240V Open Delta

[LarryFine]

One can also take two of those three phases, along with the neutral, to supply 120/208v 1ph. Yes, it is made up of two 'phases' and the neutral, but I'd never call it "two-phase"; that term has already been assigned to a 90-degree system.

120/240v 1ph supplies are also made up of two 'phases' and the neutral, but we don't call that "two-phase" either, and for good reason. A load either receives a single-phase supply or a three-phase supply, never a two-phase supply.

Why? Because a load will be made up of either line-to-neutral or line-to-line loads within, but not a single load that takes both. An individual internal component would never receive both lines and the neutral; it would be either 120v or 208v.

A simple clothes dryer is a good example. It works on either 120/240v or 120/208v, because the heater element is connected line-to-line, and everything else line-to-neutral. Both voltages are single-phase supplies, as are the loads.

 

[mivey]

One can also take two of those three phases, along with the neutral, to supply 120/208v 1ph. Yes, it is made up of two 'phases' and the neutral, but I'd never call it "two-phase"; that term has already been assigned to a 90-degree system.

Yes, the quarter-phase system has already been assigned that name. That is why you don't see that term used on the secondary. That does not mean other systems do not physically have two phases.

The 208v service you described has also been commonly assigned the name "network service" instead of single-phase service.

120/240v 1ph supplies are also made up of two 'phases' and the neutral, but we don't call that "two-phase" either, and for good reason. A load either receives a single-phase supply or a three-phase supply, never a two-phase supply.

One load I thought of was the 2-diode rectifier. It could be made in a single component with four leads (line1, line2, load, ground).

Why? Because a load will be made up of either line-to-neutral or line-to-line loads within, but not a single load that takes both. An individual internal component would never receive both lines and the neutral; it would be either 120v or 208v.

And I think that is the reason for the names we use. That does not mean that supply option (both lines and the neutral) is not available should someone find a way to use it.

As for individual components, you have to define the component. Loads are a muli-layered box so how far down in the stack do you look? A three-phase load might have individual components connected single-phase but we still call it a three-phase load. As for a utility distribution system, there are so many single-phase loads on a 3-wire open-wye system that the conglomeration of all of them melds into what essentially becomes a large 2-phase load.

A simple clothes dryer is a good example. It works on either 120/240v or 120/208v, because the heater element is connected line-to-line, and everything else line-to-neutral. Both voltages are single-phase supplies, as are the loads.

A perfect example of why the conventional name fits even if it does not perfectly describe the physical nature of the source system as a whole.

add:

Yes, it is made up of two 'phases' and the neutral, but I'd never call it "two-phase"

Bearing in mind that I am calling the "phase" in an "n-phase" system the voltage from line-neutral or line-line, not the line itself.

 

[jim dungar]

What I said was using ONLY line-line voltages was incorrect. Line-neutral voltages can also be phases.

L-N voltages only exist in systems that have neutrals, so this is cannot be a universal method of counting phases.

The difference has to do with the magnitude and phase angle.Since a phase is a voltage, the number of equal-magnitude voltages with unique phase angles is what determines the number of physical phases.

Wait a minute if a 'phase is a voltage' to a common reference point, what difference should it's magnitude make. This logic would say that an unbalanced wye system is no longer 3-phase

You have to be able to distinguish between a conventional name and the physical system. The conventional name is derived from the system and may not represent the system's complete physical make-up.

Which is why there is no need to define a system that only uses 2-phase conductors of a 3-phase supply.

"Used as an adjective" is just your opinion.

For help in the use of commas, I like the book "Eats Shoots & Leaves" by Lynne Truss.

Because of your refusal to be able to see a different perspective,...

I do see different perspectives. I just don't agree with them

...you then concluded that the author must be some non-industry-standard anomaly.

I never said the author was an anomaly, only that the language usage was not common.

Why quote standards as the definitive answer if you only agree with them when they match your own viewpoint?

I did not quote standards as being definitive. At what point did I disagree with "standards". I spoke definitively about common usage by electrical equipment manufacturers.

We already have conventional names for service drops.What makes you think they would stop using them?

I cited two large utilities that do not commonly use the term "2-phase" in the publications they provide to their customers.

If you have been reading my posts with that notion, maybe that is why you are not hearing me.Perhaps you would better understand what I am trying to say...

I understand what you are trying to say. I don't agree with it.

I have a methodology that works every time when counting the number of phases in a system and matches the terminology that is most prevalent in our industry. I count only the voltages between 'line/hot/phase' conductors (i.e. the same conductors that we say carry 'phase currents' and are historically, although slightly unfortunately , labeled as "Phase A, Phase B, and Phase C").

