240v debate....

[jim dungar]

They mention flux, current and motion. Not voltage.

You are correct it is the work done by Faraday, not Fleming, that links voltage (emf) and flux.
But if a current is flowing through a conductor, according to Mivey, we should be able to say one end of the conductor has higher potential than the other end.

Do you honestly think I couldn't design such things without understanding phase relationships? And that they would actually work?
That they do and are in service in many locations in different countries attest to the fact that they do work, and do so reliably.

Designed and supplied any such systems yourself?

Congratulations on contributing to the effective use of electricy. (This is not meant to be sarcastic, I do mean thank you)
And no I have not designed a rectifier circuit. For the past +30yrs I have dealt with the interconnection and application of transformers.

Seriously, lets stop talking about 3-phase systems and rectifier circuits.
Lets get back to a center tapped transformer winding on a single core. This is the probably the most common source found in the US.

 

[jwelectric]

Lets get back to a center tapped transformer winding on a single core. This is the probably the most common source found in the US.

Well Jim it seems that they don't know much about one of them

 

[Besoeker]

You are correct it is the work done by Faraday, not Fleming, that links voltage (emf) and flux.

I agree. An important scientist who contributed much to electricity and magnetism and worth of the fame he achieved. But let's not forget Tesla. He is much less well known to those outside this field but ought to be much more widely know considering his contribution to alternating current. Which is rather relevant to this thread.

But if a current is flowing through a conductor, according to Mivey, we should be able to say one end of the conductor has higher potential than the other end.

Different I would say. It's potential difference that makes the current flow (assuming that there is a conducting path for it)

Congratulations on contributing to the effective use of electricy. (This is not meant to be sarcastic, I do mean thank you)

That's kind of you to say so. And thank you for the edit - without that I could have taken it the wrong way.

For the past +30yrs I have dealt with the interconnection and application of transformers.

At the utility end of things?

Seriously, lets stop talking about 3-phase systems and rectifier circuits.

The waveforms I posted in #22 were for a centre-tapped arrangement with V1-N and V2-N shown as how they are. Mutually displaced by 180degE. (Note the order of the terms.) The three-phase circuit arrangements I later posted are just three-phase versions of the single-phase centre-tapped transformer.
In #49 and #66 I gave you the reference point I was using. In #86 I gave rectifier and SCR waveforms to show why they, V1-N and V2-n, must be mutually displaced by 180degE.
I thought that this would be a simple way to get the point across.

Lets get back to a center tapped transformer winding on a single core. This is the probably the most common source found in the US.

Yes, 120V-0-120V. Two hots and a common neutral. Isn't that the crux of it?

 

[jim dungar]

Yes, 120V-0-120V. Two hots and a common neutral. Isn't that the crux of it?

The explanation of the physics needs to recognize that not all loads connected to a centertapped sources actually employ a neutral conductor. A single core transformer with a single magnetic flux path does behave differently than a multi-core arrangement.


The direction of the voltages and currents created by the transformer action must be considered when interconnecting transformers whether they are in 'addition or subtraction' or joined in a 'star or a delta', paralleled or seriesed.

I think even Telsa would agree with that.

 

[jwelectric]

Yes, 120V-0-120V. Two hots and a common neutral. Isn't that the crux of it?

In post #3 the reference was made that the two 120 volt legs were 180 degrees apart which brought forth all this discussion about three phase and diodes and SCRs when the debate was started about a single phase transformer of 120/240 volts.

The questions are still not settled about this single phase 120/240 volt transformer.

How many voltages does this single phase transformer produce?
If more than one voltage are they in phase or out of phase?
If there is more than one voltage and they are not in phase how far out of phase are they?

I contend that there is only two voltages, 120 and 240.
I contend that the two legs of 120 are in phase with each other and are only viewed as being 180 degrees out of phase simply due to the method in which we look at them on the scope.

What say you?

