Andre Majorel Inscribed thus:

On 2011-02-26, Baron wrote:
Sylvia Else Inscribed thus:

I'd have to wonder whether one of the rotor windings has failed
open-cicuit. I think that could even account for the sparks. The
magnetic field for a winding that is becoming disconnected by the
brush action has to collapse because the broken winding that's being
connected cannot maintain the field.

Sounds like OC segments on the comm...

The old man and I don't know enough about motors to be sure but
we did suspect something along the same lines.

Its easy enough to test. In the old days a buzz box was used, nowadays
no one bothers ! Its far cheaper just to throw it in the scrap box and
buy a new one.

I'll bet that if you look very carefully at the commutator segments, you
will find that one or more are loose and its likely that the loose
segment is OC.

We thought that even if we determined which winding is damaged,
attempting a fix would be risky and a lot of work.

Its very rare for the windings themselves to get damaged. Open or short
circuits at the commutator segments is very common.
I don't remember the last time I saw anybody repair a bad commutator !
Not on fractional motors/generators anyway.

So we got a used (but working) motor from electrodocas.fr. That fixed
it.

Thanks folks.


I reckon that you took the best course of action. :-)

--
Best Regards:
Baron.