• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.897_898
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• 2009

This paper deal with the shape design of the flux barrier to maximize the torque density and minimize the torque ripple in IPM type BLDC motor. The variation of magnetic torque and reluctance toque according to the flux barriers is analyzed in the 120 conducting period. From the result, we confirmed the barrier can be quite worthwhile for the better performance of IPM type BLDC motor

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1055-1056
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• 2011

This paper deals with optimum design criteria for maximum torque density & minimum current density of a single phase line-start permanent-magnet motor (LSPMM) using RSM (Response Surface Methodology) & FEM (Finite Element Method). The focus of this paper is to find a design solution through the comparison of torque density and minimum current density resulting from rotor shape variations. And then, a central composite design (CCD) mixed resolution is introduced, and analysis of variance (ANOVA) is conducted to determine the significance of the fitted regression model.

• Journal of Magnetics
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• v.20 no.4
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• pp.387-393
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• 2015

Torque ripple is necessarily generated in interior permanent magnet synchronous motors (IPMSMs) due to the non-sinusoidal distribution of flux density in the air gap and the magnetic reluctance by stator slots. This paper deals with an asymmetric rotor shape to reduce torque ripple which can make sinusoidal flux density distribution in the air gap. Meanwhile the average torque is relatively increased by the asymmetric rotor. Response surface method (RSM) is applied to find the optimum position of the permanent magnets for the IMPSM with improved torque performance. Consequently, an asymmetric structure is the result of RSM and the structure has disadvantage of a mechanical stiffness. Finally, the performance of suggested shape is verified by finite element analysis and structural analysis is conducted for the mechanical stiffness.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.77-84
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• 2024

This paper introduces a study on an electromagnet magnetic gear designed for gear ratio conversion. In comparison to magnetic gears using permanent magnets, this electromagnet magnetic gear exhibits lower torque density, highlighting the need for torque density improvement. To address this, the research focuses on enhancing torque density by examining the consistent orientation of each rotor's magnetization during gear ratio conversion and attaching permanent magnets accordingly. However, an issue arises due to the uneven magnetic flux density caused by the non-uniform attachment of permanent magnets, leading to an increase in torque ripple. Therefore, building upon previous studies aimed at reducing torque ripple in electromagnet magnetic gears, this research explores the optimal methods, such as pole piece bridges and fillet configurations, to mitigate torque ripple even during gear ratio conversion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1795-1800
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• 2000

One of the principal sources of vibration and noise in permanent magnetic machines is cogging torque, which is induced by interaction between the rotor poles and the stator teeth. For its analysis, using finite element analysis is very time consuming and the calculation of performance factors is extremely sensitive to the discretization. Especially, Maxwell stress tensor method is sensitive to the location of integral path. In this paper, a cogging permeance fuction is defined and replaced by the straight line. And it is assumed that the flux density acting on the stator's tooth side is the euqal to the flux density of the slot area. Using this definition and assumption, analytical calculation of cogging torque is presented and validated. And several reduction method is introduced.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.355-362
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• 2021

Since coaxial magnetic gears use non-contact power transmission, friction, wear, noise, and heat generated in the power transmission process of existing mechanical gears can be minimized. Currently, research for application to various industries is being actively conducted, but among the characteristics of coaxial magnetic gears, the problem of rapidly decreasing torque density at a high gear ratio was discussed. This paper proposes a direction for multiple gear combination using low gear ratio coaxial magnetic gears with high torque density. In order to confirm the effectiveness of the method, the torque density was compared with a single high gear ratio model, and the combination and design direction of multiple coaxial magnetic gears were shown.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.791-798
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• 2007

The hydraulic hybrid vehicle(HHV) is an application of hydrostatic transmission technology to improve vehicle fuel economy and emissions. A relatively lower energy density of hydraulic accumulator and complicated coordinating operations between two power sources require a special energy management strategy to maximize the fuel saving potential. This paper presents a new type of configuration for parallel HHV to minimize the disadvantages of the hydraulic accumulator, as well as a methodology for developing an energy management strategy tailored specially for PHHV. Based on an analysis of the optimal energy distribution between two power sources over a representative urban driving cycle with a Dynamic Programming(DP) algorithm, a fuzzy-based optimal torque management strategy is designed and developed to control the torque distribution. Simulation results demonstrates that the optimal torque management strategy maximizes the advantages of this hybrid type of configuration, and the high power density characteristics of hydraulic technology effectively improve the robustness of the energy management strategy and fuel economy of the PHHV.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.181-188
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• 2015

