Electricians please read

[Allen Grimes]

I just got a 220v line and I just realized (well my neighbor told me) that it's a 2 phase line. My table saw is 1 phase. Strangely enough 1 phase is not available here. What do I do? He suggests getting a new motor for the saw but that is NOT something I want to do.

[Steve Clardy]

Allen. Where are you? Some other country?
All we have here in the states is Single phase and Three phase. ???

[Allen Grimes]

Yes Steve, I'm living in Mexico.

[Aaron Montgomery]

Single phase 220V really is two phases - two 110V lines that are 180 degrees out of phase. It's just generally referred to as single phase.

[Steve Clardy]

Hmmm. Well, I'm not gonna be much help then. Never been out of the states.

Your 220v table saw needs two hot wires, 110 each, then the ground.
Did your neighbor fill you in on what your 2 phase is? two hots, ground, etc etc.?

[Steve Clardy]

Single phase 220V really is two phases - two 110V lines that are 180 degrees out of phase. It's just generally referred to as single phase.
True. Good point I didn't think about. Guess we are used to the term Single Phase. lol
Steve

[Allen Grimes]

THERE IS A GOD, yeah I guess one phase is just called 2 phase here guys. Thanks a lot. I was going crazy here for a second. THANK YOU for saving my sanity.

[Allen Grimes]

Saw Mill Creek is the best.

Ok this is how it happend, for those interested. My neighbor is a retired Dupont electrician. He did the whole connection for me for $20 btw. He told me that my line being 2 phase would not be compatible with a one phase motor, so I called the electric company and asked if they had 1 phase 220 and they said it doesnt exist. But, it's really just different terminology. I don't know why we can't all just use the same measurements and terminology for everything, but Im just happy that it was all just a misunderstanding instead of a real problem.

Thanks again guys

[Frank Pellow]

In this case, it would appear that the Mexican terminology is better than that used in the USA (and in Canada).

Yes it would be good if we could agree to the same termionology but I doubt that it will ever happen. I have lived in three countries (Canada, the United Kingdom, and the USA) which sort of share the same majority language but I could write a book on the differences in terminolgy. By the way, at different times, I have represented both Canada and the USA on International Technical Committees and Standards Organizations and these groups are supposed to reduce arbitrary technical differences and terminology among countries.

[Jason Roehl]

Sheesh. Now if we could straighten out that whole matter of positive and negative with respect to current flow...I don't think ol' Ben Franklin would mind, really.

[Ken Garlock]

Allen, don't let anyone fool you into thinking your normal home/shop distribution panel is anything other than single phase.

What you have coming into your distribution panel is a single phase 240v circuit. You have 3 wires, two hot, and a ground. At the transformer that supplies your house, there is a transformer winding which supplies your 240v. That same winding is also tapped halfway along it, and grounded. Hence, you have 120v on one side of the ground, and 120v on the other side of the ground. This does not make it a 2 phase circuit. There is not such thing as 2 phase power. What happens in your distribution panel is that the two hot wires are connected to heavy copper busses. the circuit breaker are installed to press-fit onto those busses. Where the idea of a phase is most likely orignated is that your electrician should ideally try to balance your electrical load across the two LEGS of the transformer by positioning the circuit breakers in the distribution panel(remember 120v on the "left," and 120v on the "right" of the ground tap.) Over time the two 120v sources became known as phases. They are not out of phase with eachother anymore than one wire of a 120v circuit is out of phase with the other. If you touch one hot wire to the other, you are causing a short circuit, nothing more, nothing less, and it has ZERO to do with phase.

If you care to, you can regard your 240v power as the two 120v windings hooked in series as opposed to one 240v winding that is center tapped.

BTW, I am looking for investors in my contra-poler engery project where the current is 180 degrees out of phase with the voltage. It does interesting things like making soldering irons freeze over, and space heaters remove heat from the room.... I only accept large checks :rolleyes:

[Jason Roehl]

So, Ken, what would the 3 different waveforms look like super-imposed on one another? (leg 1 to neutral vs. time, neutral to leg 2 vs. time, leg 1 to leg 2 vs. time)

[Dennis McDonaugh]

Jason, as far as I am aware, only the Navy (and maybe the Brits) has a problem with current flowing from neg to pos ;)

[Chuck Wintle]

Sheesh. Now if we could straighten out that whole matter of positive and negative with respect to current flow...I don't think ol' Ben Franklin would mind, really.
Jason,
I remember many years ago at a car show remarking that all the British cars were marked with a little sticker under the hood "This car is wired positive earth". How would one have given a boost from an American car to a British car? I seem to remember reading an article about that and they claimed the reverse polarity of these cars made them harder to start in damp weather.

[Dale Thompson]

Jason, as far as I am aware, only the Navy (and maybe the Brits) has a problem with current flowing from neg to pos ;)

Dennis,
Yep! You've got the world's physicists on your side. Current DOES flow from - to +. However, calculations are a lot easier if you assume + to - flow. It all washes in the end, however. :) :)

Dale T.

[Ken Garlock]

So, Ken, what would the 3 different waveforms look like super-imposed on one another? (leg 1 to neutral vs. time, neutral to leg 2 vs. time, leg 1 to leg 2 vs. time)

Simple:
1) 240V line looks like a sine wave.
2) 120V(left of ground) looks like a sine wave
3) 120V(right of ground looks like a since wave.

