Estimating KWh electicity billing using clamp-on amp meter

[gfretwell]

I have posted it several times

[trader_4]

Thank you!

Thank you again. That's exactly what I said, if you have two AC conductors that are delivering power and they are the same phase, voltage and frequency, you can parallel them, because there is no potential difference between them. And what you have coming into a house with 240/120 service looks like two 120V voltage sources that are out of phase with each other by 180 deg, or of opposite polarity, same thing. It actually is that. By viewing it as that, all is explained:

A - With respect to the neutral, you see two 120V voltage waveforms with respect to the neutral, differing in phase by 180. And that's exactly what is there, each half of the secondary winding is a voltage source and they are connected with opposite polarities with respect to the neutral.

B - You can't randomly parallel any two 120V receptacles in the house because some are on opposite phases.

If you measure between the two phases, you get 240V.

All that flows directly. There is no need to talk about transformers, generators, or a synthesizer, if it happens to be created by an electronic UPS type device, etc. If you add in ampacity, that voltage, phase, freq info is all you need to design with it and use it.

[gfretwell]

The nonsense is talking about things that do not exist. If you have to make up scenarios from the planet MoRon to make your point it is not relevant to the planet earth.

I am not convinced you have ever even used a scope. Describe, in detail how you would set up your scope to see this parlor trick.

Don't know do you. I bet you have never even seen center delta.

You DO NOT understand 2 phase. If there is an actual phase angle difference between A and B there is also another phase angle between A and C. The complement of the angle A B. You do not need the 3d source to get 3P delta but it is still there.

[gfretwell]

No what is absurd is that you have made a 3 phase corner grounded delta and you are calling it 2 phase. As soon as you put a phase shift between 2 connected sources you have made 3 phase. The only difference between a bisected line and a triangle is adding an angle to it. 5th grade geometry

[trader_4]

OK, let's go through this one step at a time. I take two windings and put them on a generator shaft, with a difference of N degrees. I connect on end of each winding to one end of the other winding. That point is the system neutral. I connect a scope to the neutral. I look at each of the two conductors coming from the so far unconnected ends of the two windings. Do I see not see two voltage waveforms that differ by N degrees?

If I do see that, then how by connecting two loads, let's say a resistor between the conductor from one winding and and the neutral and another resistor between the other winding and neutral, do I not still have two phases and the same waveforms? What magic just happened to make 3 phases? And if I put a resistor between the two conductors, I don't see how that creates a third phase either. Following that logic, putting a resistor between two phases of our 3 phase system would create another phase too, wouldn't it and I'd then have 4 phases? If I put three resistors between phases, I'd have 6 phases?

[gfretwell]

In phase means a straight line, no angular displacement and also the same direction of current at any given time. If there is a voltage generated across this source, it is obvious the potential will be different from one end to the other. That doesn't make them out of phase.

[gfretwell]

You could certainly have 2 phase with any angular displacement you want but the thing to understand is the 2 phases are isolated from each other.

[trader_4]

Not that I've seen. So, tell us, how do you model 240/120 service without two 120V voltage source, one 180 out of phase or of opposite polarity. How do you do it with one 240V source?

My model, the IEEE Fellow's model, and I believe Mark's model would be TWO 120V 60 hz, ideal voltage sources. Take one connect it's negative side to the neutral. Take the other connect it's negative side to the neutral. One is voltage source is sin(wt), the other sin(wt+180).

Or alternatively, take one connect it's negative side to the neutral. Take the other and connect it's positive side to the neutral. Then both voltage sources are sin(wt).

That is the only way to describe, to model, to draw the circuit we're talking about.

[trader_4]

So you're back to your position that in electrical engineering we can only talk about things that already exist. Very bizarre position.

If you have to

It's exactly by analyzing a wide variety of scenarios that we test whether what we think is right or not. It's how we challenge what we think is right, how we see if it works, or if there are holes. This is like saying we can't figure out what speed a Volkswagen would fall in a vacuum on earth, because it's a moron scenario and can't be analyzed without doing it.

I've described it quite clearly before. Take your scope, hook the scope ground to the neutral, which after all is the SYSTEM reference point, by design, not some random, bizarre point I picked. Put one probe on one hot, put one probe on the other hot. You'll see two 120V sine waves, 180 deg out of phase with each other.

Then explain to us what that is that I described, if it's not two phases. This two phase thing sounds more and more like a miraculous unicorn. It must have been very special when 100 years ago they stumbled on the one and only way to make two phases, which was to use 4 wires and make it 90 deg? Nothing else is allowed, no other way? Yet somehow we get 3 phases on just 3? Where did those rules come from? How do you keep track of it all?

