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jsn_joiner
01-08-2007, 09:13 AM
i have a plasma cutter and it can run single or 3 phase right now it is running single phase. Would it be better to run on 3 phase or leave it on single. what are the advanatges og 3 phase?

thanks
jason

pcarpenter
01-08-2007, 10:34 AM
Jason-- if you have a plasma cutter that will run on single phase, there is not going to be a compelling reason for you to try to provide three phase power.

You won't be able to cost justify three phase power to your home...and I am not sure Ameren will provide it in most residential neighborhoods.

A rotary phase converter produces an iffy-looking three phase power that is perfectly fine for running motors and not so great for things with electronics that use a transformer off one of the phases to produce DC....as may be the case with your plasma cutter.

Solutions that produce true three-phase power from single phase power, electronically are very expensive....especially as you get to the point of requiring large amounts of current.

Three phase has some advantages with motors....less current per phase to produce the same HP, smoother running, motors reverse easily by switching any two leads etc.

Paul

Swarf&Sparks
01-08-2007, 10:45 AM
If you have 3 phase supply, get the 3 phase machine/welder/wotever.
IMHO, the only advantage to single phase is portability, IE, you can take it anywhere and plug it in.
In a workshop situation, I'd go 3 phase very time.
There are quite a few good deals out there on secondhand 3 ph gear, for the simple reason that few places have a convenient 3ph supply to run em.
(I speak for local conditions, of course, 240v/440v)

jsn_joiner
01-08-2007, 12:27 PM
ok lets say i buy a machine that uses 440 3 phase can i with a converter of some type convert 220 to run this machine? or is 440 the same as 220 is with 110? if im correct 220 is just 2 110 lines run together is 440 4 110 lines and can you buy a breaker for this aplication?

JCHannum
01-08-2007, 12:33 PM
The simplest way to decide whether to use three phase equipment is to call your utility company and ask the cost of installation at your location. This usually ends the discussion.

Swarf&Sparks
01-08-2007, 12:41 PM
may be different in the USA, JC, but many older homes in WA were supplied 440V 3 ph as standard. Place I'm in now has 3PH to the house. Only reason I haven't piped it to workshop is I have no 3 phase machines. Last place was single, 240V only :(

As I said, I can only speak from local experience.

pcarpenter
01-08-2007, 12:56 PM
Jason-- I think some mis-understood your original question. In this case, if I read it correct, you have a plasma cutter already which will run on either single or three phase power. As such, run it on what you have.

A machine that uses 440v three phase may indeed have a motor that can be rewired for 220V operation....but the motor nameplate will usually always reflect this.

If it can be made to run on 220v three-phase, you may be able to build a rotary phase converter to run the item provided motors are the only things to be supplied. If you had a CNC machine, for example, with electrics that run on one phase of the three phase power, the quality of the three phase power you would make with an RPC may cause problems with the electronics.

So...its not a simple answer. If it were say just an older lathe with nothing but a motor involved, then looking at the spec. plate on the motor will either say 440V or perhaps 440/220v operation.

If it were 440 only then you could step your line voltage up to 440v with a (rather expensive) transformer, then use that 440 single phase power with a 440v idler motor to build a 440v rotary phase converter to make three-phase 440V power. Usually, this is considered to be questionable at best. In doubling the voltage using a transformer, you will be looking at a substantial current draw on the 220v side.

More often than not, you will find that machinery will run 220 or 440v provided it is not so huge as to be impractical for a home shop anyway. If that is the case, wire it a such. If not, it may not make sense.

I have several machines that run on 220v three phase power and built an RPC to power them. Mail me off line if you have questions or would like to see what is involved in building one.

Paul

JCHannum
01-08-2007, 01:07 PM
may be different in the USA, JC, but many older homes in WA were supplied 440V 3 ph as standard. Place I'm in now has 3PH to the house. Only reason I haven't piped it to workshop is I have no 3 phase machines. Last place was single, 240V only :(

As I said, I can only speak from local experience.

In the US, 120/240 single phase is the norm, with three phase limited pretty much to industrial usage. Installation costs are usually quite high.

Swarf&Sparks
01-08-2007, 01:11 PM
Fair call JC.
3PH hookup price in newer homes here varies from $hock! to 'forget it!

john hobdeclipe
01-08-2007, 03:45 PM
A couple years ago, after I had my shop built, I called the power company and arranged to talk with an engineer about supplying 3 phase. The engineer showed up as scheduled, looked the situation over, and suggested I sit down before hearing the news.

