• Journal of Korean Society on Water Environment
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• v.36 no.2
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• pp.153-163
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• 2020

Magnetic separation technology is an efficient and environmentally friendly technology. Compared with the traditional wastewater treatment technology, the magnetic separation technology has its unique advantages and characteristics, and has been widely applied in the field of wastewater treatment. In particular, the emergence of superconducting magnetic separation technology makes possible for high application potential and value. In this paper, which through consulting with the literatures of Korea, Chinese, United States and other countries, the magnetic separation technology applied to wastewater treatment was mainly divided into direct application of magnetic field, flocculation, adsorption, catalysis and separation coupling technology. Advantages and limitations of the magnetic separation technology in sewage treatment and its future development were also studied. Currently, magnetic separation technology needs to be studied for additional improvement in processing mechanism, design optimization of magnetic carrier and magnetic separator, and overcoming engineering application lag. The selection, optimization and manufacturing of cheap magnetic beads, highly adsorbed and easily desorbed magnetic beads, specific magnetic beads, nanocomposite magnetic beads and the research of magnetic beads recovery technology will be hot application of the magnetic separation technology based on the magnetic carriers in wastewater treatment. In order to further reduce the investment and operation costs and to promote the application of engineering, it is necessary to strengthen the research and development of high field strength using inexpensive and energy-saving magnet materials, specifically through design and development of new high efficiency magnetic separators/filters, magnetic separators and superconducting magnetic separators.

• Journal of the Korean Magnetics Society
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• v.26 no.4
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• pp.137-141
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• 2016

There is a growing demand for non-contact current measurements for efficient use of electrical power and energy saving. In this study, I propose a non-contact current sensor using LC resonance by a resonance circuit composed of a sensor coil and 2 coupling coils for enabling a wireless measurement. The inductance of the sensor coil, which could be changed by applied current, causes the change of resonance frequency of the resonance circuit. A pair of magnet was attached to the ferrite core to apply a bias magnetic field that enabled the determination of the current direction. We obtained an output voltage change of 18 V with the current of -3~3 A. But, the output was nonlinear. In order to realize the non-contact current measuring method proposed in the present study, there is a need for a strict investigation of linearity and resolution for the future study.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.1-10
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• 2015

This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.

• Polymer(Korea)
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• v.26 no.1
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• pp.98-104
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• 2002

This study was investigated to fabricate the isotropic $Nd_2Fe_{14}B$/epoxy bonded magnets with high characteristics paroduced by compression molding. The magnetic characteristics of the bonded magnets were directly proportional to the density of the magnets and were enhanced by using raw $Nd_2Fe_{14}B$ magnetic powders, having the mean particle size of $200{\mu} m$.without additional milling process. The high characteristics of the bonded magnets were achieved at the following conditions: epoxy resin of 2.0 wt%, silane coupling agent of 0.8 wt%, curing agent of 0.7 wt% on the base of magnetic powders, and curing condition of $150^{\circ}C$/3 hrs. The bonded magnets at the optimum conditions indicated the high characteristics such as the density of 6.1 g/㎤, the remanent flux density of 7.1 kG, the maximum energy product of 9.7 MGOe, and the compressive strength of 17 kg/$mm^2$.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.23-28
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• 2008

As a part of the plasma control system (PCS) for the first plasma campaign of KSTAR, seven sets of fast feedback control loop for the superconducting poloidal field magnet power supply (PF MPS) have been implemented. A special real-time digital communication interface has been developed for the simultaneous exchanges of the current/voltage data from the 7 sets of 12-thyristor power supplies in a 200 microsecond control cycle. Preliminary power supply tests have been performed before actual cooldown of the device. A $29mH/50m{\Omega}$ solenoid dummy has been fabricated for a series of single power supply tests. Connectivity and response speed of the plasma control system have been verified. By changing hardware cabling, this load was also used to estimate mutual inductance coupling effects of two geometrically adjacent solenoid coils on each power supply. After the cooldown was complete, each pair of the up/down symmetric PF coils has been serially connected and tested as part of the device commissioning process. Bipolar operation and longer pulse attempts have been investigated. The responses of the coils and power supplies corresponding to the plasma magnetic controls in plasma discharges are also analyzed for the future upgrades.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.52-56
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• 2009

Interlayer coupling field, coercivity, magnetoresitance ratio, and magnetic sensitivity depending on the thickness of free CoFe layer for the CoFe/Cu/CoFe/IrMn multilayer are investigated. In case of CoFe layer of $30\;{\AA}$ thickness for the CoFe(t)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)/IrMn($80\;{\AA}$) multilayer with ferromagnet/non-magnet/ferromagnet structure induced by IrMn layer, the lowest coercivity and the highest magnetic sensitivity, which is contained soft magnetic property, are observed. On the other side, in case of CoFe layer of $90\;{\AA}$ thickness, there are the highest coercivity and the lowest magnetic sensitivity. The fabricated CoFe($30\;{\AA}$)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)]/IrMn($80\;{\AA}$) spin valve device with $2{\times}8{\mu}m^2$ patterning size are measured by two probe method, which is selected the sensing current as the longitudinal direction and the easy axis as the transversal direction. The measuring magntoresistance ratio and magnetic sensitivity of GMR-SV device having the soft magnetic property are 3.0% and 0.3%/Oe, respectively.