Your method of saying 3-wire (2 lines and a common) systems are '2-phase' is absolutely not useful in describing the physical systems unless you also include the angle between the voltages.

While I see that our present naming conventions have some problems, especially for the casual user (one not trained in power systems), I do not see any improvement by simply dding the term "2-phase" simply in an effort to describe how loads are connected to supplies. This is why I have regularly tried to describe my systems like: 120/240 1PH 3W, 240/120 3PH 4W, 120/208 1PH 3W, and 208Y/120 3PH 4W.

 

[mivey]

L-N voltages only exist in systems that have neutrals, so this is cannot be a universal method of counting phases.

Neither are the voltages universal. We can get both L-L and L-N from some sources. Considering that I am following the general rule of polyphase systems, the L-N & L-L voltages are phases in two different systems.

Consider for a moment the windings as a source phase, when you connect them in a wye configuration, it should be obvious that the phases are line-common.

You seem to want to ignore the common conductor's role as a conductor; I don't. After all, the polyphase systems are merely combinations of individual 2-wire phases. The common conductor just reduces the amount of wire we have to use for the combined system because the individual phases are sharing one of their conductors with the group.

Wait a minute if a 'phase is a voltage' to a common reference point, what difference should it's magnitude make. This logic would say that an unbalanced wye system is no longer 3-phase

If you will note in my previous posts that the precise term was "substantially equal in magnitude". That gets to be a mouthful to say every time. Besides, I think you know what I meant. We are all familiar with nominal ratings and such.

What you did not seem to catch was that I said a system of voltages will be grouped by magnitude. Three-phase 120v, three-phase 208v, etc. Inside each magnitude group will be sub-groups gathered by phase angle. The number of internal sub-groups determines the phase order of each magnitude group.

For help in the use of commas, I like the book "Eats Shoots & Leaves" by Lynne Truss.

I'll check it out, but that has nothing to do with how other people use commas. Maybe they did not read that book and we can't just project a specific comma use onto someone else's literature.

I do see different perspectives. I just don't agree with them

Fair enough

I never said the author was an anomaly, only that the language usage was not common.

Guess it depends on where you travel. It was pretty common for the author, and in addition to authoring many publications dealing with industrial and utility system analysis, he develops industry-leading distribution analysis software used by many utilities, schools, and engineers in the US and around the world.

I did not quote standards as being definitive. At what point did I disagree with "standards". I spoke definitively about common usage by electrical equipment manufacturers.

One of the IEEE standards says that the 4-wire and 5-wire 2-phase system would be more properly called a 4-phase system, which you disagree with. There are other industry-standard reference texts which say the same thing. Nothing wrong with disagreeing with them as long as you have a valid reason. Even your methodology has issues because there are four line-line voltages.

I cited two large utilities that do not commonly use the term "2-phase" in the publications they provide to their customers.

I would venture to say almost all of the utilities don't. There is no reason to change the conventional names.

As for the "open-wye", I would say there might be a good mixture of some who call it a "single-phase service" and some who call it a "network service", even though "network service" has probably been around longer.

I understand what you are trying to say. I don't agree with it.

Sometimes the things you paraphrase make me wonder because they are not what I have said. I'll take it on faith that you are at least making an effort.

I have a methodology that works every time when counting the number of phases in a system and matches the terminology that is most prevalent in our industry. I count only the voltages between 'line/hot/phase' conductors (i.e. the same conductors that we say carry 'phase currents' and are historically, although slightly unfortunately , labeled as "Phase A, Phase B, and Phase C").

I would (and have) question(ed) that it works every time. It certainly needs some exceptions added to what you just said. For one, there is no line-line voltage on a 2-wire grounded+ungrounded configuration and I know you don't call it zero-phase. How is it that you consider the individual phase's 2-wire voltage but want to ignore it when it becomes part of a larger group?

Your method of saying 3-wire (2 lines and a common) systems are '2-phase' is absolutely not useful in describing the physical systems unless you also include the angle between the voltages.

I have been saying all along that you use the angles along with the magnitudes.

While I see that our present naming conventions have some problems, especially for the casual user (one not trained in power systems), I do not see any improvement by simply dding the term "2-phase" simply in an effort to describe how loads are connected to supplies.

I agree that that terminology is definitely lacking

This is why I have regularly tried to describe my systems like: 120/240 1PH 3W, 240/120 3PH 4W, 120/208 1PH 3W, and 208Y/120 3PH 4W.

That is certainly a better way to go.

 

[jim dungar]

You seem to want to ignore the common conductor's role as a conductor

I don't ignore its role as a conductor, I simply say that the number of phases counted in a system should not depend on if one of the conductors is a neutral.

