....it looks like I miss read it is actually only single phase hadn't seen 460 single phase before.
Yes, Page 27, left hand side- the input only uses two legs.
Most people assume 460 as 'three', but there's no 'rule' that says one needs to use all three legs.
In TIG machines, it's very common that they're only single-phase, as they run the secondary (welding) current out as AC for aluminum and other metals, where AC causes a 'cleaning' action.
Newer inverter-based machines 'synthesize' AC by switching in both directions, and frequently, they're programmable to be assymetric (more in one direction than the other) to enhance cleaning-action. There's a few non-inverter types that use some fascinating magnetic prowess to yield an assymetric AC waveform for the same purpose... and I'll discuss it with anyone interested, but it's somewhat off the topic of this thread.