Research On Unbalance Magnetic Pull In Turbo-generator Under Multiple Loading Conditions

Eccentricity and excitation winding inter-turn short circuit are the commonest forms of turbo-generator failure. These two faults will cause the magnetic field distortion in generator, and produce the unbalanced magnetic pull acting on the rotor. The unbalanced magnetic pull is one of the key factors to affect vibration of generator unit. When changing the running condition of generator, the unbalanced magnetic pull will be changed. Accurate analysis of unbalanced magnetic pull changing characteristics with operating conditions can provide theoretical support to alleviating the vibration of generator unit by adjusting power allocation. The main work of this paper are as follows.(1)The influence of excitation winding inter-turn short circuit fault and rotor eccentricity fault to the generator air-gap magnetic flux density were analyzed. The type of QFSN200-2 turbo-generator is the research object of this paper. The structure model of the turbo-generator was established by means of the finite-element simulation tools Ansys. The eccentricity and excitation winding inter-turn short circuit were set in the model, to calculate the distribution of magnetic field, and different fault variables’ s influence to generator air-gap magnetic flux density were analyzed.(2)The unbalanced magnetic pull in generator with eccentricity varies with the operating conditions was analyzed. The discretization formula of unbalance magnetic pull was deduced using air-gap magnetic flux density, and by means of this formula, the unbalanced magnetic pull of the generator under multiple operating conditons was calculated. The influence of eccentric degree and direction to unbalanced magnetic pull, and the changing characteristics of unbalanced magnetic pull with the gererator operating conditions were analyzed. The changing rules of unbalanced magnetic pull amplitude along with power regulation of the generator are obtained in ideal conditon.(3)The electro-magnetic characteristics of generator steady-state after the excitation winding inter-turn short fault was analyzed, and the changing rule of unbalance magnetic pull with the power regulation was obtained. The change of operating parameters after the inter-turn short fault was calculated. The unbalanced magnetic pull after excitation winding inter-turn short fault was calculated, and the influence of different inter-turn short degree and position to unbalanced magnetic pull were analyzed. The changing rules of unbalanced magnetic pull caused by excitation winding inter-turn short fault amplitude along with power regulation of the generator are obtained in ideal conditon.