• Journal of Power Electronics
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• v.9 no.2
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• pp.146-155
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• 2009

The static frequency converter (SFC) systems are used as a method of driving large synchronous machines in many power and industrial plants. In this paper, new control algorithms of SFC systems for starting gas turbo sets are proposed for a four quadrant operation: start-up at standstill; an acceleration up to the speed of the rated voltage; field weakening to reach the rated speed; synchronization to the main alternating current (AC) source; and dynamic braking to stop safely within the rating of the synchronous machine. Experimental results show that the proposed algorithms are proper and effective.

• Progress in Superconductivity and Cryogenics
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• v.7 no.3
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• pp.21-28
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• 2005

Superconducting synchronous motors and generators have the field coil composed of superconductor with almost zero resistance at superconducting state. Therefore, copper loss at the conventional field coil is eliminated and the superconducting machine gets higher efficiency. The armature coil of the superconducting machine is composed of copper wire and supported by non-magnetic material such as FRP (Fiber Reinforced Plastic) This paper contains the design Procedure of a 1MW superconducting synchronous motor using high-temperature superconductor only for the field coil. Especially, the armature coil is designed by water-cooling in order to dissipate Joule heat easily. Moreover, 3-dimensional electromagnetic design is conducted to get a proper design result and reduce design errors from 2-dimensional approach.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.132-138
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• 2014

We investigated the harmonic voltages generated by a synchronous machine adding d-axis and q-axis harmonic field windings to reduce the harmonics in a power line. First, electronic circuits such as a frequency multiplier, band-pass filter, and phase shifter were newly designed and made to carry out the experiment. Next, an experimental circuit, for which an AC voltage of frequency 6f synchronized to the power line voltage of frequency f could be obtained, was constructed to examine the generation of harmonic voltage in more detail. Finally, an experiment involving the generation of harmonic voltage was performed using an experimental synchronous generator with harmonic windings in the d-axis and q-axis. In this paper, the power spectrum and the waveforms of the harmonic voltages in the armature winding are presented. Moreover, the values calculated from theoretical expressions of harmonic voltages in armature winding are compared with the values obtained by the experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.104-112
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• 2006

SFC(Static Frequence Converter)system has come to be used as drive large synchronous machine in many industry applications. Many papers have been presented on the control algorithm of SFC system, not the acceleration and start-up but the rated speed operation with line connection and the braking operation with regeneration which is used in the industry. Among this, this paper presents the regeneration breaking control algorithm for a large synchronous machine using SFC system. The results of experiment show that the proposed algorithm is proper and effective.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.32-36
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• 2007

On the contrary of a conventional motor with very narrow air-gap. it is difficult to calculate the accurate magnetic field distribution and the performance of an air-cored superconducting motor by 2 dimensional analysis. which does not use high permeability material except outer machine shield. This paper aims to do analysis of magnetic field and force distribution from the 3 dimensional modelling of a 1MW class superconducting synchronous motor. Especially. the field coil composed of Bi-2223 high-temperature superconductor and the outer machine shield are modelled by finite element analysis software according to their structures and the self-inductance and Lorentz force are calculated based on the 3 dimensional magnetic field calculation. Moreover. the influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.19-20
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• 2009

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.61-67
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• 2007

In this article, a special kind of axial flux permanent magnet machine has proved to be suitable for high torque and low speed applications. An innovative design of the machine has been proposed in order to make the machine suitable for traction applications by means of field-weakening. The aim of this paper is to analyze, in general terms, the basic equations that describe the operating conditions of such machines. Optimal sizes for design can be obtained by calculating the power density and the air-gap flux density, etc.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.437-442
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• 2013

For open-end permanent magnet synchronous machine(PMSM) with dual inverter system, where one inverter is connected to the source and the other is flying, the dc link voltage of the flying inverter can be boosted through the machine. For this reason, when compared with single inverter drive system, higher voltage can be applied to PMSM, and higher torque can be generated in the flux weakening region. In this case, however, active and reactive powers are separately supplied by each inverter to maintain the dc link voltage of flying inverter. Therefore, the required flux weakening control is different from the conventional method for a single inverter drive system. This paper proposes the novel flux weakening control method which maximizes the active voltage component in a dual inverter PMSM drive system. The proposed method was demonstrated and verified through experimental results.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1360-1361
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• 2011

본 논문은 Synchronous Machine을 기반으로 하여 250[kVA]의 용량을 가지는 플라이휠을 모델링하고 그 예를 수학적으로 해석함으로써 분산전원으로서의 신재생에너지와 연계하여 에너지를 저장/출력할 수 있는 타당성을 검토할 수 있도록 한다.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.8-14
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• 2007

This paper deals with the electrical design and analysis of a 300HP, 60,000rpm permanent magnet synchronous motor for turbo machine. The design is performed by analytic method of magnetic field theory. And electrical losses of the motor driven by current with sinusoidal and harmonic form are analyzed by using FEM.