3Phase/1Phase Question

If you're asking what the difference is between a 3-phase and 1-phase circuit, the answer probably lies in the functionality of the equipment you connected to it.

Or, about 200v.

230 V 3 Phase is (around here) a high leg system. Between any of the 120 v legs and the high leg you would get 230 v. If you connect between the 120 v legs in my experience you end up with more like 220v. Unless your really pushing the welder that voltage should not be noticeable. If the welder was 3 phase before and now your running it on 1 phase, sure you would see a difference. Check the voltages at the welder and verify it is connected to the right voltage taps. Most that I have seen handle more than one voltage.

Do you have 208V and he is used to 240V?

Would you follow up with some voltage and current readings at the operating welder's mains terminals, and also some nameplate data?

--s falke

In single phase 240 volt, the two phases are in line with each other. With three phase they are 120 degrees apart. The thing to remember here is that a "phase" is not just a "hot" leg. If you know what a SINE wave is and HERTZ are this is easier to explain. With alternating current the voltage goes from a zero volts to a positive back to zero and then to negative volts back to zero. With one cycle of this positive to negative is a Hertz. In the U.S. this happens 60 times in one second, hence 60 Hertz. With two hot legs of single phase which are in line with each other, both legs are going to positive to negative in line with each other at the same time. So if you where to take a meter to one leg of a single phase 230v to ground or a neutral you would get 115 volts. With three phase they are not in line. They're 120 degrees apart meaning that with one leg of three phase it actually climes to a higher voltage then just half of the two legs. With a meter, if you check a 230v three phase to ground or neutral you would get

133 volts. The reason for this is that leg A needs to clime higher because leg B is lagging behind at 97 volts and leg C would be -36 volts. A formula to remember is, two line voltage of three phase divided by 1.73 equals single line voltage, i.e. 480/1.73=277 volts, popular for industrial lighting. Your welder is actually hooked to two phases of a three phase system making it actually operating on Two Phase rather then Single Phase. This might be the reason why the person noticed a difference in the weld. The welder was probably hooked up to a single phase system before and is now hooked up to two phase. This is a simple "laymen's" explanation since I'm just a simple laymen maintenance guy. "Bob Floyd" wrote in message news: snipped-for-privacy@corp.supernews.com...

what is the difference between " two phase" and single phase?and is there a four phase?

I think you have a good question here. There should be no difference between using one leg of 240V three phase and a 240V single phase connection.

They either have a 208V 3 phase system or the connection was made between the 240V high leg and neutral of the center-tapped leg (also

208 volts).

Of course if the supply was 240V Delta (very common on the world's shipping fleet), what the OP did is correct and should work fine..

Sounds reasonable, but I think the OP needs to supply a bit more information - starting with exactly where in the world he is - otherwise we're all just guessing.

Cameron:-)

It should work fine. Only two variables that I can think of.

1. He connected to an existing hot and neutral instead of two hots, which would not give him 220v.
2. The welder was previously connected internally for a higher voltage (480) and needs to be modified for your existing voltage. If this is a new welder, it could have come from the factory like this, tho there should have been a sticker to indicate this.

Actually, since the 240-120 volt system is derived from a grounded center tapped transformer secondary, the two "hot legs" of the system you are referring to are 180 deg apart with respect to the grounded neutral - not in phase.

For systems derived from wye transformer secondarys phase-phase voltage is

1.73... times phase-neutral voltage. There are many other types of distribution configurations out there with their own peculiar phase-neutral characteristics; such as, CENTER-TAP GROUNDED DELTA, CENTER-TAP GROUNDED OPEN DELTA, etc. There wasn't enough info given to determine what type of system the original poster has.

Perion

Maintech

In single phase 240 volt, the two phases are in line with each other.

I don't think so. One leg is simply reversed from the other from the same phase source, in this case a winding. Bob AZ

He has put approx 415V across the welder instead of 230V. That's why it's broke. The laminations have probably opened up.

It is not your problem it is the Welder's

Did you read the original post? You can put 230 into a 480 connected welder and have trouble welding. If you put 480 into a 230 volt welder, you will have a fire, or at least a loud pop and a lot of smoke.

He has 230v in this installation.

Yes I did read it. He hadn't finished the SP installation the Welder used two phases. Quite clear. It should be clear to anyone with some elementary knowledge of circuit theory.

In article , User 1.nospam writes

I think we are dealing with the pond separation. In the US, a "230 volt three-phase" system is 230 volts line-line (it is actually 240 nominal). We don't have 415 volts.

The most he could have put on the welder was 240 volts. However, he might have connected it line-neutral, which would have put only 120 volts (or 208 if the system had a high leg) on the welder, and would explain why it wasn't working well. Or, as someone else suggested, the system might actually be

208 volt, thus reducing the welder power.

Ben Miller

Really? I've never seen that here in Toronto (yet). Everything industrial seems to be 347/600V, and commercial being 600V stepped down to 120/208V. Where abouts are you in Canada?

Romy