• Journal of Electrical Engineering and Technology
• /
• v.10 no.1
• /
• pp.176-187
• /
• 2015

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.1
• /
• pp.52-57
• /
• 2008

In the transformer that is used for the contactless power transmission system, the primary and secondary sides are separated structurally unlike general transformers. When the contactless transformer is built, it forms relatively bigger air gap than the general transformer. Thus it is difficult to transfer energy from the primary side input to the secondary side output with high power efficiently because of low coupling coefficient. This paper proposes a contactless transformer using the rectangular type core that maintains high coupling coefficient even when it has relatively large air gap. The performance characteristics of the proposed transformer are compared with the transformer using general EE core to the air gap variation. The proposed contactless system using rectangular type core and dc-dc full bridge converter, and the system using EE core type and dc-dc full bridge converter are respectively implemented and their performance characteristics are verified by the simulation and experiment.

• Proceedings of the KIEE Conference
• /
• 2004.07d
• /
• pp.2386-2388
• /
• 2004

Recently, rapid process of network technology has an effect on the field of control engineering. And it gives effect to network control system(NCS) research that grafts existing control system and network has been studied. According to one-chip development of TCP/IP that is the most useful in LAN server for hardware, it can usefully and conveniently apply to network control system before. This paper construct network control system that can work close-loop control takes advantage of Ethernet that is the most for general data transmission network. Here, protocol uses for data transmission makes use for TCP/IP. This work the basic data transmitter-receive experiment to take advantage of network node was produced. And then, DC-motor can be control plant. Finally, I will prove to build speed control system of multiple DC-motor through Ethernet.

• Journal of Mechanical Science and Technology
• /
• v.18 no.1
• /
• pp.82-91
• /
• 2004

This article deals with a minimum energy control law of S-CVT connected to a dc motor. The S-CVT can smoothly transit between the forward, neutral, and reverse states without any brakes or clutches, and its compact and simple design and its relatively simple control make it particularly effective for mechanical systems in which excessively large torques are not required. And such an S-CVT equipped power transmission has the advantage of being able to operate the power sources in their regions of maximum efficiency, thereby improving the energy efficiency of the transmission system. The S-CVT was intended to primarily for use in small power capacity transmissions, thus a dc motor was considered here as the power source. We first review the structure and operating principles of the S-CVT, including experimental results of its performance. And then we describe a minimum energy control law of S-CVT connected to a do motor. To do this, we describe the results of an analysis of the dynamics of an S-CVT equipped power transmission and the power efficiency of a DC motor. The minimum energy control design is carried out via B-spline parameterization. And we show numerical results obtained from simulations illustrate the validity of our minimum energy control design, benchmarked with a computed torque control algorithm for S-CVT.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.5
• /
• pp.245-249
• /
• 2006

Corona characteristics of conductors are dependent on the electric field conditions in the immediate vicinity of the conductors. In case of DC transmission line, particularly, the space charge plays an important role in the electric field distribution. Therefore, DC corona cage simulation is necessary for long-term test in the same conditions. This paper presents the results of designing and constructing hardwares such as DC power supply, measurement system and DAS to carry out the simulation. The corona cage longitudinally is divided into five equal length sections and three inner sections of those are isolated from the ground of outer cage. The measurement items are radio noise, corona current, television noise, audible noise and meteorological conditions. In the next step, various simulations about the type and configuration of two or three candidate conductors will be conducted. And then finally an environmentally-friendly conductor for HVDC overhead transmission line will be decided.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.11 no.5
• /
• pp.479-484
• /
• 2016

In this paper, a design of DC level shifter transmitting and receiving control and data signal which have various DC level through daisy chain interface between master IC and slave is introduced in the cell voltage monitoring (CVM). Circuit designed with a latch structure have a function to operate in high speed and for output of variable DC level through transmission gate. As a result of the simulation and the measurement, it was confirmed that control and data signal could be transferred according to the change of DC level from 0V to 30V. Delay time was measured about 170ns. but, it was considered as a negligible tolerance due to a parasitic capacitance of measuring probe and test board.

