• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.78-78
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• 2009

In this study, multilayer piezoelectric ceramics was manufactured using the PMW-PNN-PZT ceramics. Then, their physical characteristics for applicaton of electric power generation were investigated according to the numbers of multilayer. With increasing the numbers of multilayer, effective electromechanical coupling factor($k_{eff}$) and capacitance were decreased and increased, respectively.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.17.2-17.2
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• 2007

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1081-1083
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• 1999

The capacitive coupling technique has been used as conventional method for PD detection on the power cable line. Recently, however PD measurement using by high frequency is known to have an excellent sensitivity comparison with low frequency on-site. In this paper, the high frequency characteristic of two type of metal foil sensor was studied and the technique was proved to be more effective diagnostic method than conventional method for qualification of EHV cable and accessories.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.149-149
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• 2009

본 연구는 고압전력용 중전기기의 몰드절연 및 옥외용 LED의 절연소재는 기기내부에서 발생된 열에너지를 외부로 방사시키는 것이 무엇보다 중요한 것이다. 이런 이유로 고압전력용 전력기기 대부분은 상당한 체적분을 가지고 있기에 초절연을 가지면서 고열전도를 갖는 나노콤포지트를 개발하기위해 에폭시 메트릭스 기반 질화알루미륨의 표면 처리를 실시하여 에폭시 AIN Nanocomposites를 제조하였다. 나노입자의 균질분산은 나노콤포지트 열전도와 초절연성능에 크게 영향을 주게 된다. 이런 소재개발을 위해 에폭시메트릭스에 나노입자의 충진함량을 3wt%로 하였다. 전처리공정을 통하여 에폭시-나노콤포지트에 두 종류의 금속성 coupling agent (Tyzor TE, Tyzor AA-75)를 질화알루미륨 나노입자 표면처리를 건식법으로 실시하였다. 제조된 Epoxy-AIN Nanocomposites의 열적특성과 전기적 특성을 측정하였다. 전기적특성으로 초절연성의 특성인 형상파라미터가 10.93을 그리고 척도파라미터는 176 kV/mm로서 Weibull Plot 누적확률밀도로서(63.2%)의 통계분석된 값을 얻었다. 또한 열적특성 평가를 위해 유리천이온도와 DMA의 온도특성를 조사하였고, 열적.전기적 특성과 나노콤포지트 내부분산(내부 모폴로지:TEM영상)와 연관되어 연구한 결과, 상당히 일치한 결과를 얻을 수 있었다.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.21-25
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• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.440-445
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• 2011

This paper presents a new regenerative brake system of electric vehicles that employs a continuous variable transmission(CVT) and a flywheel. The developed device has advantages over existing regenerative brakes from a standpoint of reliability and versatility in actual driving conditions. The system consists of a CVT, two wheels, a flywheel, a coupling and auxiliary powertrain components. The CVT is designed as a combination of two cones and a roller, which causes the velocity difference between the wheel and the flywheel. The power flow of the flywheel system is controlled by the CVT roller and the coupling through step motors. A prototype has been developed and then its performance has been investigated for various operating conditions. Results show that the storage efficiency of the flywheel is much affected by the vehicle's velocity and it is reduced below 20% for high speed, as compared to the 25% efficiency for an ideal condition. The CVT is a primary factor for lowering the flywheel efficiencies due to large friction and slipping between the cone and the roller.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.211-225
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• 2011

Railroad signalling systems are to control intervals and routes of trains. There are ATS(Automatic Train Stop), ATP(Automatic Train Protection), ATO(Automatic Train Operation) and ATC(Automatic Train Control) system. Trains are operated in the section which is met on the signalling system because various signalling systems are used in Korea. On the other words, trains are not operated in the section which is used in the other signalling system. To solve this problem, recently combined on-board system has been developed. The combined on-board system is designed by doubling the ATS, ATP and ATC system. Information signal is received by magnetic sensors in the ATC system and is received by antennas in the ATS and ATP system. Therefore, it is possible to arise transmission problems by magnetic coupling. In this paper, electric model of the ATS and ATP antenna is suggested and interference frequency by the magnetic coupling between the ATS and ATP antenna is estimated numerically. As a results of the magnetic coupling, the value of the magnetic coupling is presented without magnetic induction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.501-510
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• 2006

In this paper, the electromagnetic coupling through a slit in a flanged parallel-plate waveguide with a conducting strip is studied. The coupled integro-differential equations for the electric field over the slit and the induced current over the strip are derived and solved by use of the method of moments. The characteristics of some types of maximum coupling phenomena are investigated from the examinations of the variations of the equivalent slit admittance and the coupled power against various parameters such as the location of conducting strip, operating frequency, and strip length.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.221-226
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• 2005

In this paper, a dynamic model for the rotor shaft-coupling-blade system is developed. The blades are attached to a disk and driven by an electric motor shaft which is flexible in torsion. We assumed that the shaft torsional flexibility is lumped in the flexible coupling which is usually adopted in rotor systems. The Lagrangian approach with the small deformation theory for both blade-bending and shaft-torsional deformations is employed for developing the equation of the motion. The assumed modes method is used for estimating the blade transverse deflection. The numerical results highlight the effects of both structural damping of the system and the torsional stiffness of the flexible coupling to the dynamic response of the blade. The results showed strong coupling between the blade bending and shaft torsional vibrations in the form of inertial nonlinearif, stiffness hardening and softening.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.426-433
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• 2014

The high-altitude electromagnetic pulse(HEMP) generated by a high-altitude nuclear explosion. This paper presents the comparison of electric field penetration in Bell laboratories and IEC 61000-2-9 standard when HEMP source penetrates through Naval Warship conducted coupling path and radiated coupling path. Also we analyze the effects of two kinds of coupling and propose Protective measures. Simulation results confirm IEC 61000-2-9 standard is more strict than the Bell Laboratories standard except for a lower frequency band, so we proposed IEC 61000-2-9 standard as a Naval HEMP standard. Finally, we offer the protective measures such as the shielding coating, Honeycomb ventilation, TVS in order to meet the military criteria.