• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.50-57
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• 2003

In this study, the structural optimal design was applied to the girder of over head crane. The optimization was carried out using ANSYS code fur the deadweight of girder, especially focused on the thickness of its upper, lower, reinforced and side plates. The weight could be reduced up to around 15% with constraints of its deformation, stress and buckling strength. The structural safety was also verified by the buckling analysis of its panel structure. It might be thought to be very useful to design the conventional structures fur the weight save through the structural optimization. The objective function and restricted function were estimated by the orthogonal array, and the sensitivity analysis of design variable fur that was operated.

• Journal of Institute of Convergence Technology
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• v.12 no.1
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• pp.7-12
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• 2022

The reduction ratio of the magnetic gear is determined by the ratio of the number of poles between the high-speed permanent magnet layer and the low-speed permanent magnet layer. In general, it is known that the greater the least common multiple of both poles, the smaller the torque ripple called by cogging of the magnetic force generated in the magnetic gear. However, little is known about the effect of the harmonic modulator that filters the magnetic field in the magnetic gear to magnetically couple the high-speed side and the low-speed side except for the number of poles. In this study, torque ripple characteristics according to changes in modulator shape such as opening ratio and tooth thickness are analyzed using a finite element analysis tool.

• Journal of the Korean institute of surface engineering
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• v.42 no.2
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• pp.86-94
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• 2009

Various types of multilayer coatings including Al/$Al_2O_3$ structure have been prepared on Nd-Fe-B permanent magnet to modify the morphology of the coating and to enhance the corrosion resistance of the magnet. Magnetron sputtering has been employed to make the multilayer coatings. $Al_2O_3$sputtering conditions were optimized in reactive sputtering by varying the deposition parameters. The formation of $Al_2O_3$ film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. 3 types of coating structures were designed and prepared by magnetron sputtering. The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/$Al_2O_3$ multilayer coatings. Surface and cross-sectional morphologies showed that Al/$Al_2O_3$ multilayer grew as a layered structure, and that very compact Zone 3 like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1im in the Al/$Al_2O_3$ multilayer. From the salt spray test and pressure cooker test, it has been shown that the multilayer coatings showed good corrosion resistance compared to Al single or modified layer coatings.

• Progress in Superconductivity
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• v.13 no.1
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• Progress in Superconductivity and Cryogenics
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• v.20 no.1
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• pp.19-22
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• 2018

The thermal and electrical properties of the conductor are critical parametersfor the design and optimization of the superconducting magnet. This paper presents simulation code to analyze electrical and thermal stability characteristics of the second generation (2G) high-temperature superconductor (HTS) by varying copper stabilizer thickness. Two types of commercial 2G HTS coated conductor tapes, YBCO and GdBCO were used in this study. These samples were cooled by Liquid Nitrogen ($LN_2$) having boiling at 77.3 K and an equivalent electrical circuit model for them is choosen and analysed in details. Also, an over-current pulse test in which a current exceeding a critical current was performed. From the simulation results, the influences of the copper stabilizer thickness on the stability characteristics of these samples are presented.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.460-466
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• 2015

The remaining features in this study using the Freecad proceeds according to the overall effect was not supported by the modeling Freecad were conducted a study to complement using the CATIA program or other commercially available. The focus of this study is that there can be obtained the stability through the center of gravity of the balancing of two parts by increasing the weight of the other magnet through a Fortuna other end of the weight of the bar, using the center of gravity. Finally, to find the optimal design of the weight and thickness of the main bar through the center of gravity balancing is the purpose of this study.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.270-271
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• 2006

Nd-Fe-B type powder was sintered using spark plasma sintering method. Fabricated compact sintered at the temperature of $700\;^{\circ}C$, is found to be a composite magnet with Nd-Fe-Co-B and ${\alpha}-Fe$. The compact sintered at $700\;^{\circ}C$ shows slightly low coercivity and large remanent magnetization comparing to the compact sintered at $600^{\circ}C$ due to the formation of ${\alpha}-Fe$ phase, resulting in the large maximum energy product. Maximum energy product tends to decrease with decreasing thickness of sintered compacts below 0.5 mm in thickness.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.888-892
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• 2014

In the design of the rotor of an interior permanent magnet synchronous motor (IPMSM), the bridge between the permanent magnets helps prevent the scattering of permanent magnets and pole pieces during high-speed operation. In the design of a motor, if the bridge is too thick, its performance will be largely degraded because of flux leakage. Additionally, if the bridge is too thin, its mechanical safety cannot be guaranteed. Thus, an accurate analysis method is required to determine the thickness of the bridge. Conventional stress analysis methods determine the thickness of the bridge by only considering the centrifugal force of the rotors. In this study, however, a method that additionally considers the radial force generated by the air-gap flux density based on the conventional methods is proposed and reflected in the design of a traction motor for electric vehicles. Finally, the validity of this study is verified through a reliability test related to high-speed operation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.65-69
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• 2004

The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flash memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 m thickness. The thickness of focusing actuator is within 2 mm and the total working range is $+/-100{\mu}m$, with the resolution of less than $1{\mu}m$. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flux density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The working range and resolution of focusing actuator are analyzed with FEM and experiment.

• Journal of Electrical Engineering and Technology
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• v.4 no.2
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• pp.240-248
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• 2009

An approach to control the position for an interior permanent magnet synchronous motor (IPMSM) based on an adaptive integral binary observer is described. The binary controller with a binary observer is composed of a main loop regulator and an auxiliary loop regulator. One of its key features is that it alleviates chatter in the constant boundary layer. However, steady state estimation accuracy and robustness are dependent upon the thickness of the constant boundary layer. In order to improve the steady state performance of the binary observer and eliminate the chattering problem of the constant boundary layer, a new binary observer is formed by adding extra integral dynamics to the existing switching hyperplane equation. Also, the proposed adaptive integral binary observer applies an adaptive scheme because the parameters of the dynamic equations such as the machine inertia and the viscosity friction coefficient are not well known. Furthermore, these values can typically be easily changed during normal operation. However, the proposed observer can overcome the problems caused by using the dynamic equations, and the rotor position estimation is constructed by integrating the rotor speed estimated with a Lyapunov function. Experimental results obtained using the proposed algorithm are presented to demonstrate the effectiveness of the approach.