What Is The Reason For The Large Vibration Of The Alternator When It Is No Load

After the unit is started, when the axial and transverse vibration values of the AC synchronous generator exceed the values specified in Table 36 under the no-load state, it indicates that the vibration of the generator is large during operation.

1、 Cause of failure.

① The rotor is mechanically unbalanced. The main reason is that the dynamic balance is not calibrated or the accuracy of dynamic balance does not meet the requirements.

② The wear of the generator rotor bearing makes the air gap between its stator and rotor uneven more than 10%, and the large unilateral magnetic pull causes the vibration of the synchronous generator.

③ Poor bearing accuracy is one of the strong vibration sources of high-speed generator. The main performance is the radial deflection of the inner or outer ring of the bearing, the ovality of the ring, the excessive clearance in the cage hole, and the waviness of the raceway surface or local surface defects.

④ The assembly quality of bearing and rotating shaft or end cover is poor.

A. The bearing fits too tightly with the shaft or end cover.

B. The bearing is installed by knocking method, and the process is incorrect.

C. The grade of lubricating grease used for bearing is incorrect. Too thick grease has poor damping effect on rolling body vibration, while too thin grease will cause dry friction and other disadvantages.

2、 Treatment method.

① The rotor of each generator must be calibrated for dynamic balance to achieve the dynamic balance accuracy specified in the drawing.

② The bearing with acceptable accuracy shall be selected according to the grade specified in the drawing. Check the unevenness of the air gap between the stator and rotor, and adjust the assembly until the unevenness meets the requirements.

③ Install the bearing, rotating shaft and end cover according to the specified matching accuracy.

④ It is forbidden to use the knocking method for bearing installation, and it is better to use the hot sleeve method of heating the bearing in the oven.

⑤ Grease must be selected according to the brand specified in the drawing.

The common fault phenomena, fault causes, inspection and treatment methods of brushless AC synchronous generator are analyzed in detail above. In order to facilitate the use and maintenance personnel of diesel generator set to find the fault point conveniently and quickly.

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