Originally Posted by
RaderSidetrack
The "ground" wire is not the same wire as the "neutral" wire. In a 120VAC device there is a hot wire and a neutral wire. Both of those are current carrying conductors. There SHOULD also be a "ground" wire, which does not carry a current but is there for safety reasons. There may be a dedicated screw on a terminal block for "ground", or it could be just connected to the machine frame.
When you convert the machine to 240VAC, you have two different hot wires, but the ground connection remains the same as it was in the 120VAC scenario.
If you do the conversion by changing the power cord "plug", what was previously the neutral wire typically gets repurposed to become the 2nd hot wire. If the machine doesn't have a plug and is connected directly, similarly what was previously the neutral wire typically gets repurposed to become the 2nd hot wire by moving the wire connection.
The ground wire should remain undisturbed. In the case of your isolation transformer, if you don't have dedicated ground terminal already, one of the transformer mounting bolt (holes visible in the bottom foreground of the photo) could serve as a ground connection -- assuming the transformer is mounted to part of the machine steel/metal frame.