• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.508-514
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• 2004

A fluxgate magnetic sensor consists of a solenoid excitation coil, pick-up coil, and magnetic core. We presents the effect of magnetic core shape in a micromachined fluxgate sensor. To observe the performance of fluxgate sensor with magnetic core side width and gap, side width of 125 ${\mu}{\textrm}{m}$, 250 ${\mu}{\textrm}{m}$, and 500 ${\mu}{\textrm}{m}$ were designed in a rectangular-ring shaped core and the gaps of 0 ${\mu}{\textrm}{m}$, 50 ${\mu}{\textrm}{m}$, and 100 ${\mu}{\textrm}{m}$ were also fabricated in a racetrack shaped core. The solenoid coils and magnetic core were separated by benzocyclobutane(BCB) which had high insulation and good planarization characters. Copper coil patterns of 10 ${\mu}{\textrm}{m}$ width and 6${\mu}{\textrm}{m}$ thickness were electroplated on Ti(300 $\AA$) / Cu(1500 $\AA$) seed layers. 3 ${\mu}{\textrm}{m}$ thick N $i_{0.8}$F $e_{0.2.}$(permalloy) film for the magnetic core was also electroplated under 2000 gauss to induce the magnetic anisotropy. The magnetic core had the high DC effective permeability of ∼1,300 and coercive field of ∼0.1 Oe. Because the magnetic cores of 500 ${\mu}{\textrm}{m}$ side width and 0 gap had a low magnetic flux leakage, high sensitivity of ∼350 V/T were measured at excitation condition of 3 $V_{P-P}$ and 2 MHz square wave. The power consumption of ∼14 ㎽ was measured. The fabricated fluxgate sensor had the very small actual size of 3.0${\times}$1.7 $\textrm{mm}^2$. When two fluxgates were perpendicularly aligned in terrestrial field, their two-axis output signals were very useful to commercialize an electronic azimuth compass for the portable navigation system.m.m.m.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.564-569
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• 2012

This paper proposes a hybrid-excited linear synchronous motor (LSM) that has potential applications in a magnetically levitated vehicle. The levitation and thrust force characteristics of the LSM are investigated by means of three-dimensional (3-D) numerical electromagnetic FEM calculations and experimental verification. Compared to a conventional LSM with electromagnets, a hybrid-excited LSM can improve levitation force/weight ratios, and reduce the power consumption of the vehicle. Because the two-dimensional (2-D) FE analysis model describes only the center section of the physical device, it cannot express the complex behavior of leakage flux, which this study is able to predicts along with levitation and thrust force characteristics by 3-D FEM calculations. A static force tester for a hybrid-excited LSM has been manufactured and tested in order to verify these predictions. The experimental results confirm the validity of the 3-D FEM calculation scheme for the description of a hybrid-excited LSM.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.157-159
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• 1996

For the optimal design of the induction heating cooker, precise and accurate analysis of the magnetic field inside the jar must be achieved first. Until now, design methods based on experience has been used in industry field. But this takes a lot of trial and error, high cost and also long development time. So the analysis of the magnetic field distribution is very important. In this paper the magnetic field inside the induction heating cooker is analyzed by using axisymmetrical FEM(finite element method). And the method of the coil location design for the optimal heat source distribution using sensitivity analysis is developed. In addition, the shielding effect of the non-axisymmetrical 3-D ferrite structure used in induction heating cooker is also analyzed by the integral method.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.542-553
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• 2011

A magnetic cable that can safely deliver high frequency AC electric power in flammable or sensitive workplaces by preventing from arcs and electric shocks is firstly proposed in this paper. Several new magnetic cable structures with magnetic shields, which are composed of such cancel coil, cancel copper plate, and cancel copper pipe, were compactly implemented by considering and analyzing fringe field and thus the parallel leakage flux is drastically reduced. The output power and efficiency of a prototype magnetic cable with 1.5 m length and 5 cm gap were measured as 353.8W and 68%, where the source current and switching frequency were 10 $A_{rms}$ and 20 kHz, respectively. The proposed magnetic cables are fully analyzed and verified by finite-element method (FEM) simulations and experiments. The results are in a good agreement.

• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.72-78
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• 2003

To observe the effect of excitation coil pitch on the micro fluxgate magnetic sensor, two sensors are fabricated using multi layer board process and the pitch distance of excitation coil are $260\;{\mu}m$ and $520\;{\mu}m$, respectively. The fluxgate sensor consists of five PCB stack layers including one layer of magnetic core and four layers of excitation and pick-up coils. The center layer as magnetic core is made of a Co-based amorphous magnetic ribbon with extremely high DC permeability of ${\sim}100,000$ and has a rectangular-ring shape to minimize the magnetic flux leakage. Four outer layers as excitation and pick-up coils have a planar solenoid structure and are made of copper foil. In case of the fluxgate sensor having the excitation coil pitch of $260\;{\mu}m$, excellent linear response over the range of $-100\;{\mu}T$ to $+100\;{\mu}T$ is obtained with sensitivity of 780 V/T at excitation sine wave of $3V_{p_p}$ and 360 kHz. The chip size of the fabricated sensing element is $7.3\;{\times}\;5.7\;mm^2$. The very low power consumption of ${\sim}8\;mW$ is measured. This magnetic sensor is very useful for various applications such as: portable navigation systems, telematics, VR game and so on.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1075-1080
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• 2015

