Welder Power

Connect the welder to the two "hot" wires and safety ground. It is 220 (or more likely 240-250 V) between the two hot wires of the dryer outlet.

Jon

It's not really two "phase" -- it'll be the typical North American two legs and ground system, where each leg is 120V off of ground, and the two legs (both of which go to the dryer outlet) are 240V from each other.

You say "house is 20A" -- do you mean there's at least a 20A circuit to the dryer? If so -- plug it in and have fun.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

I hope that damn 2 phase 220 house wire does not start up again. There is a true 2 phase and then then there is the split phase 240 that is common in most of the houses in the US that some try to claim is 2 phase.

If the power is comming from a standard 240 volt dryer connector, there will be 3 wires. Two of them are hot and the third is a combination of neutral and ground.

If the welder has only 2 wires and a ground, then hook up the two hot wires of the welder to the two hot wires at the outlet. Then connect the ground/chasses of the welder to the ground/neutral wire of the outlet.

s a

OK - I live near Philadelphia - which, together with Baltimore, MD shares o ne of the last areas in the US where one may still get actual 2-phase power . 2-phase, 4-wire power was developed primarily for heavy motor use in that era when the battle of AC vs. DC was not yet settled and 3-phase power was barely a gleam in Tesla's Eye. (SIDE NOTE: The last DC building in NYC fed from the Pearl Street Station (for ~125 years) went down in 2007.) For wha tever reason, both Philadelphia and Baltimore accumulated an inventory of h eavy freight elevators that use 2-phase motors to this day, such that the l ocal utilities continue to supply the power to a very few customers in spec ific locations within each city. I had the privilege of working on several such elevators and heavy water pumps in my youth while working my way throu gh school as an electrician.

NOTE ALSO: some few households at the time also got 2-phase. And both PA an d Reading railroad workers living along the rights-of-way got 25-Hz current - used for railroad traction motors, also to this day.

Standard household power in the US is 1/3 of a Delta-connected 3-phase syst em, being hot-to-Hot at a nominal 240V and hot-to ground at 120V. Single-ph ase as only 1/3 of the total capacity is realized. All this is done in the single-phase transformer at the sub-station, not the distribution transform er at the pole (vault) in the neighborhood.

Peter Wieck Melrose Park, PA

Your house dryer connection is still single phase but has a neutral if it has four terminals. It will have a L1, a L2, a Neutral, and a Ground terminal. You will want to connect the welder to the L1 and L2 terminals (240 volts) and the Ground. Three wires total. Dryers usually use a 30 amp connector so you will want to find the correct connector and use 30 amp wiring into the welder. Some older dryer connections were just three wire and used the ground as the center tap (for the 120 volt parts of the dryer).

That is the best I can tell you without seeing everything.

I know that in some parts of the country you may run into many different kinds of power in the houses, just not too common.

Only reason I mentioned the 2 phase stuff was because of the origional question. I doubt that a house hold dryer would be 2 phase, but who knows ?

I bet it would be difficult for the average home owner to have a house wired with anything but the standard 120/240 system of most of the country and get anything to work.

Living in the south I doubt much if any of that 'odd ball' power was used. About the only "odd" voltage I see is some 208 volts phase to phase with 120 to the neutral instead of the 240 p to p.

Might want to take a look at the wires going to that dryer connection...there was a period some years ago when Aluminum wire was in vogue for such things as dryers and kitchen stoves. 1960's time frame if I recall right. That's not really a good thing for a welder...and lots of other loads.

All multiphase came from Tesla. And AC was widely thought to be useless until Tesla. Tesla had patents for both 2-phase and 3-phase. Tesla patents also covered essentially all possible AC induction motor designs.

It is common to use 480/277V 3-phase wye as the power distribution in large buildings. Transformers from 480/277V to 208/120V are located throughout the building in electrical rooms. Transformers have 3-cores for the 3 phases. Small transformers may be simpler, with 2 cores T-connected (Scott). These cores run at true 2-phase. The disadvantage is the power factor on the cores is screwed up and they have to be derated.

For the houses in my area (and probably all of Minneapolis), a single

8kv L-N distribution leg is tapped off from the 13.8kv 3-phase wye distribution. Something like 4 blocks are fed from each tap. A pole mounted transformer feeds 240/120V to something like a block.

Show me the phase difference between your "TRUE" 2 phase and the "FALSE" 2 phase that you seem to know so much about.

I really want to know because I would like to see if you really understand what the term "PHASE" actually means?

Have a bad day..

Jamie

There REALLY WERE, honestly, 2-phase systems in use quite some time ago. They had a 90 degree phase angle between the two phases. They could be delivered in a 3-wire system, looked just like split-phase 120/240, but were apparently commonly set up with 4 wires. The motors were wired with 2 windings in quadrature, and would start without any starting devices (switches, capacitors, etc.) just like a 3-phase motor. It was quickly figured out that 3-phase was slightly better (less torque ripple, for instance) and the 3-phase system took over.

Google "2 phase utility power" and they have an article on it.

Of course, standard residential power in the US is NOT 2-phase, but single- phase.

Jon

I don't intend to get suckered into a long thread about the difference. All I am going to say is that by definition the 2 phase power is seperated by 90 deg instead of the 180 deg that the more common split phase is as some try to make it .

An easy way to tell is to hook a simple 2 wire iduction motor across the lines. If it starts, it is 2 phase, if not single phase. The single phase motor needs some means of starting such as a capacitor start circuit. That was one of the reasons 2 phase power was used.

I ment to say 3 wires , not 2.

I thought so.

Jamie

Ah, this old argument... I put some graphs at [1] that show the differences using non-sine waveforms.

Stepper motors use 2 phase power. The zero crossings occur at different points in time to give the motor a "rotating" power profile.

Houses use single phase power with a central tap. It's no different than having a power transformer for your project that provided 5, 15, and 24 VAC via different taps. A house transformer provides 120 and 240 VAC via taps. We typically tie the central 120vac tap to neutral, providing -120 and +120 taps instead. This is no different than tying your project's 5v tap to "ground", providing -5, +10, and +19 vac taps.

One way to "prove" the difference: look for upstream noise on the power line. With two phase power, the other power line should have the same noise 90 degrees later (or not at all). In single phase power, the other power line has the same noise but negated.

I.e. houses have two 120VAC taps which differ in magnitude (or polarity,

+120 vs -120), not phase. Like batteries, you can use one tap for 120v or use both in series to get 240v.

Another way is to look at my driveway, which only has one power line coming from the road (plus a ground) (I have my own transformer). If I had two phase power, I'd need at least two (originally 2 phase used four, which is why three phase won out - fewer wires) power lines.

[1]

208 phase to phase means you're looking at two legs of three phase power, and not split phase 120-120 like in a typical home.