 

[Rick Christopherson]

The waveforms I posted in #22 were for a centre-tapped arrangement with V1-N and V2-N shown as how they are. Mutually displaced by 180degE. (Note the order of the terms.) The three-phase circuit arrangements I later posted are just three-phase versions of the single-phase centre-tapped transformer.
In #49 and #66 I gave you the reference point I was using. In #86 I gave rectifier and SCR waveforms to show why they, V1-N and V2-n, must be mutually displaced by 180degE.
I thought that this would be a simple way to get the point across.

How can one's chosen reference point impact how a circuit functions? Isn't this what makes it something that can be chosen at will? Doesn't the circuit function exactly the same regardless what reference we choose?

If this 180? phase shift exists only because some choose the neutral as a reference point, how then, can the downstream circuit prove the existence or not of a 180? phase shift?

Do you see the flaw in the logic?

 

[Besoeker]

The explanation of the physics needs to recognize that not all loads connected to a centertapped sources actually employ a neutral conductor.

Agreed.

A single core transformer with a single magnetic flux path does behave differently than a multi-core arrangement.

Also agreed and I have not disputed either of those points.

 

[Besoeker]

In post #3 the reference was made that the two 120 volt legs were 180 degrees apart which

Which, wrt to neutral, they are.

 

[Besoeker]

How can one's chosen reference point impact how a circuit functions? Isn't this what makes it something that can be chosen at will? Doesn't the circuit function exactly the same regardless what reference we choose?

If this 180? phase shift exists only because some choose the neutral as a reference point, how then, can the downstream circuit prove the existence or not of a 180? phase shift?

Do you see the flaw in the logic?

Then please explain why, in the absence of that 180deg shift between Van and Vbn, the SCR pulses in my diagram in post #86 have to be 180deg apart for Ia and Ib?

 

[Rick Christopherson]

Then please explain why, in the absence of that 180deg shift between Van and Vbn, the SCR pulses in my diagram in post #86 have to be 180deg apart for Ia and Ib?

Mivey made the following comment yesterday and I started to write a follow-up to it several times but decided not to because it was relating something he was saying to something you were saying. With your new posting, his words are again re-applicable.

I believe it is the fault of becoming accustomed to thinking about things in one way for so long that one forgets there is a different way that is also valid. But what boggles my mind is the dispute after so much discussion, especially from those who know the theory. They are just mis-applying the theory.

I don't want to put words in your mouth (Besoeker), but for quite some time during this discussion, you have made statements and assertions that seem to imply that you believe there is one way and only one way to view a system. Your adamancy on this viewpoint is the reason why I began to wonder whether you had obtained the original viewpoint education that I know is present in engineering coursework. (No insult intended. I am just explaining why I had previously questioned it.)

I had asked you several days ago whether you asserted that the 180 degree phase shift was absolute and independent of viewpoint, and you asserted that it was, but never responded to the discussion after that point. So I will ask again. Are you under the belief that the 180 degree phase shift is present irrespective of whether the neutral is chosen as a common reference point?

 

[mivey]

I had asked you several days ago whether you asserted that the 180 degree phase shift was absolute and independent of viewpoint, and you asserted that it was, but never responded to the discussion after that point. So I will ask again. Are you under the belief that the 180 degree phase shift is present irrespective of whether the neutral is chosen as a common reference point?

I may have missed that post. Did he say the phase difference of Vbn to Van or for all voltages taken from terminals b & n relative to voltages from terminals a & n?

I thought he has been saying the direction we take the voltages makes a difference. That is my viewpoint anyway.

Add: I also say that either way of viewing the system is valid (with either two in-phase voltages or with two phase-opposed voltages).

 

[Rick Christopherson]

I'm on my way out the door, so I'll have to come back to this later, but I was left with the clear impression that it was irrespective of voltage references.

 

[mivey]

I'm on my way out the door, so I'll have to come back to this later, but I was left with the clear impression that it was irrespective of voltage references.

Then I would take issue with that because it is the choice of reference that makes the difference.