A hybrid electric vehicle (HEV) powertrain has more than one energy source including a high-voltage electric battery. However, for a high voltage electric battery, the average current is relatively low for a given power level. Introduced to increase the voltage of a HEV battery, a compact, high-efficiency boost converter, sometimes called a step-up converter, is a dc-dc converter with an output voltage greater than its input voltage. The inductor occupies more than 30% of the total converter volume making it difficult to get high power density. The inductor should have the characteristics of good thermal stability, low weight, low losses and low EMI. In this paper, Mega Flux^® was selected as the core material among potential core candidates. Different structured inductors with Mega Flux^® were fabricated to compare the performance between the conventional air cooled and proposed potting structure. The proposed inductor has reduced the weight by 75% from 8.8kg to 2.18kg and the power density was increased from 15.6W/cc to 56.4W/cc compared with conventional inductor. To optimize the performance of proposed inductor, the potting materials with various thermal conductivities were investigated. Silicone with alumina was chosen as potting materials due to the high thermo-stable properties. The proposed inductors used potting material with thermal conductivities of 0.7W/m·K, 1.0W/m·K and 1.6W/m·K to analyze the thermal performance. Simulations of the proposed inductor were fulfilled in terms of magnetic flux saturation, leakage flux and temperature rise. The temperature rise and power efficiency were measured with the 40kW boost converter. Experimental results show that the proposed inductor reached the temperature saturation of 107℃ in 20 minutes. On the other hand, the temperature of conventional inductor rose by 138℃ without saturation. And the effect of thermal conductivity was verified as the highest thermal conductivity of potting materials leads to the lowest temperature saturations.

• Journal of Power Electronics
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• v.11 no.2
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• pp.163-172
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• 2011

Oxidation models of a rotor bar and end ring segment in an induction motor are presented to simulate the behavior of an induction machine working with oxidized rotor parts which are modeled as rotor faults in progress. The leakage inductance and resistance of the rotor parts arc different from normal values because of the oxidation process. The impedance variations modify the current density and magnetic flux which pass through the oxidized parts. Consequently, it causes the rotor asymmetry which induces abnormal harmonics in the stator current spectra of the faulty machine. The leakage inductances of the oxidation models are derived by the Ampere's law. Using the proposed oxidation models, the rotor bar and end ring faults in progress can be modeled and simulated with the motor current signature analysis (MCSA). In addition, the oxidation process of the rotor bar and end ring segment can motivate the rotor asymmetry, which is induced by electromagnetic imbalances, and it is one of the major motor faults. Results of simulations and experiments are compared to each other to verify the accuracy of the proposed models. Experiments are achieved using 3.7 kW, 3-phase, and squirrel cage induction motors with a motor drive inverter.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.407-410
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• 2002

As a part of electro-mechanical totally implantable artificial heart, a transcutaneous energy transmission system has been developed. By mutual magnetic induction between the first coil on the skin and the subcutaneously implanted second coil, the system transfers electrical power through the skin. This research aimed a minimizing the size of the implanted part as well as maximizing the transfer efficiency. When an air gap is 1$\sim$2cm, voltage gain and current gain low and it is hard to transfer energy due to large leakage flux. That is, the required input voltage and input current must be large compared with the output voltage and output current, respectively, This paper research the inverter topology and the control method in order to increase the voltage gain and the current gain. For this purpose, this inverter employs double tune to compensate the large leakage inductance of primary and secondary of the transcutaneous transformer. And the output energy of transcutaneous energy transmission system supply for Lithium-ion battery charger.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.75-80
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• 2003

In this paper, we designed add current scan system basically. Although NDT system using AC method in now days had problem with limit of detection rate and limit of device organization, in this paper, we made up these problem so that designed device smaller than system used, reduction of cost of system organization and precision of measuring crack. Also, AC leakage flux system had high accuracy about minute crack in the surface and advantage of designing system easily so that we designed system for concerning about crack of surface. Furthermore, it can be able to detect exact crack of reference in wide area by using DSP320C31 chip to reduce the time of measuring crack.

• Journal of the Korean Magnetics Society
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• v.14 no.4
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• pp.143-148
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• 2004

Effects of residual flux density M$_{res}$ and number of inspection on the detection voltage and flux density B of the gas pipeline were investigated in MFL inspection, which is widely used for the non-destructive inspection in a gas pipeline. A simulation equipment composed of the magnetizer and iron ring attached on an aluminum disc was constructed instead of a huge gas pipeline facility. With this system. the iron ring could be perfectly demagnetized and signals from the bolt screw stuck on the disc could be clearly detected so that the effects of M$_{res}$S and the inspection number on the detection voltage and B of iron ring were effectively investigated. With increasing the number of inspection, M$_{res}$, B of the iron ring and the detection voltage decreased and then kept at constant values while final M$_{res}$ increased with increasing initial M$_{res}$. If inspection condition were kept unchanged, the detection voltage was proportional to the last M$_{res}$ of the iron ring instead of B. This was probably due to magnetic hysteresis of the iron ring inherited from magnetic domain so that consideration on the magnetic hysteresis was inevitable in the analysis of MFL signal from defects of a gas pipeline. A new inspection scheme using the magnetizer with reversed magnetization in the subsequent inspection was proposed from the result that a high detection voltage could be obtained in the first inspection of gas pipeline with positive M$_{res}$.