in which the direction of the magnetic line of force was adjusted, and the radial magnetic density in the air gap was reduced by changing the local tooth profiles of the stator and the rotor. The effects of initial rotor position and turn-on angle and turn-off angle on radial Electromagnetic Force (EMF) and maximum torque were investigated. The results indicate the radial EMF and torque increase significantly with the advancement of the turn-on angle or the delay of the turn-off angle. In the orthogonal experimental design, initial rotor position, turn-on angle, and turn-off angle were taken as the factors, and the optimal set of parameters that minimized radial EMF was determined according to a greater output torque. In contrast to conventional SRM, the radial EMF of the SRM with DAS significantly reduces when the optimal set is applied.

INVESTIGATING INFLUENCES OF TAPPED SHOE ROTOR POLES ON ELECTROMAGNETIC TORQUES AND RADIAL FORCES OF SWITCHED RELUCTANCE MOTORS

The shape of rotor poles has a significant influence on the performance of electromagnetic torques and radial forces, because the air-gap flux density is depent on the stator and rotor areas and surfaces. Serveral articles have studied influences of the stator/rotor designs on radial forces and electromagnetic torque waveforms as well. Moreover, the electromangetic characteristics of switched reluctance motors are also defined by tapped-shoe-skewing of the stator and rotor poles with the inner holes. However, the total solution designs of the tapped-shoe rotor with diferent tapped angles have not yet implemented by those papers so far. For that, in this paper, the tapped shoe rotor pole design is proposed by different angles for the high speed switched reluctance motor of 30 kW and 18000 rpm.

Research On Radial Electromagnetic Force and Vibration Response Characteristics of Squirrel-Cage Induction Motor Fed By PWM Inverter

In order to study the influence of current harmonics generated by PWM inverter on radial electromagnetic force and vibration response of squirrel-cage induction motor, an analysis method is introduced in this paper. Firstly, the relationship among the order and frequency of electromagnetic force wave of the motor under the action of harmonic current is analyzed theoretically. Secondly, a squirrel-cage induction motor is used to build a vibration response analysis model with multiple physical field coupling. The electromagnetic force wave and vibration response spectrum of the motor under sinusoidal power supply and PWM harmonic power supply are obtained. The results show that: for the prototype, the frequency components of 0-order, 2 (2p) order electromagnetic force wave will be introduced when the harmonic current of the inverter is supplied. Finally, the correctness of the analysis method is verified by the vibration experiment of the prototype.

Experimental Vibration Studies on a Solid-Rotor Switched Reluctance Machine

Vibration characteristics of a solid-rotor switched reluctance machine (SRM) are measured in the static as well as dynamic conditions. A series of impulse hammer-based static measurements are carried out on the assembled machine. The impulse hammer tests identify the main resonant frequencies of the rotor assembly, bearing housing and enclosure. For the dynamic vibration tests, the SRM is run at different speeds using single-pulse control and current control. The measured currents are utilized to obtain the electromagnetic radial force on the stator through finite element analysis. The frequency components of the estimated radial force are observed in the vibration spectrum measured in the dynamic tests. The dynamic vibration spectrum also include the resonant frequencies of the SRM subassemblies. The natural frequencies of the rotor assembly are found to influence the vibration spectrum significantly. Harmonics of speed are the other significant components in the measured vibration spectrum at any given speed; the magnitudes of these components increase with rotor speed.

Modeling and suppression of unbalanced radial force for in-wheel motor driving system

Considering the negative vertical dynamics effect of switched reluctance motor on an in-wheel motor driving system, this article presents a modeling and suppression method for unbalanced radial force of the in-wheel motor driving system. To tease out the coupling relationship within the in-wheel motor driving system, this investigation, respectively, explores the principle of unbalanced radial force and the coupling relationship between rotor eccentricity and road excitation based on the suspension response model with unbalanced radial force under road excitation. The switched reluctance motor nonlinear analytical model was fitted by the Fourier series, and its radial electromagnetic force was modeled and analyzed by the Maxwell stress tensor method. To mitigate the influence of radial electromagnetic force fluctuation and unbalanced radial force amplitude value under eccentricity condition on the in-wheel motor driving system, the elitist non-dominated sorting genetic algorithm was adopted to improve radial electromagnetic force fluctuation and unbalanced radial force amplitude value of the switched reluctance motor. The simulation results show that the proposed optimization method can suppress the radial electromagnetic force fluctuation and unbalanced radial force amplitude value, and the negative effect of vertical dynamics of the in-wheel motor driving system is conspicuously mitigated.

