Analysis On Fault Characteristics Of Generator Under The Coupling Of Static Air-gap Eccentricity And Field Winding Interturn Short Circuit

During the operation of the generator,there are some faults that affect the working efficiency of the generator and even cause serious harm.Static Air-Gap Eccentricity and field winding interturn short circuit are common faults of generator that are easy to occur.Based on the hazards of the two types of faults,the diagnosis and monitoring are necessary.In this paper,theoretical analysis and finite element simulation are combined and then supplemented by experimental verification.The electromagnetic torque and phase current of the generator under the conditions of static air-gap eccentricity,field winding interturn short-circuit and coupling faults are carried out.Analyze and compare it with the parameter characteristics of normal operating conditions,and obtain the change rule law the parameter characteristics before and after the fault.Firstly,through the analysis of the variation air gap magnetic field before and after the fault,the analytical expressions of air gap magneto motive force and air gap permeance per unit area are obtained.The analytical expressions of magnetic field density are obtained by the product of air gap magneto motive force and air gap permeance per unit area.Based on this,the expression of the electromagnetic torque is obtained according to the energy method,and the expression of phase current is obtained according to Faraday’s law of electromagnetic induction and Ohm’s law.The change laws of the electromagnetic torque and the phase current before and after the fault are qualitatively analyzed.Then,relying on the Ansys Electromagnetics finite element calculation platform,based on the main parameters of the CS-5 fault simulation generator,the electromagnetic environment finite element calculation of its finite element two-dimensional model is carried out.Obtained the change law of the electromagnetic torque and the phase current amplitude and frequency components of the generator under normal conditions,static air-gap eccentricity,field winding interturn short-circuit,and static air-gap eccentricity and field winding interturn short-circuit coupling faults.Finally,taking the CS-5 generator as the experimental verification object,the change laws of the electromagnetic torque and the phase current are obtained under normal conditions,the static air-gap eccentricity,the field winding interturn short-circuit,and static air-gap eccentricity and field winding interturn short-circuit coupling faults,Respectively.Through the comparative analysis of the theoretical analysis,the finite element calculation and the experimental verification results,it is found that the changing trends are basically consistent.The results in this paper reveal the corresponding relationship between the electromagnetic torque and the phase current of generator and normal conditions,static air-gap eccentricity,field winding interturn short-circuit,and coupling faults.It effectively supplements the existing generator fault diagnosis criterion system.