Influence on the stability of generator rotors due to radial and tangential magnetic pull force
2007 (English)In: IET Electric Power Applications, ISSN 1751-8660, Vol. 1, no 1, 1-8 p.Article in journal (Refereed) Published
Forces due to nonuniform airgaps in rotating electrical machines have been a researchtopic for over 100 years. However, most research in the area of rotating electrical machines hasbeen performed on motors. Large forces in hydropower generators can lead to expensive damageand failures. Therefore, it is of interest to calculate the forces that arise in a large synchronousgenerator with an eccentric rotor and study the influence these forces have on the stability of thegenerator rotor. A 74 MVA synchronous hydropower generator was simulated with an eccentricrotor, using a time-stepping finite-element technique. The forces were calculated using Coulomb’svirtual-work method and simulations were performed for no-load and load cases. The resultingforce was found to be reduced significantly when a damper winding was taken into account. Aninteresting effect of the rotor damper winding was that it reduced the eccentricity force andintroduced a force component perpendicular to the direction of eccentricity. The results from thefinite-element simulations were used to determine how the forces affect the stability of the generatorrotor. Damped natural eigenfrequencies and damping ratio for load and no-load conditions arepresented. When applying the forces computed in the time-dependent model, the damped naturaleigenfrequencies were found to increase and the stability of the generator rotor was found to bereduced compared with when the forces were computed in a stationary model.
Place, publisher, year, edition, pages
2007. Vol. 1, no 1, 1-8 p.
generator rotor stability, radial magnetic pull force, tangential magnetic pull force, nonuniform air gaps, rotating electrical machines, large synchronous generator, eccentric rotor, synchronous hydropower generator, time-stepping finite-element technique, Coulomb's virtual-work method, damper winding, damped natural eigenfrequencies, damping ratio, load conditions, no-load conditions, electromagnetic forces, 74 MVA
Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-14002DOI: 10.1049/iet-epa:20050430ISI: 000245100000001OAI: oai:DiVA.org:uu-14002DiVA: diva2:41772