• 드라이브 ㆍ 컨트롤
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• 제9권4호
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• pp.1-7
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• 2012

The voice coil linear force motor is a kind of a direct drive motion device that uses a permanent magnetic field and coil winding to produce force. In order to design a voice coil linear force motor, an exact calculations of the required force, the flux density in air gap and the flux pathway are needed. A conventional method can be used usually to calculate the flux density in air gap, but with this method it is needed to find a magnetic circuit revision constant. In this paper a voice coil linear force motor is designed by conventional design method and analyzed by 3D simulation program "Flux". For the prototype linear force motor, the results of the calculated by conventional design method and the analyzed by 3D simulation program are compared with the test result. Finally it is showed that the magnetic circuit revision constant which is found by comparing of the analyzed and the measured data can be used for the design of the voice coil type linear force motor to minimize the trial and error.

• 대한전기학회논문지
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• 제32권8호
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• pp.277-283
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• 1983

The pulse generating circuit system of the so-called turbulently-heated theta pinch is experimentally investigated, and its results are compared with the predictions based on the conventional theory. The conventional theory assumes that the impedance of the pinch coil is independent on the time rate of change in voltage (or current) across the pinch coil. The experimental pulse height of the voltage actross the pinch coil is about 1.5% fo that predicted by the conventional theory.

• 조명전기설비학회논문지
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• 제28권3호
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• pp.32-43
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• 2014

This paper presents the intra capacitance modeling according to the winding method, section bobbin and coil structure for hybrid choke coil capable of the EMI attenuation of broad bands from lower frequency bands to higher frequency bands and high frequency type common-mode choke coil capable of the EMI attenuation of high frequency band used in the EMI Block of LED-TV SMPS. In case of high frequency type CM choke coil, it can be explained the parasitic capacitance of A type and section bobbin type winding methods among them is much smaller than the other. The first resonant frequency of the proposed CM choke coil tends to increase as the parasitic capacitance becomes small and its impedance characteristics also show improved performance as the first resonant frequency increases. In case of hybrid choke coil using rectangular copper wire, it has investigated its parasitic capacitance compared to CM choke coil of conventional toroidal type becomes small. Also it has confirmed through the experiment results that CE margin and RE margin in frequency bands 0.5MHz to 5MHz and 30MHz to 200MHz are respectively 10dB and 15dB greater than that of conventional type in case of one stage EMI filter structure adopting hybrid choke coil compared to two stage EMI Filter structure using two of each CM choke coil used in the lower and higher frequency bands or two of CM choke coil used in only the lower frequency bands. In the future, the hybrid choke coil and CM choke coil of high frequency type show it can be practically used in not only LED/LCD-TV SMPS but also several applications such as LED Lighting, Laptop Adapter, Server Power Supply and so on.

• 한국전기전자재료학회논문지
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• 제18권4호
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• pp.370-374
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• 2005

AC loss of a superconducting conductor has a strong influence on the economic viability of a superconducting fault current limiter, which offers an attractive means to limit short circuit current in power systems. Therefore, the AC loss characteristics in several fault current limiting elements of a coil type have been investigated experimentally. The test result shows that AC losses measured in the fault current limiting elements depend on arrangement of a voltage lead. The AC loss of a bifilar coil is smallest among the fault current limiting elements of the coil type. The measured AC loss of the bifilar coil is much smaller than that calculated from Norris's elliptical model. However, the loss measured in a meander, which is frequently used in a resistive fault current limiter, agrees well to the theoretical one.

• 한국자기공명학회논문지
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• 제7권1호
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• pp.25-36
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• 2003

The performance of radio frequency (RF) coils, used in MRI units, is determined by the image uniformity and the signal-to-noise ratio (SNR). Birdcage and surface coils are commonly used. A birdcage coil provides a good image uniformity while a surface coil produces a high SNR. In this study, therefore, a staircase coil was designed from a standard version of a birdcage coil, with some structural changes to increase SNR while maintaining image uniformity. In phantom experiments, the improvement of the image to uniformity and the SNR increase of the staircase coil compared with the values for the birdcage coil were about 3.5% and 35%, respectively. In clinical experiment, the SNR increase of the staircase coil, compared with the value for the birdcage coil was about 40% in bone, muscle and blood-vessel tissues. These results show that the performance of the staircase coil was very improved over the standard birdcage coil in terms of SNR, and that image uniformity was maintained. Therefore, the staircase coil designed by this study should be useful in experimental and clinical l.5T MRI systems, and this coil offers an alternative method of quadrature detection.

• 전력전자학회논문지
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• 제25권3호
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• pp.162-170
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• 2020

In this paper, we report our study of the current measuring technique by implementing a pick-up coil in the PCB pattern instead of the current measuring sensor in a power converter using a WBG device. The proposed PCB pattern coil structure has a higher mutual inductance value than the conventional pattern by constructing the coil using the multi layer board. It has high sensitivity and is configured without additional process outside the PCB. In the current measurement, the integrator is measured by integrating the coil at the back end and the current waveform measured using proposed pick-up coil is confirmed by comparing it with the original current waveform through DPT simulation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1378-1383
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• 2004

Rogowski coil is a kind of sensor for high amplitude and very short period current and suitable for the measurement of PD pulse. This paper have simulated the relations between PD signals and Rogowski coil which has its own equivalent circuit and investigated signals of Rogowski coil induced by PD pulse current. and compared with the PD signal obtained from conventional PD measuring system in accordance with IEC60270.

• 한국멀티미디어학회논문지
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• 제20권7호
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• pp.1024-1029
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• 2017

A novel analytic solution has been derived for the bird-cage receiver coil of a magnetic resonance imaging (MRI) system, which is widely used in 3-dimensional medical imaging, by transforming the coil into an equivalent circuit model by using a transmission matrix-based circuit analysis. The bird-cage coil composed of N legs is divided into a cell for which input impedance is to be analyzed and the remaining N-1 cells, and then a transmission matrix corresponding to the N-1 cells is converted into a circuit to transform the 3-dimensional bird-cage coil into the 2-dimensional equivalent circuit model, which is suitable to derive the analytic solution for the input impedance. The proposed method derives directly the analytic solution for the input impedance at an arbitrary point of the coil unlike the conventional analytic solution of a bird-cage coil, so that it can be used not only for resonance frequency calculations but also for various coil characteristics analyses. Since the analytic solution agreed well with the results of computational simulations, it can be useful for the impedance matching of a coil and the analysis and the design of a multi-tune bird-cage coil.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.363-364
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• 2002

We describe quadrature type surface coil for functional magnetic resonance imaging at 3T MRI system. The coil consisted of two coplanar resonators and was used as both transmitter and receiver. The signal-to-noise ratio (SNR) of the coil was compared with that of a standard birdcage head coil. Visual cortex activation on normal subjects using LED flicker was performed. The SNR of surface coil was found to be better than that of the conventional head coil.

• 비파괴검사학회지
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• 제36권2호
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• pp.155-159
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• 2016

Eddy current testing (ECT) is an important nondestructive testing technology for the inspection of flaws in conductive materials. However, this widely used technology is not suitable for inspecting lamination when a conventional pancake coil is used because the eddy current (EC) generated by the pancake coil is parallel to the lamination and will not be perturbed. A new method using a rectangular coil placed vertical to the work piece is proposed for lamination detection. The vertical sections of the rectangular coil induce ECs that are vertical to the lamination and can be perturbed by the lamination. A parametric study of a rectangular coil by finite element analysis was performed in order to examine the capability of generating vertical EC.