BuckeyeDennis wrote
I’m curious, AmishMachinist. What do you see as the advantage of a DC motor and drive over a 3-phase Frame 56 AC motor, paired with a VFD? I haven’t priced that hardware in a while, but your budget would probably cover it up to 1 hp and maybe more, and you’d never have to worry about brush replacement or commutator wear.
For me, it’s really because I currently work with DC motors and drives every day, they’re simple and easy to diagnose, good voltage good amperage no problems. VFDs are fantastic, but seem to get finicky with fluctuating draw on same circuits and fluctuating phases. I think it takes a very expensive high grade VFD to not see these issues. (Then again for a shopsmith these aren’t really an issue as opposed to a manufacturing machine where close tolerance and speed are necessary) DC drives are very simple and the newer boards have greater tuning capabilities than earlier drives. I haven’t seen any quality VFDs in the same price range as DC drives.
I also think it’s an advantage having serviceable brushes. Brushes have also come a long way, granted they are very dirty, but I’ve seen machines with hundreds of hours and I check the brushes and they still have 3/4 life left on them.
All in all for me it’s familiarity and personal preference, eventually AC/VFDs will overtake DC drives once they become common place in another 40 years and manufacturing is more competitive between brands.
