Hey Phil,
Long story short, all of your PSUs will not be able to use 3 phase, so you will either give them 2 of the phases and a ground, or 1 phase + 1 neutral + 1 ground. Always go with 2 phases and a ground as you will need less outlets, wire, etc when using the higher voltage that is from 2 of the phases.
It sounds like you have a high leg delta system, so I believe one of the legs will be 240, off the top of my head I think the other 2 legs will be 208. I have never used a delta system, they are older and were for supplying extra volts to start motors. Your a smart guy, grab a multimeter and you will figure it out quickly (just be careful with live wires).
that is the plan
Also grab one of those amp meters you can put around each of the phases (to see how many amps are being used). They will allow you to answer weird questions like say you are using 10 amps on each phase, and you add another 5 amp psu (using say 1200 watts) to 2 of the phases or 1 phase and neutral. Does that increase each leg by 5 amps, 2.89 amps, or 2.5 amps? 5 minutes of testing and it will all make sense, have fun, 3 phase is good stuff!
the pdu's have built in amp meters so I will attempt to have each one at 4
You will want the meter to see what is going on at the level of each phase. If you are going to push what is available at the location, you will want to see what each of the phases are pulling at the service entrance. You know, if you have a 100 amp service, make sure you keep it at 80 amps for each phase, that kind of stuff.
Personally, I have a lot of machines and it would be impossible to see the big picture at the service entrance unless you measure it there. If you just have a few machines, no need for the meter.
He can spare 30 amps of it which = 3 pdu's at 10 amps each as a max.
my goal is 6 miners using 3 psu's at the 1000 watt level which should be only 4 or 5 amps a pdu.
I have 2 x 1200watt plats
I have 1 x 1600 watt plat
I have 1 x 750 watt plat
I have 1 x 650 watt plat
I have 2 x 1300 watt gold
I have 1 x 650 watt gold
I would be able to go 2x it if things are working out well. So it is not a question of have to get pdus or psus
Just need to be sure what each of the 3 balanced plugs will supply me 208 volts or 240 volts.