In message , The Natural Philosopher
writes
On 25/03/17 18:51, Tim Lamb wrote:
bought a recon motor some year s back for around 75 exchange when mine
did this.

wasn't brushes. Was a short from a winding to earth on the armature.

75 sounds better:-)

These brushes are badly worn. I wonder if the copper in contact with the
com. leads to excessive arcing.

I've given the com a clean up with emery cloth and raked out the
segments. Thorough blow through with compressed air and I'll see what
new brushes achieve.


if you have it out check resistance to the frame/armature stampings
from the commutator segments. Its rare for arcing to blow an RCD unless
you have **** loads of electronics (RFI caps) between live and earth in
the house and a rather high impedance supply.

On the desk beside me. I don't have access to a Megger but I can try my
multimeter.

I don't think there is anything high impedance about an agricultural 3
ph. supply and I'm not aware of any line/earth shunts other than what is
hidden in our various bits of domestic electronics.


--
Tim Lamb