Wiring all 3 togther will saturate the core.
If you want to do something 'quick' then the trans will only give 1/3 of its original rating by just using one coil, and that is assuming you have access to the star point for the neutral (and the trans was wound star not delta).
You could get most of its power rating by adding 2 caps, to generate the 3 phases, mains in one, then a cap for a phase shift to the second coil and another for the third, this is assuming the trans was originaly wound star, however you'd need some pretty bg caps.
Another way you can do it, and I've seen this done is use a single to 3 phase motor variable speed drive to give you the 3 phases, the trans would probably be more efficient at 100hz, however this works out expensive, and a vfd gives you 3 x 220v not 3 x 415v, you can get round this by connecting the dc bus - of the vfd to the star on the trans, assuming again its wired star.