Re: [CAD_CAM_EDM_DRO] Re: weird DC motor

stevesng@... wrote:

> You should be able to run it fine as a plain DC motor. There
> are many variable speed controlers avaiable that can handle
> the 220 volts at 10 Amps, more than the current expected with
> these motors. The commutators would be wired in parallel and
> with the same polarity and operated at 220 volts. Polarity
> can be check by running one set at a time.

Wiring the two commutators in parallel could cause large
circulating currents between the two sets of armature windings
unless the windings (and the field flux that penetrates to them)
are identical. If the windings are done with one set on top of
the other, as they almost have to be, then they won't be balanced.

I am concerned because the original writer said the motors ran
much faster when the two windings were connected in series.
This doesn't make much sense. Has he really seen two sets
of brushes, or is this just a 4-wire motor that he doesn't know
much about, internally? A certain (very early) vintage of Bridgeport
CNC machines (CNC control may not have been made by Bridgeport)
used motors that had both PM and wound fields. They reduced
the PM field with the wound field to make the motors run faster
for the rapid feed. this was also done in some computer tape
drives to get fast rewind speeds.

Jon