So you have a AC Tech - SM230S VFD, which is a 3 Hp single phase input model.You will need to have it connected to something like a 30a 240VAC dual pole breaker with 10AWG wire going to the machine. The machine has an input line reactor installed, which is wired prior to the the VFD, this provides some reserve/smoothing for the the input current and can help tame transient spikes. Your incoming power would connect to this and not the VFD. Uncommon on this size machine, but looks like a very clean install. Once powered up you will need to figure out the controls, it appears that he is using a remote VFD panel to run the VFD. I would want to see some form of E-Stop if not equipped, and you will need to see how the machine operates. Most likely the motor is likely a stock (or non-inverter rated) unit, so the maximum speed (Hz is probably set for 60-80Hz, wouldn't want to go above that unless you have an inverter motor, and one needs to be cognizant of the maximum lathe speed so you may want to get a tach at some point). Lower end of the speed range is probably around 20Hz.
Attached you will find the VFD users manual and the remote keypad instructions. I would have the electrician power up everything and then go over the VFD operations with you. Most likely the previous owner had everything programmed, so should be ready to run.
Very nice score, I am sure it will be a very nice lathe that you got at an unbelievable price.