One of the IEEE standards says that the 4-wire and 5-wire 2-phase system would be more properly called a 4-phase system, which you disagree with. There are other industry-standard reference texts which say the same thing. Nothing wrong with disagreeing with them as long as you have a valid reason. Even your methodology has issues because there are four line-line voltages.

I said the term 2-phase is not common, not that it is never used in some standards.
I recall saying that I knew of no system that used the L1-L1', L1-L2', L2-L1', or L2-L2' voltages, therefore there are(were) only two usable L-L voltages, hence the term two-phase was acceptable.

I would venture to say almost all of the utilities don't. There is no reason to change the conventional names.

Then what have you been promoting?

For one, there is no line-line voltage on a 2-wire grounded+ungrounded configuration...

Wrong there is no Neutral, therefore there must be two lines even if one is grounded.

I have been saying all along that you use the angles along with the magnitudes.

Yet, you consistently neglect to include them in most, if not all, of your uses of '2-phase' when describing physical connections.

 

[mivey]

I don't ignore its role as a conductor, I simply say that the number of phases counted in a system should not depend on if one of the conductors is a neutral.

That seems odd to me. If a system is comprised of L-N voltages, how can we not include the neutral? After all, there is a 120v 3-phase wye system.

I said the term 2-phase is not common, not that it is never used in some standards.
I recall saying that I knew of no system that used the L1-L1', L1-L2', L2-L1', or L2-L2' voltages, therefore there are(were) only two usable L-L voltages, hence the term two-phase was acceptable.

Hence the difference in the name & usage vs what is available in the physical system.

Then what have you been promoting?

Having people that question the anomilies in the names to understand we might call something single-phase because of the way it is used, not because it does not have two phases (voltages with different phase angles) available.

Wrong there is no Neutral, therefore there must be two lines even if one is grounded.

Then that logic would lead you to say there is no neutral in the 3-wire open-wye because it is not really a neutral but just a grounded shared conductor. If L-G in the single-phase case is acceptable, then L-G in the other case should be as well.

Yet, you consistently neglect to include them in most, if not all, of your uses of '2-phase' when describing physical connections.

I meant the use of the angle in determining the phase count of the physical system of voltages. I thought it was clear by my description and the context of my posts what system of voltages I was referring to. I think you have followed along as well. If I had a need for a set of formal descriptive names, I would certainly make one. If there is a system of voltages I described where you did not know the angle I meant, please let me know and I will be glad to clarify.

 

[mivey]

That seems odd to me. If a system is comprised of L-N voltages, how can we not include the neutral? After all, there is a 120v 3-phase wye system.

Consider that the multi-phase system is just a combination of single-phase two-wire circuits. Why would you say the original phase voltage between the original two wires is no longer a phase voltage just because those two circuits share a wire?

By allowing the circuits to share a wire, we have not eliminated phases. Instead, we have added voltage options and made a more versatile combined circuit. Instead of one system per circuit, we now have a multiple-system combined circuit. An illustration:

This combined circuit now has the capability to provide a multi-phase system of voltages. This could be used by a load connected L-N and using two phases. See the following example:

 

[LarryFine]

Having a supply made of two phases is not the same thing as having a two-phase supply (or load). While (open-Delta) three-phase can be dervived from two phases and a neutral, that doesn't make the open-Y primary three-phase or even two-phase. (JMO)

Again, (and we agree that we're really discussing semantics, since the system obviously exists, right?) I still disagree with the term "2-phase" as used here. Comprised of/derived from two phases, yes; actual two-phase, no. Two-phase is a 90/180-degree system.

 

[mivey]

Having a supply made of two phases is not the same thing as having a two-phase supply (or load). While (open-Delta) three-phase can be dervived from two phases and a neutral, that doesn't make the open-Y primary three-phase or even two-phase. (JMO)

What do you think an n-phase supply is? By its very fundamental definition an n-phase supply is a supply with n phases. An n-phase load needs an n-phase supply (a supply with n phases).

Again, (and we agree that we're really discussing semantics, since the system obviously exists, right?) I still disagree with the term "2-phase" as used here. Comprised of/derived from two phases, yes; actual two-phase, no. Two-phase is a 90/180-degree system.

That is the difference in context. Are we talking about the system label "two-phase" or the system type "two-phase"? Are talking about a wire as a "phase conductor" or are we talking about a wire as a short-hand/representative of the "phase voltage"? "Phase" is used in multiple ways. Usually, the context will reveal the meaning (we hope).

In reference to the quarter-phase system "two-phase" means the system label as well as the system type. For systems with angles other than 90?, "two-phase" means the system type.

