• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.235-243
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• 1998

For motor operation at low speeds and loads, torque pulsation by the cogging torque is often a source of vibration and control difficulty. In this paper, the magnetic field of a motor is calculated by finite element method. The periodic cogging torque is determined using Maxwell stress method and time stepping method, and then decomposed using fourier series expansion, The purpose of this paper is to characterize design parameters on the cogging torque and to design a permanent magnet motor with a cogging torque less vulnerable to vibration, without sacrificing the motor performance. The design parameters include stator slot width, permanent magnet slot width, airgap length and magnetization direction. A new design with a less populated frequency spectrum of the cogging torque is proposed after characterizing individual effect of design parameters. Magnet pole edge shaping, by gradually increasing the cogging torque with reduced higher harmonics.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.4
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• pp.189-198
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• 2006

In order to improve the reliability of stator windings for hydro generators, it is necessary to detect the defective point and life assessment of the high voltage windings. Especially the on-line partial discharge (PD) test provides the ability to monitor effects, such as slot discharge, internal discharge, and end-winding discharge without interrupting generators, this method has been proven the major testing technology in high voltage rotating machines nowadays. The purpose of this paper is to describe the method of the on-line PD measurement on stator windings for hydro-generator with 13 [kV] class ceramic coupler (CC), on-line PD measuring system, terminal box, and index parameters. Also, the developed PD measuring system and 13 [kV] class CC were installed Daechung-dam generator #2. It was found that this installed sensor and system had good electrical characteristics to detect PD activity during the operating condition with its detection frequency band is between several and several tens MHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.211-212
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• 2007

There have three kinds of partial discharge diagnosis testing: online, offline and dismantled testing on high voltage rotating machine. Our lab testing is dismantled testing, taking off pieces into individual parts of stator coil of high voltage rotating machine in laboratory. We investigate internal discharge, slot discharge, corona discharge and normal state on pre-made stator winding by using spiral patch antenna sensor. In this lab test we compare the experimental results of our spiral patch antenna sensor and reference commercial HFCT sensor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.64-69
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• 2012

In this paper, the optimal design of notch and barrier was carried out in order to improve characteristics of constant torque with minimizing the cogging torque occurred by teeth and slot structure. Optimized design was carried out by design of experiment and various characteristics including torque were studied by finite element method(FEM). In addition, in order to verify resonance frequency, natural frequency of the stator was analyzed by modal analysis.