Abstract：The support stiffness of the shafting is the characteristic parameter of the shafting vibration system. However, there is no effective on-site measurement method. An approximate calculation method based on the swing test data is proposed. Firstly, based on the hydroelectric generation rotor and runner centroid trajectory equation, the coupling relationship between the rotor and the slewing ratio is used to decouple the stiffness coupling term in the equation of motion. Secondly, according to the steady-state characteristics of the vibration of the shafting system, the influence of the shafting torsion, regardless of the damping coefficient acting on the generator rotor and the turbine runner, is ignored, and the simplified centroid trajectory equation in steady state is obtained, then an approximate calculation model of the equivalent stiffness of the shaft is derived. Thirdly, combined with the special opera-ting conditions of the hydropower unit, the additional external force is applied to the runner and the rotor, and the calculation method for calculating the stiffness of the shafting by using the vibration test data of special operating conditions is given. Finally, using the unit operation simulation system for simulation calculation, the simulation shows that although the stiffness data obtained by the approximate calculation method proposed in this paper and the given stiffness data of the simulation system have certain errors, which basically reflects the relationship between the stiffness of the shafting and the vibration. It has certain reference value for practical engineering.
