• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.340-342
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• 2005

This paper describes the speed-sensorless vector control system of a three-phase induction motor using sliding mode flux/speed observer. The sliding mode observer estimates the rotor speed. The error between the actual and observed currents converges to zero which guarantees the accuracy of the flux observer. The convergence of nonlinear time-varying observer along with the asymptotic stability of the controller was analyzed. To define the control action which maintains the motion on the sliding manifold, an "equivalent control" concept was used. It was simulated and implemented on a sensorless indirect vector drive for 750[W] three-phase induction motor. The simulation and experimental results demonstrated the effectiveness of the proposed estimation method.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1221-1226
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• 2008

Present, the cooling method of using a phase-change heat transfer such as immersed type, heat pipe etc is applied in cooling of high-capacity power semiconductors of the main power system for the high speed train with the concentrated traction. In order to apply these phase-change cooling system to the high speed EMU to be developed, needed are technological researches of consideration of installing space, air passage, light weight material and miniaturization. Although this research establishes design specifications through theoretical analysis and computational analysis from the basic design process of the cooling system of the propulsion system for the high-speed EMU, when details design is completed, present improvement subject and optimum design before manufacturing the prototype of the cooling system on the basis of analysis results. And then, carried out will be the performance tests through prototype manufacture and reliability estimation by components of cooling system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.3
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• pp.66-73
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• 2008

This paper presents a position sensorless control system of SRM over wide speed range. Due to the doubly salient structure of the SRM, the phase inductance varies along with the rotor position. Most of the sensorless control techniques are based on the fact that the magnetic status of the SRM is a function of the angular rotor position. The rotor position estimation of the SRM is somewhat difficult because of its highly nonlinear magnetizing characteristics. In order to estimate more accurate rotor position over wide speed range, Neural Network is used for this highly nonlinear function approximation. Magnetizing data patterns of the prototype 1-hp SRM are obtained from locked rotor test, and used for the Neural Network training data set. Through measurement of the flux-linkage and phase currents, rotor position is able to estimate from current-flux-rotor position lookup table which is constructed from trained Neural Network. Experimental results for a 1-hp SRM over 16:1 speed range are presented for the verification of the proposed sensorless control algorithm.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.4
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• pp.219-221
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• 2002

This paper presents an electric scooter development using blushless DC motor. In recent scooters was to develop for sport leisure and short transportation. Most of scooter are used petroleum gas. This gas scooter has disadvantage to pollute the air. Some of scooters have developed by DC motor which require a brush. However brushless motors have higher maximum speed and greater capacity, save maintenance labour and produce less noise. There is also greater freedom in planing the usage of brushless motors. In this paper we develop an electric scooter driving BLDC motor for design smart system and control speed of scooter with current reference signal to apply voltage to motor by means of three phase inverter. Using accelerator device we generate current reference to control speed and send the current to a MICOM by A/D converter. This MICOM produces the voltage signal and hall sensors signal and PWM controller drive three phase inverter to minimize error between the reference and an actual current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.455-458
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• 2011

4:10 deserializer is proposed to recover 1:10 serial data using 1/4-rate clock. And then, 1/4-rate CDR(Clock and Data Recovery) circuit was designed for SERDES of high-speed serial display interface. The reduction of clock frequency using 1/4-rate clocking helps relax the speed limitation when higher data transfer is demanded. This circuit is composed of 1/4-rate sampler, PEL(Phase Error Logic), Majority Voting, Digital Filter, DPC(Digital to Phase Converter) and 4:10 deserializer. The designed CDR has been designed in a standard $0.18{\mu}m$ 1P6M CMOS technology and the recovered data jitter is 14ps in simulation.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.318-320
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• 2007

Single-phase cycloconverters are widely used for ac-ac power conversion especially for speed control of ac drives. In this paper, a new single-phase to single-phase Z-source cycloconverter topology is proposed. The proposed single-phase Z-source cycloconverter can boost to a desired voltage with various frequency. Thus, it is called a frequency step-down and amplitude voltage step-up converter. The operating principle of the proposed topology is presented. Analysis and simulation for this single-phase Z-source cycloconverter are also presented.

• Korea-Australia Rheology Journal
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• v.16 no.3
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• pp.153-160
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• 2004

Open microcellular foams having small-sized cell and good mechanical properties are desirable for many practical applications. As an effort to reduce the cell size, the microcellular foams combining viscosity improvers into the conventional formulation of styrene and water system were prepared via high internal phase emulsion polymerization. Since the material properties of foam are closely related to the solution properties of emulsion state before polymerization, the flow behavior of emulsions was investigated using a controlled stress rheometer. The yield stress and the storage modulus increased as viscosity improver concentration and agitation speed increased, due to the reduced cell size reflecting both a competition between the continuous phase viscosity and the viscosity ratio and an increase of shear force. Appreciable tendency was found between the rheological data of emulsions and the cell sizes of polymerized foams. Cell size reduction with the concentration of viscosity improver could be explained by the relation between capillary number and viscosity ratio. A correlative study for the cell size reduction with agitation speed was also attempted and the result was in a good accordance with the hydrodynamic theory.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.12 s.189
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• pp.30-37
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• 2006

In this work, the surface integrity smoothened with a ball end mill was investigated. Because surface integrity mainly affects the manual finishing process, $RV_{AM}$(Remaining Volume After Machining) was introduced, and it gives the relation between machining process and finishing process. Runout and phase shift which adversely affect surface integrity were considered in the generation of surface topography. Cutting points in ball end milling were identified with positional vectors and a set of vectors which have the minimum height in unit area was selected for the generation of surface and $RV_{AM}$. $RV_{AM}$ variation according to runout and phase shift was calculated and experimentally verified in proposed HSM conditions for mold machining. From the simulations and the experiments, a desirable High Speed Machining condition was suggested.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.9
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• pp.6-13
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• 1993

In is well-known that system performance in the high speed digital radio communication system is usually deteriorted due to the frequency selective fading distortion. In this paper, bit error rate(BER) performance by the reception phase error in cellular mobile communication systems is derived and analyzed. The system is modeled as a frequency selective fast Rayleigh fading channel corrupted by additive white gaussian noise(AWGN) and co-channel interference(CCI). Our numerical results show that for the 24KBaud(48Kb/s) $\pi$/4-DQPSK operated at carrier frequency 800 MHz and C/I<20 dB, the BER will be dominated by CCI if the vehicular speed is below 100 Km/h. The results show that performance, when reception phase error is below $\pi$/12, is deterioreted less than 3 dB, and that performance, when reception phase error is above $\pi$/12, is degraded over 3 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.861-864
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• 2005

In this paper, we system the system design and numerical analysis of the ultrafast optical delay line using by optical phase modulator. The numerical analysis carried out with 1310nm, lops laser and electro-optic phase modulator. As the results of numerical analysis, we show a scanning rate of 0.5 GHz and a delay range of 19.0ps. Compare with mechanical delay line, the optical delay line has a high scanning speed and a high repetition rate.