• Journal of electromagnetic engineering and science
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• 제17권2호
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• pp.76-85
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• 2017

We investigate the indirect-fed magnetic resonant wireless power transfer (MR-WPT) system for wireless charging for mobile devices by rearranging the loops and coils. Conventional MR-WPT is difficult to apply to consumer electronic products because of the arrangement of the resonators. In addition, there are restrictions for charging using a wireless technology, which depend on the circumstances of the usage scenarios. For practical applications, we analyzed the transfer efficiency of the MR-WPT system with various combinations and positions of resonators. Three rearranged configurations (Out-Out, Out-In, In-In) have been considered and experimentally investigated using hollow pipe loops and wire copper coils. There were four types of loops and two types of coils; each one had a different diameter and thickness. The results of the measurements show that the trends of the transfer efficiencies for the three configurations were similar. A transfer efficiency of 82.5% was achieved at a 35-cm distance between the 60-cm diameter transmitter (Tx) and receiver (Rx) coils.

• 전력전자학회논문지
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• 제10권1호
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• pp.45-51
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• 2005

본 논문에서는 서치코일이 장착된 SRM(Switched Reluctance Motor)의 정지시 회전자 위치를 추정하는 방법을 비교하여 제시하였다. 서치코일이 장착된 SRM은 초기에 정지상태이므로 서치코일에서 유기기전력이 발생하지 않는다. 따라서 정지상태에서 회전자의 위치를 검출하기 위한 방법이 필요하게 된다. 본 논문에서는 유클리디안 제곱거리, 퍼지, 신경망 등 세 가지 방법을 이용하여 회전자의 위치 추정을 위한 시뮬레이션을 실행하였고 그 결과를 비교하였다. 또한 시뮬레이션 결과가 우수한 유클리디안 제곱거리를 이용하여 회전자 위치 추정을 위한 실험을 실시하여 본 논문에서 제안한 방법의 타당성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1266-1268
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• 1996

In this study an automatic roiling-coli labeling system using robot vision system and peripheral mechanism is proposed and implemented, which instead of the manual labor to attach labels Rolling-coils in a steel miil. The binary image process for the image processing is performed with the threshold, and the contour line is converted to the binary gradient which detects the discontinuous variation of brightness of rolling-coils. The moment invariants algorithm proposed by Hu is used to make it easy to recognize even when the position of the center are different from the trained data. The position error compensation algorithm of six degrees of freedom industrial robot manipulator is also developed and the data of the position of the center rolling-coils, which is obtained by floor mount camera, are transfered by asynchronous communication method. Therefore even if the position of center is changed, robot moves to the position of center and performs the labeling work successfully. Therefore, this system can be improved the safety and efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.735-737
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• 2003

A superconducting motor consisting of high temperature superconducting (HTS) rotor and air-core stator is under development in Korea Electrotechnology Research Institute. HTS motor was designed for having the rated power of 100hp at 1800 rpm. HTS field winding is composed of sixteen HTS race track shaped coils wound with stainless steel-reinforced Bi-2223 tape conductor by react and wind fabrication method. Nomex Paper was used for electrical insulation. Each of four magnet pole assemblies was constructed with four double pancake sub-coils, mechanically stacked and electrically in series. Four magnet assemblies were fixed on an aluminum support structure to make effective heat transfer. Critical current (Ic) of HTS field winding was 41A but minimum Ic of sub-coils was 35A at 77K and self field. Joule heat generated in HTS field winding was 2.11W at 77K and 35A.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1612-1614
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• 2003

80pF capacitive couplers were connected to six 6.6kV motor model coil terminals. The voltage applied to the coils were 3.81kv, 4.76 kV and 6.6kV, respectively. These stator coils have various types of artificial insulation defects such as large voids, semi-conductive coating damage and strand insulation fault. Digital PD detector(PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in PD were measured with a conventional digital PD detector. Most of the defect mechanism of large motor stator winding can be associated with PD patterns such as internal and slot discharges. PD patterns coincide with PDD and TGA. These instruments have an input bandwidth of 40-400kHz and 0.1-350MHz. Surge testing detects faults in inter-turn winding of high voltage motor model coils.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1252-1254
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• 2005

