Title explains most of it. Supply is 2 phase 240v (2 hots, 1 neutral). I would rather not use a transformer in this process. The main schematics I keep coming across gives +340 and -340 while I'm trying to get 676VDC relative to ground. If anyone has a route towards this goal (full wave rectification and doubling) that I'm missing I would be happy to hear. Thanks!

 

Example of rectification circuit I've been seeing.

 

How much Current will you expect ???
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BTW, that is referred to as split phase (single phase), not 2 phase.

 

Full wave version of the voltage doubler will do the job. (Assuming that you 240V supply is 240V phase-to-neutral)