Singlephase 240V

[mivey]

090910-0752 EST

mivey:

Your posts 76 and 79 are excellent.

.

Thanks. It seems simple once you stop trying to tie back to motor coils, # wires, windings, common phraseology, etc.

I was reading through texts from the late 1800's and early 1900's along with Wagner & Evans and it was clear that the number of phases is the number of waveforms with different angles (equal magnitudes). I also noticed that sometimes a system is labeled by how the phases were being used instead of using the general case.

It makes it much easier to see how the labels we use were derived. Unfortunately, people spread the labels to a broader case than originally intended. The labels we use are often sub-sets of a more general case.

It can lead to a misunderstanding when you mix multiple systems like in the center-tapped delta or when you have a subset of a regular system, like the two phases of a three-phase Wye system.

It is clear when you look at the type load being served and the # phases being used.

 

[Smart $]

I am considering the waveforms, not getting bogged down with the number of windings or how the waveforms were created (could be no windings). Forget the windings, because the number of phases is the number of waveforms with different angles.

We call it single phase when we only have one angle.

A 4-wire delta is a combination of a 3-phase supply and a single phase supply.

This is the whole case in a nut shell.

Yes, split phase can be observed as a two-phase source, but it can simultaneously be observed as a multi-voltage single-phase source, where both waveforms can be observed as having the same angle. Regarding the latter, and I'll go as far as to say it is just my opinion, anytime two voltage waveforms of the same system can be observed as having the same angle, they are thus disqualified from being called two-phase, polyphase, or multiphase... and this is also true of the conventional two phase system you are calling a 4 phase system.

Shall we continue to reiterate the same speculations without resolution???

 

[mivey]

This is the whole case in a nut shell.

Yes, split phase can be observed as a two-phase source, but it can simultaneously be observed as a multi-voltage single-phase source, where both waveforms can be observed as having the same angle. Regarding the latter, and I'll go as far as to say it is just my opinion, anytime two voltage waveforms of the same system can be observed as having the same angle, they are thus disqualified from being called two-phase, polyphase, or multiphase... and this is also true of the conventional two phase system you are calling a 4 phase system.

Shall we continue to reiterate the same speculations without resolution???

That is your opinion and it is in conflict with historic fact and many of the fundamental reference texts we use today.

 

[Smart $]

That is your opinion and it is in conflict with historic fact and many of the fundamental reference texts we use today.

Well, I've always regarded myself as having a not-so-common perspective on all relevant matters... thanks for the confirmation

 

[mivey]

Well, I've always regarded myself as having a not-so-common perspective on all relevant matters... thanks for the confirmation

Rebel. :grin:

 

[Smart $]

Rebel. :grin:

Yep!!!

...and along those lines, I disagree with your remark about historical fact. Perhaps in conflict with modern texts... can't contend something I'm not familiar with

You say ta-mah-to, I say to-may-to... and despite the geriatric connotation of that comment, this dinosaur still rocks :grin:

 

[mivey]

Yep!!!

...and along those lines, I disagree with your remark about historical fact. Perhaps in conflict with modern texts... can't contend something I'm not familiar with

You say ta-mah-to, I say to-may-to... and despite the geriatric connotation of that comment, this dinosaur still rocks :grin:

If you consider my references modern then you must be older than dirt because the texts I'm referring to are Fitzgerald & Kingsley's "Electric Machinery" originally published in 1952, Wagner & Evan's "Symmetrical Components" originally published in 1932, C.L. Fortescue's 1918 "Symmetrical Co-ordinates" paper, and many other turn of the century texts & books (plus some more "modern" texts from the 1970's to current).

 

[mivey]

...and along those lines, I disagree with your remark about historical fact. Perhaps in conflict with modern texts...

Disagree all you want but the history has already been written. You can find many of these texts on line but here is a sample from the 1921 book Principles of Alternating Current Machinery pgs 262-263 by MIT professor Ralph Lawrence where he is discussing connecting the two windings of a 2 phase bank at their midpoints to create a 4-phase system:

A symmetrical four-phase system may be obtained by connecting the secondary windings together at their middle points...

The point n of the common connection is the neutral point of the four-phase side. The secondaries may be considered to give either a four-phase or a two-phase system. The four-phase voltages are na’, nb’,nc’ and nd’ with n as a neutral point. The two-phase voltages are a’d’ and b’c’.

So historically, it was not a problem to split a winding to create two phases. You will find this to be true as far back as you care to look.

Like I said, the familiar labels are for specific cases and not the general case and I think it has to do with the way the loads are being connected. You can create multiple systems, but we normally do not use them all.

 

[Smart $]

If you consider my references modern then you must be older than dirt because the texts I'm referring to are Fitzgerald & Kingsley's "Electric Machinery" originally published in 1952, Wagner & Evan's "Symmetrical Components" originally published in 1932, C.L. Fortescue's 1918 "Symmetrical Co-ordinates" paper, and many other turn of the century texts & books (plus some more "modern" texts from the 1970's to current).

Disagree all you want but the history has already been written. You can find many of these texts on line but here is a sample from the 1921 book Principles of Alternating Current Machinery pgs 262-263 by MIT professor Ralph Lawrence where he is discussing connecting the two windings of a 2 phase bank at their midpoints to create a 4-phase system:
So historically, it was not a problem to split a winding to create two phases. You will find this to be true as far back as you care to look.

Like I said, the familiar labels are for specific cases and not the general case and I think it has to do with the way the loads are being connected. You can create multiple systems, but we normally do not use them all.

