The poll -- Phasing of Voltages out of a Transformer

Please select the best answer from these choices:

  • No AC voltages powered by single core transformer are out of phase.

    Votes: 0 0.0%

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    6
  • Poll closed .

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JWelectric

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[1] The two halves are 180 degrees apart with respect to center point. It may also be called three-wire, single-phase, midpoint neutral system.
A couple of key things that needs to be addressed by the author of this Wiki post is the relationship to the neutral and the use of the word voltage.

First is the voltage which is nothing more than the amount of pressure that is pushing the electrons around on the conductor. Voltage is not kinetic and does not move. Voltage changes polarity or the direction of the pressure.

What is moving is the electrons and the movement of electrons is measured as amps and called the current of the circuit. As the pressure or volts starts from zero and climbs to a peak the current flow starts from zero and climbs to a peak. The relationship of the current and voltage will depend on a couple of things. Is the circuit inductive or capacitive. The sine wave of the current to voltage will either lag or lead depending but for the sake of this post it will be in sync.

A dryer is a 240 volt appliance that also uses the neutral. The heating element is 240 volts but the motor and controls are 120 volts. Current will leave the transformer and return to the transformer for both voltages. The current will travel first clockwise then counter clockwise changing 60 times a second.

Put the controls on one leg and the motor on the other leg with the heating element on both legs. As the current leaves the transformer on leg A and is returning on leg B in a clockwise direction both the control and motor will see a clockwise movement of the current. The controls will see current moving clockwise from A to N and the motor will see current moving clockwise from N to B.

What the author of the Wiki post is saying is that if we were standing on a railroad track and looked first in one direction then we would have to turn our direction of sight 180 degrees to look in the other direction. This looking first one way then the other way does not change the fact that the railroad track is in one straight line going from point A to point B. It simply means that in order to looking first one way and then the other we as humans must turn 180 degrees. Also notice that the author said nothing about anything being 180 degrees out of phase.
 

DonL

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Did this Thread Die ?

I was just getting ready to learn something New.


Pull something out of your hat.
 

BobL43

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Did this Thread Die ?

I was just getting ready to learn something New.


Pull something out of your hat.
no it did not die, it just phased out.

One time in the 80's I was working at a customer in Philadelphia, and they had the weirdest 3 phase power I ever encountered. I don't remember the issues with it, but I know it was not just a high leg system. Not sure if they still have that power config there or not. Wye, or Delta don't remember that either. It was about 30 years ago.
 

Bluebinky

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Oh wow, I missed this thread!

Since this seems to be theoretical in nature, I'll throw in my $0.0000002.

The phase relationship between the two legs depends on your "point of view" or "point of reference". If you measure each leg with respect to the center and are not willing to assign a polarity to to an AC voltage, then the two are said to be 180 degrees out of phase. You'd have to measure both legs at the same time, otherwise it would be meaningless to say anything about their phases and/or the voltage between them. This kind of reasoning is required to study any of the "hard sciences" such as physics, chemistry, thermodynamics, orbital mechanics, or whatever starting at the freshman level.

This is merely a convention that used because it falls in line with the easiest reasoning (math) when things get more complicated. It really has nothing to do with the physics involved, but merely the symbols used by us humans to describe things.

Go ahead and use the common jargon for this special case that "in phase" is the same as "180 degrees out of phase". This works fine for the cases where one can do the math mentally or from a cookie cutter formula anyway.

I guess it depends on which crowd you hang out with. I often wonder if I made the right choice...
 

Bluebinky

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Hold on, I think I finally understand what the confusion is about...

Forget about the center tap at "C" and its connection to point the point between the two resistors. None of that is needed to explain. Remove all that and just look at what would happen with the resistors.

If you were able to shrink down and watch the electrons at the point between the resistors, what would you see? You'd see that whenever electrons were flowing in from one conductor an equal number would be flowing out the other. Since this would be happening in a nice symmetric pattern at regular intervals, you could describe your observation in one of two ways:

1) Both conductors were doing exactly the opposite thing (polarity).
2) Both conductors were doing exactly the same thing but exactly opposite each other time-wise within the periodic cycle (phase).

(It is usually more common to speak in terms of phase for AC, at least for sine-waves).

The phase angle of an AC electrical circuit refers to an angle in time, not up/down/left/right/clockwise/counter-clockwise/etc direction of electrons moving.

The two conductors in a circuit are always at opposite polarity or phase, but not both, depending on how you choose to describe things.
 

JWelectric

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Okay I think you have just about taught me something. the battery is dead in the lawnmower so I need to get me a battery charger that has two phases that are 180 degrees out of phase with each other to charge the battery.

of course some of us knows that a difference in potential does not make two phases
 

Bluebinky

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Okay I think you have just about taught me something. the battery is dead in the lawnmower so I need to get me a battery charger that has two phases that are 180 degrees out of phase with each other to charge the battery.

of course some of us knows that a difference in potential does not make two phases
You make it sound so complicated my head hurts. I'd hate to have this discussion with you in the frequency domain...

Two wires do not make two phases -- even I know that. When you bring the two wires together into a circuit and measure them relative to some shared point, you get two polarities or phases. How you describe them is merely notational. What you can't say is that the two wires are of opposite polarity and opposite phase that would be nonsense -- just like saying they had the same polarity and same phase...

I will admit one thing. It's only about the usage of a word (and the somewhat irrelevant math that follows behind it), not about some deep mysterious understanding.
 
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ActionDave

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....I will admit one thing. It's only about the usage of a word (and the somewhat irrelevant math that follows behind it), not about some deep mysterious understanding.
I have seen this debate go on more than once and what you said right there is what it all boils down to.
 

DonL

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I used to Phase Speakers and Mics in Teleconferencing rooms.

Everyone needed to be seated for it to work best.

Some sound bounces off and some gets absorbed from a Fat man or lady in the room. If one leaves the meeting, you have to readjust everything.


Phasing Antennas is Funner.
 

BobL43

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I used to Phase Speakers and Mics in Teleconferencing rooms.

Everyone needed to be seated for it to work best.

Some sound bounces off and some gets absorbed from a Fat man or lady in the room. If one leaves the meeting, you have to readjust everything.


Phasing Antennas is Funner.
I liked the episode of Mr. Bean where he did his TV antenna
adjustments. Did you see that one?

 
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DonL

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I liked the episode of Mr. Bean where he did his TV antenna
adjustments. Did you see that one?

lol.

That was funny.

I think I seen it years ago on PBS here.


Thanks for the laugh. RF is FM...
 
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BobL43

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lol.

That was funny.

I think I seen it years ago on PBS here.


Thanks for the laugh. RF is FM...
I am frequently modulated by amplitude.

My post count is increasing but you are double mine. I am a quiet person, some would say I'm shy (blush).
 
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