• Journal of Magnetics
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• v.22 no.1
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• pp.14-22
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• 2017

The NMR's probe consists of the static magnetic field generator (magnetic source) and the RF coil. It is very strict for the homogeneity of the static magnetic field intensity of the magnetic source, so the cost of the magnetic source is more expensive in the entire nuclear magnetic resonance instrument. The magnetic source generally consists of electromagnet, permanent magnet and superconducting magnet. The permanent magnet basically needs not to spend on operation and maintenance and its cost of manufacture is much cheaper than the superconducting magnet. Therefore, the permanent magnet may be the only choice for the static magnetic field device if we want to use the magnetic resonance instrument as an analyzer for production by reducing price. A new probe magnet was developed on the basis of the permanent magnet ring in this paper to provide a technological way for reducing the manufacturing cost, weight and volume of the existing nuclear magnetic resonance instrument (including MRI) probe.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1025-1034
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• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.28-33
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• 2009

Average torque of PMa-SynRM(Permanent Magnet-assisted Synchronous Reluctance Motor) is changed by magnet form inserted to the barrier. Because the magnet structure inserted to the barrier influences to the magnet-torque and reluctance torque. Therefore, this paper present a suitable permanent magnet form design for maximum torque when the magnet quantites are always fixed. And each motor characteristic such as average torque, torque ripple, cogging torque and back-EMF are analyzed by FEM(Finite Element Method) for optimal design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.47-53
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• 2015

IPMSM(Insert Permanent Magnet Synchronous Motor) is a very high degree of freedom in the design according to the permanent magnet insertion position. And the performance of IPMSM is affected a lot on barrier shape which determines the magnetic flux path from magnet. Thus the position of permanent magnet and the barrier shape has to be designed by considering both specification and operation condition. In the paper, the permanent magnet and barrier shape which is suitable for direct drive motor of washing machine has been studied. In addition, in order to verify the validity of the study, the test was evaluated by making a prototype motor.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2209-2217
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• 2014

A permanent-magnet-assisted switched reluctance motor (SRM) having small excitation poles, where phase coils are concentrically wound on the poles and thin permanent magnets are inserted inside the poles, is proposed in this paper. The insertion of permanent magnets into the stator excitation poles has a significant influence on positive torque improvement leading to a boost in efficiency. Three key design parameters such as the thickness of permanent magnets, space between two adjacent permanent magnets, and the width of stator excitation poles are determined during a design procedure in terms of the enhancement of positive torque. Step-by-step design modification and a comparison between the proposed permanent-magnet-assisted SRM and no-permanent-magnet SRM have been conducted by means of static torque comparison along with dynamic performance. The first prototype from steel laminations up to its physical assembly has been constructed.

• Journal of Magnetics
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• v.18 no.3
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• pp.276-282
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• 2013

In this paper, magnetic flux distributions of several permanent magnet arrays, including Halbach array, are analyzed and compared. Also, braking force characteristics on a moving solid conductor in the eddy current brake systems with such magnet arrays are analyzed. Then, a new performance index taking into account the maximum braking force and the volume of the magnet is introduced for the comparison and case study of permanent magnet arrays. By changing the lengths, magnetization directions and the height of the permanent magnet arrays, a higher braking force per volume of the magnet can be achieved.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.70-75
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• 2014

Permanent magnets have recently been considered as device that can be used to control the behavior of mechanical systems. Neodymium magnets, a type of permanent magnet, have been used in numerous mechanical devices. These are permanent magnets made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. The magnetic selection, magnet core design and mechanical errors of the magnetic component can affect the performance of the magnetic force. In this study, the coercive force, residual induction, and the dimensions of the design parameters of the magnet core are optimized. The design parameters of magnet core are defined as the gap between the magnet and the core, the upper contact radius, and the lower thickness of the core. The force exercised on a permanent magnet in a non-uniform field is dependent on the magnetization orientation of the magnet. Non-uniformity of the polarization direction of the magnetic has been assumed to be caused by the angular error in the polarization direction. The variation in the magnetic performance is considered according to the center distance, the tilt of the magnetic components, and the polarization direction. The finite element method is used to analyze the magnetic force of an optimized cylindrical magnet.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1334-1340
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• 2001

In this paper, the experimental modeling of the force between permanent magnet and iron-core solenoid is suggested for more accurate control of 3 D.O.F. motor using the electromagnetic force. In the case of iron-core solenoid, the general equation of solenoid cant be used simply because of its nonlinearity. Therefore, the magnetic flux density is estimated through the concept of equivalent permanent magnet. The force distribution between permanent magnet and iron-core solenoid is more dependent on the magnetization of iron core caused by the permanent magnet than any other parameters. Therefore, the equation of the force estimation between these magnetic systems can be modeled by the experimental function of the magnetization of iron core. Especially, if the distance between iron-core solenoid and permanent magnet is far enough, the force equation through experiment can be expressed from only the current of coil and the distance between iron-core solenoid and permanent magnet. It means that Coulombs law can be used for magnetic systems and it is validated through the experiment. Therefore, force calibration is performed by the concept of Coulombs law.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.11
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• pp.547-554
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• 2006

The detent force of a permanent magnet linear motor(PMLM) consists of the end force and cogging force, and should be reduced for high precision purpose applications. The cogging force comes from the electromagnetic interaction between the permanent magnets and interior teeth(or the slots) of the stator, and of which the magnitude depends on the ratio of the numbers of the armature and permanent magnet poles as well as the geometrical shape of the permanent magnet and armature pole. In order to reduce the cogging force of a PMLM, this paper proposes a new configuration which has 9 permanent magnet poles and 10 armature winding slots. By theoretical investigation of the principle of cogging force generation and simulating using finite element method, the proposed PMLM configuration is proven to give much less cogging force than the conventional configuration which has 8 permanent magnet poles and 12 armature winding slots. A proper winding algorithm, modified (A, A, A) winding method, for the proposed configuration is also suggested when the proposed PMLM is operating as a 3 phase synchronous machine. A theoretical and numerical calculation shows that the proposed configuration makes slightly bigger back-emf and thrust force under same exciting current and total number of winding turns condition.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1954-1959
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• 2014

This paper attempts to design and present a comparison of classical Direct Torque Flux Control (DTFC) for Line-Start Permanent Magnet Synchronous Motor (LSPMSM) and its equal Permanent Magnet Synchronous Motor (PMSM). In order to present an in-depth analysis, both motors for DTFC Voltage Source Inverter (VSI)-fed in the same situations of different conditions are simulated and tested. The advantages of the proposed method for LSPMSM over the PMSM are discussed and analyzed.