• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.679-690
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• 2022

This research effort examines the flow behavior and heat transfer assessment of water carrying iron (iii) oxide magnetic fluid due to a rotating and moving plane lamina under the influence of magnetic dipole. The effect of rotational viscosity and magnetic body force is taken into consideration in the present study. The involvement of the moving disk makes a significant contribution to the velocity distribution and heat transfer in rotational flow. Vertical movement of the disk keeps the flow unsteady and the similarity transformation converts the governing equation of unsteady flow into nonlinear coupled differential equations. The non-dimensional equation in the present system is solved through the finite element procedure. Optimizing the use of physical parameters described in this flow, such results can be useful in the rotating machinery industries for heat transfer enhancement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.349-350
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• 2009

Superconducting magnetic bearing and rotating system were developed by utilizing the high magnetization YBaCuO superconductor. The pellets prepared by quasi-melt process had a high magnetic levitation force and a high magnetic attractive force. The shaft also could be moves its position and orientation of the rotating axis freely. Is is essential to enhance the materials properties and to improve the system design for the application of the system to industrial purpose.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.135-148
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• 2015

The present investigation is concerned with a study effect of magnetic field and non-homogenous on the elastic stresses in rotating orthotropic infinite circular cylinder. A certain boundary conditions closed form stress fields solutions are obtained for rotating orthotropic cylinder under initial magnetic field with constant thickness for three cases: (1) Solid cylinder, (2) Cylinder with a circular hole at the center, (3) Cylinder mounted on a circular rigid shaft. Analytical expressions for the components of the displacement and stress fields in different cases are obtained. The effect of rotation and magnetic field and non-homogeneity on the displacement and stress fields are studied. Numerical results are illustrated graphically for each case. The effects of rotating and magnetic field and non-homogeneity are discussed.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.61-69
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• 2021

This paper presents the analysis and experiment results on the electrical and thermal characteristics of metal insulation (MI) REBCO racetrack coil, which was wound with stainless steel (SS) tape between turn-to-turn layers, under rotating magnetic field and conduction cooling system. Although the field windings of superconducting rotating machine are designed to operate on a direct current, they may be subjected to external magnetic field due to the unsynchronized armature windings during electrical or mechanical load fluctuations. The field windings show the voltage and magnetic field fluctuations and the critical current reduction when they are exposed to an external magnetic field. Moreover, the cryogenic cooling conditions are also identified as the factors that affect the electrical and thermal characteristics of the HTS coil because the characteristic resistance changes according to the cryogenic cooling conditions. Therefore, it is necessary to investigate the effect of external magnetic field on the electrical and thermal characteristics of MI-SS racetrack coil for further development reliable HTS field windings of superconducting rotating machine. First, the major components of the experiment test (i.e., HTS racetrack coil construction, armature winding of 75 kW class induction motor, and conduction cooling system) were fabricated and assembled. Then, the MI racetrack coil was performed under liquid nitrogen bath and conduction cooling conditions to estimate the key parameters (i.e., critical current, time constant, and characteristic resistance) for the test coil in the steady state operation. Further, the test coil was charged to the target value under conduction cooling of 35 K then exposed to the rotating magnetic field, which was generated by three phrase armature windings of 75 kW class induction motor, to investigate the electrical and thermal characteristics during the transient state.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.124-125
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• 2001

The electro-magnetic vector equation(F=$qv{\times}B$ ; F：force, B：magnetic field, q：plus charge, v ：velocity of the charge) explains well about the rotations of electron and positron under the magnetic field[Ref.1], as in Fig.1(a). Because the electro-magnetic wave is also a motion of the alternating charge and magnetic field as in Fig.2, the force vector has all the time inwarding direction and then the wave has a rotating motion. The positron in the proton has constant charge and alternating one at the same time[Ref.2] and then the alternating charge makes the absorbing force with the alternating charge of the rotating wave ($\pi$-ray) around the nucleus[Ref.2]. (omitted)

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.621-622
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• 2008

This paper deals with the magnetic properties under the rotational magnetic field on the electrical steel sheet by using Single Sheet Tester with two excitation coils. Actually, the magnetic flux of stator cores in running motors have the behaviour of rotating and alternating flux. In order to improve motor characteristics, it is require to estimate these magnetic properties. When the magnetic field vectors are rotating around in the plane of the sheet during one period of cycle, the magnetization properties and the core loss are measured and then, the results are compared with the magnetic properties obtained by the alternating magnetic fields.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.107-115
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• 2001

Most of rotating machineries supported by contact bearing accompany lowering efficiency, vibration and wear. Moreover, because of vibration, which is occurred in rotating shaft, they have the limits of driving speed and precision. The rotor system has parametric variations or external disturbances such as mass unbalance variations in long operation. Therefore, it is necessary to research about magnetic bearing, which is able to support the shaft without mechanical contact and to control rotor vibration without being affected by external disturbances or parametric changes. Magnetic bearing system in the paper is composed of position sensor, digital controller, actuating amplifier and electromagnet. This paper applied the robust control method using quantitative feedback theory (QFT) to control the magnetic bearing. It also proposed design skill of optimal controller, in case the system has structured uncertainty, unstructured uncertainty and disturbance. Reduction of vibration is verified at critical rotating speed even external disturbance exists. Unbalance response, a serious problem in rotating machinery, is improved by magnetic bearing using QFT algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.46-46
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• 2010

In order to detect exact corona discharge point at stator winding of a rotating machine, an inductively coupled magnetic probe has been developed, which consists of U-shaped and truncated manganese ferrite inductor as a helix. The measured current intensity is somewhat higher than commercially developed probe. It has been shown that the measured intensity of proposed probe is suitable for manual localization as to off-line stator winding monitoring of rotating machine.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1029-1031
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• 2005

A magnetic position sensor is a apparatus that detect the rotating position by measuring the value of the flux density of the rotating position. In this paper, the magnetization system of the permanent magnet in the magnetic position sensor which detects the rotating position was designed. The permanent magnet was magnetized for the flux density into the hole element to be sinusoidal distribution according to the rotating position. To make the sinusoidal distribution of flux density, the magnetization values according to the position in permanent magnet were varied by adjusting the air gap between the pole of the magnetization fixture and the surface of the permanent magnet.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.253-259
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• 2005

Magnetic encoder with relatively low pulse per rotation is generally used for detecting speed of the high-speed rotating machine. It is due to the fact of the mechanical problems of vibration and bearing stiffness and also the limit of maximum output pulse of the mounted encoder. The magnetic encoder is divided into two types, that is, toothed gear-wheel method and magnetic wheel method according to the shape of the rotation disk. In case of detecting speed by the tooth gear-wheel, the encoder itself can be acted as the additional inertia where the number of tooth determining the output pulse and the width of the wheel detecting the change of the magnetic flux density are relatively enough large considering the volume of the rotating machine. While the magnetic wheel method has the limit of the magnetizing number of the ring magnet, there is relatively few, if nv, the influence of inertia on the machine. In this paper, it is proposed a simple magnetic wheel encoder suited for the high speed rotating machine and the method of signal processing and the output characteristics are examined through the V/F operation of max 48,000(rpm) and 2.4(KW) spindle motor.