7200 volt to 120/240 volt single phase transformer

[mivey]

Which is it, yes or no? First you say it does show that it is showing 180 and then you say no.
The changing of direction has no influence on this discussion

On the contrary, it has everything to do with this discussion.

as you are saying that the two sine waves of a 120/240 single phase transformer are 180 degrees out of phase for 1/120 of a second which means they would be opposing each other just as the reversed battery.

You still are not following what I am saying. Disagree with me if you must, but at least understand what I am saying and take issue with that. You keep arguing against something I have not said.

You even agree with this although you don?t openly admit to it.

I'm not shy. I'll openly admit to anything that I have to say.

You even made this comment.
Here you say that should you read the transformer in series the two sine waves would lap over each other and this is saying that the transformer is in phase with itself at all times.

You don't even understand what I said so how can you hope to dispute it? Besides, a transformer is in phase with nothing. Nothing in that transformer is in phase with anything else without some directions being defined first. You say the voltage directions have been "pre-picked" by some force of nature that "knows" the "correct" direction. I'm saying you can take the positive voltage to be in either direction. Real world cirucit responses to these conventions prove that to be true.

 

[jwelectric]

Interesting thing, that polarity difference....
Look at the following picture of the voltage waveforms:

The show V_an [outside looking in] and V_bn [outside looking in] being of equal magnitudes but different polarities for one complete cycle.
Do you see now that the polarity difference is the same as a 180deg displacement between the two waveforms?
The two are just different ways of describing the same thing.

red inserts are mine and show what you are saying in your last sentende, jusr a different way of seeing the same thing. This is true that both sine waves are twins that look and act alike but in order to see them we have to look at them in two different ways. This in no way means that they are out of phase with each other or at different polarities.

 

[mivey]

What direction would you assign if you work talking about work done by you vs work done by someone else?

Should read:
What direction would you assign if you were talking about work done by you vs work done by someone else?

 

[Besoeker]

red inserts are mine and show what you are saying in your last sentende, jusr a different way of seeing the same thing. This is true that both sine waves are twins that look and act alike but in order to see them we have to look at them in two different ways. This in no way means that they are out of phase with each other or at different polarities.

The red inserts are irrelevant and unnecessary.
The subscripts adequately and concisely describe what is being shown.

 

[jwelectric]

You still are not following what I am saying. Disagree with me if you must, but at least understand what I am saying and take issue with that. You keep arguing against something I have not said.

You say that in the transformer the two 120 volt sine waves are opposing each other by 180 degrees.

I say that if they were opposing each other through ? of a cycle and then repeated this opposition throughout the entire time the transformer was energized that it would be the same as inserting one of the 1.5 volt batteries in reverse of a two cell bank.

My test book says that using vector addition that these opposing signals will cancel each other out.

Just as the current that flows through that transformer or the polarity of the coil of the center tap will be the same all the way through the coil (from end to end past the center tap) and reverse on the next half cycle all the way through the coil (from end to end past the center tap) and it will not have a difference of polarity half way through.

 

[mivey]

Should read:
What direction would you assign if you were talking about work done by you vs work done by someone else?

Or better yet, the energy you are expending vs. the energy you are taking in.

Suppose you were an object that radiated energy for 1/2 cycle then absorbed energy for the next half cycle? Suppose this was a lossless exchange with an object identicle to you? What direction of energy flow is "universally" defined as positive vs negative? Is your alignment with the Sun or Moon relevant to the direction you pick?

Polarity is what defines the relative exchange of energy (you absorb while the other object radiates and vice versa). The direction we pick for energy flow is completely arbitrary until we decide to do something that is direction dependent.

If I want to become an intermediary that does not change your energy exchange with the other object, I can decide in what direction I want the energy to flow through me. The timing of the energy exchange and the flow at the time I interact becomes important. A different intermediary could pick things completely opposite to the way I pick but the ultimate energy exchange is still going to happen between you and the other object with the same direction and timing as before.

The transformer polarity and voltage directions are related, but are not the same thing.

 

[mivey]

You say that in the transformer the two 120 volt sine waves are opposing each other by 180 degrees.

I say that if they were opposing each other through ? of a cycle and then repeated this opposition throughout the entire time the transformer was energized that it would be the same as inserting one of the 1.5 volt batteries in reverse of a two cell bank.

My test book says that using vector addition that these opposing signals will cancel each other out.

You still do not understand. The forces are not opposing each other.