I thought you were, and I was, referring to the history of the electrical industry and the multitude of personel that have and will continue to call and observe the system as single phase. As for my viewpoint on the history of electrical texts, the cited references are modern texts from the perspective of the history of texts in general, or all historical texts, whichever way you care to look at it.

In either case, I wasn't necessarily referring to my personal history (...much the same as I'm really not a dinosaur ).

Tell ya what. When more than 50% of tradespeople start referring to the system under discussion as a two phase system, I'll jump ship and swim over to your beach...

 

[mivey]

I thought you were, and I was, referring to the history of the electrical industry and the multitude of personel that have and will continue to call and observe the system as single phase.

Given the loads served, it would still be called single phase.

Tell ya what. When more than 50% of tradespeople start referring to the system under discussion as a two phase system, I'll jump ship and swim over to your beach...

First things first: We need to find some 180 degree 2-phase loads that would need such a system. Since I don't see that happening, I think I'll stay aboard ship for now. :grin:

 

[LarryFine]

So, does this all mean that our side wins? :grin:

 

[mivey]

So, does this all mean that our side wins? :grin:

It means that your side will continue to limit themselves to the current parameters without a deeper appreciation of the origins using the general definitions.

In other words, you will be constrained to voyage on the ship with Smart $ without the will to take excursions to the beach. However, some of us will be able to travel in both worlds.

So, I guess if you choose to simplify your life, you can call that a win. :grin:

 

[Smart $]

It means that your side will continue to limit themselves to the current parameters without a deeper appreciation of the origins using the general definitions.

LOL

In other words, you will be constrained to voyage on the ship with Smart $ without the will to take excursions to the beach. However, some of us will be able to travel in both worlds.

I can travel (and survive) in both worlds... but I, rather unfortunately, can only be in one place at a time.

 

[LarryFine]

So, I guess if you choose to simplify your life, you can call that a win. :grin:

I certainly see the other point of view; I don't believe one can argue a point well without doing so.

I can travel (and survive) in both worlds... but I, rather unfortunately, can only be in one place at a time.

"How can you be in two places at once when you're not anywhere at all?!" ~ Firesign Theatre

 

[winnie]

I study 'high phase order' motors. These are motors which use more than the usual 3 phases. Among the various articles that I've read on this topic, there was one dating from the mid-1970s that used an interesting terminology for this discussion. Unfortunately this terminology doesn't seem to have taken hold.

If you look at an ordinary 3 phase motor, you actually have _6_ different types of 'phase bands' used. A phase band is a set of conductors driven at a particular phase angle. The phase bands are commonly labeled (in order) A, C', B, A', C, B' (and around back to A). A and A' are related by being 180 degrees out of phase, and are electrically generated by being opposite sides of the same coil. In theory, you could have a 3 phase motor with just A, B, and C...but this implies a motor that doesn't actually have _coils_ of conductors; a very high current, low voltage beastie.

If you want to build a '6 phase' motor, you have two reasonable choices. You can have phase angles 0, 60, 120, 180, 240, 300; or you could have phase angles 0, 30, 120, 150, 240, 270. Internally to the motor, the first phasing arrangement gives the _same_ results as a conventional three phase system. The second phasing arrangement doubles the number of available phase angles in the motor.

The authors wanted to differentiate between phases that were related by a simple inversion, and phases that required more than an inversion. In their naming scheme, things that differed by 180 degrees were 'hemi-phases'. Using this, a normal three phase motor is a 6 hemi-phase motor, and the different arrangements of '6 phases' above are the '6 hemi-phase' arrangement and the '12 hemi-phase' arrangement. 6 separate supply lines, and either 6 or 12 available phase angles.

-Jon

 

[mivey]

I study 'high phase order' motors. These are motors which use more than the usual 3 phases. Among the various articles that I've read on this topic, there was one dating from the mid-1970s that used an interesting terminology for this discussion. Unfortunately this terminology doesn't seem to have taken hold.

If you look at an ordinary 3 phase motor, you actually have _6_ different types of 'phase bands' used. A phase band is a set of conductors driven at a particular phase angle. The phase bands are commonly labeled (in order) A, C', B, A', C, B' (and around back to A). A and A' are related by being 180 degrees out of phase, and are electrically generated by being opposite sides of the same coil. In theory, you could have a 3 phase motor with just A, B, and C...but this implies a motor that doesn't actually have _coils_ of conductors; a very high current, low voltage beastie.

If you want to build a '6 phase' motor, you have two reasonable choices. You can have phase angles 0, 60, 120, 180, 240, 300; or you could have phase angles 0, 30, 120, 150, 240, 270. Internally to the motor, the first phasing arrangement gives the _same_ results as a conventional three phase system. The second phasing arrangement doubles the number of available phase angles in the motor.

The authors wanted to differentiate between phases that were related by a simple inversion, and phases that required more than an inversion. In their naming scheme, things that differed by 180 degrees were 'hemi-phases'. Using this, a normal three phase motor is a 6 hemi-phase motor, and the different arrangements of '6 phases' above are the '6 hemi-phase' arrangement and the '12 hemi-phase' arrangement. 6 separate supply lines, and either 6 or 12 available phase angles.

-Jon

Sounds like an interesting article. But the term hemi-phase was not used around the time AC was in its infancy. The folks at the time would call a split winding on a 2-phase setup 4-phase. Even IEEE today says a 2-phase is really just a part of a 4-phase system. I wonder how it became such an issue to see things that way?

Even the author you mentioned was looking for a different naming scheme. Was it because of the fear of calling a 180 degree difference two phases or because of the difference in usefulness of such a system vs a 2 phase system with a non-180 degree separation?