Measuring Phase to Phase voltage using Multimeter

[Baluncore]

I can work with professorelectron. I just need a couple of different hats that I can change as I think about the different parts of the system.

A phase voltage and a phase current refer to a single physical internal phase-winding of a generator, transformer, or a load. Those three internal phases can be connected in wye or delta to the terminals. The internal term “phase” does not reach the line terminals.

I must remember that a line voltage is measured between two lines, but a line current is measured on only one line.

 

[awaygood]

"Two fundamental terms which frequently cause confusion, when studying three-phase alternating-current systems are: ‘phase‘ and ‘line‘. This is hardly surprising, because the terms are often used quite incorrectly, not only in the field, but very often, unfortunately, in textbooks too!" - professorelectron

But, you see, those terms do exist, you and this professor guy just don't like them and wish they would be used "properly". Good luck with that. I, for one, won't say you're wrong. I also won't help you fix it.

Kind of like how I hate the word irregardless. I doubt that I'll fix that either.

I absolutely agree that these terms DO exist, particularly in the field. But they simply don't make sense and those who wish to learn about three-phase circuits would be better off if they learned to use the correct terminology. And as this is a science/engineering site, doesn't it also make sense if everybody used the correct terminology? So, let's think about it. There are three windings in a wye connected transformer. These are the 'phases' of that wye connection. So what ARE you describing when you say 'phase to phase'? Are you describing the voltage cross the outer limbs of two phases? There are three windings in a delta connected transformer. These are the 'phases' of that delta connection. So what ARE you describing when you say 'phase to phase'? Are you describing the voltage cross one of those three phases? When you take about a 'phase-to-phase' voltage, I assume you are describing a 'line voltage' as opposed to a 'phase voltage'? So does't it make sense to describe a 'line voltage' as the 'voltage between lines', and a 'phase voltage' as a voltage across phases? The terms 'line to line voltages' and 'phase voltages' are absolutely clear with no room for misunderstanding. If you look at either a wye or a delta connection, 'phase to phase' is ambiguous... especially for those learning about three phase ac theory.

.

 

[Rive]

I absolutely agree that these terms DO exist, particularly in the field. But they simply don't make sense

The really interesting part is, that whether the participants of an international educational forum, with very heterogeneous knowledge, origin and background should be spammed to use a terminology which you think makes sense, or should they be allowed to keep the terminology what their local mentor (and likely: safety supervisor) and team/labmates thinks makes sense.

 

[awaygood]

The really interesting part is, that whether the participants of an international educational forum, with very heterogeneous knowledge, origin and background should be spammed to use a terminology which you think makes sense, or should they be allowed to keep the terminology what their local mentor (and likely: safety supervisor) and team/labmates thinks makes sense.

I have heard electricians saying that 'Ohm's Law is universal', 'energy is delivered to a load by electrons', 'work and heat are forms of energy', and numerous other misconceptions. Are you suggesting that, because a concept is widely misunderstood, it should not be challenged? Regarding the terminology of three-phase circuits, it's not a matter of what I think is correct. I'd LOVE to hear your explanation of why a 'line voltage' should be expressed as a 'phase to phase voltage' and why students wouldn't be confused between 'phase to phase voltage' and 'phase voltage'?

Incidentally, I assume you use the terms 'line current' to describe a current passing along a line conductor, and 'phase current' to describe a current passing through a phase winding or load. If so, why not 'line voltage' to describe voltages across pairs of lines, and 'phase voltage' to describe voltages across phase windings or loads?

 

[Averagesupernova]

No. A 'line to line' voltage is a 'line voltage'. There is NO SUCH THING as a 'phase to phase voltage'. See explanation at www.professorelectron.com

Could you please show me where I said phase to phase voltage?

 

[awaygood]

Could you please show me where I said phase to phase voltage?

I didn't say YOU, specifically, said that. I was referring to the general thread.

 

[Averagesupernova]

I didn't say YOU, specifically, said that. I was referring to the general thread.

Then don't quote me.

 

[awaygood]

If you didn't say it, then how could I have quoted you?

 

[PeterDonis]

If you didn't say it, then how could I have quoted you?

