After replacement of the rotor windings of the a synchronous motor

severe vibration occurred on a 125 MVA pulsed motor-driven Generator as it sped up to near 1800 r/min.Counter-weight balancing of the motor rotor for several times

but effectiveness hadn't obtained.It is believed from analysis that the cause of vibration may be the extension end with slip ring of the rotor is too long.After counter weighting on the extension end of the rotor

shafting vibration of the pulsed motor-driven generator can meet all the requirements.The max.vibration peak-value of the bearing is less than 35 μm under the first order critical speed of 1800 r/min

and less than 25 μm under 2980 r/m.