Split phase service--one or two?

[rattus]

This thread is a spin off from "Is Impedance a Phasor"?

Well, one difference between them is that with three phase power the waveform of one phase cannot be morphed into that of another simply by changing the amplitude.

Are you saying that the fact that the two voltages are inverses prevents them from being called phases?
The definitions do NOT say that.

 

[mivey]

A three phase wye has three phases separated by 120 degrees, right? I thought so. So why is it somehow different with a split phase system with two phases separated by 180 degrees? Would it make any difference if we didn't know the source of the voltages? Why?

The idea seems to be that there is something magical about that last 0.00000...00001? change in the transition to a 180? phase difference.

Well, one difference between them is that with three phase power the waveform of one phase cannot be morphed into that of another simply by changing the amplitude.

That's because the amplitude has not changed. It is the phase angle that is different and the split-phase result happens all the time with 4-phase, 6-phase, 12-phase...

Are you saying that the fact that the two voltages are inverses prevents them from being called phases?
The definitions do NOT say that.

There tends to be an idea that somehow one of the voltages in the split winding is being inverted. That is not the case because as you have stated in the past, you chose Van and Vbn from the beginning, NOT Van and Vnb.

The winding direction, instantaneous electron movement, etc. are not the smoking guns the others are looking for because the same currents, winding flux, etc. present in the center-tap winding can be produced by two in-phase voltages or two phase-opposed voltages. It is simply a matter of two smaller voltages being present across the same winding that produces a larger single voltage. The winding makes several voltages available and two of these voltages happen to be phase-opposed.

 

[Rick Christopherson]

There tends to be an idea that somehow one of the voltages in the split winding is being inverted. That is not the case because as you have stated in the past, you chose Van and Vbn from the beginning, NOT Van and Vnb.

When you compare your voltage with the actual electron flow, it becomes quite clear that you have in fact inverted your references. The electron flow is absolute and doesn't depend on any sort of chosen reference. The electron flow occurs from the voltage, and your voltage reference opposes the electron flow.

 

[gar]

120403-1245 EDT

Rick:

What does electron flow have to do with the phase difference of two waveforms?

The word phase with or without modifiers is mostly used as a difference measurement (numerical value), or a name of a source voltage or current (just a word to provide identification).

.

 

[rattus]

When you compare your voltage with the actual electron flow, it becomes quite clear that you have in fact inverted your references. The electron flow is absolute and doesn't depend on any sort of chosen reference. The electron flow occurs from the voltage, and your voltage reference opposes the electron flow.

There is no electron flow because no current is specified.

 

[iceworm]

This "split phase" thing of which you speak - Would this be akin to a single-phase service such as a 120/240V supplied to a residence?

If so, where are you getting this definition of "split phase"? The term "split phase" does not in any way, shape, or form apply to a single phase residential service.

For those that wish to pick past the nits to the up, down, strange, charm, bottom, top level, really should consider cleaning up your slang.

Please, call it what it is.

ice

 

[rattus]

Point is:

Point is:

I brought up the 3-phase case because defining phase as "t/P" would make all the phases the same, the 3-phase motors wouldn't run, the 208V loads would receive 0 volts as well. Someone must have included the phase angles into the expressions for Va, Vb, and Vc. Were they wrong?

 

[Rick Christopherson]

There is no electron flow because no current is specified.

It should be a pretty obvious sign that you are grasping at straws when you keep needing to add in more and more qualifiers to keep your discussion alive. First it was the need for ideal transformers. Then it was only ideal sinusoidal waveforms. Now you need to specify that we can only discuss transformers that have no load connected to them.

Every time something comes up that doesn't fit neatly into your viewpoint, instead of discussing that topic, you change the rules to exclude the topic.

A sure sign that a viewpoint is not correct is when it has to be limited to a very specific set of conditions. If it was truly valid, then it would still hold true for all conditions.

What does electron flow have to do with the phase difference of two waveforms?

The word phase with or without modifiers is mostly used as a difference measurement (numerical value), or a name of a source voltage or current (just a word to provide identification).

Because electron flow is absolute and cannot be altered by changing reference points. At any instant in time, the direction of electron flow will be the same for all points (with zero flows also occurring at the same times). For any instant in 1/2 of the period, electron flow will be from A -> N -> B, and for the other half of the cycle from B -> N -> A.

For these same instants in time, the voltage difference between nodes will also follow exactly the same direction. There will be an increasing potential from A -> N -> B and from B -> N -> A.

 

[mivey]

When you compare your voltage with the actual electron flow, it becomes quite clear that you have in fact inverted your references. The electron flow is absolute and doesn't depend on any sort of chosen reference. The electron flow occurs from the voltage, and your voltage reference opposes the electron flow.

The same electron flow can be created by in-phase or phase-opposed voltages.

 

[K8MHZ]

This "split phase" thing of which you speak - Would this be akin to a single-phase service such as a 120/240V supplied to a residence?

If so, where are you getting this definition of "split phase"? The term "split phase" does not in any way, shape, or form apply to a single phase residential service.

For those that wish to pick past the nits to the up, down, strange, charm, bottom, top level, really should consider cleaning up your slang.