• KEPCO Journal on Electric Power and Energy
• /
• v.1 no.1
• /
• pp.39-46
• /
• 2015

A outdoor termination installed at the outdoor substation is required to connect undergroud cables and overhead transmission lines. The joint box for AC transmission system is already developed and widely used to interconnect overhead and undergroud systems. But the development of the joint box for DC transmission system was only introduced from China and Japan, but theire developemnt staus and core technologies were not fully reported. In order to implement HVDC systems connecting ovehead transmission lines and undergroud cables, a outdoor termination should be developed, but the detailed specifications and information of this device were not reported. It is estimated that the development of the joint box for DC environment has some technical obstacles including insulating materials, electric field mitigation, thermal temperature rise, and space charge accumuations. Among this, the most important one is the DC elctrical insualtion design. Therefore, in order to investigate the DC elctrical insualton design of outdoor termination, the design of AC slip-on type outdoor termination is reffered, and DC electric field analysis performed to verify the possiblity of application of AC joint box into DC joint box. Especially for DC electric field analysis, temperature rise of insualting materials of a joint box was considered, because the conductivity of materials could be changed due to temperature rise. Furthermore, DC electric field analysis considering transinet state, and polarity reversal state were also investigated to verify which state is the most severe condition for the DC joint box. From the simualtion resulsts, it was shown that the value and the position of maximum electric field was obtained comparing AC state, DC state without temperaure rise, and DC state with temperaure rise. And it was confimred that severe DC electric field was observed considing temperaure rise. Finally, in order to reduce DC eletric field intensifation, different configuration of the joint box was applied and it was not possible to obtain satisfactory results. It means that the slight change of configuration of AC joint box was not the suitable soluton for DC joint box. It is essential to establish novel DC insulaton design skills and method for DC joint box to commercialze this product in the near future.

• Journal of Power Electronics
• /
• v.11 no.2
• /
• pp.156-162
• /
• 2011

The control loop time delay caused by sampling, the zero-order-holder effect and calculations is inevitable in the digital control of dc-dc switching converters. The time delay will limit the bandwidth of the control loop and therefore degrade the transient performance of digital systems. In this paper, the quantization time delay effects with different time delay values based on a generic second-order system are analyzed. The conclusion that the bandwidth of digital control is reduced by about 20% with a one cycle delay and by 50% with two cycles of delay in comparison with no time delay is obtained. To compensate the time delay and to increase the control loop bandwidth, a duty ratio predictive control scheme based on linear extrapolation is proposed. The compensation effect and a comparison of the load variation transient response characteristics with analogy control, conventional digital control and duty ratio predictive control with different time delay values are performed on a point-of-load Buck converter by simulations and experiments. It is shown that, using the proposed technique, the control loop bandwidth can be increased by 50% for a one cycle delay and 48.2% for two cycles of delay when compared to conventional digital control. Simulations and experimental results prove the validity of the conclusion of the quantization effects of the time delay and the proposed control scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.2
• /
• pp.72-75
• /
• 2012

In this paper, high-efficiency DC-AC converter is implemented for the wireless power transmission. The DC-AC converter is implemented by combining the oscillator and power amplifier. Because the conversion efficiency of wireless power transmitter is strongly affected by the efficiency of power amplifier, the high-efficiency power amplifier is implemented by using the Class-E amplifier structure. Also, because the output power of oscillator connected to the input stage of power amplifier is low, high-gain two-stages power amplifier using the drive amplifier is implemented to realize the high-output power DC-AC converter. The dual band harmonic suppression filter is implemented to suppress 2nd, 3rd harmonics of 13.56 MHz. The output power and conversion efficiency of DC-AC converter are 40 dBm and 80.2 % at the operation frequency of 13.56 MHz.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.6
• /
• pp.25-29
• /
• 2017

This paper presents a hetero-integration of electrostatically actuated RF MEMS Switch and step up DC-DC converter on a redistribution layer using commercial PCB process. RF characteristics of Duroid with $56{\Omega}$ impedance GCPW transmission line and that of FR4 with $59{\Omega}$ impedance CPW transmission line were analyzed. From DC to 6GHz, RF characteristics of Duroid were better than that of FR4, insertion loss was 2.08dB lower, return loss was 3.91dB higher, and isolation was 3.33dB higher.