Effect of Eccentricity Factors on End Winding Electromagnetic Force in Turbo-generator

Abstract

Static eccentricity will cause the abnormal distribution of air gap magnetic field and further affect the electromechanical characteristics of the generator. This paper comparatively studies on the end winding electromagnetic force of turbo generator under different eccentricity ratio and eccentricity angle. The analytical expression of end winding electromagnetic force is derived after eccentricity. Meanwhile, the three-dimensional transient finite element simulation is carried on under several eccentricity cases. Then the amplitude variation characteristics with eccentricity ratio and angle are analyzed. Further, the force characteristics are verified by experimental vibration acceleration of CS-5 simulating generator. It is found that the static eccentricity will not change the frequency components of the end winding force. However, it will change the amplitude of the electromagnetic force, and the increase or decrease tendency depends on the winding position, eccentricity ratio and eccentricity angle. The number of force amplitude increasing coils is close to half of the total number, and it changes slightly with the eccentricity ratio and eccentricity angle. The force increment of coil near the minimum air gap will be larger with the increase of eccentricity ratio, but it is not affected greatly by eccentricity angle. Moreover the coil with the most obvious force increase is located in the interphases position near the minimum air gap.