This is the problem with continuous brush.Using manual or automatic brush lifting and short circuiting will ensure that the starting characteristics of slipring motor and running like cage thereafter are derived.Since brushes will be in contact with the slipring only during the starting much cleaning is avoideded.Normally it is blown away by air and brushes are checked .
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To avoid crticism do nothing,say nothing,be nothing
What type of slip rings are they? Steel, Bronze, Gunmetal etc. What is the surface like? Do they have a spiral groove? What type of brushes are installed? Did the failures start recently? Has there been a change of brush grade or manufacturer?
Something to watch out for is if the brushes are M_____s especially if the original brushes were something else (including any company M______s may have bought).
Stones (fine and polish are the grades to buy) which neatly fit in the brush holders can be purchased to dress up the rings but the stones themselves must be kept nice and flat across the section. I purchase mine from Australian Carbon, for the UK I suggest you look for your Hellwig distributor. They only cost us about $50 ea.
If they don't require stoning ensure the enclosure is thoroughly blown out with clean dry air, clean any deposits of brush material from all surfaces (especially important for copper graphitic).
Quiz the brush manufacturer closely about grade changes and don't expect to be told the truth. It wasn't until after the sixth blow up in 3 weeks that we finally forced the truth from above.
Currently I am working on a similar problem with steel slip rings eroding which started 6 years ago when the original supplier was bought out. Original R320 grade no appreciable erosion or corrosion, now we get both in spades.
Check the connections to the rings which are often a threaded rod which can come loose, but if it is multiple failures beware of red herrings of that kind and focus on the brush supplier.
Cleaning of Brush Gear
Re: Cleaning of brush gear
