Rotor Generator slip ring


Thread Starter


What is the difference between left and right slip ring helical groove? If it s against rotor direction, will have a negative effect on brushes and break them?

Has the generator been running with the grooves in the current orientation?

Have there been any problems with the brushes?

Are the grooves oriented the same on both "left" and "right" slip rings?
No, the orientation changed. it was left but now right, view from exciter side. becoz we changed old slip rings with new, both..

No, there was any problem with brushes before, but now the slip ring close to Genbearing No:2 break brushes and overheat 135 C.

Large Turbogenerator 320MW, 3 Bearings.

Vibration data:
Gen vibration(turbine side): 71 micron
Gen vibration (exciter side):78 micron

Runout check is good, Both
electrical tests are good.
generator is operating at full: 320MW, 100 MVAR
but brushes break.

there are 3 options:
1- Vibration
2- slipring Looseness
3- changed slip ring helical groove direction
what do you think of?


I believe I have seen "opposing" helical grooves on opposite slip rings and there were no problems with brushes breaking or overheating or excessive vibration. But, I seem to recall that the brush holders were not arranged similarly for the two sets of slip rings--which is what initially caught my attention, and then brought my attention to the different helical groove orientation.

So, I would suggest that if the groove(s) was(were) changed, but the brush holder arrangement was not suitably changed, then that could be a contributor to the problems you are experiencing. Most of the brush rigging I have seen had staggered brush holders, and I believe the staggering is done in conjunction with the orientation of the helical grooves.

I say a 'contributor' to the problems you are experiencing because I also suspect there is more than one issue. The run-out may be excessive on the new slip rings; you should contact the generator manufacturer for specifications.

The brushes may not have been re-installed correctly--too much or too little gap between the holders and the slip rings.

I have also seen new brushes exhibit this problem when they were installed without first "shaping" them to the same curvature as the slip rings. Too little contact area can cause heating and vibration and lead to breakage.

So, there are several things to check.

But, the most telling thing you wrote was to say that before the slip rings were changed, and the helical grooves have a new orientation, there were no problems.

Please write back to let us know what you find.
Hi friends

brushes break causes in below cases:

1-slip ring runout (very important)
2-slip ring surface roughness
3-slip ring or rotor vibration


There is a really good World Wide Web Forum particularly suited for this type of question:

Membership is free, and you have a LOT of forum and sub-forum choices to choose from when posting questions.

In my experience, most slip ring damage is caused by heat--too much current flowing through too few brushes (because the brushes are far too often neglected and far too infrequently replaced). Also, some brushes require shaping before installation and many maintenance personnel do not know that nor do they know how to shape the brush ends if they require it before installing them.

Burnishing slip rings is also a forgotten art, and can be very useful in keeping slip rings clean and helping with current transfer and reducing heat and wear.

But, I think you would find more and possibly better answers to this type of non-controls related question. We do answer many mechanical questions here--because many times the control system includes mechanical components which must work correctly. But, when it comes to maintenance of slip rings, that's really not something that control systems can do or be programmed to do.

Hope this helps!