• Journal of Power Electronics
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• v.16 no.6
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• pp.2162-2172
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• 2016

This paper presents a Direct Torque Control (DTC) strategy for the five-phase induction motor driven by a three-level five-phase inverter in order to improve the performance of the five-phase induction motor. In the proposed DTC technique, only 22 voltage vectors out of 243 available voltage vectors in a three-level five-phase inverter are selected and are divided in 10 sectors each with a width of $36^{\circ}$. The four different DTC combinations (DTC-I, II, III and IV) for a three-level five-phase induction motor drive are investigated for improving the performance of five-phase induction motor. All four of the DTC strategies utilize a combination of the same large and zero voltage vectors, but with different medium voltage vectors. Out of these four techniques, DTC-II gives the best performance when compared to the others. This DTC-II technique is analyzed in detail for improvements in the performance of five-phase induction motor in terms of torque ripple, x-y stator flux and Total Harmonics Distortion (THD) of the stator phase current when compared to its two-level counterparts. To verify the effectiveness of the proposed three-level five-phase DTC control strategy, a DSP based experimental system is build. Simulation and experimental results are provided in order to validate the proposed DTC technique.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.556-565
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• 1995

The physical model of interest is based upon the concentric cylinder, where the outside cylinder is filled with optically thick and high temperature phase change material(PCM). The fluid is flowing through the inside cylinder to transfer the appropriate energy. The fluid is flowing through the inside cylinder to transfer the appropriate energy. The governing equations for the phase change material including internal thermal radiation and for the turbulent transfer fluid have been employed and numerically solved. The optically thick phase change justifies the P-l spherical harmonics approximation, which is believed to be appropriate choice particularly for the much coupled problem like in this study. The solid/liquid interface, temperature distribution within the PCM and the heat flux from the PCM to the transfer fluid have been obtained and compared with those of laminar transfer fluid. The numerical results show that the turbulent transfer fluid accelerates the solid/liquid interface and results in the increase of heat transfer rate from the PCM. The internal thermal radiation within the PCM, however, does not always playa role to increase the heat transfer rate throughout the inside cylinder. It is believed that the combined heat flux has been picked up more in the inflowing area than in the pure conductive phase change material.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.33-38
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• 2008

For study on the unsteady blockage effect, flows around a rotationally oscillating circular cylinder with relatively low forcing frequency in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The computed results of the oscillating cylinder in the test section showed that the fluctuations of lift and drag are augmented by the blockage effects. The drag further increases because of low base pressure. The pressure on the test section wall shows the harmonics having the oscillating and the shedding frequencies contained in the blockage effect.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.103-108
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• 1995

We propose an analyzing method of the harmonics of output voltage in salient pole syochronous generator. In simulation, 2-D finite elerrent method is used for calculating the stator coil flux linkage considering the rotor movement. As an application of the proposed method, we calculated the harrronics of output voltage in the 150 kw class syochromus generator and compared it with the experirrental result.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.38-40
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• 2008

This paper presents the torque ripple and vibration characteristic of interior type permanent magnet (IPM) motor according to rotor design. In the design methods, the optimal notchs are put on the rotor pole face, which have an effect on variation of permanent magnet (PM) shape or residual flux density of PM. Through the space harmonics field analysis, the positions of notch are found and the optimal shapes of notch are decided by using Finite Element Method (FEM). The validity of the proposed method is confirmed with experiments. Therefore, the vibration, starting current and efficiency of IPM is measured by experiment.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.453-456
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• 2001

The thrust control characteristics of single-sided linear induction motor (SLIM) is achieved using PI controller in this paper. The trembling of air gap length between the primary winding and the secondary structure of the SLIM must be minimized in order to get quick response results. Also, the input voltage of SLIM is involved with the time harmonics because most SLIM is driven by inverter. According to the feedback linear control system, this paper describes with applying the non-linear control, speed and estimated flux algorithm. At the result of this experiment, we reached to the improvement of thrust characteristics with PI controller.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.619-622
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• 1991

In this paper, a digitalization of Induction Motor Vector Control System is proposed, where all processings are executed by using a processor. In Vector Control System, where the motor voltages are controlled by using the motor voltage model, the variation of the rotor flux-interlinkage is very small however the deviation of the torque becomes large. Thus, in order to enhance the torque performance, voltage model based vector control scheme with minor current loops, which can eliminate the high frequency current harmonics is used.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.122-124
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• 2003

This paper deals with the magnetic field analysis and compution of cogging torque using an analytical method in high speed brushless motor/generator. The magnetic field is analyzed by solving space harmonics field analysis due to magnetizing distribution and the cogging torque is analyzed by combining field analysis with relative permeance.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.11-14
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• 2001

Direct torque control (DTC) scheme provides a very quick torque response without the complex field-orientation block and inner current regulation loop. DTC is known as an appropriate scheme for high power induction motor drives because it can be used at lower switching frequency There are a major drawbacks with the application of DTC schemes it is large current harmonics due to flux drooping in a low speed range. In order to solve the problem, the fuzzy variable switching sector scheme are adopted in this paper. A meaningful contribution of this paper is to propose a simple realization scheme of the fuzzy variable switching sector technique. Experimental results show the effectiveness of this proposition.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.109-113
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• 2001

A high-efficiency electronic ballast for HID lamps is presented. The ballast consists of a PFC and a resonant inverter. To reduce losses of ballast,7C link voltage is determined by taking into account the peak voltage of lamp and a filter-inductor at Bridge diode is employed in order to remove harmonics from PFC. The flux density B$_{m}$ is kept 0.2[T] on all of inductors. A small inductor is connected in series with an electrolytic capacitor of PFC to be operated no high-frequency components. The acoustic resonance is eliminated using the spread spectrum technique. Electronic ballast for 250W metal-halide lamp is implemented and the experimental results show that 97% efficiency, no acoustic resonance and low conducted EMI level.l.