Jump to content
I Forge Iron

2 phase

Steve Sells

Recommended Posts

:) it blimmin well seems like magic to me....but then again so do telephones... and tvs... and radios.... and record players.....

thanks PE glad its not just me. its a miracle i have not hurt myself with it, my knowledge of it is so rudimentary, im always totally paranoid about welding in water too...should i be??????

Link to comment
Share on other sites

Some thoughts on electricity.

Rule number UNO! At the factory where electrical things are made, special magic smoke is put into the device. If you take care of the device, the smoke stays in and the device functions. If you make a mistake, some or all of the magic smoke will leak out and the device will work only part way or not at all if too much of the magic smoke has leaked out. Sometimes one can send the device to an electrical repair shop and have fresh magic smoke put back in and the device is then as good as new. Sooo... If you see the magic smoke leaking from an electrical device, you are safe in assuming it will no longer function as intended until the smoke is replaced.

Steve Sells put up a nice diagram of the 2 phase. Three phases has 3 of those nice sine graphs. And the spacing of the 3 sine waves is different. At most American homes, the electrical power coming in, at the main panel is 220 single phase. There are 2 wires that have power and a common. Now imagine that the you put a volt meter across the two "Power wires" you would see 220 volt indicated. That is because one wire has a sine wave the is about 110volts RMS and so does the other wire. BUT, KEY BUT, HERE, the two sine waves are 180 degrees apart. So in your minds eye, draw a nice sine wave, and then draw another exactly opposite the first one. In the center of that graph is the ZERO line. So when one sine wave is at 110V positive, the other one is 110V negative. The zero line is the common, so if you measur from any single power wire to the common you get 110, measure across both and presto 220. And remember that those sine waves are changing at the "frequency" usually referred to as Hertz. Usually 60 hertz in the US and usually 50 in Europe. So in the US at 60 hertz, the sine waves reverse 60 times a second. Remembere that RMS I had above, that is Root Mean Square, and is way of sorta averageing the distances from 0 the sine waves go. So if you put your alternating current into an ociliscope and get the time base to stop the wave you will see that 110V Rms is actually more than 110V from zero at the peak, but because of the times the wave is heading to the opposite side and is much closer to the zero line it all averages out to something like 110V Rms

Now in the breaker panels every other slot down each side is say power wire #1 and the remaining is the #2 power wire. That is why a single pole breaker has one black wire hooked to it and is a 110V and a double pole, has 2 wires and has the double toggles joined together and is 220V.

Clear as mud?

In the US when we have 460 volt 3Ph, we often refer to each of the 3 power wires as a hot leg. Go between a hot leg and the common and you get 277V, often used in factorys for lighting. ( You have seen the 277V listing and wondered who uses 277V?)
Single phase motors use more apparent power, and run hotter. 3 phase motors are much more efficient, run cooler. But if one of the 3 legs blows the breaker, or is disconnected, the motor will run at very reduced strenght, get very hot and very soon the magic smoke leaks out.

And now why alternating current and Direct current. DC comes from batteries and generators. Alternators make AC. You can Rectify AC to DC and you can use an inverter to take DC and make AC.

AC 3Ph Invented by Nickoli Tesla, called "Polyphase" and his Transformers have brought you the comforts you know. If we had DC only, there would have to be powerhouses generating the DC every few blocks in every city. DC takes HUGE wires to transmit very far, and the voltage drops quickly.
AC is able to be run through a transformer, and is transmitted at VERY high voltages. And since E=I/R, when the voltage goes very high, the amps goes the opposite way and becomes very low,and resistance is not such an issue. That lets "high Tension" lines maybe 1/2" diameter carry the smae "Power" that would take many feet diameter in DC, since the dc can not be changed in a transformer.
Once at the point of need the transformer then is used again to drop the voltage and raise the amps, And that is why you see Mr. Tesla's transformers on all those power poles where the lines branch off to the house.

In a factory, often power comes in at 13,600Volts three phase and is transformed down to 460 3 phase and other useful voltages like 220V 3 phase.
And then you can take say 277 and run it thru a transformer and get 220V single phase of 110V single phase to run that coffee pot on you work bench.

But in the end the most important thing to remember is Rule Number UNO!

Link to comment
Share on other sites

...and rule number two is why we get paid the big bucks to put the magic smoke back into the big toys.

A member was asking about a 2 phase motor he got, so I posted this here so he could see why I am not sure how to use 3 phase to run his 2 phase motors with out a converter. So this helped to explain. I worked on many things but never 2phase out of a class room, so I am researching to get info for him and me.

Link to comment
Share on other sites

I got a 2 phase motor with my hammer as well. I was thinking of having it rewound but I found a used motor for less money. I found it was the simplest and cheapest solution. It took me quite a while to find one because I was looking for a 680 rpm 550v motor but I did find one.

There are a couple of large dealers for used electric motors who have large selections of used large motors. Romanoff industries was where I finally found mine.

Link to comment
Share on other sites

Beth, electricity and water are a poor mix. Most outdoor welding stops esecially if lightning is about. Usually the DC current used in welding is low enough even though the amps are high that one gets a frightning rather than a killing shock. BUT note the very important USUALLY.
I am not sure of what you mean by water is about. I don't like to run any electrical equipment standing in water, My shop floor is crushed limestone over dirt and is often moist. I do not ever have a problem, But I also strive to never be a part of the circuit.

AC current in very low amps and not very high volts can kill you. Interesting that 110V AC @ 60 hertz is almost perfectly suited to fry the bodies natural pacemaker and you heart stops if the current passes thru that area. The US ARMY taught us in Electronics school several safety bits that I seldom see practiced but make sense:

1. Remember that electricity has to have a full circuit to flow. The damage to a human is when the human becomes part of the path. So they taught us to use one hand only if at all possible when working with energized circuits, placing the non used hand firmly in our rear pocket to prevent a hand to hand circuit, since that tends to go thru the heart.
2. They had studied and found that most electrical related injuries in the electronic missile maintenance field I worked in were not from the shock, but rather the automatic reflex to yank back the hand that got shocked. When reflexably yanked the hand or arm tended to find a screw point or other sharp projection in the box of electronics and severe cuts resulted.

Link to comment
Share on other sites

Part of where I was going, and lost track of was welding in most cases is DC. Tig is usually high frec AC.
BUT a Buzz box transformer type welder will not usually be pure DC. Is is usually a "Chopped wave DC meaning half of the AC wave is removed and so you only see the positive side and so sorta kinda DC. Even the very good Buzz box welders usually have a small AC component hiding in the dc and you have to have an Ociliscope to see it. That hiding AC is the part that can hurt you.
Most true motor generator DC welders are nearly pure DC and probably why the pipe welder crowd love the engine driven Lincohn "pipeliners" that give a super weld from the pure DC.
Go from a cheap buzz box to a motor generator welder and you won't believe the difference.
I have both:)

Link to comment
Share on other sites

I have worked with many electricians over the years and the weirdest group were somd dudes from Poland that rewired my old house to meet current code. They didn't wait for the local utility company to reconnect the primary feed to the house they just up and did it themselves like they would have had to do in Poland where it takes six months or more to get the power company to do the swithch. I was scared witless watching them. These guys never seemed to flip a breaker for anything, just worked every circuit hot, that way they knew which one they were working on. Me, I stay away from working on elcectricity, I hire someone to do the complex stuff. I have been the receipent of lightening strikes twice and just like the feel of it all that much.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...