Analysis of unbalance magnetic pull in eccentric turbo-generator under multiple loading conditions

This paper analysed the unbalance magnetic pull (UMP) which act upon the rotor of a turbo-generator with air gap eccentricity fault under multiple loading conditions. This work would provide theoretical support to alleviating unit vibration by power regulation. The type of QFSN200-2 turbine generator is the research object of this paper, it´s structure model was established by means of finite-element simulation tools. Firstly, operation data of unit with loads varying widely were loaded into the model to calculate the accurate distribution of magnetic field on the motor cross section. And then, for various directions of rotor eccentricity, the unbalance magnetic forces on the rotor were calculated by the discrete formulas. The changing rules of UMP amplitude along with active power and reactive of the generator are obtained in ideal condition that the terminal voltage is maintained at rated value. It is seen that the amplitude of UMP varies with the operating conditions and eccentric direction in a certain extent, and to variation range of UMP, reactive power variation of generator has greater impact than active power variation. The results shows that it is possible to suppress the UMP by adjusting power allocation between the units in parallel, and which is helpful to alleviate the unit vibration and useful to keep the operation of units safe and stable.