Re: (ET) E15 motor is not a compound.

["David Roden" <etpost drmm net>]

On 15 Sep 2012 at 19:09, The CZ Unit wrote:

> There is another reason; because a shunt field motor can't draw 
> a lot of amps through the field, starting torque and power is limited. 

The impression I had from Walt's post is that the series winding has a 
relatively slight but useful effect under heavy load.  I will say that I 
don't sense a great weary weakness in my E15.  It's towed a lot of heavy 
stuff.  ;-)

Actually in this context I think we should call the GE ET's a separately 
excited motor, since the field is not constantly in parallel with the 
armature.  A sep-ex motor can have ample starting torque; that's a 
function 
of the flux the field is able to generate.  

As I understand it, when sufficiently excited, a sep-ex motor's field can 
be 
just as strong a flux as a series motor's.  However, the controller will 
be 
more complex and expensive because it has to manage the field separately.  
OTOH it's relatively easy to add regenerative braking to a sep-ex motor, 
which is not the case with a series motor.

Maybe one of the list's motor engineers can comment on this.


David Roden - Akron, Ohio, USA

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