It's 54 years since I served an apprenticeship as an armature winder, so the memory is dull, especially after 4 G&Ts, two glasses of red and 4 whiskies, but you seem to be mixing ac and dc in your question. No shunt and series fields in an ac alternator, only in dc.
I'm sure that someone will come up with some answers, but I'll look back in tomorrow when the eyes can focus better. Hic.
(On holiday for 3 months in Mandurah, Australia)