• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.2
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• pp.9-14
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• 2001

Because salient pole rotor type single phase SRM(Switched Reluctance Motor) has a simple structure and can be use both radial and axial direction magnetic flux at the same time, its output power per unit volume is high. Therefore, the shaft length can be minimized when compared with same output motors. However, salient pole rotor is hard to design due to its complex magnetic circuit. In this paper, salient pole rotor type single phase SRM with minimized shaft length is designed and selected the most suitable dimension of rotor, stator, pole arc and salient pole.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1094-1095
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• 2007

현재 산업분야에서는 보편적으로 방경방향 자속(Radial Flux)형 전동기가 사용되고 있다. 때문에 대용량의 경우 축방향 길이가 길어지게 되고 구조적 제약이 있는 곳에서의 적용이 어렵다. 이와 달리 축방향 자속(Axial Flux)형 전동기의 응용 범위는 광범위하며 기구적, 구조적으로 많은 이점을 지니고 있다. 본 논문에서는 7.5kW급 축방향 자속형 Brushless DC(BLDC) 전동기의 구동회로 및 속도제어 알고리즘을 구성하고 시뮬레이션과 실험을 통하여 그 결과를 검토하였다.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.18-25
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• 2013

MFL PIG (Magnetic Flux Leakage Pipeline Inspection Gauge) is called the system which detects the defect for underground pipelines by using magnetic flux leakage method in nondestructive testing. This method is very suitable for testing pipelines because pipeline has high magnetic permeability. MFL PIG generates the magnetic fields to the pipe axially oriented, and detect the signal of leakage flux by using hall sensor. However, MFL PIG is hard to detect the axially oriented crack with small size because the magnetic flux leakage is not enough to be occurred. To detect the small size and axially oriented crack, the circumferential MFL (CMFL) PIG is being proposed and it can maximize the leakage flux for the axial crack by performing magnetic fields circumferentially on the pipe. In this paper, CMFL PIG is applied to detect the axially oriented crack with small size and the analysis for the distribution and the amplitude of the leakage flux signal is performed by using three dimensional finite element method. From sensing signals, the method how to determine the shape of axially oriented cracks is proposed and verified with experiment.

• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.76-81
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• 2003

Non-linear anisotropic materials were used to simulate the effects of tensile stress in 3D finite element analysis (FEA). FEA was used to calculate the effects of far and near-side pit depth and tensile stress on magnetic flux leakage (MFL) signals. The axial and radial MFL signals were depended on far and near-side double circular pit depth and on the stress, but the circumferential MFL signal was not depended on them. The axial and radial MFL signals increased with greater pit depth and applied stress, but the circumferential MFL signal was scarcely changed.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1917-1926
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• 2018

In view of the current state of the reserves of electric energy generated resources and the share of electric motors in electricity consumption, many researches and studies related to efficiency in electric motors are being made. The presented work is related to the Axial Flux Permanent Magnet Synchronous Motor (AF-PMSM), which has recently undergone significant work based on the development of magnet and motor technology. In this study, a novel AF-PMSM was designed analytically through Finite Element Method (FEM) which can be started by connecting to a line such as an asynchronous motor in a transient state and can operate with high efficiency and power factor after synchronization in steady state without the need for an expensive motor drive. According to the obtained FEM results, a design with an efficiency class of IE4 of 5.5 kW shaft power, a 4 poles motor was obtained. As a result, economic calculations indicate that the extra cost of the designed Line start AF-PMSM with respect to the asynchronous motor is rapidly compensated by energy saving due to a more efficient operation, especially constant speed operations. As a result of the analysis obtained, the targeted values are reached. For induction motors and radial flux permanent magnet synchronous motors, a good alternative motor that can operate with high efficiency and power factor has been obtained.

• Nuclear Engineering and Technology
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• v.31 no.1
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• pp.80-87
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• 1999

An analytic axial xenon oscillation model was developed for pressurized water reactor analysis. The model employs an equation system for axial difference parameters that was derived from the two-group one-dimensional diffusion equation with control rod modeling and coupled with xenon and iodine balance equations. The spatial distributions of nu, xenon, and iodine were expanded by the Fourier sine series, resulting in cancellation of the flux-xenon coupled non-linearity. An inhomogeneous differential equation system for the axial difference parameters, which gives the relationship between power, iodine and xenon axial differences in the case of control rod movement, was derived and solved analytically. The analytic solution of the axial difference parameters can directly provide with the variation of axial power difference during xenon oscillation. The accuracy of the model is verified by benchmark calculations with one-dimensional reference core calculations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.959-967
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• 2012

The theory for a new electromagnetically biased diskless combined radial and axial magnetic bearing is developed. A typical magnetic bearing system is composed of two radial magnetic bearings and an axial magnetic bearing. The axial magnetic bearing with a large axial disk usually limits rotor dynamic performance and makes assembling and disassembling difficult for maintenance work. This paper proposes a novel electromagnet biased integrated radial-axial magnetic bearing without axial disk. This integrated magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. The axial magnetic bearing unit in this combined magnetic bearing utilizes reluctance forces developed in the non-uniform air gaps such that the axial disk can be removed from the bearing unit. The 4-pole homopolar type radial magnetic bearing unit is also designed and analyzed. Three dimensional finite element model for the bearing is also developed and analyzed to illustrate the diskless combined magnetic bearing.

• 전기의세계
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• v.31 no.3
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• pp.197-203
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• 1982

The effects on the characteristics of 20-W fluorescent lamp were studied when applying magnetic field to its positive column. First, when the direction of the magnetic field is axial, i.e., along the lamp, if the magnitude of the field is stronger than the critical field, lamp voltage is increased, lamp current decreased, luminous flux increased, starting voltage decreased, as increasing the applied magnetic field. At the magnetic flux density is 130 gauss, luminous flux is increased to about 6 percents and starting voltage is increased to about 45 percents. Second, when the direction of the magnetic field is transverse to the lamp axis, as increasing the applied magnetic field, lamp voltage is increased, lamp current decreased, luminous flux increased and starting voltage is nearly constant, but the rates of increase or decrease of this case is different from those of the first. At the magnetic flux density is 300 gauss, luminous flux is increased about 45 percents. In both cases, electric power dissipated by lamps is the same as that of the lamp which magnetic field is not applied to.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.382-395
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• 2002

An experimental study on transient critical heat flux (CHF) under flow coastdown has been performed for the water flow in a non-uniformly heated vertical annulus under low flow and a wide range of pressure conditions. The objectives of this study are to systematically investigate the effect of the flow transient on the CHF and to compare the transient CHF with steady-state CHF The transient CHF experiments have been performed for three kinds of flow transient modes based on the coastdown data of a nuclear power plant reactor coolant pump. At the same inlet subcooling, system pressure and heat flux, the effect of the initial mass flux on the critical mass flux can be negligible. However, the effect of the initial mass flux on the time-to- CHF becomes large as the heat flux decreases. The critical mass flux has the largest value for slow flow reduction rate. There is a pressure effect on the ratio of the transient CHF data to steady-state CHF data. Except under low system pressure conditions, the flow transient CHF was revealed to be conservative compared with the steady-state CHF data. Bowling CHF correlation and thermal hydraulic system code MARS show promising results for the prediction of CHF occurrence .