Placing the left and right beside each other, you will see that where the left trace ends, the right trace picks up and continues the wave form.

[pretend rant on] ;)
What you are trying to do is to get me to say that they are out of phase and that is not the case any more than taking two transformers of equal capacity(voltage& current) and cross-wiring them thus causing a short circuit. Wire them up correctly and you will have the same terminal voltage with twice the current capacity. Yes, phase is important when interconnecting two AC items, just as when hooking up two car batteries. But, you don't talk about car batteries having phases. The fact that you have one pair of wires emanating from a single transformer winding on a pole outside your house, defines that power as single phase, period, exclamation point. Never in an engineering course will you hear a lecture on two phase power because it does not exist. Last, consider this, a single phase source is totally in phase with itself. You can regard voltage phases as points on a circle. A single phase is a single point on a circle. A three phase source has at least 3 wires(delta conected) or 4 wires(star connected) with one of those wires being neutral/ground. With the 3 wire all three wires are hot, and there is no ground. Now the 'phase' comes from the fact that each wire is 120 degrees out of phase with the adjacent wire, and hence 3 points on the circle. Visualize it as 3 separate windings, spaced equally around the armature of the generator. Measure the voltage across any two of the three wires(points on the circle) and you get the same reading, but the phases will be shifted by 120 degrees.
[pretend rant off] ;)

Pardon me for getting carried away, but I just watched seven yes s e v e n minutes of commercials on CBS at the end of the "Category 6, Day of Destruction" movie. That is a political discussion that I will not go into. Yes, I can turn the channel but I wanted to see if there indeed there would be 7 minutes of commercials. Thanks Washington :mad:

I hope this helps, and doesn't confuse even more :D

[Allen Grimes]

Kind of cunfused me there Ken, but thats ok, I dont know the first thing about electrcity. Im just happy about having a 1 phase connection. Trust me though, bad terminology is the least of my complaints about this country.

[Bill Neely]

I remember reading about 2 phase distribution systems years ago in Rosenberg's. Four wire system and pretty rare I would say. Here's a link to a motor wiring diagram.

http://www.tpub.com/content/neets/14177/css/14177_88.htm

[Jason Roehl]

Ken, actually, I wasn't trying to get you to say they are different phases, I was honestly curious as to what the 3 sine waves would look like on top of each other. (I was in a little discussion about this on a Ford truck forum). I think your answer helps a little, but I guess I'm too much of a graphical person--I would want to see some graphs of what I mentioned in my previous post, and of what three phase looks like as well. My BIL is an EE in the lighting industry, and I'll see him for Turkey Day, so maybe I can squeeze it out of him. Thanks!

[Aaron Montgomery]

This should clear things up.

http://science.howstuffworks.com/power9.htm

It might have been more correct to say that the two 120V lines are 180 degrees out of phase with respect to ground. The 240 is single phase.

[Ken Fitzgerald]

Aaron.....I don't know where that website got it's information :confused: ...Every technical and engineering couse I've taken states that when referencing ac power, the phases are 120 degrees out of phase with each other. 120 vac is single phase to ground. 240 is measured phase to phase and is 120 degrees apart from each other. 3 phase.... each of the 3 phases are 120 degrees apart from each other. :confused:

P.S. I did go check one of the course manuals from 20 years ago...

[Ken Fitzgerald]

Aaron.....I stand corrected....I think :confused: In the transmission of ac voltage here in the US we typically use 3 phase power because it's more efficient. In 3-phase transmission, the phases are 120 degrees apart.
However....when we bring power into a house or shop...the transformer steps it down to a single phase, 240 vac and we center tap the secondary transformer and make it neutral and typically also ground it. Because each 120vac leg is coming off a different end of the secondary of a transformer, it is single phase AND it is 180 degrees out of phase. Clear as mud, right......

[Chris Padilla]

Ken,

Not quite...the transformer does zero about phase translation...it only steps-down the voltage. Otherwise, I think ya got it! :)

[Ken Fitzgerald]

Chris..........the secondary output of the stepdown tranformer .....each leg of the 240 is taken from opposite ends of the secondary and therefore would be 180 degrees out of phase with respect to each other.........

The misunderstanding I think is that most major (I'm talking high power) transmission lines are in fact, 3 phase........... in 3 phase the ouputs are 120 degrees out of phase with respect to each other.

A lot of the stuff (CTs & MRs) I work on require 3 phase input....after all these years you'd thought I'd figured out.......208 versus 220-240.....DUH....I guess maybe you might not be able to teach an old dog new tricks but you might be able to wake him up! :confused: :eek: :rolleyes: :D

[Chris Padilla]

Ken,

I think phase probably has too many meanings. I think, for this forum and our homes, it is mostly safe to assume that our power is delivered single phase even though, at the source, the power is 3-phase. Most residential home do not get 3-phase, unfortunately (now why is that??).

Also, I was just nit-picking on that one sentence...transformers do NOT mess with phase...they mearly transfer the signal (phase and amplitude and all) from one side to the other. The can provide isolation, step-up or down voltages, and can also provide impedance matches.

[Jason Roehl]

The can provide isolation, step-up or down voltages, and can also provide impedance matches.

You're alright so far, Chris, but if I see you start posting convolutions, I'm gonna report you to the moderators for use of profanity... :D

[Chris Padilla]

Nah, convolutions are a pain...in the time domain. Move into the frequency domain and they are a simple multiplication! ;)