• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.3
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• pp.253-257
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• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.59-68
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• 2010

The aim of this work is to analyze high temperature flows around an axisymmetric blunt body taking into account chemical and vibrational non-equilibrium state for air mixture species. For this purpose, a finite volume methodology is employed to determine the supersonic flow parameters around the axisymmetric blunt body. This allows the capture of a shock wave before a blunt body placed in supersonic free stream. The numerical technique uses the flux vector splitting method of Van Leer. Here, adequate time stepping parameters, along with Courant, Friedrich, Lewis coefficient and mesh size level are selected to ensure numerical convergence, sought with an order of $10^{-8}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.517-520
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• 2003

The snow-fatting measurement system including the snow sensor applying the photo-coupler is investigated in this study and using this snow sensor the height of snow fallen is measured. To measure the snow depth, five photo sensors are arranged with 5 mm distance. The snow-falling measurement system, which is measuring the motor revolution controlled with stepping motor, is mounted above the snow surface. From this work, it is feasible to measure quantitatively the snow on real time. Its software implements a proven method to achieve valid measurements also under difficult conditions as future study. In cases where the snow sensor is applieded to the prediction of snow in the meteorological observation system and the snow removing system, it is recommend the GRS-Option in order to improve the quality of snow measurements for better compensation.

• Journal of Magnetics
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• v.20 no.4
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• pp.400-404
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• 2015

Various kinds of winding arrangements can be used to enable fault current limiters (FCL) to tolerate higher forces without resulting in a substantial increase in construction and fabrication costs. In this paper, a distributed winding arrangement is investigated in terms of its effects on the short-circuit forces in a three-phase FCL. The force magnitudes of the AC supplied windings are calculated by employing a finite element-based model in the time stepping procedure. The leakage flux and radial and axial force magnitudes obtained from the simulation are compared to those obtained from a conventional winding arrangement. The comparison shows that the distributed winding arrangement significantly reduces the radial and, especially, the axial force magnitudes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.269-275
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• 1988

In this paper, a high efficiency motor drive system which improves the multi-step response of PM step motors by reducing the transition time of the motor drive current, is studied by designing a dual-voltage drive circuit. The designed drive circuit eventually prevents the motor from decreasing drive torque while the stepping rate is increased. The method of designing a dual-voltage drive circuit with the motor specifications is suggested in order to improve the response of step rate and drive efficiency. Also, despite improving the power efficiency on motor driving, the response characterstics suggested by the motor manufacture's specifications are satisfied without any special deficiency.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.680-681
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• 2015

This paper proposes a comparative study of dual-airgap flux switching permanent magnet (FSPM) and spoke-type interior permanent magnet (S-IPM) machines equipped with phase-group concentrated-coil (PGCC) windings. Both of the investigated machines are the same size and material amounts which are compared at the same operating conditions. All the relevant machine performance including back electromotive force (EMF), cogging torque, and electromagnetic torque are analyzed by a 2-D time-stepping finite element method (FEM).

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.312-316
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• 2005

The single phase induction motor has been commonly applied to small-sized electrical appliances because of its low cost, but it has low efficiency and large torque ripple, and it is incapable of speed control. However, two-phase induction motors have small torque ripple, high efficiency and variable speed control, because they are inverter fed. In this paper, the dynamic characteristics of the two-phase induction motor, such as the torque ripple, current and speed, are analyzed by using the time-stepping finite element method, and compared with the cage-type single phase induction motor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.797-806
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• 2000

In this paper, the torque characteristics and the bar loss distribution are analyzed when a general cage induction motor with skewed slots is fed by a 6-step inverter. For the electromagnetic analysis, time-stepping finite element method is used. And the multi-slice technique and sliding surface technique are respectively utilized to consider the skew effect and the rotation of the rotor. As a result, the effects of skewed rotor bar and the inverter output voltage on the characteristics of the torque and bar loss in the rotor are investigated. The simulation results are verified by measurement of flux density distribution axially in the stator teeth.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.611-613
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• 2000

Rotor eccentricity exists extensively in BLDC motors because of manufacturing imprecision or bearing defects. In this paper, magnetic fields of a BLDC motor with static rotor eccentricity are analyzed by the time- stepping finite element method. Torque ripple, cogging torque, winding current, counter-em! and unbalanced magnetic force characteristics are obtained. These results are compared with those of a non-eccentric BLDC motor.

• The Journal of Korea Robotics Society
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• v.12 no.1
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• pp.78-85
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• 2017

This paper presents the development of a 3D printer based piezo-driven vertical micro-positioning stage. The stage consists of two flexure bridge structures which amplify and transfer the horizontal motion of the piezo-element into vertical motion of the end-effector. The stage is fabricated with ABS material using a precision 3D printer. This enables a one-body design eliminating the need for assembly, and significantly increases the freedom in design while shortening fabrication time. The design of the stage was optimized using response surface analysis method. Experimental results are presented which demonstrate 100nm stepping in the vertical out-of-plane direction. The results demonstrate the future possibilities of applying 3D printers and ABS material in fabricating linear driven motion stages.