Study of the impact of eccentricity in large synchronous generator with finite elements

Dirani, Hind Chit; Merkhouf, Arezki; Giroux, Anne-Marie; Al‐Haddad, Kamal

doi:10.1109/icelmach.2014.6960193

Cited by 10 publications

(7 citation statements)

References 10 publications

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“…Although the attraction forces resulting from magnetic phenomena are considered to be large [4], [16], the difference of the air gap after the load applied to the generator was not more than 0.6 mm. This is a little bit less than 1 mm (the value suggested by early developers of air gap measurement systems [4]).…”

Section: Discussionmentioning

confidence: 99%

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

Cerpinska

Elmanis-Helmanis

2017

Latvian Journal of Physics and Technical Sciences

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The paper provides the data collected over a three-year period to illustrate the dynamic air gap change depending on generation modes of four hydropower generators with similar design. The tests were performed on hydropower units at the rated apparent power of 105 MVA and the air gap of 20 mm. The results obtained showed that the average air gap change in different modes could reach up to 2.1 mm. Around 90 % of air gap change results from thermal expansion and 10 % were determined by centrifugal and magnetic forces. In coasting mode when the power was switched off and the speed of the generator decreased, the air gap increased up to 0.7 mm. Attraction forces resulting from magnetic phenomena accounted for 0.1-0.6 mm decrease in the air gap.

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Section: Discussionmentioning

confidence: 99%

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

Cerpinska

Elmanis-Helmanis

2017

Latvian Journal of Physics and Technical Sciences

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“…Compared with induction motors and permanent magnet motors with small volumes and capacities, the vibration caused by rotor eccentricity inside large synchronous generators is a Correspondence to: Yucai Wu. E-mail: wuyucaincepu@163.com the rotor center, and O S is the stator center more serious [2,19,20], and research on this problem is currently of great value. The no-load EMF and the harmonic characteristics of the generator were analyzed in [21].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Dynamic and Static Eccentric Faults in Turbo Generator

Cai

et al. 2019

IEEJ Transactions Elec Engng

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Rotor eccentricity is a common fault in turbo generators, but there is currently no effective means of evaluating the eccentric state of the generators. In this article, the air‐gap permeance method was used to analyze the influence of rotor eccentricity on the no‐load main magnetic field, and the installation of U‐type detection coils within the stator core was proposed. Using this method, the dynamic eccentricity level can be measured by detecting the 2nd harmonic amplitude of the coil‐induced voltage, and the static eccentricity level can be measured using the difference in the induced voltages from the U‐type coils. Two dimensional numerical simulation results show that the U‐type detection coil is suitable for the detection of dynamic and static eccentric faults. Therefore, this method can be used for the evaluation of the eccentric state in turbo generators. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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“…Some level of inherent eccentricity is expected, however, and this is due to the very small air-gap between the rotor poles and the stator teeth [6]. The impact of the rotor weight affects the level of the static eccentricity in large electrical machines over time.The impact of eccentricity on synchronous machines has been studied in the past [6][7][8][9]. The radial and tangential forces are known to increase in the presence of eccentricity conditions [7].…”

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confidence: 99%

“…The impact of the rotor weight affects the level of the static eccentricity in large electrical machines over time.The impact of eccentricity on synchronous machines has been studied in the past [6][7][8][9]. The radial and tangential forces are known to increase in the presence of eccentricity conditions [7]. It has been presented in reference [8] that variation of the air-gap magnetic reluctance will generate eddy currents in the rotor damping cage, even at unloaded operation [8].…”

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confidence: 99%

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Diagnosis of Static Eccentricity in 3-Phase Synchronous Machines using a Pseudo Zero-Sequence Current

et al. 2019

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Large synchronous generators are the heart of the modern world, while producing the vast majority of the electric power consumed globally. Although they are robust devices, they are prone to degradation and failure. If such failures are not detected at an early stage, then the negative impact may be catastrophic in terms of financial costs, repair times, human lives and quality of life. This is the reason for continuous research in the field of condition monitoring aiming towards the reliable operation of synchronous generators. This paper proposes a novel technique for the diagnosis of the static eccentricity in synchronous generators. The proposed approach is off-line and non-intrusive, allowing the estimation of the fault severity with stator current measurements only. The performed work has been carried out with Finite Element Simulations and extensive experimental testing. Energies 2019, 12, 2476 2 of 16where the electrical machine operates under an asymmetrical air-gap due to displacement of the rotor. The eccentricity fault may be either static when the rotor's dislocation is fixed in space and time, or dynamic when the rotor geometric center changes continuously over time. If the two conditions co-exist, then this is known as the mixed eccentricity condition [5].The static eccentricity fault usually appears at the commissioning stages and starts as a manufacturing fault. It can be caused by improper alignment of the shaft or the stator inner ovality. Some level of inherent eccentricity is expected, however, and this is due to the very small air-gap between the rotor poles and the stator teeth [6]. The impact of the rotor weight affects the level of the static eccentricity in large electrical machines over time.The impact of eccentricity on synchronous machines has been studied in the past [6][7][8][9]. The radial and tangential forces are known to increase in the presence of eccentricity conditions [7]. It has been presented in reference [8] that variation of the air-gap magnetic reluctance will generate eddy currents in the rotor damping cage, even at unloaded operation [8]. A paper on the Unbalanced Magnetic Pull (UMP) caused by eccentricity faults in synchronous machines presented the independence between the static and dynamic eccentricity [6]. Finally, it was shown that the impact of the damper cage in case of eccentric conditions is very weak, an attribute associated with its high ohmic resistance [9]. However, the damper cage's impact on the forces due to the eccentricity fault is small, an attribute due to the cage's high ohmic resistance.Moreover, focusing on the actual diagnosis of the eccentricity fault in synchronous machines, it is clear that most past works focus on either permanent magnet [10][11][12][13] or reluctance machines [14-16], while literature is very limited for salient pole ones. Despite this unequal research effort, some contributions have been identified and are listed here. Intrusive techniques such as the installation of flux sensors to capture the air-gap magnetic flux give...

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Study of the impact of eccentricity in large synchronous generator with finite elements

Cited by 10 publications

References 10 publications

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

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

Evaluation of Dynamic and Static Eccentric Faults in Turbo Generator

Diagnosis of Static Eccentricity in 3-Phase Synchronous Machines using a Pseudo Zero-Sequence Current

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