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Research Papers

Computational Model for Investigating the Influence of Unbalanced Magnetic Pull on the Radial Vibration of Large Hydro-Turbine Generators

[+] Author and Article Information
Yong Xu

Zhaohui Li

 School of Hydropower & Information Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road Wuhan, Chinazhhli@mail.hust.edu.cn

J. Vib. Acoust 134(5), 051013 (Jun 08, 2012) (9 pages) doi:10.1115/1.4006648 History: Received January 01, 2012; Revised March 01, 2012; Published June 07, 2012; Online June 08, 2012

A radial unbalanced magnetic pull (UMP) can be produced by an eccentric rotor and leads vibrations in large hydro-turbine generators. The influence of nonlinear UMP on the radial vibration of a large hydro-turbine generator is analyzed in this paper. The UMP is determined as a function of eccentricities and field currents by means of a simple analytical method instead of the finite element (FE) method. The analytical method employs the no-load characteristic curve of an electrical machine and saturation effects of the ferromagnetic materials are taken into consideration. FE rotor model of a large hydro-turbine generator unit, taking account of guide bearings, thrust bearing and periodic forces, is developed to investigate the influence of UMP on radial vibrations. The FE rotor model and the analytical method for UMP constitute the computational model. UMP is calculated under different rotor eccentricities and field currents by the proposed method. Comparing with other analytical methods, the effectiveness of the proposed method is verified. Dynamic responses of the FE model under different analytical methods for UMP are calculated to investigate the difference in vibration between different analytical methods. A simulated excitation test is performed and a comparative analysis between the calculated results and the field data is provided. The computational model is proved to be reasonable according to the analysis.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of eccentric rotor in stator

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Figure 2

Diagram of magnetic circuit in a salient-pole synchronous generator (dotted line)

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Figure 3

Curve of If - Bδ transformed from a no-load characteristic curve

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Figure 4

Effective air gap length of a 96-pole rotor with a uniform air gap length of 20 mm and 10% eccentricity at −90 deg

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Figure 5

Sketch of shaft system for a Kaplan-type large hydro-turbine generator unit in Gezhouba hydropower plant

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Figure 6

A rotational Timoshenko beam element and coordinates of its nodes

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Figure 7

UMP as a function of the field current under different relative eccentricities

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Figure 8

Comparisons of the UMP calculated by different analytical methods under different field currents, (a) field current If  = 189 A, terminal voltage E = 3.45 kV; (b) rated field current If  = 876 A, rated terminal voltage E = 13.8 kV; (c) field current If  = 1286 A, terminal voltage E = 16.56 kV

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Figure 9

Comparison of the peak-peak values for the dynamic response at direction Y of node UGB for different methods

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Figure 10

Comparison of the amplitude spectrums for the dynamic response at direction Y of node UGB for different methods, only considering dynamic eccentricity with field current of 876 A

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Figure 11

Orbits of rotor center for dynamic response calculated by our method with salient poles, with field current of 876 A

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Figure 12

Comparison of the amplitude spectrums for the dynamic response at direction Y of node UGB for different methods, considering both static and dynamic eccentricity with field current of 876 A

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Figure 13

Screenshot of the website of HOMIS recording the process of excitation test

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Figure 14

Changes of the peak-peak values in the simulated excitation test

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Figure 15

Comparison of axis orbits of the field data, (a) UGB before excited, (b) UGB after 100% excited, (c) TGB before excited, (d) TGB after 100% excited

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