Does your test book cover subscripts? Read it, because I think that is where you can't seem to follow what I am saying. Also, you keep refering to batteries and that is what is keeping you from seeing there is a force that is in opposite directions every 180?.

Nothing dictates that we have to use the forces in both halves of the winding as positives in the same direction. If we pick opposite directions, every 1/2 cycle each direction will experience a positive force. Besoeker's circuit illustrates that fact.

Just as the current that flows through that transformer or the polarity of the coil of the center tap will be the same all the way through the coil (from end to end past the center tap) and reverse on the next half cycle all the way through the coil (from end to end past the center tap) and it will not have a difference of polarity half way through.

But the direction we take positive pushes of force from the transformer does not have to be the same. We can connect a circuit to get a positive push in either direction and these positive pushes are displaced by 180?. Of course the other is also true: we can also connect a circuit to get two positive pushes in the same direction at the same time. Either way is a valid way to take voltages from the transformer and both deliver real forces, not just math tricks.

Please read these three sentences several times and try to understand what they mean.

Polarity and the direction we take voltages are not the same thing. Van and Vbn are both real voltages and neither is a "math trick".

 

[Rick Christopherson]

Which is it, yes or no? First you say it does show that it is showing 180 and then you say no.

You have to read what Mivey says with a magnifying glass. I don't know if it is deliberate or not, but it is very confusing without that magnifying glass.

The bottom line is that he is not disagreeing with what has been a common consensus regarding the instantaneous forces in a transformer. However, for whatever reason he has, his answers appear to be deliberately cryptic and misleading. See below.

The direction of we take positive voltages can be different. The transformer is producing a force in opposite directions every 180?.

<snip>

No. The transformer really is producing forces in two different directions at a 180? displacement.

If you took just this last sentence, it would appear that Mikey was saying that in the same instant, each half of the transformer is producing forces that are in 180? opposition. When in fact, he is simply stating the obvious, that the forces in any AC wave are reversing every half cycle. That's obvious, but not directly germane to the specific topic being discussed.

I'm also a professional writer, and once I began to notice this in Mivey's postings, I can't help but wonder whether this isn't intentional baiting to instigate conflict where no conflict really exists. Read his postings more carefully and you will see that he is not disagreeing with the current consensus, but how the information is presented makes it sound like he is saying something else.

 

[Besoeker]

I'm also a professional writer, and once I began to notice this in Mivey's postings, I can't help but wonder whether this isn't intentional baiting to instigate conflict where no conflict really exists. Read his postings more carefully and you will see that he is not disagreeing with the current consensus, but how the information is presented makes it sound like he is saying something else.

The topic is of a technical nature.
Please keep it that way. Personal deprecating remarks are proscribed.

 

[Rick Christopherson]

The topic is of a technical nature.
Please keep it that way. Personal deprecating remarks are proscribed.

That wasn't. I was explaining to JWElectric why he is getting confused by the discussion. He already noted that there appeared to be contradictions in what he was reading.

 

[Besoeker]

That wasn't. I was explaining to JWElectric why he is getting confused by the discussion. He already noted that there appeared to be contradictions in what he was reading.

"intentional baiting"
would seem to be personal and deprecating.
Please don't do it.

 

[mivey]

You have to read what Mivey says with a magnifying glass. I don't know if it is deliberate or not, but it is very confusing without that magnifying glass.

The bottom line is that he is not disagreeing with what has been a common consensus regarding the instantaneous forces in a transformer. However, for whatever reason he has, his answers appear to be deliberately cryptic and misleading. See below.

I assure you I'm not deliberately trying to be criptic. Perhaps I've become a bit too wordy because of some of the past posts, maybe a bit too specific at other times. I have no money riding on the thread so I have no reason to be criptic or anything similar. I glad you at least can pick through what I am saying and understand it.

If you took just this last sentence, it would appear that Mikey was saying that in the same instant, each half of the transformer is producing forces that are in 180? opposition. When in fact, he is simply stating the obvious, that the forces in any AC wave are reversing every half cycle. That's obvious, but not directly germane to the specific topic being discussed.

The reversing is what makes picking a positive voltage in either direction valid. It is not just about slapping on a negative sign. There is a positive push in both diretions. This is not the same as the +/- on a battery where force direction is constant.

I'm also a professional writer, and once I began to notice this in Mivey's postings, I can't help but wonder whether this isn't intentional baiting to instigate conflict where no conflict really exists. Read his postings more carefully and you will see that he is not disagreeing with the current consensus, but how the information is presented makes it sound like he is saying something else.