Your post #29 did quote @Averagesupernova. He is saying that your response was not appropriate to the post of his that you quoted, post #23, since in that post he did not use the phrase "phase to phase voltage".

 

[Baluncore]

Here is a definition of the term "phase voltage" as a conductor voltage relative to neutral.
https://en.wikipedia.org/wiki/Three-phase_electric_power#Terminology
Throughout the article that follows, the terms “phase”, "phases", and "phase voltage" are used to refer to the 3φ line conductors.

Where is there something more reliable than the professorelectron blog, that defines these terms?

 

[awaygood]

Unfortunately, the Wikipedia article contradicts itself with its terminology. I would simply argue that the term 'line voltage' defines the voltage between any pair of the three supply conductors and, therefore, 'line voltage' describes the voltage between any pair of LINES (i.e. 'line voltage' = 'line-to-line voltage'). The term 'phase-to-phase' is confusing because lines aren't phases, they're lines! The expression 'phase-to-phase' is confusing... e.g. does 'phase-to-phase' apply to both delta AND wye, or one but not the other? Again, I would argue that newcomers to the subject will be confused by 'phase-to-phase' if you are measuring voltages between lines. I fully realize that this term (phase-to-phase) is widely used in the field, but our duty as educators is to be more precise than that.

 

[sophiecentaur]

Phase voltages are measured ACROSS phases; line voltages are measured BETWEEN lines.

I have just read this and I suspect you think you have made it totally clear. However, any 'Voltage' is measured relative to something. When you say "across phases", do you mean the volts between pairs of 'phases' or phase-ground volts? Measuring volts implies attaching your meter to two physical points on lines so what are you trying to highlight in that sentence?

Is all this not just basic theory? A diagram with agreed notation could help.

 

[Baluncore]

I fully realize that this term (phase-to-phase) is widely used in the field, but our duty as educators is to be more precise than that.

I am not interested in the opinion of the many players.
I am asking for a highly reliable reference, that defines the terminology.
If that can be found, then Wikipedia may need to be corrected.

 

[awaygood]

Sophiecentaur, 'Voltage' is NOT measured 'relative to something'. Voltage is absolute. You are confusing 'potential' with voltage. Voltage is simply another word for 'potential difference', not 'potential'. Potential is always expressed as being 'with respect to' some fixed reference point. Potential is analogous with 'height' because height is always expressed relative to some arbitrary fixed point (e.g. 'above sea level', or from 'the base of a mountain') -change the reference point you change the height (potential), whereas voltage (potential difference) is analogous with a 'difference in height' which is fixed.
When I say 'across phases', I mean across opposite ends an individual phase winding (in the case of a transformer or generator) or across opposite sides of an individual load... whether they be wye or delta connected. You ask for a diagram, so can I direct you to this topic discussed on the blog: www.professorelectron.com? There, you will find diagrams which describe exactly where 'lines' start and end and where 'phases' start and end. Finally, I would suggest that 'line voltage' describes the voltage between any (pair) of lines... i.e. it's a 'line-to-line voltage', and NOT a 'phase-to-phase' voltage.

 

[awaygood]

Bulancore... Well, I could refer you to the IEC (International Electrotechnical Commission) definitions, in which 'line voltage' is defined as 'the voltage between two line conductors', and where 'phase-to-phase voltage' is described as 'deprecated'? Or to the UK's BS 7671 'Electrical Wiring Regulations' which after years of describing the 'hot' conductor as 'phase wire', now describes it as 'line'.

 

[Baluncore]

@awaygood
If you were to question members over their statements there might be some education possible, but if you insist they are wrong, then you make yourself look like a gaslighter, one who operates by undermining rather than educating or accepting. The gaslighter is a particularly dangerous species of troll and will need to be banned.
To be part of this community, you must produce more solid references to definitions, so members can see where they are wrong, not be told that they are wrong.
https://en.wikipedia.org/wiki/Gaslighting

 

[BvU]

Bulancore... Well, I could refer you to the IEC (International Electrotechnical Commission) definitions, in which 'line voltage' is defined as 'the voltage between two line conductors', and where 'phase-to-phase voltage' is described as 'deprecated'? Or to the UK's BS 7671 'Electrical Wiring Regulations' which after years of describing the 'hot' conductor as 'phase wire', now describes it as 'line'.

Perhaps you can provide a link ? I find their website particularly chaotic and every time I am almost where I think I want to be -- a login is required


And a reference for

'Voltage' is NOT measured 'relative to something'. Voltage is absolute. You are confusing 'potential' with voltage. Voltage is simply another word for 'potential difference', not 'potential'. Potential is always expressed as being 'with respect to' some fixed reference point.

would be nice too.

I have a firm impression the participants are in full agreement, just unable to communicate that.

$\$

 

[phinds]

I have a firm impression the participants are in full agreement, just unable to communicate that.

I am NOT in agreement w/ his statement that 'Voltage' is NOT measured 'relative to something'

What does he think is the voltage on the + terminal of a AA battery? According to him you can't measure it relative to the negative terminal, because that WOULD be measuring it relative to something. So ... what could it possibly be?

 

[awaygood]

Bulancore... Well, I could refer you to the IEC (International Electrotechnical Commission) definitions, in which 'line voltage' is defined as 'the voltage between two line conductors'.

I can work with professorelectron. I just need a couple of different hats that I can change as I think about the different parts of the system.

A phase voltage and a phase current refer to a single physical internal phase-winding of a generator, transformer, or a load. Those three internal phases can be connected in wye or delta to the terminals. The internal term “phase” does not reach the line terminals.

I must remember that a line voltage is measured between two lines, but a line current is measured on only one line.

Spot on!

 

[awaygood]

I am NOT in agreement w/ his statement that 'Voltage' is NOT measured 'relative to something'

What does he think is the voltage on the + terminal of a AA battery? According to him you can't measure it relative to the negative terminal, because that WOULD be measuring it relative to something. So ... what could it possibly be?

Let me put it this way. The 'potential difference' (voltage) across an AA cell is 1.5 V. Period! The 'potential' of the positive terminal, RELATIVE TO THE NEGATIVE TERMINAL, is +1.5 V. The 'potential' of the negative terminal, RELATIVE TO THE POSITIVE TERMINAL, is -1.5 V. Better still, let's consider two AA cells in series. The potential difference (voltage) across this arrangement is 3 V. Period! The potential at the positive end, WITH RESPECT TO THE NEGATIVE TERMINAL OF THE SECOND CELL is +3 V. The potential at the positive end, WITH RESPECT TO THE CONNECTION BETWEEN THE TWO CELLS, is +1.5 V. The potential at the centre, with respect to the positive terminal, -1.5 V, whereas the potential at the centre, with respect to the negative end is +1.5V. So, 'potentials' are very much dependent on where the reference point is, whereas the potential difference (voltage) is fixed.

 

[Averagesupernova]

Phase voltages are measured ACROSS phases; line voltages are measured BETWEEN lines.

While I agree that lines/legs are not phases, how can phase voltage not be interchangeable with line voltage as you have described it?

 

[awaygood]

'Gas lighting' is not a phrase I'm familiar with. But I have NOT 'just said' that anyone is WRONG... I have backed my opinions up with the reasons why I believe them to be wrong. I have even referred to definitions used by the IEC and ITE and referred them to a web blog which explains my reasons. What else would you have me do?

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

I repeat that my comment was aimed at the thread, because if he didn't actually say 'phase-to-phase voltage' how could I possibly be quoting him? You do know what 'quoting' means?

"Quoting" means you quoted someone else's words directly using the PF "quote" feature, just as I quoted you above in this very post. You're quibbling, and your attitude is not constructive, and this is not your thread, it's someone else's. That is neither good forum etiquette nor helpful to the person who started this thread, or to others who might read it.

But I have NOT 'just said' that anyone is WRONG... I have backed my opinions up with the reasons why I believe them to be wrong.

Your reasons have nothing to do with the actual physics or electrical engineering involved; they're all about words. You want to use words like "voltage", "line", and "phase" a certain way; other people want to use them a different way.

referred them to a web blog

A web blog is not a valid reference. If there are official publications of the organizations you mentioned that give the definitions you are using, you could reference those. Or you could if this thread were going to stay open, which it's not. But you should keep all that in mind for future threads.

 

[PeterDonis]

The OP is gone and the thread topic has been sufficiently addressed. The thread will remain closed.