• 한국전기전자재료학회논문지
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• 제19권11호
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• pp.1067-1071
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• 2006

Prior to destructive testing, diagnostic tests were performed in ten high voltage motors. Diagnostic tests included polarization infer, ac current, dissipation factor$(tan{\delta})$ and partial discharge magnitude. The rewind of motet slater insulation at rated voltage is assessed by the results of these tests. After completing the diagnostic tests, the stator windings of motors were subjected to gradually increasing ac voltage, until the insulation punctured. No. 8 motor failed near rated voltage of 19.0 kV. The breakdown voltage of No. 4 motet was 7.0 kV which is lower that expected for good quality coils in 6.6 kV class motors. The failure was located in a line-end coil at the exit from the core slot. These two motors began operation in 1994. While testing No. 7 motor, flashover occurred between the stator winding and the stator frame at 15 kV. The relationship between the diagnostic test and the drop in insulation breakdown voltage was analyzed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.228-228
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• 2009

In stator windings of a 6.6kV rotating machine, internal discharge, corona discharge, and surface discharge are mainly caused by internal voids and insulation degradation. In the case of the discharge spark and electromagnetic pulse generated from a discharge source, we can detect it using various RF resonators like an EM sensor. In order to detect these types of electromagnetic sources, we designed and fabricated a planar patch sensor using a CST-MWS simulation, and PD signals from artificial defected stator windings were also measured by the sensor proposed in this study. Furthermore, In the results of the experiment, it showed similar performance to the HFCT sensor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.93-94
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• 2008

Diagnostic tests were performed in three high voltage motors. These tests included insulation resistance, polarization index, ac current, dissipation factor($tan{\delta}$) and partial discharge magnitude. The rewind of motor stator insulation at rated voltage is assessed by the results of these tests. After completing the diagnostic tests, the stator windings of motors were subjected to gradually increasing ac voltage, until the insulation punctured. NO.1 and No.2 motors failed near rated voltage of 14.0 kV, respectively. These motors are lower that expected for good quality coils in 6.6 kV class motors. The breakdown voltage of No.3 motor was 15.0 kV.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.39-40
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• 2014

In this paper, a novel 12/8 segmental rotor type switched reluctance motor (SRM) is proposed. Different from conventional structures, the proposed rotor consists of a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Moreover, in this structure short flux paths are taken and no flux reverse exists in the stator. While the auxiliary poles are not wound by the windings, which only provide the flux return path. Compared with conventional 12/8 SRM, the proposed structure increases the electrical utilization of the machine and decreases the core losses, which may lead to high efficiency. To verify the proposed structure, finite element method (FEM) is employed to get static and dynamic characteristics. Finally, a prototype of the proposed motor is tested for characteristics comparisons.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1619-1622
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• 2001

Recently many researches on the diagnosis of stator winding insulation for large rotating machines have been developed sine the 1970s. Capacitive coupler has been the most widely used sensor for on-line partial discharge(PD) in rotating machines. The 105 [pF] ceramic coupler(CC) has been developed to continuously measure the PD activity in operating motor stator windings. This paper presents frequency characteristics and laboratory test to compare traditional 80 [pF] epoxy-mica coupler(EMC) and 105 [pF] CC for PD measurement in 6.6 [kV] stator windings.

• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.491-498
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• 2008

In this paper a decoupled control of a doubly-fed induction machine(DFIM) feed by a matrix converter is presented. It provides a robust regulation of the stator side active and reactive powers by the direct and quadratic components of the stator current vector, presented in a line-voltage-oriented reference frame. In this case, the stator windings are directly connected to the line grid, while the rotor windings are supplied by this later through a matrix converter controlled by a space vector modulation technique. The proposed solution is suitable for both energy generation and electrical drive applications with restricted speed variation range.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1701-1703
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• 2002

This paper introduces a on-line monitoring system for insulation diagnosis of high-voltage motor stator windings. This system monitors the insulation condition of the stator winding with sensor, coupling capacitor. Partial discharge (PD) signals are able to be continuously measured and digitalized with a Peak-hold A/D converter to build the database of the high-voltage motor's insulation condition. This system can communicate with the central monitoring system via RS-485 This paper introduces an economic solution for data acquisition of partial discharges.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2101-2103
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• 1999

The insulation condition of stator windings was measured by dissipation factor($tan{\delta}$) test in the six high voltage motors(rated 6.6kV) which had been in service for two years. The ${\Delta}tan{\delta}$ of motor D and E was higher than that of the rest motors. The specimens were drawn out from stator windings of the high voltage motor and their were analyzed using scanning electron microscope (SEM). SEM result shows that large voids are present in the interface both turn insulation and groundwall insulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1717-1720
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• 1998

In pumped storage Generator-motor stator windings gradually deteriorates due to mechanist, thermal, electrical stresses. These stresses combine to result in loose windings, delamination of the stator insulation and/or electrical tracking of the endwinding, all of which can lead to stator insulation failures. Since the degration of generator-motor is gradually occurred, regular inspection system is necessary to monitor degrading. The result of this diagnosis is a basic for the maintxnance of generator-motor.

• 전기학회논문지P
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• 제59권3호
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• pp.311-316
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• 2010

According to increase of combined cycle power generation, the manufacturing market of gas turbine generator has become more competitive, so there is high pressure on the manufacturer to reduce generator price. Global VPI(vacuum pressure impregnation) method is effective to save the production cost and time for manufacturing stator windings, but it has an abrasion problem by vibration between stator windings and slots. This paper presents the insulation breakdown case, which is for VPI type generator during high voltage insulation tests, and also shows the cause analysis, repair works as well as reliability test. the purpose of this paper is to understand the insulation properties of VPI type generator and to know prevention of insulation weakness.