I guess you could make distinguishing labels if needed, but the context of the usage should make the system configuration clear. If not, like in a discussion of multiple systems, you could clarify by using unique identifiers like: "3W 2-phase_90?", "4W 2-phase_90?", "5W 2-phase_90?", "3W 2-phase_wye", "#W n-phase_360/n?"

 

[mivey]

What do you think an n-phase supply is? By its very fundamental definition an n-phase supply is a supply with n phases. An n-phase load needs an n-phase supply (a supply with n phases).

I am using phases to indicate voltages, not conductors. I noticed you said: "...three-phase can be derived from two phases and a neutral"

 

[jim dungar]

That seems odd to me. If a system is comprised of L-N voltages, how can we not include the neutral?

The a wye system could be called 6-phase, after all there are 2 groups of 3 equal magnitude voltages.

Then that logic would lead you to say there is no neutral in the 3-wire open-wye because it is not really a neutral but just a grounded shared conductor.

A 2-wire source absolutely does not have a neutral, although it can have a grounded conductor.

The 4-wire wye source defines which ones are the phase conductors in an open-wye 3-wire circuit.

 

[mivey]

A 2-wire source absolutely does not have a neutral, although it can have a grounded conductor.

And because of where this usually comes from, the grounded conductor is commonly called a neutral. You know that as well as I do.

So: the difference between the label and the physics. Funny how that works isn't it? Here you are promoting calling the wire by its physical type instead of by its common label. Yet, when discussing the poly-phase systems, you want to disagree when I want to state a system's physical type instead of its common label. Doesn't that strike you as a bit funny?

The 4-wire wye source defines which ones are the phase conductors in an open-wye 3-wire circuit.

The grounded conductor in the 4-wire is the neutral point. It is not the neutral point for the open-wye 3-wire circuit. Again, the difference between the common label and the physical characteristics.

Neither the single-phase circuit nor the open-wye 3-wire circuit has a real neutral point in the grounded conductor so my original post statement still stands: "Then that logic would lead you to say there is no neutral in the 3-wire open-wye because it is not really a neutral but just a grounded shared conductor."

The a wye system could be called 6-phase, after all there are 2 groups of 3 equal magnitude voltages.

That's almost right. You have 2 different groups, therefore you have two different n-phase systems. You have the n' system with three voltages (say 120v) and the n'' system with three voltages (say 208v). You do not have a n = n' + n'' system because you do not mix the two magnitudes.

If you are talking about a polarity change, then you have used the same 2-point set twice.

After as many times as I have explained it, this is the most surprising of the points in your last post. But, taking it on faith that you are making a valid effort, I will go through it again in more detail. Please take the time to follow as I am repeating what I have typed beau-coups of times through the different threads.

# of phases in an n-phase system:

The canonical rule for the number of phases in an n-phase system is that the # of phases equals the number of substantially-equal magnitude and equal frequency waveforms that have a different phase angle and where waveforms of opposite polarity (180? phase angle difference) are counted as separate phases. Waveforms are taken from any two points as long as the set of points is only used once.

A regular system of n phases will have waveforms that are successively displaced by angles of 360?/n, otherwise the system is said to be irregular.

4-wire wye example:

First let's list the 2-point voltage possibilities:
120@0?
120@240?
120@120?
208@30?
208@270?
208@150?
120@180?
120@60?
120@300?
208@210?
208@90?
208@330?

Grouped by magnitude:
120@0?
120@240?
120@120?
120@180?
120@60?
120@300?

208@30?
208@270?
208@150?
208@210?
208@90?
208@330?

Then grouped so no two-point set is used twice (polarity exclusion):
120@0?
120@240?
120@120?

120@180?
120@60?
120@300?

208@30?
208@270?
208@150?

208@210?
208@90?
208@330?

So, we have grouped all of the voltages into regular n-phase systems of voltages and we find that there are 4 different regular 3-phase systems of voltages that we can get from the 4-wire wye.

If we want to exclude the polarity changes so we are not using two different reference points at the same time, we have 2 different 3-phase systems we can use at the same time: a 120 volt system and a 208 volt system, or as we call it: 3PH 4W 208Y/120

It might be worth noting that we also have some embedded single-phase systems and two-phase systems. The single-phase systems would be regular systems (one angle) and the two-phase systems would be irregular (two angles, but not evenly displaced, just like the 3-wire quarter-phase system).

 

[jim dungar]

But, taking it on faith that you are making a valid effort, ...

You have not been able to provide me with sufficient proof that my methodology is wrong, and that i need to change. My results are consistent with the predominant usage in our industry, that defines systems by the supply and not by how the load is wired.

