• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.47-51
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• 2022

With the innovative development of bio, pharmaceutical, and semiconductor technologies, it is essential to demand a next-generation transfer system that minimizes dust and vibrations generated during the manufacturing process. In order to develop dust-free and non-contact transfer systems, the high temperature superconductor (HTS) bulks have been applied as a magnet for levitation. However, sintered HTS bulk magnets are limited in their applications due to their relatively low critical current density (J_c) of several kA/cm² and low mechanical properties as a ceramic material. In addition, during cooling to cryogenic temperatures repeatedly, cracks and damage may occur by thermal shock. On the other hand, the bulk magnets made by stacked HTS tapes have various advantages, such as relatively high mechanical properties by alternate stacking of the metal and ceramic layer, high magnetic levitation performance by using coated conductors with high J_c of several MA/cm², consistent superconducting properties, miniaturization, light-weight, etc. In this study, we tried to fabricate HTS tapes stacked bulk magnets with 60 mm × 60 mm area and various numbers of HTS tape stacked layers for magnetic levitation. In order to examine the levitation forces of bulk magnets stacked with HTS tapes from 1 to 16 layers, specialized force measurement apparatus was made and adapted to measure the levitation force. By increasing the number of HTS tapes stacked layers, the levitation force of bulk magnet become larger. 16 HTS tapes stacked bulk magnets show promising levitation force of about 23.5 N, 6.538 kPa at 10 mm of levitated distance from NdFeB permanent magnet.

• Journal of IKEEE
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• v.22 no.4
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• pp.1206-1209
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• 2018

Single-layer winding configuration in a 12-slot 10-pole Permanent Magnet Synchronous Motor (PMSM) has been adopting in electrical power steering (EPS) systems to get the high fault tolerance capability of the motor. However, the motor with single-layer winding has magnetic circuit saturations in the teeth, which deteriorates its performance. In this paper, we propose asymmetric teeth widths to get over the demerit, and analyze the effect of the teeth width ratio variations on the performances of the PMSM. As a result, we suggest the most valuable teeth width ratio for designing the PMSM with a single-layer winding configuration.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.649-652
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• 1992

ECR(Electron Cyclotron Resonance) occure at ${\omega}_c$=${\omega}$, ${\omega}_c$:electron cycltron frequency, ${\omega}$:electromagnetic wave frequency. ECR system have several merit, 1) power transefer efficiency 2) low neutral gas pressure (below 1 mTorr) 3) high plasma density($10^{12}$ $cm^{-3}$). It is applicated variously in the field of semiconductor and new materials as the manufacturing equipment. Magnetic field in ECR system contruct resonance layer (${\omega}$=2.45GHz, $B_z$=875 Gauss) and control plasma. Plasma is almost generated at resonance layer. If the distance between substrate and resonance layer is short, uniformity of plasma is related with profile of resonance layer. Plasma have the property "Cold in Field", so directonality of magnetic field is one of the control factors of anisotropic etching. In this study, we calculate B field and flux line distribution, optimize geometry and submagnet current and improve of magnetic field directionality (99.9%) near substrate. For the purpose of calculation, vector potential A(r,z) and magnetic field B(r,z), green function and numerical integration is used. Object function for submagnet optimization is magnetic field directionality on the substrate and Powell method is used as optimization skim.

• Journal of Magnetics
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• v.21 no.3
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• pp.405-412
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• 2016

In general, surface mounted PM synchronous motors (SPMSMs) are mainly adopted as a driving motor for high-speed applications, because they have high efficiency and high power density. However, the SPMSMs have some weak points such as the increase of magnetic reluctance and additional losses as a consequence of using a non-magnetic sleeve. Especially, the magneto-motive force (MMF) in the air-gap of the SPMSMs is weakened due to the magnetically increased resistance. For that reason, a large amount of PM is consumed to meet the required MMF. Nevertheless, it cannot help using the sleeve in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. Thus, in this paper, a multi-layer interior PM synchronous motor (IPMSM) not using the sleeve is presented and designed as an alternative of a SPMSM. Both motors are evaluated by test results based on a variety of characteristics required for an air blower system of a fuel cell electric vehicle.

