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Despite continuous effort to minimize torque ripple, the reduction of vibration has not been yet achieved due to the lack of link between these two performances. The difficulty of investigating the relationship stems from the fact that torque is solely influenced by tangential force whereas vibration is directly tied to radial force. In this paper, the correlation between torque ripple and vibration in an IPMSM (Interior Permanent Magnet Synchronous Motor) is established by examining the air-gap flux density in both radial and tangential directions. Its temporal and spatial harmonics are analyzed. A six-pole nine-slot IPMSM is used as a base configuration, and the air-gap flux density is varied by changing the height of a stator tooth tip. In the previous study, the same approach has been done to observe how to reduce torque ripple effectively. In this study, however, it is found that the trend of torque ripple is not the same as that of vibration with respect to the height of a pole tip, and the relation between the two is thoroughly observed and explained. [ABSTRACT FROM AUTHOR]

Variable flux memory machines (VFMMs) have become a research hotspot due to their adjustable air-gap flux with the employment of low coercive force (LCF) permanent magnets (PMs). Series hybrid magnet VFMMs (SHM-VFMMs) utilizing series-magnetic-circuit high coercive force (HCF) and LCF PMs are extensively investigated due to their excellent unintentional demagnetization (UD) withstand capability. Nevertheless, the existing researches still focus on the UD of LCF PMs under heavy load operation, and the remagnetization issue remains unreported. Therefore, in this paper, the over-load unintentional remagnetization (UR) effect of the a dual-layer-SHM-VFMM (DLSHM-VFMM) is first revealed, and its mechanism is investigated and analyzed in depth based on finite element (FE) analyses. A DLSHM-VFMM prototype is manufactured and tested to verify the effectiveness of the theoretical analyses. [ABSTRACT FROM AUTHOR]

A novel mechanical flux-adjusting permanent magnet linear eddy current brake with high performance and its nonlinear analytical model are proposed. The innovative point lies in attaching an additional mechanical magnetic adjuster directly above the interior permanent magnet bar, which can achieve flexible adjustment of the air-gap flux and improve the generation capacity of the braking force and its regulation range. Considering the importance of the analytic model in practical design, the average air-gap flux density and eddy current density are estimated based on the equivalent magnetic circuit method and Ampere's law, where the critical flux-weakening effect and leakage flux effect are calculated quantitatively. Then a practical theoretical model of braking force is derived based on the energy conversion and verified by the 3D finite-element method. Through analysis of the magnitude and regulation range of the braking force in a given range of speed, the advantages of the device and the electromagnetic force model are proved separately. Moreover, design suggestions for selecting the key geometrical parameters are further given, which offer useful information for pre-design and optimization. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) having high power density and high efficiency are rigorously researched in various premium applications. Among PMSMs, many studies have been conducted on interior permanent magnet synchronous motors (IPMSMs) to improve torque ripple, but its accurate estimation is not straightforward. Therefore, a six-pole nine-slot (6p/9s) IPMSM is adopted as a base model due to its popularity in academia and industries, and other two pole/slot combinations (8p/12s and 10p/15s) are additionally selected to investigate the influence of a pole/slot combination on torque ripple. Torque performance is easily identified by analyzing tangential force due to their direct proportional relation. In this paper, magnetic flux densities in radial and tangential direction are systematically analyzed since tangential force is determined by the product of the two magnetic flux densities. The modification of a stator pole regarding its tip thickness is chosen as a key parameter in 6p/9s IPMSM. The thickness of a stator pole tip opposite to the direction of spin is more critical in torque ripple improvement. It is verified that the proposed method is sufficient for accurate torque prediction. [ABSTRACT FROM AUTHOR]

Vibration absorbers usually aim to control the steady-state vibration of harmonic excitation based on the traditional fixed point theory, but few efforts focus on suppressing the transient vibration caused by impulse excitation. In this paper, the excitation is regarded as impulse in modeling, and it can be used for impulse excitation. Thus, the transient vibration absorber is designed to control the transient vibration, and the stiffness of the absorber is a key factor to control the response of the primary system. This paper presents a tunable electromagnetic transient vibration absorber to avoid direct mechanical contact for the absorber. The analytical results of the transient response indicate that the vibration can be attenuated by adjusting the stiffness of the absorber. In order to establish the model of the electromagnetic stiffness, the absorber is divided into three equivalent virtual springs. The circular current loop is equivalent to the rectangular current loop to show the spatial distribution of the magnetic flux density in the air gap. The experimental tests demonstrate that the transient vibration of the primary system can be attenuated by 13% when the current of the coil is 6 A. [ABSTRACT FROM AUTHOR]

