Analysis on Electromagnetic Force Properties of End Windings in Turbo-Generators

Electromagnetic forces on the end windings will stimulate intensive vibrations and cause insulation wearing, and the vibration wear will further induce the coil short circuit. Eventually accidents and losses will be brought. Therefore, it is of great significance to study the electromagnetic force properties of end windings. This paper studied on the electromagnetic force properties of end windings in turbo-generators. Firstly, the magnetic field in the end region was analyzed by winding MMF superposition principle and air gap magnetic conductivity method, and the electromagnetic force is got with Ampere law. Then, taking QFSN-600-2YHG turbo-generator as study object, the 3 directional electromagnetic forces and the mechanical responses on the end windings were calculate by electromagnetic-structure coupling finite element analysis method. Finally, the experiment vibrations are tested, and the acceleration data was compared with simulated result. It is shown that each directional electromagnetic force contains both the DC component and even harmonics, which will result in the winding vibration mainly at the double fundamental frequency. Meantime, the radial acceleration is the largest and the axial one is the least, so the radial vibration should be paid more attention to in daily monitoring. Moreover, the max deformation mainly occurs on the nose and middle part of the involute, and these locations should be strengthened in design and manufacture.