Please, call it what it is.

ice

Split phase is not slang. Here is a definition and source:

A split-phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. It is the AC equivalent of the original Edison 3-wire direct current system. Its primary advantage is that it saves conductor material over a single ended single phase system while only requiring single phase on the supply side of the distribution transformer.[1] Since there are two live conductors in the system, A split-phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. It is the AC equivalent of the original Edison 3-wire direct current system. Its primary advantage is that it saves conductor material over a single ended single phase system while only requiring single phase on the supply side of the distribution transformer.[1] Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two-phase". The two live or "hot" conductors' waveforms are offset by a half-cycle, or 180 degrees offset, when measured against the neutral wire. The two live or "hot" conductors' waveforms are offset by a half-cycle, or 180 degrees offset, when measured against the neutral wire.

http://en.wikipedia.org/wiki/Split_phase

This bears repeating:

Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two-phase".

 

[Rick Christopherson]

The same electron flow can be created by in-phase or phase-opposed voltages.

As stated, your statement is wrong. That's because your statement doesn't reflect the existence of your hidden double negative.

 

[mivey]

This "split phase" thing of which you speak - Would this be akin to a single-phase service such as a 120/240V supplied to a residence?

If so, where are you getting this definition of "split phase"? The term "split phase" does not in any way, shape, or form apply to a single phase residential service.

For those that wish to pick past the nits to the up, down, strange, charm, bottom, top level, really should consider cleaning up your slang.

Please, call it what it is.

ice

While "split-phase" is normally associated with motors, the term "phase splitter" is a common electrical term and not so unrelated as you might think. A phase splitter is realized by many different circuit means including op-amps and such but also with a center-tapped winding.

 

[mivey]

If it was truly valid, then it would still hold true for all conditions.

Our world is filled with too many of these occurrences to even begin to count.

Because electron flow is absolute and cannot be altered by changing reference points. At any instant in time, the direction of electron flow will be the same for all points (with zero flows also occurring at the same times). For any instant in 1/2 of the period, electron flow will be from A -> N -> B, and for the other half of the cycle from B -> N -> A.

For these same instants in time, the voltage difference between nodes will also follow exactly the same direction. There will be an increasing potential from A -> N -> B and from B -> N -> A.

The direction is arbitrary because we can take the positive direction to be either way.

 

[ggunn]

This thread is a spin off from "Is Impedance a Phasor"?



Are you saying that the fact that the two voltages are inverses prevents them from being called phases?
The definitions do NOT say that.

No, you can call them anything you like. I am saying that in split phase power the two waveforms are derived from a single phase, where in three phase the phases do not have a common ancestor.

 

[mivey]

This bears repeating:

Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two-phase".

"Two-phase" is a name reserved for the quadrature system. No one is suggesting we change the label.

But as C.P. Steinmetz recognized, the fact that we can take one smaller phase to be the return of the other smaller phase, which equates to a larger single-phase system, does not mean that the two smaller phases are not present.

 

[rattus]

This "split phase" thing of which you speak - Would this be akin to a single-phase service such as a 120/240V supplied to a residence?

If so, where are you getting this definition of "split phase"? The term "split phase" does not in any way, shape, or form apply to a single phase residential service.

For those that wish to pick past the nits to the up, down, strange, charm, bottom, top level, really should consider cleaning up your slang.

Please, call it what it is.

ice

ice, let's not get overly pedantic. Split phase is very descriptive of the service, and is commonly used.

 

[mivey]

As stated, your statement is wrong. That's because your statement doesn't reflect the existence of your hidden double negative.

No hidden negative has to be present. I can produce these results by spinning the shaft on a generator through a 180? turn.

 

[mivey]

No, you can call them anything you like. I am saying that in split phase power the two waveforms are derived from a single phase, where in three phase the phases do not have a common ancestor.

What about producing a 3rd phase from two phases by taking the voltages in opposite polarities in center-tapped windings? What about producing 4-phase, 6-phase, and 12-phase systems by taking the voltages in opposite polarities in center-tapped windings?

 

[rattus]

No, you can call them anything you like. I am saying that in split phase power the two waveforms are derived from a single phase, where in three phase the phases do not have a common ancestor.

We know that. But, the voltages in question carry DIFFERENT phase angles, ergo they must be of DIFFERENT phases--just like in three phase.

There is nothing in the definition of phase that even hints that the voltages (or currents) must have a common ancestor.

 

[Rick Christopherson]

The direction is arbitrary because we can take the positive direction to be either way.

I was about to make an addition to what I said above to address this, but you beat me to it while I was contemplating whether to bother or not.

In a resistive system (ignoring reactive components just to avoid the complexity of the words), for any instant in time when the voltage of B is greater than the voltage of A (B>A), then all of the following is true:

• The voltage relationships between all three nodes is B>N>A
• The electron flow will be B <- N <- A
• Since current flow opposes electron flow, the current flow will be B -> N -> A

For any instant in time when the voltage of A is greater than the voltage of B (A>B), then all of the following is true:

• The voltage relationships between all three nodes is A>N>B
• The electron flow will be A <- N <- B
• Since current flow opposes electron flow, the current flow will be A -> N -> B

These statements are absolute because they still hold true regardless where your chosen reference point exists. Your statements are true only for a specifically chosen reference point. They are therefore, relative statements.