• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.89-89
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• 2004

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.466-469
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• 2008

As the industry develops, they are interested in the fault of electric machines and the effect on human beings by electromagnetic fields and waves which generate through much use of electric machines and appliances. In foreign country, they confirmed the standard about electromagnetic interference and compatibility(EMI/EMC) of electromagnetic fields and waves generating electricity transmission/distribution equipments and electric appliance. In Korea, such criteria are applied too. Before EMI/EMC standard is applied, it is important to prepare the plan to predict and reduce electromagnetic fields and waves which generate in the inner and the outer part of electric machinery. To solve such a problem, they calculated Maxwell's equations by finite element method(FEM) and finite difference method(FDM) in most papers. However, these methods have the disadvantage that mathematical expansions are complex and need much memory allocations for grid and mesh generations. In this paper, we introduce transmission line matrix(TLM) method that media of which trains consists are regarded as transmission lines for electromagnetic field calculation in Korean High Speed Train, calculate the electric and magnetic field, and analyze the results.

• 월간포장계
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• 통권323호
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• pp.77-82
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• 2020

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.505-508
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• 2012

A permanent magnet flux switching (PMFS) machine has a simple rotor, whilst both magnets and coils are set in the stator, resulting in easy removal of heat due to both copper loss and eddy current loss in magnets. However, the volume of magnets used in PMFS machines is usually larger than in conventional PM machines, and leakage flux does exist at the non-airgap side. To make full use of the magnets and gain higher power density, a novel 3-dimensional (3D) field PMFS machine is developed. It combines merits of the tubular linear machine, external-rotor rotary machine and axial-flux rotary machine, hence, offers high power density and peak torque capability, as well as efficient utility of magnets owing to the unique configuration of triple airgap fields.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.855-856
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• 2006

Inductance can be defined as several kinds of slops on the B-H curve, and at is classified into apparent, effective, incremental inductances, etc. In many research cases, its calculation and measurement are partially dealt. However it is hard to find the clear explanation of the inductance in the voltage equation of PM machines, and even its relationship with those classified inductances in the view point of design and characteristics analysis. Moreover some previous definition of inductance can not be used for the inductance of coils in PM machines. Therefore, in this paper the inductance is redefined for voltage equation of PM machines, and the methods of calculation by using finite element analysis method and measurement are explained.

• 대한전기학회논문지:전력기술부문A
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• 제54권6호
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• pp.315-322
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• 2005

In this article, 1 would like to explore the estimation method of time-varying voltage sags in large industrial systems considering the short circuit contributions of rotating machines. For the power distribution system of KEPCO(Korea Electric Power Corporation), the magnitude of initial symmetrical short circuit current is generally not changed. However, in industrial systems which contain a number of rotating machines, the magnitude of voltage sag is generally changed from the initial to the clearing time of a fault due to the decreasing contribution of rotating machines for a fault current. The time-varying characteristics of voltage sags can be calculated using a short circuit analysis that is considered the time-varying fault currents. For this, the prediction formulations of time-varying voltage sags are proposed using a foreign standard. The proposed method contains the consideration of generator and motor effects. For the test of proposed formulations, a simple system of industrial consumer is used for the comparison conventional and proposed estimation method of voltage sag characteristics.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권3호
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• pp.143-151
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• 2004

High-speed permanent magnet machines are likely to be a key technology for electric drives and motion control systems for many applications, since they are conductive to high efficiency, high power density, small size and low weight. In high-speed machines, the permanent magnets are often contained within a retaining sleeve. However, the sleeve and the magnets are exposed to high order flux harmonics, which cause parasitic eddy current losses. Rotor losses of high-speed machines are of great importance especially in high-speed applications, because losses heat the rotor, which is often very compact construction and thereby difficult to cool. This causes a danger of demagnetization of the NdFeB permanent magnets. Therefore, special attention should be paid to the prediction of the rotor losses. This paper is concerned with the rotor losses in permanent magnet high-speed machines that are caused by permeance variation due to stator slotting. First, the flux harmonics are determined by double Fourier analysis of the normal flux density data over the rotor surface. And then, the rectilinear model was used to calculate rotor losses in permanent magnet machines. Finally, Poynting vector have been used to investigate the rotor eddy current losses of high-speed Permanent magnet machine.

• 한국전자통신학회논문지
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• 제16권3호
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• pp.471-476
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• 2021

분말 야금 기술에 의한 복합 연자성 재료는 전기기기에 일반적으로 사용되는 종래의 전기강판보다 많은 장점을 가지고 있으며, 그 관련 기술은 최근에 상당한 발전을 거듭하고 있다. 복합 연자성 재료는 일반적으로 분말의 형태로 인해 자기적 등방성 가지므로 3차원 자속 및 복잡한 구조의 전기기기 구성에 적합하다. 하지만 SMC와 같이 등방성 자기 특성을 가지는 재료는 복잡한 벡터 히스테리시스를 가지므로 정확한 손실 특성을 예측하는 것이 매우 어렵다. 따라서 본 논문에서는 전기강판 및 SMC의 링 타입 시편을 제작하고 시편 크기에 따라 자기적 특성을 측정한 후, 측정된 자기적 정보를 이용하여 800Hz 이상에서 구동하는 고속 영구자석 전동기의 전자계 해석을 수행하였다. 또한, 해당 모델의 시작품을 제작하고 효율 측정 및 비교를 통해 본 논문의 신뢰성을 입증하였다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.769-777
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• 2017

The research of air gap flux density has a significant effect on predicting and optimizing the structure parameters of electrical machines. In the paper, the air gap coefficient, leakage flux factor and saturation coefficient are first analytically expressed in terms of motor properties and structure parameters. Subsequently, the analytical model of average air gap flux density for surface-mounted permanent magnet synchronous machines is proposed with considering slotting effect and saturation. In order to verify the accuracy of the proposed analytical model, the experiment and finite element analysis (FEA) are used. It shows that the analytical results keep consistency well with the experimental result and FEA results, and the errors between FEA results and analytical results are less than 5% for SPM with high power. Finally, the analytical model is applied to optimizing the motor structure parameters. The optimal results indicate that the analytical calculation model provides a great potential to the machine design and optimization.

• Journal of Power Electronics
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• 제18권4호
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• pp.1111-1126
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• 2018

In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.