In order to overcome the disadvantages of 12/8 pole bearingless switched reluctance motors (BSRMs), such as high commutation frequency, more stator windings, and more power devices, a 6/4 pole BSRM with half the commutation frequency and number of windings is studied. The structure characteristics and operation characteristics of the 6/4 pole BSRM are investigated through modeling, simulation, and prototype experiment, and the main performance indices, such as suspension force, inductance performance, and air-gap flux density, are evaluated to reveal the levitation control mechanism of the 6/4 pole BSRM with permanent magnets in its stator yoke. The motor can suspend stably in the radial direction, and the correctness and feasibility of the theoretical analysis are verified. [ABSTRACT FROM AUTHOR]

A novel magnetic properties tester is designed to accurately and conveniently change the air gap of the core, which can fix cores of various types. The dynamic magnetic characteristics of the amorphous core under sinusoidal excitation within 20 kHz is measured with different air gap lengths and magnetic flux density. It is found that in the case of the small air gap, the total loss decreases as the air gap increases. When the frequency is 20 kHz and the flux density is 0.1 T, the loss can even be reduced by 7%. This paper analyzes the experimental data and summarizes the influence of the air gap and magnetic flux density about the core loss. Besides, the influence of air gap on magnetic flux density distribution is illustrated and analyzed by the means of FEM (Finite Element Method). It is valuable for the design of high frequency transformer and inductor. [ABSTRACT FROM AUTHOR]

To reduce the volume, axial length and cost, a radial three-pole five-degree-of-freedom (5-DOF) integrated hybrid magnetic bearing (HMB) is studied, which the rotor can be levitated stably in one unit. Firstly, the configuration and suspension principle are introduced. The mathematical models of suspension forces are deduced by the magnetic circuit analysis. Then, according to radial and axial bearing capacity, the design method of main parameters is given. Finally, the magnetic circuit, suspension mechanism, air gap flux density, force-current relationships are calculated and analyzed by three-dimensional finite element method. The research results have shown that the structure of the 5-DOF integrated HMB is reasonable, and the suspension mechanism, mathematical model and design method are correct. [ABSTRACT FROM AUTHOR]

This paper presents the magnetic field characteristics of a synchronous generator with a salient pole structure using a simple magnetic equivalent circuit (MEC) method. This method aims to reduce the analysis time considering nonlinearity. By using the MEC, a solution for the magnetic flux density is obtained. The linkage flux is derived using the magnetic flux density of the air gap and the armature voltage is obtained. Additionally, results obtained using the finite-element method and MEC are validated against experimental data. [ABSTRACT FROM AUTHOR]

Alfenol (Fe-Al) and Galfenol (Fe-Ga) are iron-based structural magnetostrictive alloys that, for compositions of ∼81% iron, are increasingly being used in sensing, actuating, and energy harvesting devices [Park et al., AIP Advances 6(5), 056221 (2016)]. Recent improvements in the development of magnetostrictive materials using the deformation processing methods of rolling to produce highly textured thin sheet [Park et al., AIP Advances 6(5), 056221 (2016)] and ball milling to produce (001)-oriented micron-size flakes [S. M. Na, J. Galuardi, and A. B. Flatau, IEEE Transactions on Magnetics 53(11), 1–4 (2017)] provide the opportunity to develop a non-contact torque sensor. Torque-induced shear forces at the surface of a shaft lead to a measurable change in the flux passing through the air above the surface of a shaft to which a magnetostrictive layer has been bonded. The current study builds on prior work which demonstrated that torque influenced the magnitude of magnetic flux in the air gaps located between a piece of Galfenol and the rest of a magnetic circuit [Raghunath et al., Proceedings of the ASME, 2013]. The current work overcomes limitations of the prior work. This work demonstrates that using a magnetostrictive layer made of a patch of Alfenol, an alloy that is less expensive, more ductile, and less magnetostrictive than Galfenol, but has almost the same saturation magnetization of ∼1.5T, slightly outperformed the patches made of Galfenol. Additional contributions of the present work include a first look at the application to a shaft of an epoxy-based paint containing micron-sized flakes of (001)-oriented Galfenol, and a comparison of square and ring-shaped patches (aspect ratios of 1 and of ∼4). Data are presented from quasi-static testing and from dynamic tests at rotational rates of up to 1000 rpm. [ABSTRACT FROM AUTHOR]