For many years I have used servo drives that included the DC supply as one unit, A-M-C, Copley Controls etc, there were others.
The drive just rectified and capacitor smoothed the mains supply.
IOW, no transformer, no galvanic isolation.
These drives were used in conjunction with Galil Motion etc, where the signal was ±10vdc analogue.
I recently had reason to implement a step/Dir system and one motor was a large DC brushed and previously ran off of a rectified 120v mains supply direct.
I wished to use this motor with one of the few manufacturers that offered step/Dir drives in this size and voltage capacity.
All the ones I found, said the supply MUST be linear of the isolated variety, this would then involve a large, expensive and space consuming device!
There are also many devices, Treadmills that also use this calibre/size of motor with mains fed motors with no apparent problems.
There is no logical reason why you should need the large required transformer for a isolated supply if proper Grounding and bonding is observed!
(Hint All VFD's operate this way!)
Al.