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Whirling frequencies and amplitudes due to deviations of generator shape
Umeå University, Department of Mathematics and Mathematical Statistics.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0001-6016-6342
2008 (English)In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 43, no 9, p. 933-940Article in journal (Refereed) Published
##### Abstract [en]

Earlier measurements in large synchronous generators indicate the existence of backward whirling motion, and also relatively large deviations of shape in both the rotor and the stator. These non-symmetric geometries produce an attraction force between the rotor and the stator, called unbalanced magnetic pull (UMP). The target of this paper is to analyse the whirling frequencies and amplitude of the response for large synchronous generators with a high number of poles, due to deviations of shape in the rotor and stator. A mathematical model is developed to describe the shapes of the rotor and stator, and the corresponding UMP is obtained by using the law of energy conservation. The UMP is analysed due to different deviations of shape. The result gives the average angular frequency and the magnitude of the UMP for certain deviations of shape. From this result, the whirling frequency and the amplitude of the corresponding response can be approximated. Simulations of the response of a Jeffcott rotor model show good agreement with the theoretical results of the UMP for some generator geometries. The conclusion is that different whirling frequencies, both backward and forward whirling, can occur in these machines due to deviations in shape of the generator. Therefore, the shape of the generator can excite resonance vibrations on several other frequencies than the rotation frequency. During maintenance of hydropower generators the shapes of the rotor and stator are frequently measured. The results from this paper can be used to evaluate such measurements and to explain the existence of complicated whirling motion.

##### Place, publisher, year, edition, pages
2008. Vol. 43, no 9, p. 933-940
##### National Category
Applied Mechanics
Solid Mechanics
##### Identifiers
ISI: 000261304900016Scopus ID: 2-s2.0-53949107380Local ID: 172ba4d0-735a-11dd-a60f-000ea68e967bOAI: oai:DiVA.org:ltu-3629DiVA, id: diva2:976487
##### Note
Validerad; 2008; 20080826 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2023-09-05Bibliographically approved

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#### Authority records

Aidanpää, Jan-Olov

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Cite
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