...the grounded conductor is commonly called a neutral...

I view correcting this common improper usage as more important to our industry than simply trying to say that we count 'phases' differently depending on if a neutral is, or is not, used by the load.

 

[LarryFine]

What do you think an n-phase supply is? By its very fundamental definition an n-phase supply is a supply with n phases. An n-phase load needs an n-phase supply (a supply with n phases).

The difference is that I expect to multiply 'n' times the phase angle and end up with 360 degrees. 2 x 120 (degrees) does not.

 

[mivey]

You have not been able to provide me with sufficient proof that my methodology is wrong, and that i need to change.

And I think it would be a cold day down below before you would ever let that happen. I am not so much interested in you agreeing with me as I am in you understanding what I am saying. When you say things like "Then a wye system could be called 6-phase", then it seems clear to me that you have not understood what I am saying as I have never said or agreed to such a statement.

My results are consistent with the predominant usage in our industry, that defines systems by the supply and not by how the load is wired.

But does little to explain why the names are not consistent between systems and why they do not always match the physics of the system. That is where people have questions because common-sense tells them some information is being left out. Your method might be a good memory tool for the user, but so would just memorizing a list of system names. To me, understanding is better than memorization.

I view correcting this common improper usage as more important to our industry than simply trying to say that we count 'phases' differently depending on if a neutral is, or is not, used by the load.

Then if you agree that the common in the open-wye is not a neutral, then you should agree that the 120 volt emfs in a 3-wire open-wye system can be counted as phases. The common wire in the open-wye is the same as the common for a 3-wire quarter-phase system. Both line-common voltages represent an emf source. The only physical difference is the angle between the voltages.

 

[mivey]

The difference is that I expect to multiply 'n' times the phase angle and end up with 360 degrees. 2 x 120 (degrees) does not.

2 x 90 (degrees) does not equal 360 either. They are both irregular systems, as I explained in my post.

 

[jim dungar]

I believe you have lost objectivity into potential failings of your system.

As an experiment, try developing an argument against your own method and in favor of an opposing view. I know I have never been able to convincingly argue your usage to any other power engineer. So I am at ease with what I have been doing successfully for more than 30yrs.

 

[mivey]

I believe you have lost objectivity into potential failings of your system.

First, it is not my system. It is a method of counting phases that was formulated long ago. You may recall that in my quest a while back to understand the names we have, I initially bought into your method. But the closer I looked, the more holes I found.

What I found through my research was that there were pieces of information that were being overlooked and bits and pieces that were being omitted. The system is not one I created, but is an adoption of a method of identifying poly-phase system types that traces back to the very fundamentals of what makes up a poly-phase system.

As an experiment, try developing an argument against your own method and in favor of an opposing view.

I have done so in my research. In order to understand the fundamentals, it was necessary to pick through the pieces of information. I initially argued against some of the very things I have since found out were true.

Rather than accept what might have been an easy route, and continue to hold on to what I had been told decades ago, I felt it might be worthwhile to try to understand the conflict between the labels we use and the actual physics of the system types.

I know I have never been able to convincingly argue your usage to any other power engineer. So I am at ease with what I have been doing successfully for more than 30yrs.

30 years might seem like a long time, but there are other methods for typing n-phase systems that have been around since long before you were born. Sometimes it is educational to look beyond what we have come to know and love and see what history might reveal about those things.

 

[LarryFine]

2 x 90 (degrees) does not equal 360 either.

No, but 4 x 90 does.

 

[mivey]

No, but 4 x 90 does.

And I agree. With the 4-wire-connected and 5-wire quarter-phase system, the physical make-up is indeed a 4-phase system. However, they were used by single-phase and two-phase loads and still went by the "2-phase" label.

With the 3-wire quarter-phase system, the physical make-up is a 2-phase system and that is what it was called. Physically, it had the same two phases of the 4-wire-unconnected system. By connecting at the ends, the two phases shared a common conductor just like the open-wye system.

In the quarter-phase case, the connection between two single-phase 90? displaced voltages also provided a single-phase line voltage with equal to sqrt(2) times the phase voltages.

In the open-wye case, joining two single-phase 120? displaced voltages by using a common conductor produces a single-phase line voltage that is sqrt(3) times the phase voltages.

Care to guess what combination produces a single-phase line voltage equal to sqrt(4) times the phase voltages? You guessed it, the joining of two single-phase 180? displaced voltages.

This is simply the physical make-up of the systems, but that does not mean the physical make-up will match the label we use and that is what causes confusion for some. Telling them that the physical phases are not really there, and that they should just accept the list of names as-is, does not lead to understanding but is just memorization of a label list because someone else said so.