• Transactions of the Korean Society of Mechanical Engineers B
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• 제21권1호
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• pp.68-78
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• 1997

A numerical study on the transient vapor flow and heat transfer is performed to investigate the ideal switching operation of heat source in a high temperature heat pipe. The cylindrical 2-dimensional compressible laminar vapor flow is assumed for the vapor space and the conjugate heat transfer for the heat pipe wall, wick and vapor space is calculated. The different boundary conditions such as constant heat flux, convective or radiative boundary at the outer wall are used respectively to compare the influence of boundary conditions on the transient operation. The transient temperature profile and the internal flow of the entire pipe for the switching operation are described as a result. The results show that the transient time is not significantly affected by the boundary conditions at the outer wall in present study. During the transition, two independent flows are observed temporarily on the right side and left side of the heat pipe. It is also found that the trend of temperature variation in the vapor region is different from the variation in the wick and wall region.

• The Transactions of the Korean Institute of Electrical Engineers B
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• 제50권11호
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• pp.575-582
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• 2001

This paper presents a calculating method of switching angle for adaptive switched reluctance motor (SRM) drive of a drill. The operation of the SRM is completely characterized by the flux linked by one phase winding which depends only on the current in that same phase winding and the rotor position. An efficiently adaptive SRM drive is possible on appropriately scheduling the commutation angles with accurate rotor position, supplied current value and speed information. An adaptive SRM drive with reduction torque ripple should be controlled by an optimized phase current control along with rotor position. Therefore, we are suggested a computing method of switching turn-on and off angles for adaptationally SRM operation with varied rotor speed and load. To probe the computing method, we have some simulation and experiment, it is shown a good result that can be computing the optimized switching angles for an electric drill motor.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.131-134
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• 2002

In this work, we have developed a systematic way of utilizing the basic design tools for superconductive electronics. This include WRSPICE, XIC, margin program, and L-meter. Since the high performance analog-to- digital converter can be built with Rapid Single Flux Quantum (RSFQ) logic circuits the development of superconductive analog-to-digital converter has attracted a lot of interests as one of the most prospective area of the application of Josephson Junction technology. One of the main advantages in using Rapid Single Flux Quantum logic in the analog-to-digital converter is the low voltage output from the Josephson junction switching, and hence the high resolution. To design an 1-bit analog-digital converter, first we have used XIC tool to compose a circuit schematic, and then studied the operational principle of the circuit with WRSPICE tool. Through this process, we obtained the proper circuit diagram of an 1-bit analog-digital converter circuit. Based on this circuit we performed margin calculations of the designed circuits and optimized circuit parameters. The optimized circuit was laid out as a mask drawing. Inductance values of the circuit layout were calculated with L-meter. Circuit inductors were adjusted according to these calculations and the final layout was obtained.

• Proceedings of the KIPE Conference
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.23-26
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• 2001

This paper presents a digital motion control system for Reluctance Synchronous Motor (RSM) drives with direct torque control (DTC). The system consists of stator flux observer, torque estimator: two hysteresis band controllers, an optimal switching look-up table, IGBT voltage source inverter(VSI), and TMS320C31 DSP controller by using fully integrated control software. The stator flux observer is based on the combined voltage and current model with stator flux feedback adaptive control of which inputs are current, voltage and actual rotor angle for wide speed range. In order to prove the suggested motion control algorithm, There are some simulation and testing at actual experimental system. The developed digitally high-performance motion control system are shown a good motion control response characteristic results and high performance features using 1.0Kw RSM.

• Journal of the Korean Society of Safety
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• 제15권2호
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• pp.63-69
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• 2000

The constraint conditions are the stator voltage and the stator current to operate the motor in the flux weakening region. The maximum current is limited by the inverter current rating and the machine thermal rating. Given DC link voltage to control the motor in the flux weakening the maximum voltage is determined by considering PWM strategy, dead time, voltage drop of the inverter switching device, and the margin of the voltage for current forcing. In this paper, the new method to determine the available maximum voltage is derived by the quantitative method and by considering the factors of the voltage drop. The proposed method to determine the maximum voltage is very useful to improve the stability of the motor system and to enlarge the speed operation region in the flux weakening operation. Therefore the utility of the maximum voltage is increased.

