• Journal of Power Electronics
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• v.12 no.1
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• pp.201-207
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• 2012

This paper presents the results and gained experiences from the Project Based Learning (PBL) of magnetic component design within a Power Electronics Course. PBL was applied during the laboratory exercises through a design-project task based on a boost converter test board. The students were asked to calculate the main boost converter's circuit parameters' capacitor C and inductor L, and then additionally required to design and build-up the inductor L, in order to meet the project's goals. The whole PBL process relied on ideas from the CDIO (Conceive, Design, Implement, Operate), where the students are encouraged to consider the whole system's process, in order to obtain hands-on experience. PBL is known to be a motivating and problem-centered teaching method that gives students the ability to transfer their acquired scientific knowledge into industrial practice. It has the potential to help students cope with demanding complexities in the field, and those problems they will face in their future careers.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1217-1231
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• 2016

In this research, a slotted patch antenna sensor is designed for wireless strain and crack sensing. An off-the-shelf RFID (radiofrequency identification) chip is adopted in the antenna sensor design for signal modulation. The operation power of the RFID chip is captured from wireless reader interrogation signal, so the sensor operation is completely battery-free (passive) and wireless. For strain and crack sensing of a structure, the antenna sensor is bonded on the structure surface like a regular strain gage. Since the antenna resonance frequency is directly related with antenna dimension, which deforms when strain occurs on the structural surface, the deformation/strain can be correlated with antenna resonance frequency shift measured by an RFID reader. The slotted patch antenna sensor performance is first evaluated through mechanics-electromagnetics coupled simulation. Extensive experiments are then conducted to validate the antenna sensor performance, including tensile and compressive strain sensing, wireless interrogation range, and fatigue crack sensing.

• Korean Journal of Optics and Photonics
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• v.20 no.1
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• pp.48-52
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• 2009

We make a simple electrically controllable linear polarization rotator over $360^{\circ}$ without loss by using a thick ECB(electrically controlled birefringence) liquid crystal cell and a quarter wave plate at 514.5 nm wavelength. Its operating principle can be analyzed and explained by using simple polarization analysis and experimental data. We demonstrate that the degree of polarization of the rotator is 0.964 and the temporal variation for 1 week lies within ${\pm}1$ degree. We can easily solve the problem of nonlinearity of the dependence of the rotational angle of linear polarization on the applied voltage by changing the utilized voltage range or its fitting curve.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.100-109
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• 2008

The finite volume time domain(FVTD) technique faces serious limitations in simulating electromagnetic scattering at high frequencies due to requirements related to discretization. A modified FVTD method is proposed for electrically large, perfectly conducting scatterers by partially incorporating a time-domain physical optics(PO) approximation for the surface current. Dominant specular returns in the modified FVTD method are modeled using a PO approximation of the surface current allowing for a much coarser discretization at high electrical sizes compared to the original FVTD scheme. This coarse discretization can be based on the minimum surface resolution required for a satisfactory numerical evaluation of the PO integral for the scattered far-field. Non-uniform discretization and spatial accuracy can also be used in the context of the modified FVTD method. The modified FVTD method is aimed at simulating electromagnetic scattering from geometries containing long smooth illuminated sections with respect to the incident wave. The computational efficiency of the modified FVTD method for higher electrical sizes are shown by solving two-dimensional test cases involving electromagnetic scattering from a circular cylinder and a symmetric airfoil.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.1-6
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• 2020

This paper presents the analysis results on the electrical output performance characteristics of a 746 W high temperature superconducting generator (HTSG). The HTS field winding is charged by non-contact excitation method, i.e., contactless superconducting field exciter (CSFE) which is originated by rotary flux pump based on permanent magnet. In this paper, the preliminary current charging test was carried out using a 70 A CSFE to evaluate the performance of field exciter and analyze its non-contact excitation characteristics for the full-scale HTS field winding of the 746 W HTSG. First, the various contactless current-charging tests were conducted using assembly with HTS field winding and CSFE. Then, in order to estimate the output power performance characteristics of the 746 W HTSG, finite element analysis was conducted based on field excitation information which is experimentally measured under various operating conditions. Finally, the electrical output characteristics in no-load and load models were simulated by two-dimensional transient solver in ANSYS electromagnetics 19.0 release.

• Journal of the Korean Magnetics Society
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• v.18 no.2
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• pp.54-57
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• 2008

Magnetic torquer, which uses torque between magnetic dipole moment and earth magnetic field, has been used to control attitude of satellites. In this work, we developed a magnetic torquer for small scientific satellite and test under environmental conditions of the satellite launching and orbital motion have been carried out. The developed magnetic torquer shows saturation magnetic dipole moment of $15Am^2$, linearity of 0.3 % in the range of ${\pm}12Am^2$, mass of 0.46 kg, and power consumption of 1 Watt at magnetic dipole moment of $10Am^2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.43-51
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• 1998

Most of fuel-injection system operated with mechanical methods are difficult to control the injection quantity and injection timing as well as injection rate exactly. Moreover high pressure injection scheme is never be realized with conventional one. On the other hand, serious air pollution can be lessened with injection system equipped with those functions. Therefore, electronically controlled Unit Injuctor(UI) appeared to satify above mentioned desires. However, it is still difficult that the most important part, especially solenoid valve, is analyzed precisely, because of the existence of complex combination of electromagnetics, electrics and dynamic problems. In this study, experimental and theoretical analysis are accomplished for understanding of solenoid valve characteristics and further its design. As the result, the follows are obtained 1) As the increase of wire diameter, the response time became shorter and optimal inductance existed in relative with the response time and wire diameter. 2) According to increasing input voltage, the traction force increased, otherwise the response time was shortened. 3) As the increase of armature stroke, the traction force decreased and the response time became longer.

• Journal of the Korean Magnetics Society
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• v.26 no.3
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• pp.81-85
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• 2016

This paper introduces a performance integration method to predict variation characteristic of a performance function of electromagnetic machines or devices due to manufacturing tolerances. A normalized performance function space and a hybrid mean value technique are adapted to effectively predict mean and variance, which can identify probabilistic distribution of the performance function. To verify the effectiveness and accuracy of the proposed method, a mathematical problem and a loudspeaker model are tested, and numerical results are compared with those of existing methods such as Monte Carlo simulation and univariate dimension reduction method.

• Journal of Magnetics
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• v.18 no.2
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• pp.135-141
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• 2013

This paper proposes an efficient fault detection method for onboard degaussing coils which are installed to minimize underwater magnetic fields due to the ferromagnetic hull. To achieve this, the method basically uses field signals measured at specific magnetic treatment facilities instead of time-consuming numerical field solutions in a three-dimensional analysis space. In addition, an analytical design sensitivity formula and the linear property of degaussing coil fields is being exploited for detecting fault coil positions and assessing individual degaussing coil currents. Such peculiar features make it possible to yield fast and accurate results on the fault detection of degaussing coils. For foreseeable fault conditions, the proposed method is tested with a model ship equipped with 20 degaussing coils.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.62-67
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• 2013

This paper introduces an effective methodology for reliability-based design optimization of electromagnetic products, where a performance measure approach is adopted to accurately assess probabilistic constrains. Two design problems consisting of a loudspeaker and a superconducting magnetic energy storage system are considered. The efficiency of the proposed method in evaluating the failure probability of performances during the optimization process are compared with the existing method based on the reliability index approach. Moreover, in term of the accuracy of probability failure values, optimized design results are examined with reference values obtained from the Monte Carlo simulation.