• Journal of Power Electronics
• /
• 제13권2호
• /
• pp.250-255
• /
• 2013

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제49권7호
• /
• pp.483-487
• /
• 2000

The analysis of current distribution in a solidly modeled coil is very important for accurate of electric machines such as deflection yoke. In general, Modeling every coils is nearly impossible for analyzing magnetic field using the 3-D finite element method, so solidly modeled coil is usually used. Some methods have been developed for analyzing current distribution, but these methods have fatal disadvantages. The main disadvantages are that the methods cannot be applied to an arbitrary shaped coil and that they yield numerical errors. In this paper, a novel method for resolving the problems mentioned above is proposed. The new method is verified by the application to a test model and it shows a very accurate result.

• 한국재료학회지
• /
• 제22권9호
• /
• pp.482-488
• /
• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.

• 대한의용생체공학회:의공학회지
• /
• 제25권3호
• /
• pp.183-188
• /
• 2004

Magnetic resonance current density imaging (MRCDI) is a useful method for measuring electrical current density distribution inside an object. To avoid object rotations during the conventional MRCDI scans, we have reconstructed current density component images by applying a spatial filter to the magnetic field data measured both inside and outside the object. To measure the magnetic field outside the object with MRI, we immersed the object in a water tank. To evaluate accuracy of the current density imaging, we have made a conductivity phantom with a corresponding finite element method model. We have compared the experimentally obtained current density images with the ones calculated by the finite element method. The average errors of the reconstructed current density images were 6.6 ∼ 45.4 ％ when the injected currents were 1 ∼ 24 mA. We expect that the current density component imaging technique can be used in diverse biomedical applications such as electrical therapy system developments and biological electrical safety analysis.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.685-688
• /
• 2000

Pulse plating is about to deposit material at high current density compared to conventional DC plating. For example pulse plating can get more fine grain can improve adhension and metal distribution and current efficiency can reduce internal stress and crack. therefore we studied pulsed power supply which has high current density and improve deposition quality and increase plating speed in this paper.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
• /
• pp.19-22
• /
• 2003

In this paper, we performed analysis of electric field, magnetic field, current density in AMF electrode using the Maxwell 3D simulation. The current distribution and magnetic field in simple models are analyzed to verify its efficiency and accuracy. In the vicinity of the slits of axial magnetic field type electrode a comparatively high axial magnetic flux density existsIn addition the validity of FEM is confirmed by performing the analyses of distribution in current density and magnetic flux density.

• 한국표면공학회지
• /
• 제27권5호
• /
• pp.285-291
• /
• 1994

The effects of pulse current parameters on the composition and the microstructure of Pd-Ni alloy electrodeposits were studied. The cathode current efficiency of p.c. electrolysis conditions decreased with increasing both mean and peak current density and was lower than those under D.C. electrolysis condition. Palladium content of Pd-Ni alloy increased with increasing both peak current density and on-time, while it decreased with increasing mean current density and duty cycle. The preferred orientation of Pd-Ni alloys changed with increasing mean current density in the sequence of (111)+(110).(100) or (110)longrightarrow(111)longrightarrow(100) or random distribution of crystal structure. The surface morphology of Pd-Ni alloy changed mainly according to the mean current density and was related to the preferred orientation.

• 대한의용생체공학회:의공학회지
• /
• 제21권4호
• /
• pp.403-409
• /
• 2000

본 연구는 3차원 유한요소 몸통 모델을 이용한 제세동 시뮬레이션 연구로서, 제세동 자극인가시 임상에서 사용되는 세가지 전극의 위치와 크기가 심장에서의 전류밀도 분포특성에서 미치는 영향과 시뮬레이션에 사용되는 조직의 비저항 값이 시뮬레이션 결과에 미치는 영향에 대하여 시뮬레이션 하였다. 몸통 모델은 타원형 실린더를 사용하여 흉곽을 모델링하였고, 나머지 부분은 Visible Human의 2차원 영상들을 통하여 3차원 모델링을 하였다. 그리고, ANSYS 5.4를 통하여 유한요소의 전류밀도 해를 구하였다. AP(anterior-posterior) 전극 위치의 경우, 몸통 표면에서 인가한 전류가 가장 효과적으로 심장으로 흘러들어 갔으며, LL(Lateral-lateral) 전극 AP(anterior-posterior) 전극 위치의 경우, 몸통 표면에서 인가한 전류가 가장 효과적으로 심장으로 흘러들어갔으며, LL(lateral-lateral) 전극위치는 가장 균일한 전류밀도 분포특성을 나타내었다. 그러나, 전극의 크기변화는 전류밀도 분포특성에 거의 영향을 주지 않았다. 조직의 비저항 값의 변화에 대한 전류밀도 분포 실험결과는 심근의 비저항 값의 변화가 최소·평균·최대 전류밀도 해에 가장 큰 영향을 주었다.

• 한국환경과학회지
• /
• 제7권2호
• /
• pp.223-232
• /
• 1998

득량만의 조석주기에 따른 성층특성을 연구하기 위하여 우선 30여개 관측점에서 관측된 수온, 염분, 밀도, 해류, 열수지, 바람, 밀도류 자료를 조사하였다. 이 관측자료를 토대로 성층현상을 규명할 수 있는 해석적 모델을 개발하였으며 이 해석적모델을 이용하여 얻어진 연구결과에 따르면, 득량만의 성층을 이루는 요인은 조석, 태양열, 밀도,류인 것으로 나타났으며, 성층을 파과할 수 있는 조석에너지의 혼합에너지의 에너지 기여율 $\varepsilon$ 은 약 0.020 - 0.021정도 되는 것으로 나타났다.

• 한국초전도ㆍ저온공학회논문지
• /
• 제19권1호
• /
• pp.26-29
• /
• 2017

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.