On 9/15/2012 7:54 PM, David Roden wrote:
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 it might be more than we think: I was able to drive the E20 (although under high amps) when the field diodes blew up. Also in reverse I can tell that the E20 has less power for going up hills, have not tried the E15.
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.
Pretty much. The E20's is a compound motor, the question is are the E12 and E15 motors compound or true sep-ex? The field is kind of independent of the armature actually, although it's sourced by the same place as the armature (and can't ever exceed armature voltage).
I'm just reporting what I see. The E15 and E20 are different in odd ways, biggest one being that the E15 feels a lot more "abrupt" than the E20 on speed changes. I wonder if the compensating field in the E20 makes the motor more smooth as well (spikes will cause more field which will modulate the motor output).
C