Bridge rectifiers do not go up that much in price for the larger values so go with something like a GBPC3504W 400V at 35 amps.
For the transformers look up Hammond, for a 240/120 or 120/120, I would think you could go with a 4 kva at 60% duty cycle as you are probabally not going to see maximum power on all three motors for any extended time.
You will also need a electrolytic capacitor bank for 5% ripple at that voltage/current around 10,000µfd.
Some amplifier manufacturers recommend grounding the motor negative, if you do, do not ground the secondary of the transformer.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.