Abstract
This paper comparatively studies on the end winding electromagnetic force and mechanical response for generators with different numbers of poles. The analytical expression of the end winding electromagnetic force is derived under the rotor winding interturn short circuit (RISC) considering the pole number. Meanwhile, the three-dimensional transient finite element simulation is carried on two generators with one-pair poles and three-pair poles. Then, the frequency composition and amplitude variation characteristics of the radial, axial, and tangential electromagnetic forces are analyzed. Further, the maximum stress and deformation on the end winding are calculated and the similarity and difference of the coil failure law are obtained for two kinds of generators. It is found that RISC will bring odd harmonics to electromagnetic force for one-pair pole generators but it will bring odd and fraction harmonics for multipair pole generators. Moreover, the max mechanical response under RISC will decrease for one-pair pole generators but it will increase for multipair pole generators.
Highlights
The generator is mainly composed of stator, rotor, and auxiliary components
This paper mainly studies on the electromagnetic force and maximum mechanical response of the end winding before and after rotor interturn short circuit (RISC) and analyses the similarity and difference of generators with different numbers of poles
RISC will result in the variation of the original odd harmonic amplitude and the changing tendency is decided by the pole number, shorted position, and order number (see equation (3))
Summary
The generator is mainly composed of stator, rotor, and auxiliary components. When the rotor rotates, a changing magnetic field will be formed and the electromotive force and current will be excited on the stator winding. Due to the interturn insulation damage caused by the poor manufacturing process or copper wire structure defects, fatigue damage, or insulation aging caused by mechanical stress, the rotor interturn short circuit (RISC) occurs very It is an electrical fault with high frequency in the actual working process of the generator. Such fault will not seriously affect the operation of the unit when they are slight in the early stage, and the generator can work with it It will cause abnormal distribution of the air gap magnetic field [2], further affect the electromagnetic force and mechanical response of end winding, and aggravate the fatigue damage and vibration wear of some windings. When the stator interturn short circuit (SISC) happens, the port voltage only contains odd International Journal of Rotating Machinery
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