Bitcoin Forum

My newest problem: I am about to add a 1000 Amp service to my building for running miners, my problem is the service will be 3-phase and the miners run 240v single phase, how do I get from 3-phase 408v to single phase 240v?

I've seen some 3-phase PDUs, is this what I need?

Obviously, I need to balance the load or it will burn the transformer out.

Thanks in advance, Frank

If you've got 3-phase wye at 408V line-line, your line-neutral should be 240V.

Three-phase comes in so many different configurations of source and voltage you'll have to explain your setup a little better to get good advice. And also hope NotFuzzyWarm is paying attention. That guy knows things.

Who, lil ol' me? http://www.sherv.net/cm/emoticons/embarrassed/shy-whistler.gif (http://www.sherv.net/)
Firstly, considering the amount of power you are adding I assume you ARE using a licensed electrical contractor right? If so - they already know what you need to have done and can explain it to you... Something like this is NOT for DIY!

 As Sidehack said, assuming you are getting wye (aka star) incoming service then you will already have 240VAC from each phase to the Neutral so that part is fine.

If the incoming is delta then you will need a transformer to change that from the 408 delta to 208-240V and gets a little more complicated: If you do not need any 110v service then the transformer can be for 208-240V phase-to-phase with no Neutral connections

From the incoming service entrance, split off into a few main 3-phase feeders @ around 250-500A each to feed distribution breaker panels filled with 20A breakers. As for balancing, as long as the breaker panels are mostly used only to feed miners and all breakers are same size they will balance themselves out as you add breakers. The slots go L1, L2, L3, L1, L2, L3, etc.

Whoa that’s a lot of power. Like Fuzzy said you need to use a licensed electrician. Rule of thumb, if it hums hire someone. 480v is no joke and should be dealt with accordingly. What you are trying to do is easy as long as they are legit. Good luck.

Thanks! We're also setting up some large natural gas gen-sets and your answers helped with that too.

We're going to be using a primary transformer to step down the 480v to 240v. Thanks again!

Ah, 480VAC -- not 408 as you originally posted.
Ja for that you definitely need a transformer to bring you down to 208-220v as 480v 3-phase puts phase-to-neutral voltage at nearly 280v. Again, for distribution panels feeding only 208-240v miners, fan motors, whatever, then you do not need to run a neutral wire to them, only need the 3 lines and ground. Only panels that you want to split off 110v need a neutral wire.

For what it's worth, 380-410VAC is a recognized voltage standard for various parts of the world hence the initial mixup.

Yeah that was my bad, we have 408v 3-phase coming in our building and 480v 3-phase coming off our gen-sets.

Thanks for the help!

I am not sure if you are from U.S where everything seems to be measured differently , but talking from an international standard of electricity , a 3 phase set up usually comes in 4 wires  ( 3 phase and 1 neutral wire ) . now anything you measure between the neutral wire and the phase is 220v ( based on 3 phase = 380V). which is the exact set up i have here.

so what you have to do is.  get 3 main circuit breaker , connect each phase ( wire that is not neutral ) to 1 breaker. and then you going to treat each of the 3 breaker as a different source of 220v, of coz do not forget to pass the neutral to every breaker as well.

excuse my poor vocabulary but i hope you get the picture.