Research On Shaft Force And Vibration Characteristic Under Generator Internal Faults

Static air-gap eccentricity(SAGE)and rotor inter-turn short circuit(RISC)are common single factor faults in generator,and these two faults often occur simultaneously.In this thesis,the generator electromagnetic torque under generator internal faults is theoretically analyzed and experimentally studied.Firstly the electromagnetic torque expressions under different performing conditions are deduced.Then the generator modeling and the corresponding simulation under different conditions are accomplished with the finite element software ANSOFT.Finally experiments are taken on a simulating generator to verify the theoretical analysis and simulation results.It is shown that the electromagnetic torque only has DC component under normal condition,in which the DC component amplitudes will decrease as the short circuit degree develops.The electromagnetic torque has 1st harmonic component under RISC,the development of RISC will increased the 1st harmonic amplitudes but meanwhile decrease the DC component amplitudes.The electromagnetic torque has 2nd harmonic component under SAGE,in which the DC component and the 2nd harmonic amplitudes will increase as the eccentricity degree develops.When under the composite faults(CF),the 1st and 2nd harmonic component will be induced.As the short circuit degree develops,1st harmonic amplitude will increase while the DC component and 2nd harmonic amplitude will decrease.Besides,the increment of the eccentricity degree will increase the DC,1st and 2nd harmonic amplitude.In addition,the unbalanced magnetic pull(UMP)on rotor is studied by finite element calculation and dynamic response experiment.It is shown that the main harmonic components of UMP under SAGE are the DC component and the 2nd harmonic component,while the main harmonic component of UMP under RISC is the DC component and the 2nd harmonic component,and the main harmonic components of UMP under CF are the DC component,the 1st,2nd and 3rd harmonic component.Among them,in addition to the DC component,every harmonic component will motivate the rotor vibration.The achievements obtained in this thesis offer a reference for the monitoring and diagnosis at SAGE,RISC and CF of the generators in actual production and therefore have active meaning.