240v debate....

[Rick Christopherson]

As steps Don Quixote bravely forward on his stately Rocinante to battle the ferocious Giants disguised as windmills. Chivalry will surely win the day, just by the sheer veracity of our Brave and will receive his just rewards on the bosom of the lovely Dulcinea.

Ummm, did Johnny Depp play him too? I can see our resemblance. :lol:

 

[mivey]

Mivey:

I noticed that you keep referring to transformers appear to be fed from the Polly phase supply where you would still have reference to the 120? phase shift between the phases, this is where and only where you can use an open Y bank from 2 phase conductors and the neutral to create a 3 phase output from the transformer bank, after you have transformed through a single phase transformer you no longer have this option or we would never need roto phase converters, some of the references also would not apply after you have transformed through a single phase transformer, and in a building with only 240/120 single phase as this has already been done.

if I have this wrong someone educate me:happyyes: this is how I learn:thumbsup:

With a single phase transformer, you will never get anything other than voltages at D? and D+-180? because the neutral is located on the line from D? to D+-180? (or +-D if it makes you happy). Note that this is not the case with 120/208 and that is why we call it a "network" system instead of a single-phase system.

Anyway, the purpose of the open wye configuration is to show the use of forces in the single-phase transformer windings in both directions. Normally with an open-wye, we have an open delta on the secondary that allows us to close the "V" (the leg of the "Y" is missing). Here, the three voltage points are readily available and we just have to close the "V".

With the open-wye to wye transformation, we do not close the top of the "Y", but instead use the voltages in 1/2 of the windings that are displaced by 180? from the other 1/2 to create the missing leg of the "Y". This missing leg has is a voltage point that is not readily available.

The reason I used this example is because with a single transformer, some have argued that the 180? displaced voltage is not a real voltage but just a math trick. This configuration uses two transformers and uses the 180? displaced voltages in each one to create the missing voltage in the wye.

I thought this would refute the statements that the displaced voltages were not real since these systems are actually in place and create a voltage that no one can say is not really displaced 120? from the other legs of the wye. In the open-wye to wye case, we could not create the missing leg of the "Y" if the displaced voltages were not real and really displaced.

 

[mivey]

Ok in the above diagram of a single phase transformer with two secondaries that are connected together at center point we can notice the polarity dots, so with this in mind if I connected a dual trace scope in this manner trace 1 input = red to 3 black to 4 trace 2 input red to 5 black to 6 I should get two identical wave forms that will trace in the same path across the screen in step with each other and positive at the same time and visa versa, I would try this but I would have to use an input isolator for my quad trace as the inputs are common on the shield and I don't have an isolator.

Correct.

 

[hurk27]

With a single phase transformer, you will never get anything other than voltages at D? and D+-180? because the neutral is located on the line from D? to D+-180? (or +-D if it makes you happy). Note that this is not the case with 120/208 and that is why we call it a "network" system instead of a single-phase system.

Anyway, the purpose of the open wye configuration is to show the use of forces in the single-phase transformer windings in both directions. Normally with an open-wye, we have an open delta on the secondary that allows us to close the "V" (the leg of the "Y" is missing). Here, the three voltage points are readily available and we just have to close the "V".

With the open-wye to wye transformation, we do not close the top of the "Y", but instead use the voltages in 1/2 of the windings that are displaced by 180? from the other 1/2 to create the missing leg of the "Y". This missing leg has is a voltage point that is not readily available.

The reason I used this example is because with a single transformer, some have argued that the 180? displaced voltage is not a real voltage but just a math trick. This configuration uses two transformers and uses the 180? displaced voltages in each one to create the missing voltage in the wye.

I thought this would refute the statements that the displaced voltages were not real since these systems are actually in place and create a voltage that no one can say is not really displaced 120? from the other legs of the wye. In the open-wye to wye case, we could not create the missing leg of the "Y" if the displaced voltages were not real and really displaced.

Well I guess I have forgot that one, as for some reason I had it in my mind that the two legs displaced the third 60? to add to create the 120? for the missing leg?:? I have no idea where I got that from:happyno: me thinks I need to go back and hit some books:happyyes:

To much beating frequency's together to create another I need to go to bed

 

[hurk27]

Correct.

