[brian_]

The series winding is the big issue. If you disconnect the field winding from the armature, and arrange a controlled power supply for the field, then you could use it as a separately excited generator (or motor).

 

[brian_]

Is there a reason you'd excite the field and not the armature ? Seems like most generators use a permanent field in the rotor.

The Impulse and similar brushed DC motors feed the rotor (armature) windings through a commutator, so the stator (field) has constant polarity - it could even be a permanent magnet. Machines built as alternators are normally the opposite: the constant side is the rotor (wound and fed a controlled current through slip rings, not a commutator) and the alternating side is the stator (connected to a rectifier). So the common automotive alternator is like a brushed DC motor inside-out: you control the rotor of the alternator and take the output from the stator; you would control the field (stator) of the Impulse and take the output from the rotor (armature).

Since this is a commutated setup, I imagine it will naturally produce a pulsed DC output that will require a smoothing capacitor but no rectification ?

Yes, and that's a big difference from a typical automotive alternator.