Okay so far in what I have learned I am still confused about this point. I understand the voltage is on a wave alternating to about +170V to -170V at 60 Hz meaning 60 times per second but averaging at + or -120V. How is it than that my single phase service can a give me 240V when I measure against both wires? Is it that the same wave twice is amplifying the voltage thus doubling it? Could you connect a circuit between any two independent 120V lines and measure 240V?

I thought you had to connect opposite legs at the breaker to get the 120V. Something just isn’t adding up for me; why the two wires coming in the main service if the same phase? If it is all the same phase than why do you need to hook up opposite legs of a multi-wire circuit or you could double the amps going back on the neutral wire (instead of the difference between the two)

Maybe the problem is when 240V was first explained to me it was connecting to different phases of electricity. I think that is what has me confused. I understand the rules but not always why, someone please help.

Electrons would have some of the properties of a wave and some like a particle right? I am pretty good at Physics so maybe that kind of explanation would help.

Thanks,

JC

Start with this:

Split-phase electric power - Wikipedia, the free encyclopedia

And get back with any other questions.

TK,

Thanks that helped a little but still pretty confusing. So I did some goggling on Split Phase Power and came up with these, which I found quite helpful.

split phase power - All About Circuits

Single-phase power systems : POLYPHASE AC CIRCUITS

So I get we are on the same phase now, but by center tapping the neutral wire at the transformer you can get the 120 or 240V with two lines running at 180 degrees opposed to each other. So even though the phase is the same they are running in reversed polarity? Its all about what you are measuring against isn't that right. They are on the same phase but measured against the neutral wire they are 180 dig opposed, (due to the location of the neutral on the transformer.

This would be another reason why the neutral on the service line has to tie into the neutral on your box.

It is starting to come together for me now. I will keep on reading - this stuff is interesting.

a**********.. *********L1 (1)
... *.. *
... HV... *.. ********... N (also tied to earch) (2)
... *.. *
b**********.. ********* (3)

Excuse the ".". This forum is not ASCII ART compatible.
Use you imagination and pretend your looking at
A transformer where the primary is a high voltage in the Killovolt range.

There is a phase relationship. And you can measure between different terminals and get different phase relationships.

A to b has the same phase as 3 to 1 or 3 to 2.

With AC synchonized and in phase you can add or subtract voltages when there are two transformers in series. Suppose I had a transformer with a 12VAC secondary and another with a 24 VAC secondary. Depending which wires are placed in series, the resullt woukd be 12 VAC or 36 VAC. They add or subtract depending on there phase.

So in single phase power, the primary has only 2 wires and this is single phase. If we broke the center tap of the transformer and had two windings of 120 VAC above, we would have an isolated two-phase system and we can add or subtract these two ouputs and end up with 0V or 120V.

Because the center tap is grounded we don't have two-phase, but rather a system of voltages (120 VAC) which are 180 deg out of phase with each other.

If power is applied from b to a then (3) to (1) is the same phase with the same reference. (2) to (3) is in the same phase because it is in the same direction as (b) to (a)

Since the center tap (2) is the reference, only (2) to (1) is the same phase as (b) to (a). (2) to (3) is 180 deg out of phase from (3) to (1)

Thus you have 240 from (3) to (1), 120 VAC from (2) to (1) and 120 Vac from (2) to (3) 180 deg out of phase.

The trick here is to look at the direction of the windings relative to the output. Some transformers migh have dots or some other markings to show the phase relationships.

I need a better drawing.

I hope this makes more sense.

That did help a lot, I think I am getting it fully now.

So when you connect 3 to 1 you are basically running the circuit all the way back to the transformer? Would this be like the AC equivalent of connecting a circuit to the positive and negative sides of a battery? Except with AC the voltage is constantly changing from positive to negative. But with AC on 240V when one hot wire is pushing and other is pulling and that is why you get the full 240?

Kind of complex but pretty cool...

-JC

P.S. Check this out for some Christmas Eve engineering fun about Santa

Engineer Explains How Santa Can Deliver Gifts in One Night

Glad you got it.

It's still oversimplified, but it is at the level of your understanding.

One thing, I will add is the neutral current is the difference of the currents flowing in L1 and L2. You would use loop equations to analyze this.

Just a 240 Load, no Neutral current. A mix of 120 loads on each leg of the 240. The difference of the currents flowing on each leg shows up on the neutral.

AC may not appear to obey ohms law at times, because ohms law is only valid for resistive loads. It's a very complex subject. The voltage and the current may not be in phase and the voltage and current waveforms can be way different.

At high frequencies (RF) it doesn't even flow through the "wire", but rather the skin of the surface of the wire. Silver plated tubes are more economical than solid conductors.

For sine waves you can use a notation like 155<0 deg. And 155<180 deg. Where the "<" is supposed to be flat at the bottom. It's read as 155V at a phase angle of 0 deg.
You then use polar and rectangular conversions to change it to a rectangular form (a+bj), do the math and change it back. "j' is used rather than I, because I is used for current and is a cause for confusion.

Math is simpler in the rectangular co-ordinate system.

For other AC analysis, you may need Laplace transforms.
Laplace transform - Wikipedia, the free encyclopedia