• Journal of the Korea Convergence Society
• /
• v.8 no.3
• /
• pp.31-40
• /
• 2017

The rise of eco-friendly personal electric mobility is a worldwide trend and the first Korean-made IT convergence electric skateboard, Youth Board, is developed to lead the trend. Youth Board is remotely controllable using either Youth Wearable Controller or Youth App through Bluetooth v4.0 communication, can speed up to 25 km/hr, and operating time is approximately 1.5 hr. A LED display located in the front side of Youth Board deck shows three different states to a rider for user convenience: remaining battery SOC, current driving speed, and braking amount. Indoor EMC test results between Youth Board and Youth Wearable Controller and outdoor Youth Board driving test results are analyzed. In particular, driving test results show the maximum current output is about 15% lowered compared to the other competitor electric skateboard and it lessens the power burden of the motor ESC. These results show Youth Board's usefulness as a personal mobility in the sense of small, light, and inexpensive aspects.

• Journal of IKEEE
• /
• v.18 no.2
• /
• pp.263-271
• /
• 2014

This paper presents design of the second-order sigma-delta modulator for converting voltage and temperature signals to digital ones in Battery Management IC (BMIC) for mobile applications. The second-order single-loop switched-capacitor sigma-delta modulator with 1-bit quantization in 0.13-um CMOS technology is proposed. The proposed modulator is designed using switched-opamp technique for saving power consumption. With an oversampling ratio of 256 and clock frequency of 256kHz, the modulator achieves a measured 83-dB dynamic range and a peak signal-to-(noise+distortion) ratio (SNDR) of 81.7dB. Power dissipation is about 0.66 mW at 3.3 V power supply and the occupied core area is $0.425mm^2$.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.3
• /
• pp.207-217
• /
• 2010

Recently, the use of DC power increased due to the increased use of digital load. Power factor of input current decrease and input current harmonics increase, and conversion loss which is occurred in the AC / DC converter is a problem to provide the proper DC voltage to the device equipped with an internal AC / DC converter. Hybrid system supplies the AC power and DC power to AC load (motor load and the transformer load) and DC loads (computers, TV, LED fluorescent light) at the same time it supplies the renewable energy and utility energy taken power from Utility to user for improving the efficiency and renewable energy improvements in ease of use. This paper studies DC characteristics of traditional AC load for Hybrid distributions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.6
• /
• pp.679-689
• /
• 2014

In this paper, an analysis of the effect of time-variant reflected impedance and its detection method on wireless power transfer(WPT) systems are presented. The reflected resistance at WPT systems is very important parameter as it indicates how well matched antenna is and will exhibit high efficiency. Proposed detection method is based on transmitter current variation analysis with respect to frequency sweep. Using the proposed design method, a wireless power transfer system operating at the frequency of 125 kHz, is design and detect reflected impedance variation. The proposed design method provides good agreements between measured and simulated results. Therefore, The proposed detecting method provides a nonintrusive method to detect harmful object in WPT system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.811-814
• /
• 2011

This paper presents smart laundry management system using wireless Radio Frequnecy Identification (RFID) reader for efficient managing a large amount of laundry and clothing. The proposed system is comprised of wireless RFID hanger, base module connected on PC, and server system. The wireless RFID hanger with RFID reader read RFID tag attached on clothes and transmit tag information using wireless communication. The server system manage customers and his clothing using Database (DB) and display the information on the web page and smart phone devices. Since the proposed system operates with battery, we can evaluate its lifetime to measure current consumption. The designed system can be utilized to manage quantities of clothes and also it will be a good service to improve efficiency of laundry process.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.1
• /
• pp.46-54
• /
• 2008

In this paper, a low-cost impedance spectroscopy system(LCISS) suitable for modeling the electrochemical power sources such as fuel cells, batteries and supercapacitors is designed and implemented. Since the developed LCISS is composed of simple sensor circuits, commercial data acquisition board and LabVIEW software, a graphic language with powerful HMI(Human-Machine Interface), it is expected ta be widely used in substitution of the expensive EIS instruments. In the proposed system, the digital lock-in amplifier is adopted to achieve the accurate measurements even in the presence of the high level of noises. The developed hardware and software is applied to measure the impedance spectrum of the Ballard Nexa 1.2kW proton exchange membrane fuel cell stack and an equivalent impedance model is proposed based on the measurement results. The validity of the proposed equivalent circuit and the developed system is proven by the measurement of the ac power losses of the PEM fuel celt stack by the ripple current.

