bearing problems
bearing problems
(OP)
I will start by stating I'm not a motor guy, I'm a water well contractor. The problem that I have run into is that I installed a all new vertical water lube turbine with a vertical hollow shaft motor, in a new well and new controls. This is a 150 hp 460 volt U.S. motor and Abb acs550 series drive. The pump runs as smooth as silk (no vibration)The pump load in under the bearing rating, and I can fine nothing wrong with the system.
The problem is that twice in the last six months the top bearing has start make horible noised and has had to be replaced under U.S. warrenty. The motor shop is telling me that the cause of the bearing failure is "shaft current problems" caused be the relationship between the drive and motor. First, does this make sense? Also can some direct me to some reference material that is specific to hollow shaft motors? Finally, any ideas on preventing this in the future? Thanks for your help in advance.
The problem is that twice in the last six months the top bearing has start make horible noised and has had to be replaced under U.S. warrenty. The motor shop is telling me that the cause of the bearing failure is "shaft current problems" caused be the relationship between the drive and motor. First, does this make sense? Also can some direct me to some reference material that is specific to hollow shaft motors? Finally, any ideas on preventing this in the future? Thanks for your help in advance.





RE: bearing problems
You can either have grounding bushings installed on the motor shaft, or you can attempt to ameliorate it with filtering of the VFD output with very specifically designed load filters for that purpose. The absolute best practice would be both.
Do a web search on "Aegis shaft grounding bushings" and then look at Trans Coil Inc (TCI) or MTE for VFD load filters. All of these sites have additional papers describing the problem in more detail.
RE: bearing problems
RE: bearing problems
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RE: bearing problems
Roy
RE: bearing problems
Normally the VFD Driven motors most be specified by the costumer, so if you buy the motor notifiying the use with VD the motor manufacturer will provide you a correct motor.
Is very strange U.S Provide a wrong motor, because normlly they don´t use hybrid or insulated bearings but they insulte the NDE shaft journal bearing, so this is enought to avoid the shaft curent, will be good if you can confirm the shop diagnostic, so you can tell to the shop to do the folowing: 1. Look the bearing grease if is black color and if smell bad. 2. Take a grease sample and watch in a microscope in ordr to find metalic particules 3. Clean the bearings and cut th external raceway with an electric saw then look inn the internal raceway if you find burning signals and small horizontal lines around all the race way. You sayds the motor is verticlly mounted, so this motors normally use special bearings to support the rotor weight, so the problem could be mechanical design too.
Regards
Petronila
RE: bearing problems
I think you should verify if it is shaft current that is causing the problem. The motor company who analysed it said so, and it is fairly easy to spot once the bearing is out but the type of pump you have, as I understand from the description, is a water lubricated type. This means the method of lubricating is active once the motor/pump starts. My limited experience on VTP is that they have to start quite quickly to get the necessary lubrication to the bearings. If you have a VFD driving it then one of the benefits can be a controlled acceleration time (minutes/hours even) but this could induce a problem if the accel time is too long and the lubrication is not getting to the bearing. 150hp would typically point towards a longer acceleration time as standard and so may be worth looking at.
RE: bearing problems
An IEEE Spectrum article discussed this within the last few years. As I recall, they stated that a shaft grounding brush was a better solution than insulating (ceramic) bearings, as the insulating bearings will simply move the problem to downstream equipment (to your pump).
RE: bearing problems
RE: bearing problems
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: bearing problems
RE: bearing problems
Keith Cress
kcress - http://www.flaminsystems.com
RE: bearing problems
like to give a STAR to all.
thanks guys
RE: bearing problems
eyec = thewellguy ? (same guy?)
The cause of failure ended up being?
The other sources of stray current were?
thanks in advance for any info you can share.
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RE: bearing problems
the failure appears caused by stray current through the lower motor bearing which facilitated pitting and final failure of top babbit bearing
possible cause leading to stray current was contaminated lubricant oil and latent moisture
the other sources of info were research and industry papers on stray current, Kingsbury in particular had some good info @ h