Design and Cosimulation of Twelve-Pole Heteropolar Radial Hybrid Magnetic Bearing

This paper presents a twelve-pole heteropolar radial hybrid magnetic bearing (HRHMB) structure. Firstly, the structure and equivalent magnetic circuit (EMC) are designed. And the radial electromagnetic force characteristics are calculated by the EMC model. At the same time, the rationality of EMC model is verified by the finite-element method (FEM) of Magnet software. Then, the 2-D model of the twelve-pole HRHMB is established in Magnet software. The flux density variations of twelve-pole HRHMB and eight-pole HRHMB under different currents are compared by using the FEM. Finally, a method of Magnet-Simulink cosimulation is proposed to analyze the suspension characteristics of the twelve-pole HRHMB and compared with the eight-pole HRHMB. Thus, the effective combination of theoretical analysis, FEM analysis, and Magnet-Simulink cosimulation analysis is realized in the design of HRHMB. The results of Magnet-Simulink cosimulation show that the twelve-pole HRHMB has the advantages of low power consumption, small coupling, large construction dynamic stiffness, and better suspension characteristics than the eight-pole HRHMB.

Radial electromagnetic force and vibration in synchronous reluctance motors with asymmetric rotor structures

Radial electromagnetic force and vibration in synchronous reluctance motors with asymmetric rotor structures

Mechanical Faults in Oil‐Immersed Power Transformers with Disc‐Type Windings Due to External Short Circuit

This study investigated mechanical faults in oil‐immersed power transformers with disc‐type windings. Short‐circuit tests were conducted on eight aged removed transformers. Before the short‐circuit tests, accelerated aging tests were conducted on all the transformers to discuss the life limit of transformers. Six out of eight transformers experienced the internal ground faults. Although the radial electromagnetic force and the tolerance of the insulation paper against it have been mainly focused in discussing the life of the power transformers, the ground faults were triggered by the crush of the pressboard by the axial electromagnetic force. The axial compressive stress applied to the pressboards varies from the transformer to the transformer, depending on the design of the windings. The transformer, whose axial compressive stress was relatively lower, passed the short‐circuit test. However, even for the similar deterioration degree of the pressboard, the transformer, whose axial compressive stress was relatively higher, experienced the ground fault. These results indicate that the axial compressive stress during an external short circuit and deterioration of the pressboard are critical factors that determine the life of transformers with disc‐type windings. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Analysis and Simulation Research on Radial Electromagnetic Force Wave of Permanent Magnet Synchronous Motor

Aiming at the problems of vibration and noise of permanent magnet synchronous motors, based on the principle of radial air gap magnetic density generation, a model of radial electromagnetic force waves is constructed, and the radial air gap magnetic density and diameter of permanent magnet synchronous motors are derived by analytical analysis Analytical expression of the electromagnetic wave, to obtain the main order, frequency and amplitude of the radial electromagnetic wave. Using Maxwell 2D simulation software to establish a simulation model, verify it, prove the correctness of the proposed method, and provide a theoretical basis for further research on the vibration and noise of permanent magnet synchronous motors.

Wide Speed Range Noise and Vibration Mitigation in Switched Reluctance Machines With Stator Pole Bridges

Noise, vibration, and harshness (NVH) issue in switched reluctance machines (SRMs), originating from their doubly salient structure and unique principle of operation, is addressed in this work by proposing a structural design modification in the stator, which increases stiffness to mass ratio of the structure. A 24-slot 16-pole (24s/16p) SRM designed with the aim of automotive application is studied here for the NVH optimization, at different target operating points, using stator pole bridges. Stator pole bridges link consecutive stator teeth to provide additional stiffness to the stator structure. Average torque reduction due to flux shorting in stator pole bridges is tackled by proposing a low-permeability material, with considerable stiffness, which has not yet seen its' application in SRM NVH domain. Multiphysics aspects of stator pole bridge design encompassing electromagnetic radial force, mechanical stress, steady-state temperature distribution, and acoustic noise analyses are presented in this article. Possible manufacturing issues are considered during the design phase and appropriate measures are implemented to facilitate easier construction of two 100-kW prototypes. The final design with stator pole bridges and a baseline design without any stator pole bridges are prototyped, after rigorous multiphysics optimization, for extensive testing. Experimental results verify simulation outputs and report a maximum noise reduction of 12.52 dBA in the stator pole bridge model compared to the baseline SRM.

A New Method for Vibration Suppression of Switched Reluctance Motor Using Liquid Cooling Medium

The vibration problem of a switched reluctance motor (SRM) comes from its structure and operation principle, and seriously affects its application. In fact, the vibration is caused by the radial electromagnetic force of SRM. The electromagnetic field numerical calculation software Magnet can simulate the direction of radial electromagnetic force. In addition, the Maxwell stress method was used to deduce the judgment rule of the direction of radial electromagnetic force in an experiment of measuring the flux distribution of SRM stator model. The finished test results confirmed the calculation results of Magnet software. On this basis, using the pressure of liquid cooling medium to reduce the radial electromagnetic force, a new type of switched reluctance motor stator structure is designed by immersing the whole stator with a moving fluid formed by the evaporative cooling liquid medium. It is proved by ANSYS and ANSYS Workbench software that under the effect of temperature difference, the evaporative cooling medium flows at a certain velocity field which strengthened the liquid pressure and the liquid pressure of the evaporative cooling medium counteract the radial electromagnetic force, and meanwhile weaken the vibration caused by it. As a conclusion, all the simulations show that the new type of SRM stator structure filled with evaporative cooling medium can reduce the SRM stator vibration speed by 40%.

