• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.1
• /
• pp.13-19
• /
• 2005

The performance of two designs of permanent magnet brushless motor, by having self-shielding magnetized magnets or sinusoidally shaped parallel-magnetized magnets with essentially sinusoidal airgap flux distributions, are compared. It is shown that the parallel-magnetized motor with shaped sintered NdFeB magnets can result in a higher airgap flux density and torque density than that of a self-shielding magnetized motor equipped with an anisotropic injection moulded NdFeB ring magnet.

• Superconductivity and Cryogenics
• /
• v.11 no.2
• /
• pp.23-29
• /
• 2009

The unique features of HTS offer opportunities and challenges to a number of applications. In this paper we focus on NMR and MRI magnets, illustrating them with the NMR/MRI magnets that we are currently and will shortly be engaged: a 1.3 GHz NMR magnet, an "annulus" magnet, and an $MgB_2$whole-body MRI magnet. The opportunities with HTS include: 1) high fields (e.g., 1.3 GHz magnet); 2) compactness (annulus magnet); and 3) enhanced stability despite liquid-helium-free operation ($MgB_2$whole-body MRI magnet). The challenges include: 1) a large screening current field detrimental to spatial field homogeneity (e.g., 1.3 GHz magnet); 2) uniformity of critical current density (annulus magnet); and 3) superconducting joints ($MgB_2$magnet).

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.9
• /
• pp.407-411
• /
• 2003

The purpose of this paper is to study the removal of nitrogen oxide(NOx) using a wire-plate type plasma reactor with magnet attached for indoor air purification. In order to produce a more effective reactor, we conducted magnetic field simulations. The results of the magnetic field simulations show that NOx can be removed more effectively. The results from the magnetic field simulation show that when 7 magnets were applied to the reactor, the magnetic flux density was at its highest amount than when using 0, 3, or 5 magnets. From the data obtained by the simulation results a plasma reactor was made and thus, several experiments were conducted. The best removal efficiency was obtained with 14 W AC power to the reactor with 5 magnets.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.1
• /
• pp.34-41
• /
• 2009

In this paper, a novel MR brake with permanent magnet is developed. This system consists of rotary disk, permanent magnet, spring and MR fluid. Permanent magnets are attached to the rotary disk and moves in the direction of radius. The magnets are linked to rotor axis by spring. As rotation speed increases, the magnets move outward from the center of the system by centrifugal force in the MR fluid. A proper design of stator or case makes the system have unique torque characteristics. The research is performed like following procedures. First, the electromagnetic characteristic of the system is analyzed using Maxwell. Next, torque is calculated using the results of the electromagnetic analysis. Finally, the performance of various types of the brake systems are investigated and compared with each other.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.82-85
• /
• 1999

Permanent magnets of Nd-Fe-B group have kept a key post in the permanent magnet market and used in various parts. Tube Process is a process to produce permanent magnets using a deformable tube for denslfication of powder magnets. Advantage claimed for this process is that it can accomplish both densification and anisotropication in one step forming. In this paper. the simulation has been carried out for a full Tube Process in a closed Qe considering the compressibility of material, arbitrary curved shape and deformable body contact between Nd-Fe-B powder magnet and copper tube. The results show that the analysis of Tube Process is applicable with great help in the stage of preform design.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.27-34
• /
• 2000

HTS wires processed by PIT method are now available for magnet applications. But, those wires can not be used over 40 K due to weak link. This leads to necessity of development of coated conductor which can retain high $J_c$ at high field in liquid nitrogen. In this paper, various technical issues and the R&D status for both PIT wires and coated conductor were discussed. The difference of coated conductor's processes were also investigated and summarized. Various requirements for a design of HTS magnets were discussed. Anisostropic $J_c$ property with respect to magnetic field was considered to determine the coil's critical current. Low n value is a critical parameter to degrade a field stability with respect to time for a persistent mode HTS magnet. The relation between the margin of operation current and n value was investigated. Prototype HTS magnets with PIT wires are being developed for various applications such as crystal growth, MRI, magnetic separator and etc. HTS magnets will come into wide use in various fields of industries if the HTS wires with a low performance cost is developed.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.3 no.3
• /
• pp.312-316
• /
• 2014

This paper describes a turnout without movable parts for magnetically levitated vehicles with hybrid magnets, which have been studied by the authors in place of streetcars. Their low construction cost and low maintenance is key to their practical use. Magnetic levitation systems using forces of attraction can generate guidance force automatically, but the damping force against lateral motion is negligible. However, the lateral damping characteristic was improved by using divided iron type magnets and rails. Using this turnout without movable parts will facilitate smooth direction switching.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.3
• /
• pp.90-94
• /
• 2002

The line start permanent magnet (LSPM) motor has been developed facilitate to the design of the synchronous motor. The rotor of this motor is composed of interior permanent magnets and aluminum bars instead of rotor windings. It is difficult to predict the performance characteristics accurately, because many characteristics are produced by the aluminum rotor bars and the permanent magnets. Therefore, in this paper the dynamic characteristics of the LSPM motor are described and compared via the time-stepped finite element method with those of the cage-type induction motor to find the characteristics of the permanent magnets and the rotor bars in the LSPM motor.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.10a
• /
• pp.375-379
• /
• 2000

In this paper higher order spectral techniques are applied to some simple mechanical systems. The system studied is the nonlinear magnetic beam. This is a simply supported beam, driven by an electromagnetic shaker. At the free end, pairs of repelling magnets are placed. By varying the position and number of magnets, the nature of the nonlinearity can be changed, be it skewed or symmetric, and by varying the distance between the magnets the strength of the nonlinearity can also be altered. Using this controllable system, auto higher order spectral methods are applied, assuming only a knowledge of an output signal.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.3-6
• /
• 2003

We have developed a small-sized superconducting magnetic energy storage (SMES) device, which provides electric power with high quality to sensitive electric loads. In large magnets such as the SMES magnets the stability, which is determined by several factors, e.g. conductors cooling condition and operating current, magnets winding structure, is a crucial problem. The effect of the cooling condition, the copper ratio, and the conductor's size upon the recovery currents was investigated experimentally. The results indicate that the recovery current characteristics of the strands vary considerably according to their insulation method. In the fully insulated strands with a low copper ratio, the recovery current densities range from 10 to 20 % of their engineering critical current densities. The recovery current density of the 30-conductor with a cooling channel is about a factor of 1.8 higher than that without a cooling channel.