• Journal of Power Electronics
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• v.12 no.1
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• pp.128-135
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• 2012

In this paper, different switching tables proposed for the Direct Torque Controlled (DTC) of a six-phase induction machine are simulated and implemented. A six-phase induction motor has 64 space voltage vectors which result in increased complexity in the selecting of inverters switching. The unsuitable selection of a switching table leads to large harmonics especially at low speed and it also reduces drive efficiency. A six-phase induction machine has large zero sequence harmonic currents of the order $6{\kappa}{\pm}1$. These harmonic currents are varied in various techniques. Decreasing this loss is essential in a six-phase induction machine. The main purpose of this paper is to improve the ST-DTC of six-phase induction machines to reduce the voltage and current harmonics and the torque pulsation. Selecting a suitable method for minimizing these harmonics is very important.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.3
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• pp.360-366
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• 2018

In shipyards hull forming is performed by the line heating method using a gas torch and by cold treatment using a roll-press. However, this forming process has some issues, such as difficulties in controlling and accurately estimating the amount of the heat input, as well as a harsh working environment due to exposure to loud noises and air pollution. The induction heating method, which is introduced in this paper, exhibits good control and allows for the estimation of precise heat input. Also, workers can carry out the induction heating in a comfortable working environment. In this research, the induction heating simulation, which consists of electro-magnetic, heat transfer and thermal elasto-plastic analysis, was developed and modified through induction heating experiments. Finally, the effective heating coil was designed for the automatic hull forming system based on the results of induction heating simulation. For the purposes of a future study, if an algorithm to obtain optimal working conditions is developed, automatic systems for hull forming can then be constructed.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.16-18
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• 2008

Several methods are proposed in the literature for losses segregation of single phase induction motor. Generally we could divide two methods for experimental determination of losses segregation for single phase induction motor. The one is relatively complicated method based on Parameter estimation of single phase induction motor. The other is simple method based on IEEE Standard 114. Segregation of losses in single phase induction motor is more complicated than that in three phase induction motor, because of the backward magnetic field component in the motor and multiplicity of different single phase type. In this paper, therefore, we studied losses segregation of capacitor-run single phase induction motor.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.611-613
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• 2004

This paper is concerned with the simulation and determination of the input voltage and frequency for the optimal efficiency operation of induction motors. In general, induction motors have a specific character that operation efficiency is dropped sharply at the light roads condition. Consequently, if the induction motor is controlled by high efficiency using the VVVF(variable voltage variable frequency) control methods at optimal values, the entire system can obtain the substantial energy savings from the efficiency improvement in induction motors. In this paper, optimal slip is derived from the modeling of an induction motor and the optimal hybrid-control method is suggested by the simulation of the proposed algorithm for a 3-phase induction motor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.286-290
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• 2003

The high temperature superconducting bulk can be used as the bearing of induction motors. This paper presents the fabrication and test results of an induction motor with superconducting bearings using HTS bulks. The bearing had eight hexahedron type YBCO bulks. Height, width and thickness of the HTS bulk were 30mm, 30mm and 10mm, respectively. Single phase induction motor was used to drive the shaft made of aluminum and the rotor of a conventional induction motor. To estimate the performance of the HTS bulk magnetic bearing, no load test, load test and Impact test were carried out. Load tests were performed by using air resistance caused by the shaft-mounted thin cylinder with buckets. Impact tests by axial direction and vertical direction impact showed that the vibration of the shaft gradually decayed. The induction motor with HTS bulk magnetic bearing rotated silently and smoothly throughout the tests. According to the test results, conventional bearings can be replaced with superconducting magnetic bearings made of HTS bulks.

• 전기의세계
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• v.24 no.2
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• pp.78-83
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• 1975

There are many studies recently, on a wound rotor induction motor operation as synchronous rotating speed, and such an induction motor is so called an induction synchronous motor. In above desciption the region of pull into-step that the wound rotor induction motor as a synchronous motor has not been calculated. This paper deals with such a region. Generally, induction synchronous motor is different from a synchronous motor in many respects. In considering these respects, characteristic equations of motion for this motor are induced adoption small signal linearization, continuous quasili-nearization and state variable grouping technique. For pulling-into-step of Induction Synchronous Motor, we first analyze these equations with digital computer and compare the former with datas calculated by motor experimentation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.138-142
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• 2014

In general, the voltage stability of induction generator is lower than synchronous generator. However, induction generator has many advantages rather than a synchronous generator in terms of price and maintenance. So Induction generator is used little by little in small hydroelectric power station rather than 1000kW recently. Squirrel cage induction generator generates a high inrush current at the grid-connection. This high inrush current causes a voltage drop on the grid. In order to increase the penetration of the induction generator, it is necessary to present a method of reducing inrush current. In this study, we suggested that it is possible to present a reactor startup method, by applying the parameter to reduce the voltage drop.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.68-74
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• 2013

Induction-heated system is innovative system which applied IH(Induction Heating) magnetic induction heating generated from induction-heated metallic package and high-frequency power circuit technique for thermal converse technique. In this occurs not burning, so that the working environment and deterioration of products can be improved. This technique is used high frequency inverter. By using high frequency inverter high frequency in the range of kHz can be made with conventional alternative current. In this contribution IGBT module is used for high frequency inverter. In this paper are discussed analysis of characteristics according to the each frequency and produced Flat plate induction heating system using 1.5kW-class half-bridge resonant inverter. In addition, operating characteristics of the system to changes in the distance between the coil and the heater, applications of system are also discussed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.1
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• pp.1-6
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• 2016

Recently, proportion of the induction motor load is gradually increased. When a contingency in the power systems, it has been discovered phenomenon that the voltage is delayed recover caused mechanical characteristics of the induction motor load. It can be a serious impact on the voltage stability of the power system considering induction motor load. The scheme to mitigate this phenomenon tripping off the motors to prevent voltage drop and delayed voltage recovery on the load demand side. Fault induced delayed voltage recovery phenomenon is caused by stalling of small induction motor load in transmission level contingencies. In this paper, fault induced delayed voltage recovery phenomenon mitigation method implementation under voltage load shedding on the korean power system considering induction motor load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.103-107
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• 2016

In general, the voltage stability of induction generator is lower than synchronous generator. Induction generator has a number of advantages over the synchronous generator on the side of price and maintenance. So Induction generator has been applied to the small hydroelectric power of low output. Induction generator usually generates a high current during grid connection. The high current that occurs during grid connection can cause a voltage drop in the system. In order to increase the supply of the induction generator, it is necessary to propose a method of reducing high current. This paper proposes some method of the soft start to reduce voltage drop caused by the large starting current. soft-start method has high voltage drop effect than direct start method, control of firing angle can be increased the voltage drop effect.