High Tc superconducting(HTS) model coil was prepared. Current-voltage(I-V) characteristic curves of model coil, sub-coils and joints were investigated at 77K and other some temperatures. Cooling system for characteristics measurement was made by using G-M cryocooler. At 77K, quench current(Iq) of model coil was 43.9A and the lowest Iq of sub-coils was 38.8A. At 55K, sub coil SP #06 was 106A. So, 100A was chosen as the operating current at 55K with margin. Joule heat of model coil was 0.65W at 100A, operating current and 58K. Joint resistances between sub-coils were about $70n{\Omega}$ at 77K and about $30n{\Omega}$ at 55K.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.50-54
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• 2018

We analyzed the temperature dependency of the AC losses in high temperature superconducting (HTS) coils. In the case of a short sample of an HTS tape, the magnetization loss at 4.2 K could be higher than the one at 77 K for a same transport current. It happens when the perpendicular magnetic field is above a certain magnitude. The AC loss characteristics of solenoidal coils have been analyzed at the temperatures of 65 K and 77 K. They were categorized by the aspect ratios. The operating current of a solenoid was normally set about 70 % of the critical current. An HTS solenoid with the same operating current of 77 K causes larger AC losses at 65 K in the most cases of the HTS solenoids. We also analyzed the AC loss characteristics due to the temperature variations for three types of superconducting magnetic energy storages. Two of them were solenoidal types and the other was toroidal type. The results showed the tendency for the coils to have higher AC losses at lower temperature with the same operating currents and scenarios.

• 한국초전도ㆍ저온공학회논문지
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• 제9권1호
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• pp.43-46
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• 2007

Solenoid coil is one of the commonly used one in superconducting power machines because it can produce uniform magnetic field at the center of the coil. Most of the AC loss in a solenoid coil is magnetization loss which is generated by the perpendicular magnetic field. This paper compares the electrical characteristics of two solenoid coils made of YBCO wire and BSCCO wire. We made and tested the BSCCO solenoid coil and YBCO solenoid coil which had the same number of turns and inner diameter. Number of turns and inner diameter of both coils were 30 turns and 10cm, respectively. AC loss of both coils were calculated by using the finite element method. Result shows that AC loss of YBCO coil was about 1/7 of that of the BSCCO coil when the current was 40A.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.20-25
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• 2009

The quench detection system of the KSTAR (Korea Superconducting Tokamak Advanced Research) primarily uses the resistive voltage measurement due to a quench. This method is to detect the resistive voltage generated by a quench, which is continuously maintained above the preset voltage threshold for a given holding time. As the KSTAR PF (Poloidal Field) coils are operated in the pulse current mode, the large inductive voltages are generated. Therefore the voltage threshold and the quench holding time should be determined by considering both the inductive voltages measured during the operation, and the maximum conductor temperature rise through the quench analysis. In this paper, the compensation methods for minimizing the inductive voltages are presented for the KSTAR PF coils. The quench hot spot analysis of the PF coils was carried out by the analytical and numerical methods for determining the proper values of the quench voltage threshold and the allowable quench protection delay time.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.1-5
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• 2009

It is important to predict AC loss in $Nb_3Sn$ and NbTi cable-in-conduit-conductor (CICC) reliably for the design and operation of large superconducting coils. The hysteresis loss in the superconducting filaments and coupling loss within strands and among strands in a cable or composite are dominant ac losses in superconducting magnets. The coupling loss in a superconductor can be characterized by identifying the coupling constant time $n{\tau}$. To reduce the coupling loss, all the strands (superconductor and Cu) in KSTAR (Korea Superconducting Tokamak Advance Research) are chromium plated with thickness of $l{\pm}0.5{\mu}m$. The ac losses of PF1, PF5 and PF6 coils has been measured by calorimetric method while applying trapezoidal current pulses with various ramp rate from 0.5 kA/s to 2 kA/s. The coupling time constants for $Nb_3Sn$ coils are $25{\sim}55$ ms and the values are not co-related with the coil size, the time constants for NbTi coil is 30 ms.