• Journal of Magnetics
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• 제21권4호
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• pp.537-543
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• 2016

Currently, an interest in electric vehicles (EVs) exhibited by automakers, government agencies and customers make it as more attractive research. This is due to carbon dioxide emitted by conventional combustion engine that worsens the greenhouse effect nowadays. Since electric motors are the core of EVs, it is a pressing need for researchers to develop advanced electric motors. As one of the candidates, switched flux machine (SFM) is initiated in order to cope with the requirement. This paper proposes a new alternate circumferential and radial flux (AlCiRaF) of permanent magnet switched flux machines (PMSFM) for light weight electric vehicles. Firstly, AlCiRaF PMSFM is compared with the conventional PMSFM based on some design restrictions and specifications. Then the design refinements techniques are conducted by using deterministic optimization method in order to improve preliminary performance of machine. Finally the optimized machine design has achieved maximum torque and power of 47.43 Nm and 12.85 kW, respectively, slightly better than that of conventional PMSFM.

• 전기학회논문지
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• 제66권2호
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• pp.315-322
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• 2017

This study presents a novel two­phase eight stator poles and six rotor poles (8/6) switched reluctance machine (SRM) that can compensate for the vibration and noise problems of two­phase 6/3 SRM and compare the characteristics of two SRMs. In the case of two­phase 6/3 SRM, the short flux path and the flux direction inside the stator are not reversed, so they have high efficiency characteristics. However, the use of three rotor poles causes problems of vibration and noise because the radial force applied to the rotor poles is not balance. The proposed two­phase 8/6 SRM has advantages of 6/3 SRM such as the flux­reversal­free stator and it can improve vibration and noise by using six rotor poles due to balanced radial force acting on the rotor poles. In order to make a reasonable comparison between two SRMs, the electromagnetic field structure of 8/6 SRM is designed to have equivalent torque characteristic to 6/3 SRM and then the copper loss and core loss are compared and analyzed. Finally, we compare the effieicney of two SRMs using finite element analysis and compare the distribution of radial force acting on the rotor poles based on Maxwell's stress method.

• Journal of Magnetics
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• 제21권2호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.482-487
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• 2001

This paper introduces a Lorentz force type four-pole self-bearing motor, where the new pole arrangement of a stator is intended to function both as a synchronous PM motor and as a magnetic bearing. The Lorentz force type has some good points such as linearity of control force, freedom from flux saturation, and high efficiency unlike conventional self-bearing motors. Mathematical expressions of torque and radial force are derived to show that they can be separately controlled regardless of rotational speed and time. To verify the proposed theory, a prototype is made, where a ring-shape outer is actively controlled in two radial directions while the other motions are passively stable supposing the radial stability. Through some experiments, it is shown that the proposed scheme can provide high capability and feasibility for a small high-speed self-bearing motor.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1038-1045
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• 2010

The theory for a new electromagnetically biased combined radial and axial magnetic bearing is developed. This combined magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. One dimensional magnetic circuit model for this combined magnetic bearing is developed and analyzed such that flux densities and magnetic forces can be obtained. Three dimensional finite element model for the bearing is also developed and analyzed. Numerical analysis shows that the calculated magnetic forces from 1D model are well matched with those from the finite element model.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.576-585
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• 2005

This paper deals with the electromagnetic field analysis of slotless brushless permanent magnet machines with three different magnetization patterns such as Halbach, parallel and radial magnetization. The magnetization modeling of Halbach, parallel and radial magnetization is performed analytically. And then, analytical solutions for open-circuit field distributions, armature reaction field distributions, flux linkages due to PMs and stator windings, torque, back-emf and inductance are derived in terms of magnetic vector potential and two-dimensional (2-d) polar coordinate systems. The analytical results are validated extensively by finite element (FE) analyses. The magnet volume required in order to produce identical flux density is compared with each magnetization. Finally, analytical solutions and derivation procedures of those presented in this paper can be applied to slotless and slotted brushless permanent magnet AC and DC machines.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.888-892
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• 2014

In the design of the rotor of an interior permanent magnet synchronous motor (IPMSM), the bridge between the permanent magnets helps prevent the scattering of permanent magnets and pole pieces during high-speed operation. In the design of a motor, if the bridge is too thick, its performance will be largely degraded because of flux leakage. Additionally, if the bridge is too thin, its mechanical safety cannot be guaranteed. Thus, an accurate analysis method is required to determine the thickness of the bridge. Conventional stress analysis methods determine the thickness of the bridge by only considering the centrifugal force of the rotors. In this study, however, a method that additionally considers the radial force generated by the air-gap flux density based on the conventional methods is proposed and reflected in the design of a traction motor for electric vehicles. Finally, the validity of this study is verified through a reliability test related to high-speed operation.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권7호
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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 Electrical Engineering and Technology
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• 제8권2호
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• pp.288-294
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• 2013

The diagnosis of motor failures using an on-line method has been the aim of many researchers and studies. Several spectral analysis techniques have been developed and are used to facilitate on-line diagnosis methods in industry. This paper discusses the first application of a motor flux spectral analysis to the identification of broken rotor bar (BRB) faults in induction motors using a multiple signal classification (MUSIC) technique as an on-line diagnosis method. The proposed method measures the leakage flux in the radial direction using a radial flux sensor which is designed as a search coil and is installed between stator slots. The MUSIC technique, which requires fewer number of data samples and has a higher detection accuracy than the traditional fast Fourier transform (FFT) method, then calculates the motor load condition and extracts any abnormal signals related to motor failures in order to identify BRB faults. Experimental results clearly demonstrate that the proposed method is a promising candidate for an on-line diagnosis method to detect motor failures.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.72-77
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• 2021

The radial distribution of etch rate was analyzed using the ion energy flux model in VHF-CCP. In order to exclude the effects of polymer passivation and F radical depletion on the etching. The experiment was performed in Ar/SF6 plasma with an SF6 molar ratio of 80% of operating pressure 10 and 20 mTorr. The radial distribution of Ar/SF6 plasma was diagnosed with RF compensated Langmuir Probe(cLP) and Retarding Field Energy Analyzer(RFEA). The radial distribution of ion energy flux was calculated with Bohm current times the sheath voltage which is determined by the potential difference between the plasma space potential (measured by cLP) and the surface floating potential (by RFEA). To analyze the etch rate uniformity, Si coupon samples were etched under the same condition. The ion energy flux and the etch rate show a close correlation of more than 0.94 of R² value. It means that the etch rate distribution is explained by the ion energy flux.