Slipring arcing

I am interested in anyone's experience of arcing over a slipring.

In the last month, we have had serious arc damage between the brush (copper graphite) and ring (copper).

There is a suggestion that a small amount of arcing is normal between the brush and ring, and that this can cause a build up of damage. However, I feel strongly that as long as some part of the brush surface is in contact with the ring, then no arc can be formed.

is there some phenomenon that I am unaware of that can cause this?

  • Is this on something that has worked fine for years previously ?

    If so I'd be looking at contamination of the rubbing surfaces (oil grease?) or a loss in spring pressure or perhaps brush shortening with age ?

    There may be be a ghost of an arc in normal use depending on the power being transferred, but if there is enough to burn the copper then something is going seriously wrong.

    I suppose if it has never worked there may be a design error. Who makes it - I'd be tempted to  ask how it is supposed to be set up.

    Mike.

  • I would say that there is always a wee bit of sparking, but I don't see why that would amount to "damage". Equally well, anything with moving contacts will be subject to wear.

  • Could it be Phenolic Breakdown?