I used mine with a "custom" 30a plug to 15a plug extension cord I made. I can't remember if it was a 3kva or a 2kva unit.
Firetrap! There is a good reason that code enforcement requires special plugs for high amperage or high voltage devices: To prevent electrical fires caused by attempting to draw more current than the wiring can support thereby causing them to get hot and start fires.
If you get a device that won't work on a standard 120v plug invest the money to create a dedicated high current circuit rather than jury-rigging an extension cord. It's just outright safer.