Re: [CAD_CAM_EDM_DRO] Re: weird DC motor

stevesng@... wrote:

>
> Pictures of the motors were posted by Dale at:
>
> http://home.mmcable.com/mediasmith/DCmotor.jpg
>
> The detail is hard to see, but on the rear the brush holders
> are flush.

Yes, I see the brush caps in the photo marked rear of motor 2.
I don't see any brush caps on the front end of the motor.
If it has external caps at the rear, I can't imagine it would have
concealed caps on the front.

> I cannot tell if there are brush holders at the
> front, but the end bells look the same. Paralleling armature
> windings that were not designed to be paralled could be a
> problem, however armature windings in single commutator
> motors run in parallel all the time because the brushes
> make contact with multiple segments of the commutator at
> once.
>
> If it is a wound field motor it should not run with
> power on only one set of wires unless there are internal
> connections putting the field across the armature. This
> seems unlikely as field control would not be possible and
> because the pictures of the open rear end bell do not seem
> to show such connections.

Ahhh, wait a minute! Dale said the motors would 'jump around'
when he had it wired in one particular way. this could be a clue
that that wiring is essentially differential compound. Anyway,
these motors are most likely not meant for series field use.

As I said before, there were motors made to use a PM field, but
that the field could be reduced with a field winding for high speed
operation.

Jon