There's a good chance that such a machine may accept DC just fine without even knowing it. Assuming the inverter/VFD has a simple full-bridge as its first stage

There's a good chance that such a machine may accept DC just fine without even knowing it. Assuming the inverter/VFD has a simple full-bridge as its first stage, the DC would just flow through the same half of the bridge all the time. A lot of PSUs can do this too; I just bought a Mean Well RSP-1500-48 which specifies its input voltage as AC 90-264V, or DC 127-370V. This means I can run it straight from the traction battery in my car (200V DC) if I care to...