• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.822-829
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density for each slits made on the contact electrode in the vacuum interrupter with axial magnetic field type using 3-dimension finite element analysis. It has been known that the presence of an axial magnetic field parallel to the current flow in the arc plasma can increase the high current breaking capacity of vacuum interrupter by carrying out the arc plasma from constricted mode to diffusion mode. The axial magnetic field is created of itself by current flow in the segments of coil electrode behind the contact electrode. The analyzed results show that if the slits are made in the contact electrode, they can increase the current density and axial magnetic flux density in the contact electrode surface and at the gap distance, which is due to decrease the effect of eddy currents flowing in the contact electrode. The phase shift due to eddy currents, defined 3s time difference between the maximum value of current and axial magnetic field, is decreased still more by increasing the number of slits made in the contact electrode at the center point of gap distance. These results demonstrate that 3-dimension finite element analysis has a great deal of merits in the development and evaluation of new electrode at the design of vacuum interrupter.

• Journal of Magnetics
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• v.21 no.2
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• pp.239-243
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• 2016

High temperature superconductor (HTS) magnet systems usually employ metal current leads which bridge between the cryogenic environment and room temperature. Such current leads are the dominant heat load for these magnet systems due to a combination of electrical resistance and heat conduction. HTS flux pumps enable large currents to be injected into a HTS magnet circuit without this heat load. We present results from an axial-type HTS mechanically rotating flux pump which employs a ferromagnetic circuit and a Cu-stabilized coated conductor (CC) HTS stator. We show the device can be described by a simple circuit model which was previously used to describe barrel-type flux pumps, where the model comprises an internal resistance due to dynamic resistance and a DC voltage source. Unlike previously reported devices, we show the internal resistance and DC voltage in the flux pump are not exactly proportional to frequency, and we ascribe this to the presence of eddy currents. We also show that this axial-type flux pump has superior current injection capability over barrel-type flux pumps which do not incorporate a magnetic circuit.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.460-467
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density on the vacuum interrupter with axial magnetic field type using 3 dimension finite element analysis. An axial magnetic field parallel to the current flow in the arc column can improve the current breaking capacity of vacuum interrupter by affecting the arc mode. The axial magnetic flux density on the contact electrode surface is analyzed by inputting external current as a function of the transient time for sine half wave. And it also is analyzed within the gap distance of the contact electrode. The peak value of current but is decreased with the descending current on the contact electrode surface and within the gap distance of the contact electrode. The residual magnetic field is generated on the contact electrode surface and within the gap distance in the instant of zero current, which is due to the influence of eddy currents. The phase shift due to eddy currents, defined as time difference between the maximum value of current and axial magnetic field, is about 1ms in the center point of gap distance.

• Journal of IKEEE
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• v.22 no.3
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• pp.759-766
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• 2018

This paper presents a high-speed axial-flux machine which utilizes the idea of sinusoidal shaped pole combined with a consequent iron-pole. The target of the proposed machine is the cost reduction of the relatively expensive Samarium-Cobalt (SmCo) permanent magnet (PM) material and the torque per PM volume improvement by using sinusoidal consequent-pole rotor. The effectiveness of the proposed machine is validated by comparing it with conventional consequent-pole and with conventional PM machines using 3-D finite element method (FEM) simulations. The comparison and analysis is done in terms of back electro-motive force (back-EMF) harmonic contents, torque per PM volume and torque ripple characteristics. The simulation results show that the proposed machine is suitable and cost-effective for high-speed and high torque per PM volume applications. Furthermore, due to the consequent pole, the magnetic flux saturation and the overload current torque-capability are also presented and discussed in the paper.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1038-1045
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• 2010

The theory for a new electromagnetically biased combined radial and axial magnetic bearing is developed. This combined magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. One dimensional magnetic circuit model for this combined magnetic bearing is developed and analyzed such that flux densities and magnetic forces can be obtained. Three dimensional finite element model for the bearing is also developed and analyzed. Numerical analysis shows that the calculated magnetic forces from 1D model are well matched with those from the finite element model.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.238-240
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• 1998

This paper deals with the design of a disk-type motor excited by permanent magnets. The main flux is oriented in the axial direction, yielding a pan cake type arrangement. the outer diameter is about 65mm, inner diameter is about 30mm, the axial length about 15mm. For reduce axial length and high efficiency, motor winding have been etched copper plate. After the introduction, the motor design is explained and characteristic of axial flux permanent magnet motor have been investigated. A prototype AFPM motor have been assembled and driving power supply are made. A characteristic of magnetical and electrical and characteristic are investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.179.2-179.2
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• 2010

This research has been performed to provide fundamental design aspects of Permanent Magnet Synchronous Generators(PMSGs) for a kilowatt class wind turbine. When it comes to kilowatt class wind turbines, the typical type of generators are Axial Flux Permanent Magnet(AFPM) generators. However, Radial Flux Permanent Magnet(RFPM) generators have been optimally designed to study the output characteristics of a kilowatt class wind turbine in Graduate School of Wind Energy, POSTECH. An existing squirrel-cage rotor has been modified for another newly designed permanent magnet rotor to utilize the commercially existing stator rotor. Electromagnetic analysis utilizing Finite Element Methods tools(ANSYS, MAXWELL 2D) has been applied to analyze the system.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.24-27
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• 1999

This paper proposed a method to reduce torque ripple of double-layer axial flux permanent magnet motor. Torque is generated by interacting between current of stator winding and airgap flux. In the case of slotless axial flux permanent magnet motor, only commutation torque component is significant. Hence, cogging and reluctance torque will not be considered. For this propose, we were supplied differential phase current in each winding and shifted rotor magnet. According to shifted rotor magnet and flux and phase of current were shifted, phase of developed torque in each side is difference. As a result, we could reduce the total torque ripple in motor and obtain minimum torque ripple in the case of 7.5 degree shifting angle between two rotors.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.1
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• pp.6-11
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• 2004

The single phase switched reluctance motor (SRM) has many merits; simple structure and driving circuits, easy operation and speed control, and etc. This paper presents the torque characteristics of disk type single phase SRM by changing the salient pole lengths and pole arcs. The prototype single phase SRM has a three dimensional magnetic flux pattern because of its structure. That is, the radial and axial magnetic flux contributes to torque generation. Thus, 3D analysis is required for computation of its magnetic field. In this paper, 3D FEM is used for analyzing the magnetic flux distribution and magnetic co-energy.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.744-745
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• 2015

This paper deals with magnetic characteristic analysis of axial flux permanent magnet coupling according to overload using analytical method. When magnet coupling has a slip, the eddy current induced in PM with conductivity. This eddy current make a distorted flux density. In this paper, we analyze the distorted flux density. The analytical results are validated extensively by comparing with 3d finite element analysis.