VPI versus Traditional Dipping & Baking
VPI versus Traditional Dipping & Baking
(OP)
We have recently experienced a motor failure which resulted in a full re-wind (bar stock) of the armature of a 400 hp DC motor. The motor manufacturer recommended the VPI process, however, that would have extended the repair by 48 hours (according to the service provider). We instead went with the traditional dip and bake, and the motor has since failed again, requiring the armature to be re-wound a second time. I guess my question is two-fold: First, regardless of the type of winding protection, would the application lead to a catastrophic failure after 11 hours of run time if correctly applied? Second, despite the superiority of the VPI process, is traditional dipping and baking frowned upon in the industry? Any thoughts or feelings would be greatly appreciated.
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Cheers
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RE: VPI versus Traditional Dipping & Baking
The VPI impregnation is superior because it deeply penetrates into all the insulation materials and fills all the air spaces with 100% solids resin (no thinners), improving the insulation and providing solid heat conductive means; however, it provides only a small part of the mechanical support. A poorly banded armature will fail in short time in spite of being VPI or dip and bake.
RE: VPI versus Traditional Dipping & Baking
RE: VPI versus Traditional Dipping & Baking
I Agree with aolalde about the VPI and Banding Tape Concepts, but I Think a second failure in only 11 Hours
needs to be research in detail. I Think your Repair shop most test properly al stator windings and make a review of the second failure cause, the burned armature winding most be analysed looking for some material or brazing failure. A winding data review will help too, looking for Winding Mistakes in Equalizers pich, winding progression or Commutator pitch. Other think to review is varnish cure time and the mechanical balancing. The shop most conduce a good no load and load test ask they for the test reports and all results.
Best Regards
Petronila
RE: VPI versus Traditional Dipping & Baking
I think petronilla has a point. Shayne, you must investigate the root-cause failure, aside from putting a biased to your self on the differences between VPI and Traditional varnishing method. Take a look the detail of control failures, like; loss of field that leads to overspeeding, overloading etc.
Good thing to start is to review the Evaluation Test Report/ Findings of probable cause(History) prior to failure. Secondly, furnished the Final Test report if provided.
We used traditional varnishing but never had problems that turns out it never exceeds to the machine repair warranty. There might be other cause that you may never take into account.
By the way, how the commutator looks like upon its failure? Can you describe?
RE: VPI versus Traditional Dipping & Baking
RE: VPI versus Traditional Dipping & Baking
140 F motor bearing temperature is OK, and the Start-UP vibration could be considered normal if you are performing a full load motor´s start. If this motor only runs 11 Hours after the second repair this is very abnormal ask to the repair shop for the failure report, this could help to give you the righ direction to find the failure.
Another think could help: ask to the maintenance people if in the failure´s moment somebody report something abnormal.What happeneed with the drive´s protection??(Shut or not) What happened with the motor´s fan?? (WAS SPINNING WITH RIGHT DIRECTION??)the maintenance people most have the information.I think is better to ask and research more about the failure´s moment.
Regards
Petronila
RE: VPI versus Traditional Dipping & Baking
Since you mentioned commutator burn out, I would look at possible wrong equalizer winding connection, improper neutral axis, wrong armature winding (???) etc.
* Basically, I would like a full-time job on part-time basis *
RE: VPI versus Traditional Dipping & Baking
As you say it's burn out, if it is totally burn out that appears to be black coloration on the surface usually cause by overload. Hint tha machine failed within in 11 hours. The Vibration reading at start up and bearing temperature is normal, thus it will be disregarded.
Possible hint to look after on the commutator surfaces is traceable commutator bar burn-intervals that is it forms a burn out pattern on the surface. If you take this to account, perhaps i can lead you to most probable cause.
Furthermore, it would be better to investigate for the failure since rewinding of 400 hp is quite expensive, exclusive of downtime.
RE: VPI versus Traditional Dipping & Baking
As suggested by others you need to analyse this failure very carefully. I beleive the reason can only be one of two things. First the rewinder has made some kind of gross error or there is a fault in the drive/control system that feeds the motor.
You need to get to the bottom of this otherwise you could end up with a third failure!
Some questions.
What is the application and drive system?
Has the reason for the first failure been identified?
Did the aramture bird nest?
Has there been a turn to turn fault behind the riser which has caused the commutator end band to burn and fail?
RE: VPI versus Traditional Dipping & Baking
Maybe shayne is indirectly handle this machine. Hence, she/he might not give further details.
RE: VPI versus Traditional Dipping & Baking
In the U.S. we have our Independence day
not return until Tuesday, or Wednesday.
During this time Work is the furthest thought we have.
Chuck