Analytical Study of Stator Tooth Modulation on Electromagnetic Radial Force in Permanent Magnet Synchronous Machines

The electromagnetic radial force acting on the stator inner periphery will induce radial vibration and acoustic noise in permanent magnet synchronous machines (PMSMs). The radial force components are transmitted through the stator teeth to the yoke to introduce deformations. The influence of the stator tooth structure can be considered as an equivalent mechanical modulation effect on these electromagnetic radial force components. As a result, high-order electromagnetic radial force components can be modulated and potentially result in eminent stator low-mode vibration. In this article, an analytical model is developed to offer an intuitive knowledge of stator tooth modulation effect on electromagnetic radial force. The validity of the proposed analytical method is underpinned by both finite-element analysis and experimental results. Such an effective yet simple analytical model can be of significant benefit for the stator radial vibration analysis. It can be employed to not only promptly investigate the stator radial vibration characteristics, but also perform effective optimization on stator radial vibration reduction in permanent magnet synchronous machines (PMSMs).

Electromagnetic noise analysis and optimization for permanent magnet synchronous motor used on electric vehicles

PurposeElectromagnetic noise of permanent magnet synchronous motor (PMSM) seriously affects the sound quality of electric vehicles (EVs). This paper aims to present a comprehensive process for the electromagnetic noise analysis and optimization of a water-cooled PMSM.Design/methodology/approachFirst, the noises of an eight-pole 48-slot PMSM in at speeds up to 10,000 rpm are measured. Furthermore, an electromagnetic-structural-acoustic model of the PMSM is established for multi-field coupling simulations of electromagnetic noises. Finally, the electromagnetic noise of the PMSM is optimized by using the multi-objective genetic algorithm, where a multi-objective function related to the slot width of PMSM stator is defined for radial electromagnetic force (REF) optimization.FindingsThe experimental results show that main electromagnetic noises are the 8n-order (n = 1, 2, 3, …) and 12-order noises. The simulated results show that the REFs are mainly generated by the 8n-order (n = 1, 2, 3, 4, 5, 6) vibrations, especially those of the 8th, 16th, 24th and 32th orders. The 12-order noise is a mechanical noise, which might be caused by the bearings and other structures of the PMSM. Comparing the simulated results before and after optimization, both the REFs and electromagnetic noises are effectively reduced, which suggests that an appropriate design of stator slot is important for reducing electromagnetic noise of the PMSM.Originality/valueIn view of applications, the methods proposed in this paper can be applied to other types of PMSM for generation mechanism analysis of electromagnetic noise, optimal design of PMSM and thereby noise improvement of EVs.

Performance Comparisons of Fractional Slot Surface-Mounted Permanent Magnet Machines With Slot-Harmonic-Only Windings

Fractional-slot slot harmonic only windings (SHOW), featured by multi-layer and varied coil turn ratios, contain only the torque-generating component and its slot harmonics in stator magnetomotive force (MMF), which makes them attractive. This paper establishes general design principles of SHOW considering different slot/pole combinations and makes detailed comparisons between SHOW and double layer (DL) windings for surface-mounted permanent magnet (SPM) machines. Firstly, fractional slot windings are classified into several categories. Similarity in distribution factors of MMF harmonics is illustrated, based on which, harmonics elimination principle of SHOW is explained. Then, general equations for calculating optimal coil turn ratios for SHOW are derived. Practical ratios approximating the optimal ones are also presented and evaluated. Furthermore, in order to show the superiorities of SHOW, 12-slot/10-pole (12s10p) and 24S10P SPM machines with SHOW are comprehensively studied and compared with their DL counterparts in terms of torque ripple, overload capability, rotor magnet loss, stator iron loss and radial electromagnetic force harmonics. Finally, 12S10P and 24S10P prototypes with SHOW are fabricated and tested for verifications.

