• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.739-745
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• 2011

This paper proposes a method for reducing the negative spatial harmonics of the radial flux density of an interior-type permanent magnet (IPM) motor. The reliability of the motor is increased by minimizing its vibrations under dynamic eccentricity (DE) state and normal state due to reduction of a negative spatial harmonics component through the influx of a zero spatial harmonics component in the radial flux density. To minimize the vibrations, optimal notches corresponding to the distribution shape of the magnetic field are designed on the rotor pole face. The variations of vibration computation by finite element method (FEM) and the validity of the analysis and rotor shape design are confirmed by vibration and performance experiments.

• Journal of Magnetics
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• v.21 no.2
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• pp.222-228
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• 2016

Correlation between coil configurations and the discharge characteristics such as plasma density and the electron temperature in a newly designed magnetized inductively coupled plasma (M-ICP) etcher were investigated. Radial and axial magnetic flux density distributions as well as the magnetic flux density on the center of the substrate holder were controllable by placing multiple circular coils around the etcher. The plasma density increased up to 60.7% by arranging coils (or optimizing magnetic flux density distributions inside the etcher) properly although the magnetic flux density on the center of the substrate holder was fixed at 7 Gauss.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.36-41
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• 2008

This report describes the analytical solution of back EMF for BLDC motor using numerical analysis of air gap flux density. The analysis of air gap flux density is the key to expect the performance of back EMF for the design of brushless motor. The numerical analysis and FEM analysis are performed to vary attachment of stator side or rotor side, radial flux magnetization or parallel flux magnetization, magnet arc angle in the condition of constant air gap. This results have more reliable data comparing with test result of the back EMF for 7 phase BLDC motor.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.790-791
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• 2015

본 논문에서는 Radial flux density($B_r$)를 고려하여 매입형 영구자석 동기 전동기(Interior Permanent Magnet Synchronous Motor, IPMSM)에서 진동, 소음 발생의 원인이 되는 코깅토크를 최적화하는 방법을 제시한다. Maxwell Stress Method에 의하면 토크는 $B_r$에 비례한다. 따라서 $B_r$과 토크의 상관관계를 이용하여 코깅토크를 저감시켰다. 코깅토크가 가장 큰 회전자의 위치에서 회전자 표면의 $B_r$을 확인한 후 에 노치(Notch)를 적용할 위치를 선정하였다. 그리고 제안한 방법이 매입형 영구자석 동기 전동기 모델에서 효과적으로 코깅토크를 저감시키는 것을 유한요소법을 통해 검증하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1571-1576
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• 2007

This report describes the analytical characteristic of sinewave air gap flux density for the brushless AC motor with surface permanent magnet. The analysis of sinewave air gap flux density is the key to expect the performance of back EMF for the design of brushless AC motor. The numerical analysis and FEM analysis are performed to adopt radial and parallel flux magnetization of magnet on the rotor. And it is also executed to vary the magnet arc angle and arc radius for the condition of constant and non constant air gap. This report is focused on the characteristic of sinewave air gap flux density for permanent magnet of surface brushless AC motor. This results also have more reliable data against the previous paper which had the representative numerical analysis of air gap flux density[1][2].

• Journal of Magnetics
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• v.20 no.4
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• pp.360-365
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• 2015

Spatial distributions of magnetic flux density in a newly designed magnetized inductively coupled plasma (M-ICP) etcher were investigated. Radial and axial magnetic flux densities as well as the magnetic flux density on the center of the substrate holder were controllable by placing multiple circular coils around the etcher properly. The plasma density non-uniformity in M-ICP (25 Gauss) can be reduced (1.4%) compared to that in ICP (16.7%) when the neutral gas pressure was 0.67 Pa and a right-hand circularly polarized wave (R-wave) can be propagated in to the etcher by making magnetic flux density increases both radially and axially from the center of the substrate holder.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.7
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• pp.315-322
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• 2001

High speed brushless permanent magnet(PM) machines need a key technology to minimize the iron core losses in stator and the eddy current losses in the retained sleeve and magnets caused by slotting harmonics. Thus, slotless or iron-coreless brushless PM machines have been applied for a very high rotational speed and/or the ripple-free torque. Unfortunately, slotless or coreless PM machines have lower open-circuit field than slotted and/or iron-cored types, which cause to reduce power density. Fortunately, Halbach array can generate the strong magnetic field systems without additional magnetic materials. In this paper, the 4-pole Halbach array is applied to the high speed machine and is compared with the radial magnetized PM array in field system. The iron-/air-cored stator of PM machine is constructed with/without winding slots. Open circuit magnetic fields of each type are presented from the analytical method and finite element method. Consequently, it is confirmed that the Halbach array field system with slotless stator is more suitable to the high speed motor because it has high flux density, sinusoidal flux distribution than others.

• Journal of Welding and Joining
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• v.27 no.2
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• pp.44-50
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• 2009

The characteristics of arc pressure, current density and heat flux distribution are important factors in understanding physical arc phenomena, which will have a marked effect on the penetration, size and shape of a weld in TIG welding. The purpose of this study is to find out the effect of the heat flux on the melting efficiency and penetration shape in TIG welding using the results of the previous investigators. The conclusions obtained permit to draw a proper method which derived the heat flux distributions by arc pressure distribution measurements, but previous researchers calculated heat flux and current distribution with the heat intensity measurements by the calorimetry. Heat flux of Ar gas arc was concentrated at the central part and distributed low from the arc axis to the radial direction, that of He mixing arc was lower than that of Ar gas, and it was wide distributed to radial direction. That showed a similar characteristic with the Nestor's by calorimetry calculated values. Throughout heat flux drawn in this study was discussed melting efficiency and penetration shape on Ar gas and He mixing gas arc.

• Journal of Magnetics
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• v.21 no.3
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• pp.437-441
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• 2016

Dipole model based analytical expression is proposed to estimate the length and depth of the rectangular defect on ferromagnetic pipe. Among the three leakage profiles of Magnetic Flux Leakage (MFL), radial and axial leakage profiles are considered in this work. Permeability variation of the specimen is ignored by considering the flux density as close to saturation level of the inspected specimen. Comparing the profile of both the components, radial leakage profile furnishes the better estimation of defect parameter. This is evident from the results of error percentage of length and depth of the defect. Normalized pattern of the proposed analytical model radial leakage profile is good agreement with the experimentally obtained profile support the performance of proposed expression.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1071-1072
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• 2011

The axial flux machine has higher power density than conventional radial flux machine, so it is widely applied to various industrial area, for instance, low speed wind power generator. For the conventional radial flux machine, 2D finite element method (FEM) is generally applied, but axial flux machine has to employ 3D FEM with long analysis time due to its own structural characteristic. This paper deals with the performance comparison of axial flux machine according to volume.