Research On The Approximate Calculation Method Of The Support Stiffness Of The Hydro-generator Shaft System

As a rotating machine,the hydro-generator unit always has the problem of vibration during the operation.The stability of the unit shafting is the most important condition to ensure the stable operation of the unit.As the capacity of hydro-generators increases,the geometrical dimensions become larger and larger,the relative stiffness of the unit is weakened,and the vibration hazard is intensified.Unit vibration not only affects the stable operation of the power station,but also causes the power gener ation quality to decline.The support stiffness of the shafting is the characteristic parameter of the vibration system of the shafting of the unit.However there is currently no effective on-site measurement method for the shaft stiffness of the unit.Therefore,a method for calculating the stiffness of the shafting support based on the vibration swing test data is proposed.In this paper,the turbine shafting is analyzed.According to the research of the shafting vibration problem of the unit,the generator rotor and turbine runner are simplified into a concentrated parameter model with moment of inertia and concentrated mass.Analyze the energy composition of the system and construct a Lagrangian function according to the Lagrangian equation.Combined with the generalized momentum definition,the lumped parameter model of the shafting vibration is constructed as a first-order differential equation system.According to the operating characteristics of the unit under steady state,the damping coefficient acti ng on the rotor and the runner is simplified,and the approximate calculation method of the support stiffness of the shafting is derived by combining the equation of motion of the unit.Taking the resistance torque on the generator rotor and the dynamic torque on the turbine runner as the input torque of the additional external force,the simulation calculation system of the hydro turbine generating set including the hydraulic system,generator,excitation system and speed control system.By giving different additional external force amplitudes and frequencies at the rotor and the runner,the actual force of the unit is simulated and the vibration simulation data is obtained.Combining the simulated vibration data with the approximate calculation method of the shaft support stiffness,the shaft support stiffness value is calculated.The simulation proves that the approximation assumption proposed in this paper is reasonable,and the proposed approximate calculation method of the support stiffness of the shafting is effective.