• The Journal of Advanced Prosthodontics
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• v.2 no.3
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• pp.65-70
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• 2010

Large oro-facial defects result from cancer treatment consequences in serious functional as well as cosmetic deformities. Acceptable cosmetic results usually can be obtained with a facial prosthesis. However, retention of a large facial prosthesis can be challenging because of its size and weight. This article describes prosthetic rehabilitation of a 57-year-old man having a right lateral mid-facial defect with intraoral-extraoral combination prosthesis. A modified technique to fabricate a hollow substructure in heat-polymerizing polymethyl-methacrylate to support silicone facial prosthesis was illustrated. The resultant facial prosthesis was structurally durable and light in weight facilitating the retention with magnets satisfactorily. This technique is advantageous as there is no need to fabricate the whole prosthesis again in case of damage of the silicone layer because the outer silicone layer can be removed and re-packed on the substructure if the gypsum-mold is preserved.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1721-1726
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• 2016

4-types of coils were prepared by coating with polyamideimide (PAI) organic/inorganic hybrid. One type was made with original PAI vanish and the other 3-types were made of double layers, that was to say, high flexural PAI layer and high anti-corona PAI/nanosilica (15 wt%) layer. Drying temperature (T/D) were $220^{\circ}C$, $240^{\circ}C$, and $260^{\circ}C$, respectively and rectangular type coil for high-voltage rotating machine was used. DC and AC electrical breakdown tests were carried out in order to study the insulation properties according to T/D temperature and coil curvature (5, 15, and $25mm{\Phi}$). As the curvature increased, electrical breakdown voltage decreased and as T/D temperature decreased, electrical breakdown voltage increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1292-1298
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• 2003

In this paper, dc reactor lot the inductive high-Tc superconducting fault current limiter (SFCL) was optimally designed by finite element method(FEM). The Prototype high-Tc do reactor was manufactured and compared to the results of design. This dc reactor consists of 4∼stacked double pancake coils which are wounded with Bi-2223 wire coated with SUS315L. Kapton tape is used for the insulation of turn to turn and layer to layer. Each pancake is connected in series by soldering Finally, optimal design and manufacture method lot the dc reactor is suggested in this paper. Through the comparison of result of optimal design and experimental result of prototype high-Tc superconducting dc reactor, reliance on the design of the high-Tc dc reactor tot the 1.2 kV/80 A SFCL is proved.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.741-742
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• 2006

This paper deals with an efficient superconducting joint method between 2G high superconducting(HTS) wire, YBCO coated conductor(CC). Recently CC is one of the most promising superconducting wire due to high n-value and critical current independency from external magnetic field. It is expected to be used many superconducting application such as fault current limiter, persistent current system and cable etc. In most HTS applications, superconducting magnet is used, and it is necessary to joint between superconducting wire to fabricate superconducting magnet system. A CC tape used in this research consists of copper stabilizer, silver layer, YBCO layer, buffer and substrate. Direct joint using soldering method was inefficient due to resistance of copper, then copper lamination is removed by chemical etching method to reduce resistance between CC tapes. Jointed tapes were fabricated and tested. Transport current through jointed area and induced voltage were measured to characterize the I-V curve. Resistance between CC wire using chemical etching was compared with resistance of direct jointed tapes using soldering method in this paper.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.152-163
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• 2004

This paper presents a sensorless speed control of cylindrical permanent magnet synchronous motors(PMSM) using an adaptive integral binary observer In view of composition with a main loop regulator and an auxiliary loop regulator, the binary observer has a property of the chattering alleviation in the constant boundary layer. However, the steady state estimation accuracy and robustness are dependent upon the width of the constant boundary. In order to improve the steady state performance of the binary observer, the binary observer is formed by adding extra integral dynamics to the switching hyperplane equation. With the help of integral characteristic, the rotor speed can be finely estimated and utilized for a sensorless speed controller for PMSM. Since the Parameters of the dynamic equations such as machine inertia or a viscosity friction coefficient are lot well known, there are many restrictions in the actual implementation. The proposed adaptive integral binary observer applies an adaptive scheme so that observer may overcome the problem caused by using the dynamic equations and the rotor speed is constructed by using the Lyapunov function. The observer structure and its design method are described. The experimental results of the proposed algorithm are presented to demonstrate the effectiveness of the approach.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.1
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• pp.1-12
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• 1999

A design and DSP-based implementation of robust nonlinear speed control of a permanent magnet synchronous motor(PMSM) under the unknown parameter variations and speed measurement error is presented. The model reference adaptive system(MRAS) based adaptation mechanisms for the estimation of slowly varying parameters are derived using the MIT rule. For the disturbances or quickly varying parameters, a quasilinearized and decoupled model which includes the influence of parameter variations and speed measurement error on the nonlinear speed control of a PMSM is derived. Based on this model, a boundary layer integral sliding mode controller to improve the robustness and performance of the nonlinear speed control of a PMSM is designed and compared with the conventional controller which employs Proportional plus Derivative(PD) control. To show the validity of the proposed scheme, simulations and DSP-based experimental works are carried out and compared with the conventional control scheme.