480/277V WYE 3p electrical service questions

Edster · Sep 2, 2011

I have a small machine shop, and I've outgrown my 240v 200a open delta 3p electrical service. I'm looking to upgrade to a 480v 400a 3p service. The power co says they have 240v open and closed delta available as well as 480/277v wye. I'm leaning toward the 480v service but I'm not sure about the wye configuration. Is this suitabe for a machine shop with cnc's?

Thanks in advance :cheers:

JST · Sep 3, 2011

Your present service sounds like it may be the "wild leg", "lighting tap", "farm" type 3 phase, which includes 120/240 single phase for lighting and office outlets.

If you get 480, you will need to:

* Re-wire all machines for 480, including resetting protectors or replacing protector heaters.

* Somehow get 120/240 for the office and lighting. Lighting may be changed to 277, but the office will require 120v, probably an added transformer.

240V full delta may be your best option, which can be as simple as the powerco adding a transformer out on the pole. That would give you about 50% more power, and you would need to do nothing to adapt to it.

Wye service is no biggie, it is still 3 phase. the issue is that it won't give you the 120V that the "lighting tap" 3 phase does.

208V would be nearly ideal, if you can use it.... 3 phase wye, with 120V from phase to neutral. Least amount of work and added stuff. But higher current per kVA than your present service.

Froneck · Sep 3, 2011

If it were me I would chose 480/277. Used single phase transformers are available 480/240vac. I had 480/277 in my previous shop. The 480vac will give you a lot of room for expansion plus 277vac lighting is also available. However keep in mind everything connected to the 480 line must be 600v. Fuses are a lot more expensive so are breakers and panel boxes but you save a little on wire because your current is half the 240 amount. My source of supply was the local junk yard! Frank

Mud · Sep 3, 2011

I started a similar thread about converting from 240 to 480 and I'm still investigating. Near as I can tell, 480 Wye is OK for CNCs, they don't care whether its Delta or Wye.

If you're going to add machines, it's probably smart to go to 480 now, I'd be ahead if I had gone to 480 when I installed the 3phase.

mike_kilroy · Sep 3, 2011

Mud said:
I started a similar thread about converting from 240 to 480 and I'm still investigating. Near as I can tell, 480 Wye is OK for CNCs, they don't care whether its Delta or Wye.

ah but they CAN tell the difference - when the lightning strikes nearby!

If it were my choice I would take the 480 wye over the 480 delta hands down in a heartbeat.

it lets you ground the wye for a nice low impedance balanced 480v on all phases that should help your machines survive lightning storms, welders running and making noise, vfds making noise etc etc etc etc.

You do not get this low Z benefit from any type of delta. some of the most sophisticated servo and spindle drives require wye connection for this reason too. so why not take the much better solution if offered for the same price?

Mud · Sep 3, 2011

If it were my choice I would take the 480 wye over the 480 delta hands down in a heartbeat.

it lets you ground the wye for a nice low impedance balanced 480v on all phases that should help your machines survive lightning storms, welders running and making noise, vfds making noise etc etc etc etc.

Do you ground it only at the service entrance, or do you ground it elsewhere too?

Do the transformers need to be Wye primary?

Froneck · Sep 3, 2011

Y-Y transformers are available but not normal. I assume you want 480/208. Delta to Wye transformer will work best with a Y power input. Grounding should be done at every transformer output. Delta may or may not have a "neutral" or lighting leg. Wye may also not have a neutral connection. Rather than get into a discussion of what should be done if you connect a transformer without a "neutral" to ground, I'll simply say that type of transformer should be avoided! Just because the input from the power company is ground referenced and you connect a transformer (except Auto Transformers) the output of the transformer will not be ground referenced so it should be grounded. Frank

mike_kilroy · Sep 3, 2011

mud, if u get 480 from power company, I assume u will use it DIRECTLY to ur 480v machines and NOT thru any type xfmr. so no concerns over xfmr types for 480v machines.

if u get 480 wye from power co, THEY will tell u if YOU should ALSO ground it at ur place (as froneck said, THEY already ground ref'ed it - BUT ASK THEM! when I am sent around the usa to help solve noise/spike related voltage issues that break servo/spindle drives and motors, I most often see power co, if good wye into building, has a way of GROUNDING and using the nuetral as a nuetral - different color wires and stuff - leave it to them. MY concern is how to stop voltage spikes from breaking stuff, and ultimately if the center of the wye is grounded, it stops a LOT of sh_t from blowing up. Im a bottom line type dude.

if u have 480 wye, i cannot imagine ANY device requiring an isolation transformer.