Perhaps if you can do some deciphering then it would help:

My issue is with someone saying that the AC voltages taken by a circuit can only have positive forces in one direction and that the other direction is not a real force but just a math trick.

By convention, we take the positive voltage direction to be in the same direction that current flows from the source to the load. In the majority of cases we see, the current flow is in the same direction for both halves of the circuit at the same time. With the 2-diode full-wave rectifier circuit, the only current flow we have in the top half of the circuit is in one direction. The only current flow we have in the bottom half of the circuit is in the opposite direction during the other half of the cycle (i.e., the 180? difference). To say that the one direction of current is the only "real" direction and that the other direction is just a "math trick" does not compute.

Is that clear or would you like to word-smith it some?

 

[Rick Christopherson]

Is that clear or would you like to word-smith it some?

Yes, I understand what you are saying here. Yes, it could use some word smithing (i'm pressed for time today). You are correct that sometimes it can be confusing when we show an AC voltage source with a +/- designator on it, or show an AC current with an arrow, because these designators are constantly changing as the wave reverses.

While the choice for which direction is chosen is more or less random, once that choice is made, then it needs to be consistently applied. A good example of this is the designation we give to electrical current (either AC or DC). Due to not fully understanding electricity at the atomic level some couple centuries ago (was this Ben Franklin?), our convention for electrical current is opposite to that of electron flow. This still works fine as long as we keep that convention consistent. However, if we mixed electron flow and electrical current in the same analysis without being careful about the difference, it would lead to problems.

The same is true for the arrows we use for AC current flow, or +/- signs for voltage references. These designators are not intended to show the actual direction of the parameter, but simply used to maintain consistency. I'm tempted to use the word "polarity", but I don't recall what you wrote regarding that topic, nor gave it too much thought at the time. Off the top of my head, to me, polarity doesn't change as the waveform cycles, but direction does. Is that the same way you viewed those two words?

 

[jim dungar]

Time out warning.
I will not let it go as long as it did last time.
Especially when we fall into a long line of "you said this in post XXX".

Now that Rick has brought up the item or arrows, maybe a new thread should be started.
Might I suggest this one. http://forums.mikeholt.com/showthread.php?t=140766

 

[mivey]

Yes, I understand what you are saying here. Yes, it could use some word smithing (i'm pressed for time today). You are correct that sometimes it can be confusing when we show an AC voltage source with a +/- designator on it, or show an AC current with an arrow, because these designators are constantly changing as the wave reverses.

While the choice for which direction is chosen is more or less random, once that choice is made, then it needs to be consistently applied. A good example of this is the designation we give to electrical current (either AC or DC). Due to not fully understanding electricity at the atomic level some couple centuries ago (was this Ben Franklin?), our convention for electrical current is opposite to that of electron flow. This still works fine as long as we keep that convention consistent. However, if we mixed electron flow and electrical current in the same analysis without being careful about the difference, it would lead to problems.

The same is true for the arrows we use for AC current flow, or +/- signs for voltage references. These designators are not intended to show the actual direction of the parameter, but simply used to maintain consistency. I'm tempted to use the word "polarity", but I don't recall what you wrote regarding that topic, nor gave it too much thought at the time. Off the top of my head, to me, polarity doesn't change as the waveform cycles, but direction does. Is that the same way you viewed those two words?

Polarity (in this case meaning the way the transformer is marked), does not change. The directions of the forces, currents, and voltages do change. And it appears we agree on that.

One big problem in our industry is that there are too many ?standards?. I have seen the term polarity in the same manner we are referring to the force directions in the transformer. I have reference books that use the phrase ?the polarity is reversing every 1/2 cycle?. I?m sure I have used it myself, and probably did so in this thread or the other thread, but it was not in an attempt to confuse or distract. It probably just seemed the most relevant way to express what I was trying to say at the time based on what where I thought the other poster was at.

I have references going back over 100 years and there is a hodge-podge of terminology used in different ways. The key is to understand what the author was trying to say, even if the terminology is a little different. I have a vast number of books and texts in my library dating from the turn of the century to current and while they may often disagree in terminology, they rarely disagree in concept.

Most of the time, I have found it more helpful to try to understand what someone is saying rather that get caught up on the specific use of a particular word or phrase. There is no one standard for a lot of these terms. We must put forth extra effort to see if we can understand what someone is trying to say, even if their terminology differs from your own. Considering the format here, and how hard it is to pass information, you can see it would be much easier and faster to discuss a topic in person.

