[chimpera]

I am building out a shop and have the choice of high leg delta three phase(240v)
High-leg delta - Wikipedia, the free encyclopedia
and standard Wye three phase(208V) from the power company. This is in the US.

I am leaning towards delta because it will run 240 equipment better and should work with most used machine tools.

One downside is that I would like to use 5 wire plugs IE NEMA L21-30 to provide 120v power to controls, only L21-30 specifies 208V max and I see no equivalent for 240 delta power.

I would appreciate input from those who have a lot of years dealing with this sort of thing.

Thanks, Ben

[underthetire]

Going cnc?
Don't get the 240. 208 is a perfect range for most cnc machines. All fanuc except the 460 option have a max of 242, so your playing with fire.

[RCaffin]

Frankly, I find the whole idea of high leg delta frightening. The opportunities for disaster seem huge, and you can't run a stock 3-phase motor off it easily.
Shudder!

[chimpera]

For those not familiar with high leg delta, the potential between L1 L2 and L3 is always 240V. Most three phase motors will run better with 240V, plus you can run 240v single phase equipment. The high leg part only involves the potential to neutral. You can only use two of the legs to neutral for 120v single phase branches.
The higher voltage means you draw fewer amps and can use smaller conductors for any given load.

The rub is that I would like to get 3 phase power and single phase 120v through the same plug for the control equipment. This requires a receptacle with 5 wires. L1, L2, L3, N, and G. unfortunately the only plug with 5 conductors L21-30, is only rated for 208V.

I have heard that Fanuc is picky about its power source but at this point I don't have any Fanuc equipment.

Has anyone run shops with both types that would like to way in?

[wizard]

I'd like to suggest plain old delta 240 with your own step down transformer for 120volt loads. Even better would be to go to 480 or whatever the power company is willing to supply, in a large facility you will save significantly on copper.

Most machine tools can be either ordered for or already support 480. Those that don't can be hooked up to a step down transformer.

[wildwestpat]

5 pin plugs and sockets are available and known as '415v 32 Amp 5 Pin Commando plug and socket'. These are available in fixed and cable ended configurations.

I think the high ended idea id fraught with problems. The main one being the lack of phase balance which will show up as changes in filament lamp brilliance in addition to the running of conventional three phase motors.

Good luck and stay safe by getting the sockets fitted by a qualified person.

regards - Pat

[RCaffin]

5 pin plugs and sockets are available and known as '415v 32 Amp 5 Pin Commando plug and socket'.

Dunno about the brand of the plug, but we run 5-pin 415 V stuff here for anything heavy. That's a delta connection of course; the Y connection gives us 240 V as usual. The Ground pin is mandatory in Australia for any stuff which is not certified Double-Insulated, and you don't get that for anything heavy anyhow. The neutral pin is for the 240 V control gear.

Which does not help the OP. I agree with the suggestion of running properly balanced wiring (not 'high-leg') of course.

Cheers

[Richard-TX]

I would not go with the high leg delta. Very messy.

If you want higher voltage version of a L21-30, a L22-30 is probably what you want.