If u have 480 delta, a lot of hi end servos/spindles will REQUIRE an iso xfmr.

pretty easy choice then huh?

if u then use an xfmr to go BACK to 208 or 240 or 120, that's another discussion. good rule of thumb to remember tho is as froneck said, use delta to wye or vs. versa when possible for ANY xfmr - it eliminates odd harmonics (noise like from vfds & some of the worst of it).

Froneck · Sep 3, 2011

Mike is right Mud, if you have 480 Wye I can't see any reason you would want a transformer for any application that will operate on 480vac. However many CNC machines will require a transformer if you have Delta. In a place where my son works they have Delta input. Just about all CNC machinery they connected required transformers because Delta power was unacceptable and they would not connect the machine until a Wye transformer was provided. I know of non that refused Wye thought you might get into a voltage problem then you would connect a transformer Delta to Wye. As Mike said and I didn't want to get into harmonic issues is why Delta to Wye should always be used. However you will not be able to get 120vac from a 480/277 vac input so you will need some kind of transformer. Any 480vac to 240/120 single phase transformer will work. If you want 208/120 then a 3 phase 480vac Delta to 208/120vac Wye will be required. Frank

Mud · Sep 3, 2011

5 of my 6 CNCs are 480 machines so apparently connecting them to 480 Wye is a no brainer. They are all on individual disconnects and transformers now.

I have a 200A 3phase panel supplying my other 240V 3 phase loads. So assuming I convert the incoming power to 480 Wye I need a 480-240 transformer for that. I have a 117.5 KVA transformer in place already, but it's a Delta/Delta transformer. Is it OK to use that for the non-cnc stuff?

mike_kilroy · Sep 3, 2011

5 of 6 have xfmrs, u have 240 power now.... sounds like you will have 5 transformers available to pick from & hook up backwards after 480 is put in. if u had an rpc you would not have a wye and lots of machines run on them, so d-d would work fine of course.

JST · Sep 4, 2011

Seems like huge Hijack here.

Edster posted the first question.

he disappeared, and "Mud" came along, with a totally DIFFERENT situation, at least we assume it is different, since he is RUNNING ON 480 now, which I assume "Edster" is not.

It's so messed up I am tempted to close it.

Froneck · Sep 4, 2011

Your right JST Seems I have been as guilty as anyone else. Edster if your reading the replies you'll read about where my son works. I worked in a place that had 480 Y. When we were up-grading to CNC I was always asked by the companies about our electrical supply type Delta or Wye. You seem to have CNC running on 240 open Delta. It may be possible that the CNC company included a transformer with the machines. The companies supplying our machines would have if we had Delta. You'd want to check if those transformers you possibly might have can be changed to 480vac or that your machines can run on 480vac. Keep in mind the change over will be expensive as all low voltage Disconnects, fuses, breakers etc. will have to be changed to 600v. You can elect to keep everything as it is and use the 480 for future expansion but you'll need a rather large transformer (I assume) to change the incoming 480vac to 240vac. Frank

Mud · Sep 4, 2011

Edster said:
I have a small machine shop, and I've outgrown my 240v 200a open delta 3p electrical service. I'm looking to upgrade to a 480v 400a 3p service. The power co says they have 240v open and closed delta available as well as 480/277v wye. I'm leaning toward the 480v service but I'm not sure about the wye configuration. Is this suitabe for a machine shop with cnc's?

Thanks in advance

JST said:
Seems like huge Hijack here.

Edster posted the first question.

he disappeared, and "Mud" came along, with a totally DIFFERENT situation, at least we assume it is different, since he is RUNNING ON 480 now, which I assume "Edster" is not.

It's so messed up I am tempted to close it.