Research on Radial Force of Permanent Magnet Synchronous Motor Based on Maxwell

In the existing permanent magnet motor drive system, the vibration and noise problems caused by motor and driver are more and more obvious and complex. Among them, the radial electromagnetic force fluctuation problem of permanent magnet synchronous motor (PMSM) stator is the most important cause of vibration and noise. The radial electromagnetic force fluctuation of PMSM stator is the main source of vibration and noise. In order to lay a solid foundation for studying the distribution of vibration and noise, the radial electromagnetic force of 12 slot 14 pole PMSM is calculated by combining Maxwell stress method and Lorentz force method. Based on the Maxwell platform, a solution model is established to analyze the radial electromagnetic force of motor in time and space. The time–space analysis diagram of radial electromagnetic force in no-load section and load section is given; it is helpful to avoid resonance point and realize low-noise design of motor.

Behaviors of Axial and Radial Electromagnetic Force for Cryogenic Disk Motor

There are axial and radial electromagnetic forces between the stator and rotor of axial flux disk motor besides the useful torque. The electromagnetic forces act on the rotor and are crucial to the stable operation in magnetic levitation applications driven by disk motor. This article concerns the behaviors of axial and radial electromagnetic forces of disk motor using for cryogenic submersible pump. It is measured experimentally that the electromagnetic properties of motor materials, including the electrical conductor and magnetic conductor materials, in room temperature (RT) and liquid nitrogen (LN2) environment. Then, the 3D finite element model (FEM) of the three-phase asynchronous disk motor in RT environment is built which is also validated by the RT experimental tests. Finally, the behaviors of axial and radial electromagnetic forces in LN2 environment are investigated using the modified FEM taking account of the effect of cryogenic environment on the motor material. It is concluded that the axial electromagnetic force decreases monotonously with the increasing air-gap thickness or the decreasing rotating speed. When the rotor exhibits radial eccentricity, there is a restoring radial electromagnetic force, trying to pull the rotor back to the central position. The radial electromagnetic force increases with the increasing rotational speed and radial eccentric displacement.

Influence of Rotor Eccentricity on Radial Electromagnetic Force Characteristics in Switched Reluctance Motors and Compensation

Aiming at the problem of severe unbalanced magnetic force (UMF) of the switched reluctance motors (SRMs) caused by eccentricity, this paper analyses the radial electromagnetic force’s spatial distribution and frequencies under eccentricity and conduct a compensation method for the UMF. Firstly, the expression of the radial electromagnetic force under eccentricity is derived by using the method of magnetomotive force multiplying permeance, combining with the modification of the permeance. Secondly, the UMF is reduced by applying compensation current to the two stator poles of the permeance-descending phase. The selection of the stator poles and the calculation of the compensation current are decided according to the direction and the value of the unbalanced flux density. Dynamic eccentricity (DE) will produce new frequencies and spatial orders of the radial electromagnetic force, and the static eccentricity (SE) only produces the new spatial orders. The results obtained by the finite element model prove that this method can effectively reduce the UMF without sacrificing the output torque performance.

Vibro-acoustic prediction and evaluation of permanent magnet synchronous motors

In this study, a multiphysics finite element method is proposed to predict and evaluate the electromagnetic vibration and noise of the permanent magnet synchronous motors. First, the expressions of radial electromagnetic force waves were derived based on the established mathematical models of airgap magnetic field using the analytical methods. Subsequently, the main circumferential spatial orders influencing electromagnetic noise were analyzed and discussed. Then, a multiphysics simulation model that consists of mechanical field, electromagnetic field, and acoustic field was established for the calculation of the electromagnetic radiation noise. Finally, the multiphysics simulation model developed for the electromagnetic vibration and noise prediction was validated by comparing the finite element analysis and experimental data. It is shown that, although the local differences exist, the results from the finite element calculation and test analysis have a good agreement on the analytical mechanism overall, both in amplitude and main orders. In addition, this paper has made a detailed analysis to the electromagnetic noise generation mechanism, which lays the basis for further study in predicting and suppressing the electromagnetic vibration and noise of the drive motors of pure electric vehicle.

Asymmetric Rotor Design of IPMSM for Vibration Reduction Under Certain Load Condition

This paper proposes the design method using a numerical formula known as the Advanced Inverse Cosine Function (AICF) to reduce vibration of the Interior Permanent Magnet Synchronous Motor (IPMSM). The proposed method reduces the vibration by modifying the rotor shape based on the numerical formula that makes the air-gap flux density sinusoidal under certain load condition. The radial electromagnetic force that is the source causing the vibration of the motor is related to the air-gap flux density under load condition. Therefore, the AICF which reduces the magnitude of the harmonic of the air-gap flux density is derived in this paper and the radial electromagnetic force due to the harmonic of the air-gap flux density decreases applying the AICF. To verify the validity of the proposed method, an 8 pole 12 slot prototype applied with the AICF is proposed. Using the Finite Element Analysis (FEA), the radial electromagnetic force and the displacement of the prototype with the AICF are compared with those of the normal model without the AICF. Finally, the results of the vibration test of the normal and AICF models are compared.

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.