• Journal of IKEEE
• /
• v.23 no.3
• /
• pp.994-1002
• /
• 2019

In this paper, we propose the development of a power conversion system for electric power take-off (e-PTO) of agricultural electric vehicles. Most e-PTOs use commercial power $220V_{AC}$. A bidirectional power conversion system having a two-stage structure consisting of a DC-DC converter and a DC-AC inverter for supplying a high output voltage using a low battery voltage of an agricultural electric vehicle is suitable. we propose a power conversion system consisting of the one-stage dual active bridge (DAB) converter and the two-stage bidirectional full bridge inverter. In addition, we propose a soft start algorithm for reducing the inrush current generated by the link capacitor charging during the initial operation. A 3kW prototype system and its corresponding algorithms have been implemented to verify its effectiveness through experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.22 no.3
• /
• pp.139-143
• /
• 2022

In this study, Among the electromagnetic induction power generation (EMG) techniques, the design specifications of the RFPM were set, and a suitable test prototype was manufactured through finite element analysis (FEM, 2D) required for characteristic calculation. In addition, a dedicated testing device (Dynamo-Tester) was designed and manufactured to measure and analyze the test prototype. The test product was measured with a test device and the result is analyzed to suggest a method that can be applied by generating as much output power as possible to charge the battery of the wearable IT device using actual kinetic energy of the human body. As a result of the test, the output power was 1.679W and the efficiency was 79.31% under the conditions of rotation speed of 780.9rpm, torque of 0.264kgf/cm, and load current of 73.6~73.9mA. Therefore, it was analyzed that it was possible to charge the wearable device with the output of the ultra-small RFPM pendulum generator.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.6
• /
• pp.203-209
• /
• 2023

Cobalt sulfide nanocomposites were synthesized through a simple hydrothermal method as anode materials for sodium ion batteries (SIBs). In this work, a cobalt sulfide nanoparticle (CoS-NF) and a cobalt sulfide nanocomposite integrated with reduced graphene oxide (CoS@G-NC) were fabricated for electrochemical energy storage performance of battery. The as-prepared CoS@G-NC electrode exhibited reversible and stable cycle performance (62 % after 30 cycles at current density of 200 mA g^-1). The improved electrochemical property was attributed to the small grain growth and uniform distribution of cobalt sulfide during synthesis, which maximized the diffusion pathway for sodium ions and effectively suppressed the delamination and volume expansion of cobalt sulfide during the conversion reaction. The results provide promising anode materials for next-generation SIBs.

• Resources Recycling
• /
• v.33 no.1
• /
• pp.31-36
• /
• 2024

The separation of Ag and Zn from the nitrate leachate of spent silver oxide batteries using Cyanex272 as an extractant was investigated. The extraction of Ag and Zn was affected by the concentrations of nitric acid and the extractant. Cyanex-272 selectively extracted Zn over Ag when the HNO₃ concentration was lower than 0.1 mol/L. The co-extracted Ag was removed by stripping with 1 mol/L thiourea. Stripping of Zn from the loaded Cyanex-272 was accomplished using 0.5 mol/L HNO₃ after the removal of Ag. The McCabe-Thiele diagrams for the extraction of Zn with Cyanex-272, the scrubbing tripping of Ag with thiourea, and the stripping of Zn with HNO₃ were constructed. The results were verified by simulated counter-current extraction and stripping experiments. Finally, a process for the separation of Ag and Zn from silver oxide batteries was proposed.