The non-contact permanent magnet gear has advantages of high efficiency and improved reliability. It has other advantages of no mechanical friction loss, very little noise and vibration, and no need for lubricant. With these advantages, the non-contact permanent magnet gear that solves the physical contact problem of the mechanical gear has drawn attention. Due to this unique non-contact characteristic, the non-contact permanent magnet gear which is capable of non-contact torque transmission has replaced mechanical gear. The mechanical gears which is in many fields of the modern industry, is used mostly for power transmitting mechanical devices. However, it also has the problem of a low torque density, which requires improvement. In this paper, a novel pole piece shape is proposed in order to improve the problem of low torque density of the non-contact permanent magnet gear. The experiment data required for predicting the relationships among them are obtained using finiteelement Operating method based on two-dimensional (2-D) numerical analysis. Therefore, this paper derived an optimal model for thenon-contact permanent magnet gear with the novel pole piece using the Box-Behnken design, and the validity of the optimal design of the proposed pole piece shape through variance analysis and regression analysis demonstrated. In this paper, we performed the thransfer torque analysis in order to improve the torque density and power density, we have performed on optimal design of proposed pole piece shape using box-behnken.

• The Journal of Advanced Prosthodontics
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• v.10 no.3
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• pp.227-235
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• 2018

PURPOSE. Implant site preparation may be adjusted to achieve the maximum possible primary stability. The aim of this investigation was to study the relation among bone-to-implant contact at insertion, bone density, and implant primary stability intra-operatively measured by a torque-measuring implant motor, when implant sites were undersized or tapped. MATERIALS AND METHODS. Undersized (n=14), standard (n=13), and tapped (n=13) implant sites were prepared on 9 segments of bovine ribs. After measuring bone density using the implant motor, 40 implants were placed, and their primary stability assessed by measuring the integral of the torque-depth insertion curve. Bovine ribs were then processed histologically, the bone-to-implant contact measured and statistically correlated to bone density and the integral. RESULTS. Bone-to-implant contact and the integral of the torque-depth curve were significantly greater for undersized sites than tapped sites. Moreover, a correlation between bone to implant contact, the integral and bone density was found under all preparation conditions. The slope of the bone-to-implant/density and integral/density lines was significantly greater for undersized sites, while those corresponding to standard prepared and tapped sites did not differ significantly. CONCLUSION. The integral of the torque-depth curve provided reliable information about bone-to-implant contact and primary implant stability even in tapped or undersized sites. The linear relations found among the parameters suggests a connection between extent and modality of undersizing and the corresponding increase of the integral and, consequently, of primary stability. These results might help the physician determine the extent of undersizing needed to achieve the proper implant primary stability, according to the planned loading protocol.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1275-1284
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• 2018

The coaxial magnetic gear with the flux concentrating structure is known that it has the torque performance advantage over the coaxial magnetic gear having surface mounted permanent magnet, thanks to the flux focusing effect. But, if the solid cores are used in the modulating pieces and rotor cores to consider the mechanical reliability and cost reduction, the operating torque of the flux concentrating coaxial magnetic gear can be significantly diminished because the iron losses at the solid cores affect the actual transmitted torque. Furthermore, the modulating pieces and rotor cores have different characteristics of the iron losses from one another, because the space harmonic components of the magnetic flux density, which cause the iron losses, are different. Thus, in this paper, we focused on the analysis of the characteristics of the space harmonic components of the magnetic flux density and resultant eddy current losses in the surface mounted PM and flux concentrating coaxial magnetic gears, when these coaxial magnetic gears have the solid cores at the modulating pieces and rotor cores. The characteristics of pull-out torque (static torque), operating torque (dynamic torque), and efficiency are also researched, and compared by the 3D finite element analysis (FEA) and experiment.