• Journal of Power Electronics
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• 제16권2호
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• pp.572-583
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• 2016

In view of the speed control characteristics of induction traction motors and the problems of direct torque control (DTC) algorithms in current applications, this paper presents a DTC algorithm characterized by a symmetrical polygon flux control and a closed loop power control in the constant-torque base speed region and constant-power field-weakening region of induction traction motors. This algorithm only needs to add a stator flux control algorithm to the traditional DTC structures. This has the benefit of simplicity, while maintaining the features of traditional algorithms such as a rapid dynamic response, uncomplicated control circuit, reduced dependence on motor parameters, etc. In addition, it obtains a smoother flux trajectory that is conducive to improvement of the harmonic elimination capability, the switching frequency utilization as well as the torque and power performance in the field-weakening region. The effectiveness and feasibility of this DTC algorithm are demonstrated by both theoretical analysis and experimental results.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권1호
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• pp.32-39
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• 2012

With the aid of genetic algorithm (GA), global optimization with multiple geometry parameters is feasible in the design of switched flux permanent magnet (SFPM) machines. To investigate the advantages of global optimization over individual optimization, which has been used extensively for the design of SFPM machines, a comparison between the two approaches is carried out for the case of fixed copper loss and volume. In the case of individual parameter optimization, the sequence in which the individual parameters are optimized is very important. In the global optimization a better design can always be achieved although the corresponding torque density is found to be only slightly better than that of individually optimized with correct design sequence. By using the obtained global optimization results, the performance in machines having two types of stator and rotor pole combinations, i.e. 12/10 and 12/14, are compared, and it is shown that higher torque is exhibited in the 12/14 SFPM machine. Finally, this paper also demonstrates that global optimization, with the restriction of equal pole width, magnet thickness and slot opening, can maximize the torque density without significantly sacrificing other performance, such as cogging torque and overload capability.

• Journal of Magnetics
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• 제19권1호
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• pp.90-100
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• 2014

Position estimation that uses only active phase voltage and current is presented, to perform high accuracy position sensorless control of a SRM drive. By extracting the amplitude of the first switching harmonic terms of phase voltage and current for a PWM period through Fast Fourier Transform (FFT), the flux-linkage and position are estimated without external hardware circuitry, such as a modulator and demodulator, which result in increased cost, as well as large position estimation error, produced when the motional back EMF is ignored near zero speed. A two-phase SRM drive system, consisting of an asymmetrical converter and a conventional closed-loop PI current controller, is utilized to validate the performance of the proposed position estimation scheme in comprehensive operating conditions. It is shown that the estimated values very closely track the actual values, in dynamic simulations and experiments.

• Proceedings of the KIEE Conference
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.627-630
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• 1991

This study is about vector controlled inverter for high quality elevator drive that is to improve the settling accuracy of elevator car and passenger's comfort in commercial buildings. In this study, an instantaneous space vector control type inverter was used to reduce the torque ripple ant to improve the velocity follow-up. This method calculates Instantaneous actual output torque and flux of induction motor by voltage and current, then compares them with a reference values by a speed regulator. The outputs of comparators select a switching mode, for an optimal voltage vector. Also, this study used IGBT (Insulated Gate Bipolar-Transistor), a high speed switching element, to reduce sound noise level, and DSP (Digital Signal Processor) was used to improve the reliability of the control circuit by fully digitalization.

• Proceedings of the KIEE Conference
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.600-604
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• 1991

In this paper, an advanced PWM modulation strategy for driving a variable-speed induction motor is introduced. According to this method, the technique of efficiently eliminating harmonics component is achived. A switching pattern was computed making use of the near-proportionality of voltage and frequency in AC machines operating with constant flux. At low magnitudes and low frequencies of the foundamental, many more harmonics are eliminated than at high magnitudes and frequencies. In order to keep the inverter switching frequency constant over the output frequency range, chopping times diminishes as the frequency of the fundamental increases.