That bollocks and I suspect that you know it is.
240v debate....
- Thread starter stickboy1375
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Understood. As stated in the Bible, there are none so.....etc.
I'm sure you get the drift.
Rick Christopherson
Senior Member
Except that you have been consistent about it. This discussion would not exist if not for the fact that you have continually restated what you now claim to be "Bollocks".
Van and Vbn are mutually displaced by 180deg.
Fact. And I have not ever claimed otherwise.
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- Connecticut
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- Engineer
Huh?:?
Its simple math.
(120<0) - (120<180) = 240<0.
(120+j0) - (-120+j0) = 240+j0 = 240<0
ooo, ooo, to resolve your dual-phased 240<0<180 circuit you went back to applying double negatives again like you said didn't exist.
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- Engineer
Yes, its called math, more specifically "subtraction." I learned it a long time ago.
And the result of the math yields an answer of 240 @ 0, not some mysterious 240<0<180 answer.
- Location
- Connecticut
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- Engineer
Now we've gone beyond just silly to the ridiculous. KVL says Vab=Vna-Vnb, and since both Vna and Vnb = 120V, then Vab=0????:happysad:
And we'll just ignore all that discussion about Van and Vbn having angles that are 180 degrees out of phase in order to make our ridiculous point? We'll even ignore our own post re: Mr. Hayt and Mr. Kemmerly's "Engineering Circuit Analysis" which says "the voltages between the outer wires and the center wire...are exactly 180 degrees out of phase."
Vab will equal 0 in the diagram by KVL if Vna and Vnb have the same angle. Vab=120<0 - 120<0 = 0.
Vab will equal 240 in the diagram by KVL if Vna and Vnb have angles which are 180 degrees out of phase. Vab = 120<0 - 120<180 = 240 <0
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- Tennessee NEC:2017
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- Semi-Retired Electrician
I know what your phone # is. It's OIC-U812!:lol:
mivey
Senior Member
If the neutral is not used, you just have a two terminal supply to the load and the neutral does not enter the picture.
Even if we did use the neutral and then have a 3-wire circuit, nothing says you must use a different methodology. I have never said you have to.
For the 208 2-wire with no use of the neutral, it is just a 2-wire network and the neutral does not enter the picture.
You originally mentioned two supplies and I thought you were referencing a 3-wire circuit. If we do not use any intermediate connections, you can connect as many supplies together as you want and you will still only have one two-terminal supply to the load and the intermediate connections do not enter the picture. These supplies will all have the same current through them and it will be the same current that goes through the load.
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- PE (Retired) - Power Systems
Then you have mis-read my postings. In every case, my questions have been in relation to a 2-wire load.
Are you saying that for a two wire load the 'voltages' from multiple sources in series (i.e. the 2 halves of a center tapped transformer) are in phase?
mivey
Senior Member
Correct on these points.
Incorrect. Shows me the formula that dictates the voltage direction.
No physical laws are being violated. I have shown a solution to your circuit back in post #290 that uses two voltages with a 180? phase difference. Would you agree that no physical laws are being violated there?
mivey
Senior Member
Your polarity markings were wrong.
Look at the solution I provided for your circuit. I did not change any polarities. I simply rotated one of the generator windings 180?, no different than if I would have had three generators tied together and sequentially rotated them 120? to get three voltages with 120? differences.
No "voltmeter mentality" to my solution at all. It is a physical fact that the two voltages had a 180? difference.
And no physical laws were violated.
Rick Christopherson
Senior Member
Your previous example in post 290 was for generators that are physically out of phase. This isn't applicable to this discussion. We are discussing a single-core center-tapped transformer.
Lenz's Law does dictate direction, and you are violating it. Not all Laws are based on an equation. Faraday was not proficient in mathematics, so you will not find any equations in his original laws either.
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
May I ask you a simple question or two?
If I am standing in the middle of a street: Are the cars coming at me or away from me?
If I am in the median between two streets: same question.
Rick Christopherson
Senior Member
The answers are pretty obvious, so I am not sure where you are headed. However, this did remind me of one important fact that possibly not everyone is fully aware of.
There are several different topics running in this discussion that are similar, but slightly different. For example, I believe David has been fairly careful with his discussions regarding Van and Vbn but unfortunately interjected these into portions of the thread where this was not being contested. There are a few other examples like this with other posters, but I would have to go dig for them to recall the specifics.
I can only speak for myself, but I am not contesting what anyone may choose as their point of reference. My contestation arises when this reference point choice is misapplied to redefining the actual system it is intended to represent.
The formula is E sin() = R I sin(). Voltage falls from a higher potential to a lower potential in the direction of current flow. It follows the wire. At any point where the wire is you can measure voltage or current. Or if you prefer, voltage moves up and down, current side to side, if you hold the wire parallel to the earth. Magnetic flux direction follows the right hand rule. Voltage determines current direction which makes flux direction.
There is an underlying physical reality the description has to be attached to. The customer only needs to know kVA rating and turns ratio.
The turns continue in the same direction, adding voltage as turns are added. For two secondary windings it is 120 v + 120 v because more turns are added at the transformer secondary. Each turn is indentical, same direction. Most loads have no polarity sensitively, so the phase shift description noes not apply to the underlying reality. Voltage due to turns ratio must be known and kVA.
Connecting identical matching 120 v loads that are polarity sensitive, yes, the load may make use of that feature, for the circuit connected that way. Phase shift is determined by how the load is connected, reversing the apparant winding turn direction by reversing the leads to the load. The transformer navitely, has turns that continue in the same direction. The transformer offers voltage increase or decrease by adding or subtracting turns in the same direction.
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
My questions were simple as I am. It is all about what reference you choose, I cannot look it in two directions at once, but whatever way I face, the cars (voltages) are real. No? My direction defines my outlook/definition. No?
The cars coming at me and the cars going away from me are not shifted to some time warp of 8.3 msecs, yet they are 180 degrees apart by observation or their places in my sight.
Rick Christopherson
Senior Member
I am not contesting a reference point. I apparently can't get that point across. What I am contesting is that some people are taking a chosen reference point and redefining the system with it.
To use your example, no matter which lane you are facing, your observation sees them as moving from right to left (in the U.S.). What some people are claiming, is that this point of reference allows them to change the compass heading for those observed lanes of traffic.
Let's change the analogy a little bit. Let's say you have a single lane of traffic that flows from North to South. If you are standing on the East side of this traffic, they will be flowing right to left. If you change your reference point to the West side of this traffic, they will be flowing from left to right. The point of reference can easily change, but the compass heading for the lane of traffic is fixed. When you move your reference point to the other side of the freeway, the cars don't change their direction to be heading South to North.
Additionally, you can even say that the cars are traveling in reverse at a negative speed (double negative). However, that still does not alter the car's actual direction of travel from North to South.
an observation point is a choice, and there are no right or wrong answers with that choice. The definition of the system is absolute and can't be changed.
readydave8
re member
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- electrician
I laughed too but not until tomorrow
since that's when I was at the time
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