• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.93-99
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• 2016

The present study aims to increase the amount of surface flux by changing the magnetic directions of a spherical magnet (NdFeB) consisting of four poles. For this purpose, the magnetic directions of quartile spherical slices constituting the spherical magnet are manipulated and their three-dimensional analyses are carried out by using finite-element method via Maxwell environment. The analysis of the magnetic quartile spheres with four different magnetic directions are compared to the each other, and then the quartile sphere with the best surface flux distribution is suggested for rotor structure. It is clear emphasized that the induced torque of the spherical motor, in which such a rotor is used, will be improved as well.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1667-1672
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• 2009

The spherical motor is an electric machine which is able to tilt its shaft on 3-dimensional space as using electromagnetic force. Recently a permanent magnet is remarkable material for applying electric machinery, because of high magnetic flux density. In this paper, a spherical motor, which has permanent magnet on its rotor, is researched. As known, the spherical motor has a special feature as 3 degrees of freedom (D.O.F) operation. This performance can be realized by using electromagnetic torque between coils and magnets. Therefore, in this paper, a permanent magnet spherical wheel motor is introduced and performance characteristics are analyzed for improving of operation stability.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.39-43
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• 2021

This study deals with the ferromagnetic shims design based on the spherical harmonic coefficient reduction method. The design method using the sequential search method is an intuitive method and has the advantage of quickly reaching the optimal result. The study was conducted for a 400 MHz all-REBCO magnet, which had difficulty in shimming due to the problem of SCF (screening current induced field). The initial field homogeneity of the magnet was measured to be 233.76 ppm at 20 mm DSV (Diameter Spherical Volume). In order to improve the field homogeneity of the magnet, the ferromagnetic shim with a thickness of 1 mil to 11 mil was constructed by a design method in which sequential search algorithm was applied. As a result, the field homogeneity of the magnet could be significantly improved to 0.24 ppm at 20 mm DSV and 0.05 ppm at 10 mm DSV.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2158-2167
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• 2018

This paper analyzed the magnetic field produced by the cylindrical stator coils of permanent magnet spherical motor (PMSM). The elliptic equations about the vector magnetic potential were given. Given that the eddy current effects are neglected, the magnet field of the PMSM is regarded as irrotational field, which can be calculated by scalar magnetic potential. The current density of cylindrical stator coil was proposed based on the definition of current density. The expression of current density of stator coil was obtained according to the double Fourier series decomposition and spherical harmonic functions. Then the magnetic flux density for scalar magnetic potential was derived. Further, the influence of different parameters on radial flux density was also analyzed. Finally, the results by the analytical method in this paper were validated by finite element analysis (FEA).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.57-63
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• 2012

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.814-815
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• 2011

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.706_707
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• 2009

This paper presents the torque calculation method of a permanent magnet spherical motor. To calculate the torque of the spherical motor by using finite element method (FEM), 3-dimensional FEM must be used. However since it spends too much time and memory in using 3-D FEM, the easier torque calculation method was presented. In this method, it is very important to get the approximation function of the torque profile curve; the authors present the approximation method of the torque profile curve. This paper shows the torque calculation result coming closer to the torque by 3-D FEM.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.431-434
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• 2010

This paper presents the torque calculation method of a permanent magnet spherical motor. To calculate using the finite element method (FEM), three-dimensional (3D) FEM must be used. However, since the method requires excessive time and memory, an easier torque calculation method is hereby presented. In the proposed method, it is very important to obtain the approximation function of the torque profile curve. We present the approximation method of the torque profile curve and show that the torque calculation result can approximate the torque obtained by 3-D FEM.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1541-1543
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• 2013

This paper presents a spherical motor which can control in multi-degree of freedom operation. The spherical motor has been researched by many types of structure. Thhis paper shows a spherical shaped airgap and surfaced permanent magnets. Especially, The motor consists of dual rotor cores. Unlike a cylindrical motor, the spherical motor design can be considered with azimuth direction on spherical coordinates. Therefore the permanent magnet surfaced on the rotor need to be designed optimally in order to generate a sinusoidal magnetic flux density in the airgap. This paper presents results of optimal design for reducing torque ripple of the multi-degree of freedom spherical motor.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.121-124
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• 2001

The research results on the superconducting magnet for whole body MRI are presented. The magnet consists of main coil with 6 solenoid coils, shielding coil with 2 solenoid coils and 6 sets of cryogenic shim coil. The ferromagnetic shim assembly is installed on the inside wall of the room temperature bore for shimming inhomogeneous field components generated due to manufacturing tolerances, installation misalignments and external ferromagnetic materials near the magnet. Also, the magnet is enclosed with the horizontal type cryostat with 80cm room temperature bore to keep the magnet under the operating temperature. The magnetic field distributions within the imaging volume were measured by the NMR field mapping system. Through the test, the central field of magnet was 1.5 Tesla and the field homogeneity of 9.3 ppm has been obtained on 40cm DSV(the diameter of spherical volume) and using this magnet, comparatively good images for human body, fruits and water phantoms have been achieved.