(ET) E-15 Traction motor series field versus shunt field combined interactions question

[john <johnreinhard rochester rr com>]

Hi All,

Chris recently replied to my request for info to program my 1268 with 
good info.

He pointed out the important motor winding description 'compound', or 
Stabilized Series / Shunt, which I had really NOT been thinking clearly 
about.

My other brushed (non traction GE, and non-Electrak) motors have 
permanent magnet fields, or high turn count / low amp fields or low turn 
count high amp fields.

Does anyone know the ratio of series turns versus shunt turns on the 
field windings ?

Since the E-15 reverses only the low amp shunt field, that field is 
fighting, and beating, the series field.

just to use easy numbers, lets say armature /series field at 100 amps.  
If shunt field only 10 amps, then turns on that would have to be 10X, to 
just equal the magnetic force generated by the shunt field.

So, if you reverse electrical polarity on that, it cancels out the 
series field, & total field strength is zero ?

So, if you had 20x turns on shunt field, its strength vs series is 2:1, 
and reverse electrical polarity, the armature reverses, but meanwhile, 
the field coils fighting causes heat buildup in the windings ?

Is there a spec or a graph that shows the heating effects, over time, & 
proportional to amps, due to using electrically reversed shunt field to 
reverse the armature ?

OEM GE E-15 controls used this for reverse, so I assume concern for 
winding damage was not high, or engineers expectation was we rarely 
drive in reverse, and maybe not at high power.


John