Steve:
don't get too wrapped up in the hype about the polar being a DC machine, it is no more
a DC machine than the alternator on your car
if it were a classic DC Generator it would have a commutator and brushes, or possibly some sort of
electronic commutation scheme other than a rectifier bank, which in the polar case is remotely mounted.
what they are trying to relate in a very broadly applied manner is the fact that eliminating conversion stages
increases efficiency. i don't have any problems with them stating the obvious but i do have issues with obfuscation
which they are boardering on heavily.
basically is is a brushless alternator with remote bridge rectification,, it has a 6 phase stator which makes a bit lower ripple
and a bit more efficiency, and what they gain with the pm excitation they have to give back with the buck section of the alternator
in order to gain control for regulation.
overall not a bad piece of engineering, but it is not the holy grail in my opinion. even though they would have you believe that it is just that
in their ad copy.
personally my bet is you could meet or exceed their efficiency claims with an STC 3 phase head that is rectified and uses an off the shelf VR that can do true 3 stage charging,, interestingly their 3 stage is not truely a 3 stage unit.
the big plus they have going for them is compact size, which is very desirable in military or marine equipment, but not much of a concern
for the offgrid crowd.
if you really want to do such an animal, look to the telecom boys
i know generac built or builds some belt driven 6kwatt alternators that are 6phase, remote rectifier, and are 24 volt nominal and they also make a 48 volt nominal unit as well, you get all the bells and whistles, and can find them very inexpensively surplused with very low hours on the clock.
bob g