Abstract: A method of reduction and calculation is used to analyze the nonlinear stability of large-scale rotor-bearing systems. That the rotating speed gained by calculation and at which rotor occurs oil whip can be regarded as a rule for estimating the nonlinear stability of this system is presented. According to a 200 MW turbine-generator rotor-bearing system, a nonlinear vibration equation with 608 freedoms is given and the number of the freedoms of the equation is reduced to 30 by the fixed interface mode synthesis method. Then, numerically the system vibration equation having been reduced by means of the Newmark integral method is computed. The results show that the efficiency of calculation and analysis is improved remarkably under guaranteeing precision. Using the reduction and computation method the typical characteristics of oil whip phenomenon and rotating speed at which oil whip happen is simulated. Then, calculation and analysis for the variety of rotating speed at which oil-whip occurs of the journal of the generator frontal bearing with the eccentricity of the rotor, the length-to-diameter ratio, clearance-to-radius ratio and oil viscidity of the bearing are centered on. The above results provide theoretical basis for analyzing qualitatively the stability of the 200 MW turbine-generator rotor-bearing system.

Key words: Reduction, Nonlinear stability, Oil whip, Rotor-bearing, Kinematic performance evaluation, Parallel mechanism