May I ask a question about the single vs two phase stuff

[RumRunner]

If I gotta live with split phase and antiphase then I say you can go ahead and say hemiphase IMO.

Perhaps you need to improve/increase your compendium of
the English lexicon.

The root word HEMI is extensively used in science and technology. It simply means half. Hemi-cycle, Hemi-sphere, Hemi-hedral, Hemi-morphic, Hemi-phase etc to name a few.


Get a copy of the English Corpus. It lists all the words in the English Language. On last count, it lists over a million words and counting.

 

[ggunn]

Perhaps you need to improve/increase your compendium of
the English lexicon.

The root word HEMI is extensively used in science and technology. It simply means half. Hemi-cycle, Hemi-sphere, Hemi-hedral, Hemi-morphic, Hemi-phase etc to name a few.


Get a copy of the English Corpus. It lists all the words in the English Language. On last count, it lists over a million words and counting.

I'd like to be able to talk better but I have a limited... whatchamacallit.

 

[mivey]

I am sure that with another mechanism you could actually get a transient to 'roll' from one phase to the next.

Which is exactly what we have with a cascaded phase converter. I have a circuit to make 3-phase from single phase.

phase 1 is the input, phase 2 is produced by taking phase 1 through a 120d delay circuit, phase 3 comes from delaying phase 2 another 120d.

 

[mivey]

I'd like to be able to talk better but I have a limited... whatchamacallit.

Is "whatchamacallit" in the English Corpus?

 

[Adamjamma]

Is "whatchamacallit" in the English Corpus?

right now it is cheese steak sammich with provolone..not yellow cheese...
cant find it for nuttin

 

[jaggedben]

Because of the way it is normally used. 120/240 or 120/208 normally serve single-phase loads so that becomes the common name.

The name is just a name and not a physical description. It has a basis but not completely descriptive of the system.

Physically, the two-phase system is just a specific subset of the four-phase system and so the 5-wire two-phase is more correctly called a four-phase system. It was used to provide two phases so the name sticks. How about some history? There are too many for me to feel like putting them all here again but here are some quotes for you on names and about a 180d phase difference:

From the article "The Design and Action of the Rotary Converter" in Engineering Magazine vol 22, by David Rushmore, 1917

From: "Engineering Circuit Analysis", William Hayt, 1962, McGraw-Hill, pg 572:

From "Alternating Current Machines", Sheldon, 1902:

From: "Center-Tapped Transformer and 120-/240-V Secondary Models" William H. Kersting:

From "Techniques of Circuit Analysis" by Carter/Richardson concerning forming polyphase sources from voltage sources separated by phase angle differences:

From "Photovoltaic Power Systems and The National Electrical Code", Sandia National Laboratories:

All those quotes are are appreciated. If nothing else, they prove that people have been arguing about 'correct' terminology for a long time. At least we're not alone. :lol:

 

[GeorgeB]

Picking at nits ...

Picking at nits ...

2 Mhz to 150 Mhz

While we're confusing ourselves over whether "out of phase" is a time issue or an inversion issue (I'm with inversion) ... Mr. Hertz has the unit of frequency named for him ... it is MHz, not Mhz ... and certainly not millihertz, mHz.

<GRIN>

 

[jaggedben]

...

IMHO this goes to the root of this whole discussion, distinguishing between the measurable phase angles in a system and the underlying mechanism that produces these phase angles.

Phase angle applies to single frequency sine waves and to periodic functions. Phase angle is _associated_ with a time shift, and _looks_ like a time shift, but could be created by an entirely different underlying mechanism. Phase angle must be understood simply as one of the parameters describing a sine wave, nothing more.

...

Well said. :thumbsup:

What irks me the most - and it is part of what turns these conversations into record breakers - is the apparent contention that the system's behavior 'IS' the mathematical expression. (A contention that a particular mathematical expression is the correct way to view it, when another produces the same mathematical result, is tantamount IMO to the same thing.) The math helps us analyze the behavior of the system and engineer it's components. The math we're discussing has limits in how far it can describe that behavior, and those limits can be acknowledged. We're not doing particle physics here, wherein there might be a worthy debate as to whether there's a meaningful distinction between the math and the subject it's describing. For the most part we're not even doing physics. For the most part we don't need to.

 

[jaggedben]

I went back and read your post 241. The problem is that for AC waveforms, -1 is OK only for a very specific set of circumstances. Almost everything we do with AC waveforms requires vector math of some sort and as such we are thus using degrees. I see no reason to use -1 when it is not applicable to the general case.
...

