Study On Electromagnetic Forces Of End Windings In Large Turbo-generators

With ever-increasing capacity, the electromagnetic forces acting on the stator end winding are significantly increased. In the normal operating condition, the electromagnetic forces acting on the end winding may cause winding vibration and insulator friction; and in fault operating situation, these forces may result in insulator crack, winding distortion, fixation break and so on. Therefore, it is essential to study the electromagnetic forces acting on the stator end winding so as to improve the design of the machine.This dissertation focuses on the analytical study of the electromagnetic forces acting on the end windings of a 600MW large turbo-generator. To summary up, the works include:1. In Cartesian coordinates, the mathematical models for the electromagnetic fields and forces in the end regions are built on the basis of the method of image. Each top bar and lower bar is divided into twenty-nine segments. For asymptote segment which is spread on a cone surface, an approximate method is proposed to model it by using equally distanced line segments. The method of image is used to consider the effect of the main part of the machine.2. The close form formulations for the electromagnetic fields and the forces acting on the stator winding in the end region of large turbo-generator are developed based on the general electromagnetic theory. In this aspect, the Biot-Savart law and an aggregation method are employed.3. The corresponding computer software is developed and employed to numerically study the electromagnetic fields and forces acting on the winding in the end region. To facilitate the description of the numerical results, the magnetic forces are expressed in cylindrical coordinate system. Finally, the details about the electromagnetic fields and forces in the end region in steady-state and short circuited operating conditions of a 600 MW large turbogenerator are studied and some conclusions are concluded.