Testing a 3-phase ev charger on an 1-3 frequency regulator
It might be possible with a single phase using a transformer.

Figure 1. A VFD outline schematic. (Image source: EE.SE unattributed.)
The charger probably has an input stage similar to the variable frequency drive above. A three-phase bridge rectifier charges up the DC-link capacitor to √2 times the peak mains voltage. In Europe this would be a 400 V supply so about 560 V. Since you're not charging you might be able to run it from one 400 V supply generated by a 230 to 400 V step up transformer and connected to two of the input terminals.
I suspect that this will generate some internal &quot;lost phase&quot; errors which may make the exercise unusable but it might work and give you a useful error message to help debug your system.
Either way the manufacturer would be the right people to ask. A &quot;frequency regular&quot; will may not give out a sine wave and may have difficulty with the capacitive load.