• Journal of Magnetics
• /
• v.16 no.1
• /
• pp.51-57
• /
• 2011

A power supply for magnetic-stimulation devices was designed via a control algorithm that involved a start current application based on a resonant converter. In this study, a new power supply for magnetic-stimulation devices was designed by controlling the pulse repetition frequency and pulse width. The power density could be controlled using the start-current-compensation and ZCS (zero-current switching) resonant converter. The results revealed a high-repetition-frequency, high-power magnetic-stimulation device. It was found that the stimulation coil current pulse width and that pulse repetition frequency could be controlled within the range of 200-450 ${\mu}S$ and 200-900 pps, respectively. The magnetic-stimulation device in this study consisted of a stimulation coil device and a power supply system. The maximum power of the stimulation coil from one discharge was 130 W, which was increased to 260 W using an additional reciprocating discharge. The output voltage was kept stable in a sinusoidal waveform regardless of the load fluctuations by forming voltage and current control using a deadbeat controller without increasing the current rating at the starting time. This paper describes this magnetic-stimulation device to which the start current was applied.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1212-1217
• /
• 2018

The electric field-induced modifications of magnetic anisotropy in CoFeB/MgO systems are studied using X-ray resonant magnetic scattering and magneto-optical Kerr effect. Voltage dependent changes of the magnetic anisotropy of -12.7 fJ/Vm and -8.32 fJ/Vm are observed for Ta/CoFeB/MgO and Hf/CoFeB/MgO systems, respectively. This implies that the interfacial perpendicular magnetic anisotropy is reduced (enhanced) when electron density is increased (decreased). X-ray resonant magnetic scattering measurements reveal that the small in-plane magnetic component of the remanent state of CoFeB/MgO systems with weak magnetic anisotropy changes depending on the applied voltage leading to modification of the magnetic anisotropy at the CoFeB/MgO interface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.6
• /
• pp.564-572
• /
• 2010

In this paper, characteristics on arrangement of coils in the wireless power transfer system based on magnetic resonance is presented. A helical structure is used for a self-resonant coil. To design a proper self-resonant helical coil, its inductance and capacitance are obtained. Using the finite element method, the self-resonant coil designed is simulated and characteristics of wireless power transfer with various arrangement between Tx and Rx resonant coils is analyzed. For verification, a prototype of a wireless power transfer system based on magnetic resonance is fabricated and efficiency of different arrangement such as both vertical and parallel arrangements is measured. From the measurement, transmission efficiency of 50 % for parallel arrangement is obtained within twice the diameter of the coil while for the vertical arrangement it is measured within one and a half diameter of the coil. Maximum efficiency of 84.25 % is observed at the distance 40 cm from the resonant coil in the case of parallel arrangement.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.11 no.1 s.22
• /
• pp.29-37
• /
• 2005

The design and development if Resonant-type Magnetometer(RM) using isotropic magnetic with high permeability is described in this paper. At first, the relationship between the inductance L if the coil winding on a magnetic material and the permeability u(H) appearing in the magnetic material with isotropic and high permeability is defined as a background theory. Then the circuit if RM, which is to obtain the values if L as the change qf frequency is implemented using simple Schmitt Trigger Circuit Through the swinging tests, which is to evaluate the measurement ability if RM, the measurement possibility for the component of earth field was confined.

• Journal of electromagnetic engineering and science
• /
• v.15 no.3
• /
• pp.194-198
• /
• 2015

Magnetic resonant coupling is more efficient than inductive coupling for transferring power wirelessly over a distance. However, a conventional resonant wireless power transfer (WPT) system requires a transmitter and receiver pair in exactly coaxial positions. We propose a resonator that can serve as an omnidirectional WPT system. A magnetic field will be generated by the current flowed through the transmitter. This magnetic field radiates omnidirectionally in the x-y plane because of the crisscross structure characteristic of the transmitter. The proposed resonator is demonstrated by using a single port. To check the received S21 and transfer efficiency, we moved the receiver around the transmitter at different distances (50-350 mm). As a result, the transmission efficiency is found to be 48%-54% at 200 mm.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.13 no.6
• /
• pp.562-568
• /
• 2013

This paper presents a design of a wireless power transfer system based on magnetic resonant coupling technology with in-band wireless communication. To increase the transmission distance and compensate for the change in the effective capacitance due to the varying distance, the proposed system used a loop antenna with a selectable capacitor array. Because the increased transmission distance enables multiple charging, we added a communication protocol operated at the same frequency band to manage a network and control power circuits. In order to achieve the efficient bandwidth in both power transfer mode and communication mode, the S-parameters of the loop antennas are adjusted by switching a series resistor. Our test results showed that the loop antenna achieved a high Q factor in power transfer mode and enough passband in communication mode.

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

• Journal of electromagnetic engineering and science
• /
• v.13 no.2
• /
• pp.104-112
• /
• 2013

A novel miniaturized artificial magnetic conductor (AMC) is proposed for dual-band operation. An AMC unit cell that employs four slots in the metallic patch is used to achieve miniaturization as well as easy control of the second/first resonant frequency ratio, which can be varied from 1.5 to 3.26 by simply changing the slot shape for a given metallic patch size. A dual-band antenna composed of a wideband monopole suspended over the proposed AMC surface is designed and tested to validate this approach. The measurements result in a satisfactory and good matching condition for the dual-band antenna.

• Journal of Power Electronics
• /
• v.19 no.2
• /
• pp.602-611
• /
• 2019

The major drawbacks of magnetic resonant coupled wireless power transfer (WPT) to the embedded sensors on spindles are transmission instability and low efficiency of the transmission. This paper proposes a novel double-loop coil design for wirelessly charging embedded sensors. Theoretical and finite-element analyses show that the proposed coil has good transmission performance. In addition, the power transmission capability of the double-loop coil can be improved by reducing the radius difference and width difference of the transmitter and receiver. It has been demonstrated by analysis and practical experiments that a magnetic resonant coupled WPT system using the double-loop coil can provide a stable and efficient power transmission to embedded sensors.

• Journal of Magnetics
• /
• v.20 no.4
• /
• pp.347-352
• /
• 2015

The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient $d_{33,m}$ and the elastic compliance $s_{33}^H$ of magnetostrictive material, $d_{33,m}$ and $s_{33}^H$ for Terfenol-D are inherently nonlinear and dependent on $H_{dc}$, leading to the influence of $H_{dc}$ on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor $Q_m$ dependences on $H_{dc}$ results in the differences between the low-frequency and resonant ME voltage coefficient with $H_{dc}$. In terms of ${\Delta}E$ effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and $Q_m$ dependence on $H_{dc}$c, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on $H_{dc}$ are mainly influenced by the nonlinear effect of magnetostrictive material.