Re: (ET) Reversing Motor

["Steve & Sandy Naugler" <snaugler earthlink net>]

Rhett, Allen, and others,
    I have rebuilt two E 15 traction motors and they both had stabilization
windings.  The E20 motor on my garage floor looks like it is built the same
as the E15 motor except slightly longer.  I suspect it has stabilization
windings as well.  I would expect that they are wound as a differentially
compound motor in forward and as a cumulatively compound motor in reverse.
    My home owner's service manual shows the E15 reversing the motor via
field reversal and the E20 reversing the motor via armature reversal.  This
manual's schematics also show both the E15 and E20 motors as having
stabilization windings.
    Allen, you are correct.  If you reverse the armature and at the same
time reverse the stabilization windings, as is the case with the GE 
traction
motors, speed stability in reverse would suffer just as much as if you
reversed the motor via the field.  (I wrote incorrectly yesterday about
this.)  If you reverse just the armature without reversing the 
stabilization
windings, speed stability would not suffer.  You need separate connections
for all windings and a bunch more relays to do this.  As you seldom load 
the
traction motor heavily in reverse, this is not much worth doing.

Steve Naugler
----- Original Message -----
From: "Rhett T. George" <rtg ee duke edu>
To: <elec-trak cosmos5 phy tufts edu>
Sent: Friday, March 03, 2000 2:51 PM
Subject: (ET) Reversing Motor


> - Greetings -
>
> Allan has asked about compensating field windings.  Let's review the
> fields that may be found in a wound-field, D-C, brush-type machine.
> There may be a shunt field or a series field, giving the definition
> to shunt-wound motor and series-wound motor.  If the motor has both
> shunt and series and they add to produce the total field, it is a
> cumnulatively-compound motor.  If the series field subtracts from
> the shunt field, it is a differentially-compound motor.  [This one
> may not be very stable over a wide torque range.]  The shunt and
> the series fields are wound in the same locations in the motor.
>
> Interpoles and/or compensating windings are wound 90 magnetic degrees
> away from the main poles.  They are used to keep the reaction field
> due to current flowing in the armature winding from shifting the total
> field away from the main poles.  This reaction field is negated as
> much as possible by armature current flowing in the compensating/
> interpole windings.  Compensating windings are put inot the faces of
> the main poles.  Interpoles are in between the main field poles.
>
> Sorry, I do not know of a sure way of determining the presence of
> compounding or compensation in a simple way without looking inside,
> presuming that such info does not come from the manufacturer.
>
> Hope this helps.
>
> Rhett George
>