I am trying to do exactly the same thing Edster is considering. Converting from 240 to 480 service. I currently have transformers from 240 to 480. I believe I made that clear. Judging from some of the responses, I did. Edster did not say so, but I suspect he either needs 480 for some of his current machines or will in the future and has transformers too. If you feel this is a hijack, I apologize, and go ahead and close it. Regardless, I will not post again.

Bentworker · Sep 4, 2011

Edster,
I know your out there somewhere...

You could double your service by installing a 400 amp 240v panel. The Poco would have to upgrade the transformers to a delta, instead of the open delta. This would probably be your cheapest option. The reason I'd go with this option is that the shop would only be down for a day or two while the panel is replaced, it gets inspected, and the Poco re-installs your service drop. You would not have to fiddle with anything else.

Chances are if you upgrade to a 480/277 wye service you would be spending some big bucks and would have more downtime because of the need to install more transformers and replace sub panels. I'd only go that route if you are planning on expanding quite a bit, as I could see this being a $15,000-$30,000 project not counting the Poco if a contractor is doing the work.

Froneck · Sep 4, 2011

Unless you have a definite reason to change over to 480vac, don't mind the change over cost and down time I'd keep the 240vac. However it is not necessary to change the Service panel, Just add another 200 amp. You were allowed 7 throws of the hand to shut down power to the building but I think it was increased. I'm sure 2 will be OK.

JST · Sep 4, 2011

The difference I see is that 'you" (Mud) are already operating on 480, even though you don't have 480 service.

That means a lot of the expense etc information is not applicable to you.

Your situation is such that 480 is easier for you, aside from lighting issues.

Edster needs (presumably) to convert all the machines to 480, AND deal with the lighting and office issues.

He may be better off to "close the delta" than to convert all the way.

I'm not going to close it, I was probably "going off" a bit too much..... But it needs to be clear that tehre are TWO situations here, not necessarily the same.

Edster · Sep 4, 2011

JST said:
Your present service sounds like it may be the "wild leg", "lighting tap", "farm" type 3 phase, which includes 120/240 single phase for lighting and office outlets.

If you get 480, you will need to:

* Re-wire all machines for 480, including resetting protectors or replacing protector heaters.

* Somehow get 120/240 for the office and lighting. Lighting may be changed to 277, but the office will require 120v, probably an added transformer.

240V full delta may be your best option, which can be as simple as the powerco adding a transformer out on the pole. That would give you about 50% more power, and you would need to do nothing to adapt to it.

Wye service is no biggie, it is still 3 phase. the issue is that it won't give you the 120V that the "lighting tap" 3 phase does.

208V would be nearly ideal, if you can use it.... 3 phase wye, with 120V from phase to neutral. Least amount of work and added stuff. But higher current per kVA than your present service.

My present service is 200A 240V open leg delta 3 phase. It has the stinger leg.

All my cnc's have transformers. My 3 Okumas have transformers supplied by the mtb. They are wired in after the machines disconnect switch. My Haas and Fadal have the same setup. My Toyokoki press brake has a standard transformer. We wired up a disconnect switch then the transformer. Hopefully the CNC builders used disconnects that can handle 480. I'll have to check on the press brakes switch.

I have two industrial condo units and they each have their own 240v 200A single phase services. I'll probably keep them just in-case I need to sell one or both of the units. I was also planning to keep the 240v 3 phase service for now. That way I don't have any downtime.

JST · Sep 4, 2011

Consider having the powerco "close the delta" if you need more power..... They will do it if you can show them you need it.

That's a cheap way to get 50% or so more juice. And downtime should be 3 or 4 hours, max. All they have to do is hang the third tranny and wire it.

Everything else should stay the same, unless you need an upgraded service box.

Bentworker · Sep 4, 2011

Are you sure that your utility will allow you to have two separate services? Most will only allow one service for one building (unless it is multiple occupancy). I'd have a good talk with your electric utility estimator as I doubt they will set another bank of transformers and string up a second service to your building. If they will, go for it, but be prepared to open your wallet. Usually they offer some discount for increased load, and will offer a small payment for the old transformers.

Peter

480/277V WYE 3p electrical service questions

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