I'm 1.1 miles from the nearest 3 phase line, and at $40,000 per mile, plus the cost of the special transformers and meter....well, you get the picture.

So I've only got 1 phase, and I've grown rather fond of it!

jdunmyer
01-08-2007, 08:16 PM
I knew a fella a while back (now deceased) who had 3-phase power in his shop in a residential neigborhood, so it's not out of the question. My own shop has 480-volt 3-phase power, but: I'm in a rural area and the 3-phase supply was on the corner, a bit over 100 yards from the barn. Back in 1979, it cost me about $1150.00 to get the wiring extended and hooked up, but the power company had a program where they'd rebate the installation cost if I used enough electricity. The way the program worked, I just about had to use "enough" all in one year, so I made sure that I did. <<smile>>

Our power company considers a second meter on the property to be "commercial" and charges more for the power, about $.10/Kwhr vs. about $.075/Kwhr. That second meter can be single- or three-phase, no difference.

Would I do it again? Darnbetcha!! My welder is a 450-amp Lincoln M/G outfit, my MIG is also a 450-amp Lincoln, my wife's big table saw is a 5-HP Delta, the LeBlond lathe has a 2Hp 3-phase motor, the air compressor is 5Hp and could be 10 if I wanted, etc, etc. As someone pointed out, 3-phase stuff is often much cheaper than single-phase simply because not everyone can use it.

Don't "assume" that you can't get 3-phase power without checking, I almost didn't and would have been fooling around with phase converters, etc. to this day.

wierdscience
01-08-2007, 08:26 PM
Here you can get "high-leg" three pahse for residential use.220V @ 100amps,more than enough for a homeshop.Reason it's availible is for larger AC units.

Power company said they would hook it up for free,but the cost of the meter panel and installation was on me.

Mcgyver
01-08-2007, 08:37 PM
A rotary phase converter produces an iffy-looking three phase power that is perfectly fine for running motors and not so great for things with electronics that use a transformer off one of the phases to produce DC....as may be the case with your plasma cutter.



Paul, Didn't know that. I suppose if you were designing for it it would be an easy matter of a transformer to a slightly higher voltage, bigger cap, and then a regulator? I can see the difficulty though if its all embedded, but if it was easy to isolate the electronic's power supply, wouldn't it be easy to work around this? just curious, I agree with your logic that there is no compelling reason to convert if equipment runs on either

John Stevenson
01-08-2007, 08:48 PM
In the UK there was a fixed charge for installing 3 phase, that's at 440 volts.
We only have 240 volts single phase here and 440 3 phase. 240 volts is one 3 phase leg and neutral.
3 phase is common as when they wire a row of houses they run 3 phase down both sides of the road, one house take red and neutral, next takes blue and neutral, next takes yellow and neutral, next takes red and neutral etc so it balances the load out.

When we only had the one Electric board up to about 15 years ago the installation charge was 150, they supplied the meter box but you had to dig the trench and lay a 3" plastic pipe in, they then pulled a cable thru, fitted the meter and connected up.

When electricity was privatised and sold off to various companies this fixed cost was abolished and it's now a free for all with out installation charges being in the 1,000's

Anyone who paid for the fixed price installation really scored as they are now fitting new industrial units for rent with the smallest supply they can get away with and if you have a higher demand you either have to rent a different place or pay for an upgraded cable.

When I had 3 phase installed I reckoned up what I needed and added a few bits on for expansion and hoped that I'd get away with it. I worked out I would need about 40 amps per phase and asked for 60.
The survey guy looked at me and said we are not messing about at 60 amp, we'll run a 200 amp per phase supply in case you need to add on !!

.

TECHSHOP
01-09-2007, 02:41 AM
Swarf&Sparks:

While the physics of electrical stuff does not change internationally, the application sure does. As it was once explained to me by a "transplant" to the USA, way that elecric power is distibuted in your part of the world is very different from here. I am not to sure about the "dirty details" in the UK (other than volts & hertz). There are differences between the USA and Canada, as to what is "legal" and how things "should be done". For a real scare try to find a few photos of code complaint and legal electrical "hook up" from Japan (think 12 year old student's science project).