All too often, you can use a particular phrase here and then spend the next 50 posts trying clarify something. Sometimes it seems like the other poster will not put forth effort to try to follow what you are saying. Instead, the poster puts more effort in trying to pin your hide on their wall over a phrase that they think can be used in only one way. It usually bugs me when a poster declares that a term can?t be used a certain way or that the term only means a certain thing. Based on the reference material I have accumulated over the years, I usually see where I could support both sides and cite valid references for both.

I would rather debate the concepts than the terminology.

 

[Rick Christopherson]

Polarity (in this case meaning the way the transformer is marked), does not change. The directions of the forces, currents, and voltages do change. And it appears we agree on that.

GREAT! I think this needs to be kept in mind, not only for those posting, but to those observing too.

With this realized that we are not necessarily on opposing sides, then it just becomes a communication issue. A little more care is needed when making statements, as well as interpreting them. It's also important to realize that sometimes someone might have switched gears to a different sub-topic without making it fully clear that their comments were not related to the core topic. I did see this happen a few times (in hindsight) in the other thread too.

Without going into the complexities of how or why, do you feel that this polarity subtopic needs to bear relevance on the original question? If so, then let's specifically state the objective first to avoid confusion over what is being discussed.

 

[mivey]

GREAT! I think this needs to be kept in mind, not only for those posting, but to those observing too.

With this realized that we are not necessarily on opposing sides, then it just becomes a communication issue. A little more care is needed when making statements, as well as interpreting them. It's also important to realize that sometimes someone might have switched gears to a different sub-topic without making it fully clear that their comments were not related to the core topic. I did see this happen a few times (in hindsight) in the other thread too.

And with the number of posts and people saying so many different things, it really is hard to keep up with who said or meant what. You may have just finished reading a post from someone coming out of left field and read a second post that sounds similar and the next thing you know, you have associated the two posts even if the posters meant two different things

Without going into the complexities of how or why, do you feel that this polarity subtopic needs to bear relevance on the original question? If so, then let's specifically state the objective first to avoid confusion over what is being discussed.

Only if polarity is going to be used to define the "the one positive and/or correct" direction for everything. Otherwise, it is not relevant because it is just used to get your forces aligned and working together.

 

[Besoeker]

Time out warning.
I will not let it go as long as it did last time.
Especially when we fall into a long line of "you said this in post XXX".

For me, that is not an issue.
In fact, tracking back to earlier posts is sometimes is the only way to keep posts cogent to the the discussion.
I'm a moderator on a couple of forums. By invitation I might add.
I think I exercise that privilege with discretion and to the extent that is reasonable according to the circumstances.
If I think a post to be beyond the limits of what is acceptable for the forum then I deal with that post. It can go from anywhere between a mild admonishment, to an infraction to a gardening leave to an outright ban.

My suggestion is that you first deal with what you see as objectionable posts. Take to task individuals who you think stepped out of line.

This is just friendly advice.
You can close the topic. Again.
That won't make it go away.

 

[Rick Christopherson]

Only if polarity is going to be used to define the "the one positive and/or correct" direction for everything. Otherwise, it is not relevant because it is just used to get your forces aligned and working together.

OK, let's get clarification on what you mean by this.

Speaking strictly for myself, when I choose polarity marks and arrows, I choose them in such a way that loads consume power and supplies deliver power. If these devices are presented by mathematical expressions, then I typically choose polarity such that positive voltage conventions are exhibited mathematically as the "variable" for time equals or just leaves t=0 (regardless whether time is ever set to a non-zero initial state).

Does this relate to what you are saying, or have I misunderstood?

 

[mivey]

OK, let's get clarification on what you mean by this.

Speaking strictly for myself, when I choose polarity marks and arrows, I choose them in such a way that loads consume power and supplies deliver power. If these devices are presented by mathematical expressions, then I typically choose polarity such that positive voltage conventions are exhibited mathematically as the "variable" for time equals or just leaves t=0 (regardless whether time is ever set to a non-zero initial state).

Does this relate to what you are saying, or have I misunderstood?

I think that is the same use. Polarity is an alignment tool, not an indicator of what direction we have to take to be a positive voltage.

In other words, when the voltage rises across a two-terminal source towards the polarity mark, current will flow across the source in the same direction. The current at that moment will leave the source at the terminal with the polarity mark, flowing towards the load, and the exact same current will return from the load and flow into the source terminal without the polarity mark.