Common causes of large bearing vibration in steam turbine generators

Common causes of large bearing vibration in steam turbine generators

Generally speaking, motor vibration is caused by unbalanced rotating part a, mechanical failure, or electromagnetic reasons.

1、 The imbalance of the rotating parts is mainly caused by the imbalance of the rotor, coupler, coupling, and transmission wheel (brake wheel).

The solution is to first find the rotor balance. If there are large transmission wheels, brake wheels, couplings, or couplings, they should be balanced separately from 

the rotor. Another issue is the mechanical looseness of the rotating parts. For example, loosening of the iron core bracket, failure and loosening of the diagonal keys 

and pins, and loose binding of the rotor can all cause imbalance in the rotating parts.

2、 The main mechanical failures are as follows:

1. The axis system of the linkage part is not centered, the centerline is not aligned, and the centering is incorrect. The main cause of this malfunction is due to poor 

alignment and improper installation during the installation process. There is also a situation where the center lines of some linkage parts coincide in the cold state, 

but after running for a period of time, the center lines are damaged due to deformation of the rotor support points, foundations, etc., resulting in vibration.

2. The gears and couplings connected to the motor are faulty. This type of malfunction is mainly manifested as poor gear meshing, severe tooth wear, poor wheel 

lubrication, skewed or misaligned couplings, incorrect tooth profile and pitch, excessive clearance or severe wear of gear couplings, all of which can cause certain 

vibrations.

3. Defects in the structure of the motor itself and installation issues. This type of fault is mainly manifested as elliptical shaft neck, bent shaft, excessive or insufficient 

clearance between shaft and bearing shell, insufficient stiffness of bearing seat, foundation plate, some parts of the foundation, and even the entire motor installation 

foundation, weak fixation between motor and foundation plate, loose foot bolts, and loose connection between bearing seat and foundation plate. Excessive or insu-

fficient clearance between the shaft and the bearing shell can not only cause vibration, but also lead to abnormal lubrication and temperature of the bearing shell.

4. The load driven by the motor conducts vibration. For example, the vibration of the steam turbine in a steam turbine generator, as well as the vibration of the fan and 

water pump driven by the motor, can cause the motor to vibrate.

3、 The faults in the electrical part are mainly caused by electromagnetic factors, including: incorrect wiring of the stator of the AC motor, short circuit of the rotor winding 

of the wound asynchronous motor, short circuit between turns of the excitation winding of the synchronous motor, incorrect connection of the excitation coil of the syn-

chronous motor, broken bars in the rotor of the cage asynchronous motor, deformation of the rotor iron core causing uneven air gap between the stator and rotor, resulting

 in unbalanced magnetic flux in the air gap and causing vibration.