 

[mivey]

First the 120 voltages that are formed from a center tap single phase transformer is not two sources but only one source, the transformer

I would disagree. They can serve two entirely separate circuits and have completely different currents. They are serving as two single-phase sources when taken separately, or as one combined double-voltage, single-phase source when the neutral is not used.

Second these two voltages are not 180 degrees apart but instead all of one accord.

We can take the positive voltage force in the same direction or opposite directions, as Besoeker's circuit has proved.

Each is one half of the one 240 volt power source just as there are two 1.5 volt batteries in my 3 volt mag light. Should I decide to I could power two 1.5 volt bulbs one from each of the two 1.5 volt batteries. This does not mean that one battery is flowing one way while the other is flowing 180 degrees in the opposite direction.

To put it simply, a battery does not alternate so the comparison is pretty weak except for very specific cases.

Now as to the direction of current flow like you said the current flows from a higher potential to a lower potential therefore the potential does dictate the direction of flow. You say we are confusing direction with polarity how do they not walk hand in hand.

Because the polarity only gives you the relative directions. In other words the direction of the voltages in one part of the circuit relative to the voltages in the other part. Polarity does not define which direction is positive and which direction is negative.

The reference point is a choice you make. As you can see with the two-source supply to the three-terminal circuit (post #290) the current directions and polarity markings on the transformers are not the same.

 

[weressl]

Congratulations on contributing to the effective use of electricy. (This is not meant to be sarcastic, I do mean thank you)

Indeed. But how do we use 'it' effectively? IMO one can utilize something to the fullest extent of its potential - and this is an all inclusive concept, does not apply to electricity exclusively - if one understands the governing laws that the 'it' is subject to. THAT is what Mac contributes to immeasurably AND patiently. Kudos to the technological lineage of Flemming, Faraday, Kelvin, Newton etc......

 

[weressl]

How can one's chosen reference point impact how a circuit functions? Isn't this what makes it something that can be chosen at will? Doesn't the circuit function exactly the same regardless what reference we choose?

If this 180? phase shift exists only because some choose the neutral as a reference point, how then, can the downstream circuit prove the existence or not of a 180? phase shift?

Do you see the flaw in the logic?

There is nothing to be seen.

Isn't connecting something in phase order ABC and BAC is simply CHANGING one's chosen 'reference' point? Will it produce different results in a 3 phase motor rotation?

Not only MUST consider the base reference, but without it the essential difference is lost.

 

[mivey]

How can one's chosen reference point impact how a circuit functions?

Again, back to Besoeker's example.

Unidirectional:
Use b as a reference, put diodes so current flows out from n and out from a (all clockwise flow). You will get two in-phase currents.

Bi-directional:
Use n as a reference, put diodes so current flows out from a and out from b (clockwise and counter-clockwise flow). You will get two phase opposed currents. Try that with a 2-terminal circuit and you get nada.

 

[mivey]

There is nothing to be seen.

Isn't connecting something in phase order ABC and BAC is simply CHANGING one's chosen 'reference' point? Will it produce different results in a 3 phase motor rotation?

Not only MUST consider the base reference, but without it the essential difference is lost.

Electricity 101 again. You would think it would be such a simple thing.

 

[mivey]

If this 180? phase shift exists only because some choose the neutral as a reference point

It is not "there" because we chose the neutral, it is there because its existence is a physical fact. "If a tree falls in the forest..."

how then, can the downstream circuit prove the existence or not of a 180? phase shift?

Downstream, the voltage is what you measure. Your meter is just a load like any other load and it is not lying to you or playing "math tricks".

Do you see the flaw in the logic?

The flaw is that you say the reverse voltage does not exist and can't be "proven" unless we somehow trace its roots all the way back to...something.

The voltage is real, and we can connect circuits to produce results that show it is real without having to back-track how the voltage was created in some land far, far away. The voltages are what they are right where they exist.

 

[iwire]

So if a tree falls in the forest it gets a shock?