Dynamic Air Gap Change of Low-Speed Generator Considering Thermal Expansion, Centrifugal Force and Magnetic Force Effects

Cerpinska, Marina; Elmanis-Helmanis, Rihards

doi:10.1515/lpts-2017-0031

Cited by 4 publications

(5 citation statements)

References 9 publications

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“…It was shown that the force of inertia and temperature effects have a critical role for the air gap variation. For Unit 1 in this study the inertia force accounted for only 0.2 mm of the variation, which is less than 0.7 mm quoted in the previous research [5]. Temperature effects accounted for 1.5 mm, which supports the previous conclusions that the thermal expansion effects could cause up to 90 % of the air gap variation.…”

Section: Shaft Displacement Resultssupporting

confidence: 78%

“…Therefore 2 % is not a critical portion of the variation. The other sources of variation were discussed in the previous publication [5], but the unit studied was of a slightly different design. It was shown that the force of inertia and temperature effects have a critical role for the air gap variation.…”

Section: Shaft Displacement Resultsmentioning

confidence: 99%

“…Three capacitive sensors were placed on the top of the stator, as previously described in paper [5].…”

Section: Methodsmentioning

confidence: 99%

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Displacement of shaft during hydropower generator air gap measurements

Cerpinska

Irbe

Elmanis-Helmanis

2018

Engineering for Rural Development

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Abstract. The objective of the study is to discuss the specific requirement of the hydropower generator health condition monitoring standard, which suggests taking into account displacement of the hydropower generator shaft when measuring the air gap. This paper quotes some research, where EMF current is used to evaluate the air gap variation considering the shaft displacement. To verify the proposed methodology, three steps were completed in this paper. Firstly, the correlation between EMF and the air gap was studied in different modes and the percentage of the change of the EMF determined by the change in the air gap was calculated. Secondly, the force vector resulting from uneven air gap is obtained using imaginary vector summation. Finally, the real values of the shaft displacement are presented and discussed. The results show that correlation between EMF and the air gap is strong, but there are also other factors that affect the EMF current, not only the air gap size. The force vector could change depending on the generation mode, but not for all units. Finally, the research shows that for the generator in healthy condition (using ISO standards as a reference for acceptable shaft displacement) the shaft displacement is only a small part of the air gap variation, approximately 2 %. However, the discussion part shows that it matters a lot, which evaluation standard is used, since 2 % of variation is a great value, when only 3 % is acceptable. To address this problem an alternative standard for dynamic air gap measurement and evaluation is quoted.

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Section: Shaft Displacement Resultssupporting

confidence: 78%

Section: Shaft Displacement Resultsmentioning

confidence: 99%

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Displacement of shaft during hydropower generator air gap measurements

Cerpinska

Irbe

Elmanis-Helmanis

2018

Engineering for Rural Development

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“…Одним из самых опасных дефектов крупных гидрогенераторов (ГГ) является нарушение формы и изменение величины воздушного зазору между ротором и статором [1][2][3]. Такой дефект может привести к серьёзным авариям с задеванием ротора за статор, разрушением обмоток, стали статора и полюсов.…”

Section: Introductionunclassified

“…Появление дефекта вызывается воздействием различных явлений в машине. Согласно [1,2] воздушные зазоры между статором и ротором в гидрогенераторах в диаметрально противоположных точках не должны отличаться друг от друга более чем на 20 % от среднего значения, если инструкциями изготовителя не предусмотрены более жёсткие нормы. Для капсульных ГГ, в которых воздушный зазор составляет всего несколько миллиметров, отклонение зазора от нормируемых значений является особенно опасным.…”

Section: Introductionunclassified

Measuring Transducer for Air Gap Capacitive Sensor in Hydrogenerator

Левицкий¹,

Зайцев²,

Березниченко³

et al. 2020

Prib. metody izmer.

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One of the most important parameters of powerful hydro generators (HG) is the air gap between the rotor and the stator, and its deviation from the set norms is a defect that can lead to serious accidents. Therefore, the size and shape of the gap must be monitored both during inspections and during operation of the machine. The aim of this paper was to develop a secondary measuring transducer providing accuracy and resolution for a capacitive gap sensor formed by coplanar parallel electrodes. It is shown that the reliability and safety of operation of powerful HG inextricably depend on the timely detection of their defects, especially during operation. One of the most important parameters of the HG is the air gap between the rotor and the stator, and its deviation from the set norms is a defect that can lead to serious accidents. Therefore, the size and shape of the gap must be monitored both: during inspections and during operation of the machine. The paper discusses the features of measuring the air gap in a powerful HG, as well as existing modern methods and means of measurement. It is shown that for measuring the gap in capsule HG, one of the most suitable means is a meter, which includes a capacitive sensor mounted on a central bore of the stator core. Commercially available gap meters with capacitive sensors are not suitable for use on HGs. Commercially available meters with capacitive sensors, by their certain characteristics, are not always suitable for use on HGs. A secondary measuring transducer with improved characteristics is proposed for a capacitive gap sensor formed by coplanar parallel electrodes. The converter is developed on the basis of a balanced compensation bridge measuring circuit. The control action in the device is formed by the phase of the unbalancing signal. The structural diagram of the converter is presented and the algorithm of its operation is described. The process of forming a measuring output signal proportional to the sensor working capacitance in the circuit is considered. The use of a capacitive sensor with coplanar parallel electrodes and the proposed secondary measuring transducer will ensure high accuracy and resolution when measuring the air gap.

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The Early Detection of Stator Winding Shorted Turns in Permanent Magnet Three Phase Generators by Analysis of its Phase Voltages

Barrett

2020

2020 IEEE 14th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG)

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Dynamic Air Gap Change of Low-Speed Generator Considering Thermal Expansion, Centrifugal Force and Magnetic Force Effects

Cited by 4 publications

References 9 publications

Displacement of shaft during hydropower generator air gap measurements

Displacement of shaft during hydropower generator air gap measurements

Measuring Transducer for Air Gap Capacitive Sensor in Hydrogenerator

The Early Detection of Stator Winding Shorted Turns in Permanent Magnet Three Phase Generators by Analysis of its Phase Voltages

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