• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.83-87
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• 2014

This paper describes the magnetic field analysis of wireless power transfer via magnetic resonant coupling. The wireless power transfer system for supplying power to electric vehicle is developed. The parameters of coil transfer system are simulated by the finite element method (FEM). Therefore the coil structure of power transfer system can be accurately analyzed. This paper deals with 3kW wireless transfer system.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.181-187
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• 2020

In this study, we propose a spherical flux concentration structure for omnidirectional wireless power transfer. Omnidirectional wireless power transfer technology is a method that can transmit power to a transmitter located in an arbitrary position in a two-dimensional or three-dimensional space. However, to improve the power transfer distance in a wireless power transfer system, the diameter of the coil or the number of windings must increase, thereby increasing the size of the transmitter. The proposed transmitter structure adds a ferrite core inside the transmitter coil so that the magnetic flux generated by the transmitter is directed toward the position of the receiver. As a result, the flux linkage and the mutual inductance increase. By implementing the omnidirectional wireless power transfer system using the proposed structure, the power transfer distance can be improved by 65% compared with the conventional system without increasing the size of the transmitter. Simulation shows that the proposed spherical flux concentration structure increases the mutual inductance of the omnidirectional wireless power transmission system.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.228-232
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• 2014

The magnetic field generated by the feeding line of a wireless power transfer system induces voltage on the rail of a railway system. The induced voltage of the rail can have a bad influence on the track circuit and on safety. This paper simulated three feeding lines to study the relation between the feeding lines and the induced voltage of the rail; it also proposed magnetic field distribution of the feeding line to reduce the induced voltage.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.5
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• pp.311-318
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• 2019

In general wireless power transfer systems (WPTSs), power transfer is controlled by the wireless communication between a transmitter (Tx) and a receiver (Rx). However, WPTS is difficult to apply in electronic products that do not have batteries, such as TVs. A WPTS with resonators based on a transformer of LLC series resonant converter is proposed in this study to eliminate wireless communication units between a Tx and an Rx. The proposed system operates at the boundary of the resonance frequency, and the required power can be stably supplied to authorized devices even though some misalignment occurs. Moreover, standby power standards for the electronic product can be satisfied.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.4
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• pp.221-226
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• 2018

In this paper, the power transfer efficiency analysis based on the resonant repeater in a magnetic resonance wireless power transfer system is proposed. The efficiency of the magnetic resonance method was verified by comparing the general frequency with the resonance frequency. The resonance repeater was arranged to increase the efficiency and increase the transfer distance. When using resonant repeaters, the maximum efficiency increase is about 36.23[%] and the transfer distance was extended to more than 20[cm]. Through this study, confirmed the effect of using resonance repeaters in wireless power transfer system. As a result, it can be expected that the overall technology related to wireless power transfer system will be more valuable for energy-IT technology.

• Smart Structures and Systems
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• v.17 no.4
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• pp.631-646
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• 2016

Although the deployment of wireless sensors for structural sensing and monitoring is becoming popular, supplying power to these sensors remains as a daunting task. To address this issue, there have been large volume of ongoing energy harvesting studies that aimed to find a way to scavenge energy from surrounding ambient energy sources such as vibration, light and heat. In this study, a magnetic resonance based wireless power transfer (MR-WPT) system is proposed so that sensors inside a concrete structure can be wirelessly powered by an external power source. MR-WPT system offers need-based active power transfer using an external power source, and allows wireless power transfer through 300-mm thick reinforced concrete with 21.34% and 17.29% transfer efficiency at distances of 450 mm and 500 mm, respectively. Because enough power to operate a typical wireless sensor can be instantaneously transferred using the proposed MR-WPT system, no additional energy storage devices such as rechargeable batteries or supercapacitors are required inside the wireless sensor, extending the expected life-span of the sensor.

• Journal of IKEEE
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• v.22 no.2
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• pp.480-483
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• 2018

Wireless power transfer (WPT) is the technology that forces the power to transmit electromagnetic field to an electrical load through an air gap without interconnecting wires. This technology is widely used for the applications from low power smartphone to high power electric railroad. In this paper, the model of wireless power transfer circuit for the low power system is designed for a resonant frequency of 13.45 MHz. Also, a feedback WPT circuit to improve the power transfer efficiency is proposed and shown better performance than the original open WPT circuit, and the methodology for power efficiency improvement is studied as the coupling coefficient increases above 0.01, at which the split frequency is made.

• Journal of Power Electronics
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• v.15 no.4
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• pp.987-993
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• 2015

Wireless power transfer technologies typically include inductive coupling, magnetic resonance, and capacitive coupling methods. Among these methods, capacitive coupling wireless power transfer (CCWPT) has been studied to overcome the drawbacks of other approaches. CCWPT has many advantages such as having a simple structure, low standing power loss, reduced electromagnetic interference (EMI) and the ability to transfer power through metal barriers. In this paper, the CCWPT system with 6.78MHz class D inverter is proposed and analyzed. The proposed system consists of a 6.78MHz class D inverter with a LC low pass filter, capacitor between a transmitter and a receiver, and impedance transformers. The system is verified with a prototype for charging mobile devices.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.275-281
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• 2016

A novel bidirectional magnetic wireless communication system is proposed in this study. This system provides the communication capability between the source and load sides by high-frequency signal while wireless power is transferred. Contrary to the conventional wireless communication systems using complex IC circuit and active components, the proposed system is simply composed of passive components. It is practical and beneficial for environmental robustness, cost effectiveness, and simple implementation. The detailed static analysis of the proposed system for power and communication lines is established. The proposed system is experimentally verified, and results show that a 0.1 voltage gain for communication line is obtained while a 2.0 voltage gain for the power line is achieved. The proposed system is adequate for practical applications as it allows the inductive power transfer system to wirelessly and easily communicate between the source and load sides.

• Journal of IKEEE
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• v.22 no.3
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• pp.846-849
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• 2018

Wireless power transfer (WPT) is the technology that enables the power to transmit electromagnetic field to an electrical load without the use of wires. There are two kinds of magnetic resonant coupling and inductive coupling ways transmitting from the source to the output load. Compared with microwave method for energy transfer over a long distance, the magnetic resonance method has the advantages of reducing the barrier of electromagnetic wave and enhancing the efficiency of power transmission. In this paper, the wireless power transfer circuit having a resonant frequency of 13.45 MHz for the low power system is studied, and the hardware implementation is accomplished to measure the power transmission efficiency for the distance between the transmitter and the receiver.