They used two of the three primary phases to generate two phases on the secondary. So what? I've said many times you can generate power sources many ways and exactly how you do it doesn't change how many phases you have in the result. It's only the result that matters, not if it came from a transformer, generator, or black box. BTW, your example there does show two phases with just three wires, what's up with that?

[gfretwell]

As soon as you connect them together, you get 3 phase delta. If you don't see that, you have no business in this conversation. Three phase delta is most commonly produced with two "sources" (transformer secondaries) It could be done with 2 windings in a generator but why would you spend all of that money on rotating machinery and not add the 3d winding to get 100% instead of 66.6% of the output? In the case of transformers the economy is there so they do it. In fact I have only seen 3p delta with 3 transformers once, in Key West and I assume they grew into it.

[gfretwell]

By center tapping it but it is still one, single phase source that happens to be cut in half.

Notice all of the trig functions in that dissertation. Hence me going back to triangles.

[trader_4]

:

That isn't a circuit model. Back to circuits 101. Draw the circuit using Thevenin voltage sources. I just did it for you, it takes TWO voltage sources, it cannot be done with one.

Notice that he starts out by saying:

Abstract: Distribution engineers have treated the standard "singlephase" distribution transformer connection as single phase because from the primary side of th e transformer these connections are single phase and in the case of standar d rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whic h now brings into focus the reality that standard 120/240 secondary systems are not single phase line to ground systems, instead they are three wire s ystems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the second ary phases are separated by 180 degrees instead of three phases separated b y 120 degrees.

And note that to start the analysis, he draws the circuit showing two

120V voltages, one across each winding, Fig 1.

[Bob]

The transformer secondary winding has two ends, L1 and L2.  Put your scope common lead on L1.  Attach one trace probe to the secondary tap and the other trace probe to L2.

Your scope should display two traces in perfect sync that vary only in amplitude.  Pure single phase.

[gfretwell]

This is about the service to your house, now you say that doesn't exist? You still miss the theoretical concept that as soon as you introduce a phase angle shift between two connected sources, you have created a delta. In the real world, it happens every day. It looks like this on the pole

Conceptually like this Wired like this

... and this is exactly like what you are talking about. They have a single phase secondary (the big transformer) and they added another secondary out of phase with it (the small transformer) and got 3 phases.

The problem is your scenario is flawed from the outset and the rest is bogus from there.

All you are proving there is one end of the secondary is plus when the other is minus. Duh If they weren't the voltage would be zero. A phase shift would be something other than 0 or 180 degrees Both of those describe a straight line with no angular displacement.

It does require 2 isolated windings. They could have any angular displacement they wanted but 90 degrees was most efficient to run motors. It turned out 3 phase was even more efficient and a better way to do transmission so they went to that.

That is 3 phase delta, not 2 phase. (note the name of the GIF) The 3d phase just showed up in a "poof" as you describe it. If I wanted 100% rating, I would add another winding across the two upper connections but it is not necessary.

[gfretwell]

Exactly. He will see this wave.

Looking one way from ground he will see the hump up, looking the other way he sees the hump down but it is still one wave.

[gfretwell]

are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Which now brings into focus the reality that standard 120/240 secondary systems are not single phase line to ground systems, instead they are three wire systems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the secondary phases are separated by 180 degrees instead of three phases separated by 120 degrees.

This guy is more confused than you. You should get a room.

[makolber]

It really is that simple. If you

And what if you make N = 180 deg

How many phases do you have now?

m

[trader_4]

I'm sorry if I keep rejecting your claim that phase requires transformers, because it does not. Again, you're confusing a particular implementation with the general case. It staggers the mind that we can get 3 phases on 3 wires, but you claim that to get just two requires 4 wires. It's absurd and totally refuted by the simple example of the generator with two windings, offset by N degrees, with a shared neutral. Again, no transformers involved.

[trader_4]

Wow, more bizarre rules that come from nowhere. I have a 3 phase generator,

0, 120, 240 deg windings. I move the 120 winding to 179 and you say it's still 3 phases. I move it to 180, and you say it all collapses somehow and there is only one phase. I feel especially concerned for that 240 phase, who killed it? Where did it go if it's now single phase? And then if I rotate the winding two degrees more, to 181 it somehow becomes "technically" 179? How the hell can that be? Among the absurdities with that is that it's obviously two deg closer in phase to the 240 winding than it was when it was at 179. Good grief, this is like the twilight zone.

[trader_4]

Who made that unique requirement, that two phases have to be "isolated" from each other? You just make it up as you go. There is no such requirement. How can we have three phases that are not isolated from each other, use just 3 conductors, but two phases requires four and they now have to be isolated? And note, I'm not arguing about what that 100 year old particular implementation of what two phase was, I'm talking about the general case.