Need to connect neutral wire?
If the machine is wired for a wye, (L1,L2,L3, and N), you have to supply all of them.
If the load is equal between the phases, it could appear that everything is ok, but
if one load is larger, or if one fuse blows, you will get wrong voltages, and currents.


If the machine is wired for delta, neutral is not needed.
It sounds your machine requires a neutral.
Run a new supply including neutral to the machine, or get a delta to wye transformer
for that machine. (if you do that, you have to ground the neutral).
The neutral wire carries unbalanced current, and ensures that the load is working on Line to neutral voltage.(fixed voltage). Without a neutral, the voltages will balance according to the loads. In a short, it is a bad idea.