Somewhere up thread I said that I respect that position. "It works for all the typical cases, so why adopt a different method for the one case where something else also works." I especially respect this position when it's stated by an engineer regarding engineering. I think that jumper would agree with me that in some circumstances we can make progress with people who are not engineers by simplifying the problem for them. I can explain the split-phase system to a sparky using polarity much more easily than phase angle. But I agree, you do have to limit that to the very specific set of circumstances. When the guy says 'what about 3-phase?' you have to say "Forget everything I just told you, and tell me whether you made it through trigonometry class".

 

[Adamjamma]

While we're confusing ourselves over whether "out of phase" is a time issue or an inversion issue (I'm with inversion) ... Mr. Hertz has the unit of frequency named for him ... it is MHz, not Mhz ... and certainly not millihertz, mHz.

<GRIN>

Hey--polish american living in london and taking care of grandsons who seem to be very hard headed..worse than I remember me being... Told one he was being a smart alec and he told me his momma wanted him to be smart

 

[LarryFine]

When the guy says 'what about 3-phase?' you have to say "Forget everything I just told you, and tell me whether you made it through trigonometry class".

:thumbsup:

 

[jumper]

All those quotes are are appreciated. If nothing else, they prove that people have been arguing about 'correct' terminology for a long time. At least we're not alone. :lol:

Yeah, it has been problematic for many, many years.

 

[jumper]

Somewhere up thread I said that I respect that position. "It works for all the typical cases, so why adopt a different method for the one case where something else also works." I especially respect this position when it's stated by an engineer regarding engineering. I think that jumper would agree with me that in some circumstances we can make progress with people who are not engineers by simplifying the problem for them. I can explain the split-phase system to a sparky using polarity much more easily than phase angle. But I agree, you do have to limit that to the very specific set of circumstances. When the guy says 'what about 3-phase?' you have to say "Forget everything I just told you, and tell me whether you made it through trigonometry class".

Jumper agrees...... but always remember I still am a math and theory dude at heart.

However, I will explain things at the appropriate level and use analogies and such if need be.

It all depends on the circumstances.

 

[__dan]

Single phase, three phase, there is still an underlying physical reality. If a guy wants to know *what* the observable physical reality is, but does not know trig, or had some in school and the memory scares him ... The math is a method of solving, a descriptive language. You can have a hard time ordering breakfast in a foreign language until you find a way of conveying useful information. I just want eggs, not the rest of the chicken or the house it lives in.

Went to a job interview ways back and the electrical crew is around a table. Each asks a question in order. One asks, why is electrical three phase.

Off the top of my head I say 'it is ideally suited to rotating machinery. The magnetic field rotates. The motor and the generator are the same machine (with variations, synchronous, induction)'. That baffled them, they're staring at me blankly. Then I start talking about the first installation at Niagara Falls. Well, there was a competition and they did not know what would be the winning choice. They considered DC, compressed air, for transmission. With AC, they could use transformers to step up the voltage and reduce transmission losses, or even make transmission possible at longer distances. So AC won because the power could be carried over longer distance compared to the competition.

Still no go, all unhappy faces. Somewhere I used the work efficiency and they helped me put it in their form 'because it's more effrickent'. Their frustration broke a little but not by much.

What is the underlying observable physical reality. Work your way up from there without dumbing it down or fibbing. If they don't know trig, they will have their own way of understanding or their own descriptive language. It is not magic or some little guy behind the curtain puilling levers, but you may have to dissuade them somehow from that belief or description in their language.

Or not. They have a right to their own beliefs. But they should also be honest with themselves about what they do and do not know. They have to be able to row out to the deep water and swim back. If they cannot, they have to be honest with themselves about that.

 

[RumRunner]

. . . . They have to be able to row out to the deep water and swim back. If they cannot, they have to be honest with themselves about that.

Commendable rejoinder! :thumbsup:

Rowing out to the deep water is foolhardy at best --if the person is not aware what's ahead.

And when he realizes it's better to swim back. . .the eddy that had built up behind him made it difficult for him to go back.
So, he drowned and took the ignorance along with him.

 

[jumper]

Perhaps you need to improve....

Perhaps YOU need to improve your social skills when participating in this forum sir.

 

[Tony S]

Perhaps you need to improve/increase your compendium of
the English lexicon.

The root word HEMI is extensively used in science and technology. It simply means half. Hemi-cycle, Hemi-sphere, Hemi-hedral, Hemi-morphic, Hemi-phase etc to name a few.


Get a copy of the English Corpus. It lists all the words in the English Language. On last count, it lists over a million words and counting.

Is that the English or American version?

 

[jumper]

Is that the English or American version?

Do you know any “Americans” who actually speak “English”?

 

[Besoeker]

Do you know any “Americans” who actually speak “English”?

I know a lot of English people who don't speak or write very good English but that's off at a tangent from the opposing sine waves that are the topic of this discussion.

 

[Adamjamma]

Nah me, mate.. ah doan speek too well, wri’ng le’ers on my compu’er.. lol...