Article 720 applies to ac or dc and is one of the smallest articles in the book!
I do a lot of work on wind turbines that sometimes use pm generators that produce AC but then is rectified to DC. SOmetimes the amps can get on up there.
I prefer 240 vac three phase output for pm generators myself.
A lot of folks do not know about this article.
I am guessing that there is a restriction for this so you dont start seeing a lot of MTW 18, 22 etc in control panels...which I already have seen!
Electricity has no respect for ignorance!