Relationship between windings, emf and armature reaction
High-power synchronous alternators (part 1)

It's worth recalling this composition, as it relates directly to the Potier diagram of an alternator with a constant, unsaturated air gap. This diagram is also used for machines with salient poles (§ 4.3 of [ ]). when only the excitation current is to be determined.

The following relations [D 3 520] give the fundamental terms of the magnetomotive forces (fmm) created by the inductor (index f ) and armature (index I ) under balanced load: