Abstract: For a 350 MW subcritical Turbo-generator Unit, the vibration of the HP-IP rotor, LP rotor and generator rotor at the critical, 3000 r/min and load conditions is too large. By analyzing the vibration test of these conditions, the result that the vibration of the main reason is the existence of mass and thermal imbalance is proposed. According to the vibration value,operating parameters, shaft center, and rotor structure and bearing support, the method of high-speed dynamic balancing is used to decrease the vibration. The balancing masses at six locations in the HPIP rotor, LP rotor and the LP-generator coupling are added at same time, and the vibration frequency values are less than 100μm in all conditions one-time.

Key words: steam turbine, imbalance, multi-planar, balancing once