• 전기의세계
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• v.19 no.1
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• pp.1-10
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• 1970

The foundation for the theoretical establishment of the linear motor lies in the investigation of the magnetic flux distribution in its airgaps. Generally speaking, the linear motor is similar, in the principle of its operation, to the general induction motor. However, there are great differences in the aspects of its structure and characteristics, especially, in the fact that the formation of its travelling magnetic field depends on the method of its winding. This paper is written in order to introduce the method of calculating the air gap magnetic flux distribution on the basis of its ampere-conductor in the case that 2 phase winding is applied on its open magnetic circuit iron core, and to present the results of investigation of the pulsation in its travelling fields. the first and second example of winding show the case of travelling magnetic field with the constant amplitude except the end region. The third example deals with the configuration of coil-side displaced outside the core and which produce the increased flux density at the ends, but, on the contrary, forms the pulsated travelling field.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.759-765
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• 2011

This paper proposes an effective assistant model for considering the stator slot-opening effect on air gap flux density distribution in conventional interior-type permanent magnet (IPM) motor. Different from the conventional slot-opening effect analysis in surface-type PM (SPM) motor, a composite effect of slot-opening uniquely existing in IPM motor, which additionally causes enhancement of air gap flux density due to magnet flux path distortion in iron core between the buried PM and rotor surface. This phenomenon is represented by a proposed assistant model, which simply deals with this additional effect by modifying magnetic pole-arc using an effective method. The validity of this proposed analytical model is applied to predict the air gap flux density distribution in an IPM motor model and confirmed by finite element method (FEM).

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.317-323
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• 2005

To increase the operating speed of the solenoid actuator, this paper proposed a modified model using a non-magnetic ring, which is welded on the magnetic guide tube, and also presents the characteristic equations, results of Finite Element Method (FEM) analysis for magnetic flux distribution and density in magnetic flux paths, and computer simulation results for the dynamic characteristics of plunger motion according to the stroke and time variation. As well, we proved the non-magnetic ring effect by experiments using prototypes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2236-2245
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• 2011

This paper deals with the levitation force characteristics of electromagnet for MAGLEV vehicle application. The magnetic flux density distribution and levitation force characteristics of the electromagnet are investigated by means of equivalent magnetic circuit model. Firstly, we defined the aligned and unaligned electromagnet module for the full-electromagnet, and magnetic flux paths are represented for each model including leakage and fringing flux paths. Because of the analysis model contains both the permanent magnet and electromagnet coil, we calculated the airgap magnetic flux density and levitation forces using flux superposition in electromagnetic circuit. The results are validated extensively by comparison with finite element analysis. Moreover, the 1/4 scaled magnetic levitation and propulsion test vehicle has been manufactured and tested in order to verify these predictions. The experimental results confirms the validity of the analytical prediction with equivalent magnetic circuit model for the description of a electromagnet.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.140-142
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• 2006

Cogging torque is often a principal source of vibration, noise and difficulty of control in permanent-magnet brushless DC motors. Cogging torque can be minimized by sinusoidal air-gap flux density waveform because it is produced by the interaction of the rotor magnetic flux and angular variation in the stator magnetic reluctance. Therefore, this paper will present a design method of magnetization system of bonded isotropic neodynium-iron-boron(Nd-Fe-B) magnets in ring type with sinusoidal air-gap flux density distribution and low manufacturing cost. An analytical technique of magnetization makes use of two-dimensional finite element method(2D FEM) and Preisach model that expresses the hysteresis phenomenon of magnetic materials in order for accurate calculation.

• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.25-29
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• 1999

The purpose of this paper is to find the magnetic filed distribution inside the motor in order to find out if the high-Tc superconducting tapes operate stably in actual motor operation in a detailed model of the actual motor was analyzed through F.E.M.(finite Element Method). As a result, it has been proved that the high-Tc superconducting tapes can with-stand 4 A of current with staility. 4 A was the amount of current with stability. 4 A was the amount of current needed to achieve 600 A·turns which is required by the previous simulation aimed at developing this the flux damper reduces armature reactance during the motor operation. But it was observed that the flux damper generates loss by means of leakage flux and this decreases the output of the motor by about 5%.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.66.3-67
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• 2015

Without scrutinizing reflection, the plasma comprising a coronal loop is usually regarded to reside within a flux rope. This picture seems to have been adopted from laboratory plasma pinches, in which a plasma of high density and pressure is confined in the vicinity of the flux rope axis by magnetic tension and magnetic pressure of the concave inward magnetic field. Such a configuration, in which the plasma pressure gradient and the field line curvature vector are almost parallel, however, is known to be vulnerable to ballooning instabilities (to which belong interchange instabilities as a subset). In coronal loops, however, ideal MHD (magnetohydrodynamic) ballooning instabilities are impeded by a very small field line curvature and the line-tying condition. We, therefore, focus on non-ideal (resistive) effects in this study. The footpoints of coronal loops are constantly under random motions of convective scales, which twist individual loop strands quite randomly. The loop strands with the axial current of the same direction tend to coalesce by magnetic reconnection. In this reconnection process, the plasma in the loop system is redistributed in such a way that a smaller potential energy of the system is attained. We have performed numerical MHD simulations to investigate the plasma redistribution in coalescence of many small flux ropes. Our results clearly show that the redistributed plasma is more accumulated between flux ropes rather than near the magnetic axes of flux ropes. The Joule heating, however, creates a different temperature distribution than the density distribution. Our study may give a hint of which part of magnetic field we are looking to in an observation.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.869-876
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• 2018

The force of a direct current (DC) electromagnetic pump used to transport liquid lithium was analyzed to optimize its geometrical and electrical parameters by numerical simulation. In a heavy-ion accelerator, which is being developed in Korea, a liquid lithium film is utilized for its high charge-stripping efficiency for heavy ions of uranium. A DC electromagnetic pump with a flow rate of $6cm^3/s$ and a developed pressure of 1.5 MPa at a temperature of $200^{\circ}C$ was required to circulate the liquid lithium to form liquid lithium films. The current and magnetic flux densities in the flow gap, where a $Sm_2Co_{17}$ permanent magnet was used to generate a magnetic field, were analyzed for the electromagnetic force distribution generated in the pump. The pressure developed by the Lorentz force on the electromagnetic force was calculated by considering the electromotive force and hydraulic pressure drop in the narrow flow channel. The opposite force at the end part due to the magnetic flux density in the opposite direction depended on the pump geometrical parameters such as the pump duct length and width that defines the rectangular channels in the nonhomogeneous distributions of the current and magnetic fields.

• Journal of Magnetics
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• v.18 no.3
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• pp.255-259
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• 2013

In this paper a new coupling method for efficient and simple analysis of single phase induction motor is presented. The circuit representation of both the stator winding and each conducting rotor loop (composed of rotor bar and end ring segment) is used in conjunction with the distribution of magnetic flux linkage instead of inductance matrix. The flux linkage is calculated using air-gap flux density distributions driven by unit currents in the stator windings and rotor bars. The field distribution of one turn of a coil is calculated by FEM and the result is used to calculate total flux linkage by employing a coordinate transformation. The numerical results give good agreement with prior literature. The method is particularly effective in analyzing the effect of the number of rotor bars.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.545-551
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• 2004

Magnetic suspension effect has been studied by using superconductor of BiPbSrCaCuO ceramics containing Ag$_2$O. Magnetic flux measurements of a toroidal magnet revealed a concave shaped field distribution with a null field along the axis of the torus at the point where the field reversed. The suspension effect was observed only for the Ag$_2$O doped and field cooled sample which is attributed to the enhanced flux pinning due to the field cooled condition. It has been cleared that Ag$_2$O acts as pinning center which plays an important role to the magnetic suspension effect. Magnetic repulsive force which affects a superconductor located in magnetic flux from toroidal magnet has been investigated. It has been concluded that the magnetic suspension effect arises from the interaction between the pinning effect and the diamagnetic effect.