My old man's (pop's shop) was in the middle of houses, but it had a "non-conforming" zoning with 3~ from the pole. In other wards, the neighborhood had changed a lot since 1900, but his building hadn't. For what it is worth, agricultural areas also might have an easier "route" to 3~ from the local power co.

Swarf&Sparks
01-09-2007, 02:50 AM
Yeah Techshop, while here in Oz we are superficially similar to the UK, 50Hz 440 3 ph, 240 single, distribution is different. Specifically for the end-user, UK has been ring-main for many years, here in Oz, we use MEN (main earthed neutral).
Mate of mine is a high voltage jointer with the WA power outfit. The fact that he's survived 20-some years, proves that he knows his job, but he's told me some horror tales. And electrical power installation and distribution is pretty heavily regulated in this country. Darwinian selection still holds tho.
Rgds, Lin

HTRN
01-09-2007, 04:13 AM
For what it is worth, agricultural areas also might have an easier "route" to 3~ from the local power co.

If your zoned for Ag, it's fairly straightforward to get it, because alot of farm machinery runs on big AC motors, like grain elevators, pumping equipment for Dairy, etc.


HTRN

TECHSHOP
01-09-2007, 04:27 AM
HTRN:

Agreed, I am presently an island of single phase, in a sea of 3~!

As always those last 300 feet are the killer, the best I will be able to manage is 400 amps/single phase, but 500 feet in any direction is an user of 3~!

Damn the "new" local busy bodies, with their "status driven retirement homes" zoning and such!

HTRN
01-09-2007, 05:12 AM
Yeah, the "last mile" is what held up broadband so long..

Be careful with getting 3 phase if you have "zoning nazis" as they'll use it as an excuse to wham you fines for running a "business" instead of a "Hobby".


HTRN

TECHSHOP
01-09-2007, 05:32 AM
So that is also why I have still have Dial up internet acces , and no cable tv. SWMBO thinks I just want to spend the $$$ on machines and such, I don't know where she got that idea:rolleyes:

Wirecutter
01-09-2007, 01:37 PM
i have a plasma cutter and it can run single or 3 phase right now it is running single phase. Would it be better to run on 3 phase or leave it on single. what are the advanatges og 3 phase?

thanks
jason
If it runs fine on single phase, you're golden. Three phase is what motors really like. If you've got other machines in your shop and can get 3 phase installed affordably, do it. It's like asking if you should build the shop smaller or larger. Otherwise, I wouldn't worry about it.

I asked my electric utility about getting 3-phase at home. They said that if I lived in the house up the street (with the transformer box in the yard), I could have 3-phase for about $300. Where I am, I'd have to pay to have it trenched down the street several hundred feet. As an alternative, the guy said that I could have my house's service upgraded from 200A to 400A service for something like $100 + put in a new panel. If it turns out I need it, that's what I'll do.

-Mark

pcarpenter
01-09-2007, 03:21 PM
Mcgyver-- I was sort of speaking out of school...the information on RPC's with electronics is something I had heard about with reference to some CNC equipment as a potential source of problems. From what I understand, the CNC equipment makers typically recommend the electronic three-phase generation solutions for use with their equip. if three-phase is not readily available.

I think we sort of lost sight of the original question...which was effectively "if I have a welder that will run fine on single phase or three phase power, should I find some way to get or make three phase?" Answer.....why spend even a few hundred dollars to get three phase power to solve a non-problem?

If the question were the one we all seem to be answering--"I have this thing that needs three phase power in order to run, what should I do?" then the RPC solution or actual three phase power or another solution may make sense.

I made the suggestion I did about three phase power based on the fact that Jason lives just across the river from me and I knew what the local utility will charge to get the job done....its totally cost prohibitive around here. I have a separate feed and meter for my single-phase power in my shop and I already have to bend over monthly:mad: The local utility (Ameren-CILCO) treats any extra feed or building that is not your priciple residence as a commercial venture and charges you accordingly with a nasty minimum monthly charge based on peak-month usage, a higher per KWh rate etc. I spend around $50/month for power to the shop even though I use a few dollar's worth of power. The shop was just too far away and poorly located to run off the service to the house. Sigh....
Paul

jontwo13
01-09-2007, 05:30 PM
I had my house and shop put on the same meter. They wanted $30 a month to put a meter on the shop. They had to set a pole and move the transformer that cost me about $200 and $250 for a CT unit on the pole, pays for itself in a couple of years. They wanted about $10 for 1500 feet for 3 phase.