Abstract
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.
Highlights
The stator winding of turbo-generator is a group of huge current carriers
Deformation can be excited by the electromagnetic force and it is the displacement of vibration
This paper investigates the electromagnetic force of the end wingding by theoretical analysis, simulation calculation and experiment study
Summary
The stator winding of turbo-generator is a group of huge current carriers. During operation, the conductors in the end region will endure great electromagnetic forces, which will stimulate intensive vibrations and cause insulation wearing. Yuda Hu presented the expression of the fundamental-frequency current density by Fourier series On this basis, detailed expressions of the magnetic induction strength in the end region were derived with the Maxwell equations [2]. The above two methods need accurate stator current information, and it is limited for application in some complex running cases, for example, the winding inter-turn short circuit or rotor eccentricity. Yu-Ling He analyzed the stator and rotor vibration characteristics in eccentricity and inter-turn shortcircuit composite faults by magneto-motive force (MMF) superposition principle and air gap magnetic conductivity method [3, 4]. Thereafter, the mechanical responses of the end windings are calculated in ANSYS, and the simulated acceleration data can be obtained to verify the correction of the force result. Given that the vibration acceleration data is obtained in 3 directions, the end winding force components in this paper are obtained in radial, axial, and tangential directions
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