So in the real world they are in-phase? but from the "point of view" (common point) they are 180? out? isn't that what I tried to say before?

 

[mivey]

So in the real world they are in-phase? but from the "point of view" (common point) they are 180? out? isn't that what I tried to say before?

Not correct. You are saying that the "real world" only recognizes the forces to be in one direction when in fact the reality is that you can take the force to be in either direction. A voltage is only defined by picking a reference point first.

You are trying to say that if we pick the reference for the voltage between points a and n that we are constrained to use the same orientation for any voltage between points b and n or between points a and b and that is simply not true. The usage of voltages in both directions is well documented throughout our industry and many examples have been given in this thread.

It is true that the following have a zero phase difference: Van vs. Vnb, Van vs. Vab, Vnb vs. Vab, Vbn vs. Vna, Vbn vs. Vba, Vna vs. Vba

It is is also true the following have a phase difference of 180?: Van vs. Vbn, Van vs. Vba, Vnb vs. Vba, Vna vs. Vnb, Vna vs. Vab, Vbn vs. Vab

It is simply true that the voltages from either 1/2 of the winding can be taken in either direction and we do that in many applications in electrical engineering. How about thinking about this one: the currents in both halves of the windings will not always be in phase.

 

[Rick Christopherson]

It is true that the following have a zero phase difference: Van vs. Vnb, Van vs. Vab, Vnb vs. Vab, Vbn vs. Vna, Vbn vs. Vba, Vna vs. Vba

It is is also true the following have a phase difference of 180?: Van vs. Vbn, Van vs. Vba, Vnb vs. Vba, Vna vs. Vnb, Vna vs. Vab, Vbn vs. Vab

With every posting you make, it is becoming more and more obvious that the only basis for your arguments is that you are mandating everyone to conform to your ways. Not because they are wrong, but because you need everyone to do as you do.

You're losing ground Mivey.

 

[Rick Christopherson]

Appearances aside, and mesh analysis preferences aside, the fact remains that a force in either "direction" is a valid EMF (not sure "direction" is the best choice of words but just go with it for now). With the force oscillating in direction, a force in the "other" direction does not just appear mathematically as a force, it is a real force.

No, let's not ignore mesh analysis....let's embrace it!!

Here you go Mivey. Here is a 120/240V system with all of the mesh analysis descriptors already placed for you. I re-labeled the B-Phase source for 115@180. Just in case you thought I might be lying, I removed the inductor for simplicity, but left the symbol so you knew it was originally present. I wouldn't want you to think I was being secretly deceptive.

Please tell us how you are able to complete this analysis without having your B-Phase current not contradict your B-Phase voltage! (Watch your minus signs, because you darn well know I will be watching them.)

 

[iwire]

And your confusion is exactly why I am willing to risk my personal reputation on this topic to resolve this in light of some very adverse opposition.

I am not the only person from this forum that opposes the misinformation that is being presented in this discussion, but I am apparently the only one willing to risk my reputation to stand up to it. I have taken a lot of hits for it, but it should be becoming clearer and clearer that these hits are less and less reputable.

I have been called a fool for going toe-to-toe with the "old boy's club", but if you pay attention to the discussion, you will note the complete absence of any information proving me wrong. To the contrary, what I state is supported by engineering text, yet the old-boys wish to dismiss this as tricks from the editor.

I am not foolish enough to think that I can teach the "ol' boys" that they are wrong, but I can at least make sure that other people are well informed as they make their own decisions.

:lol::lol::lol:

Thanks for the laughs.

 

[Rick Christopherson]

:lol::lol::lol:

Thanks for the laughs.

And you expect me to respect a sheep following the herd? I hear they are more timid in some areas and you can have your way with them without complaint.

I assume that with your last couple of comments that you have recused youself as a moderator of this thread. If not, then I will have you removed from your position.

 

[iwire]

And you expect me to respect a sheep following the herd?

What I asked for, and you failed to do was to be less condescending to the other members of this forum.

I assume that with your last couple of comments that you have recused youself as a moderator of this thread. If not, then I will have you removed from your position.

You do what you gotta do Rick.

 

[Rick Christopherson]

What I asked for, and you failed to do was to be less condescending to the other members of this forum.

If you wish to send this message, then your own posting should not display what you ask to be restrained.

Don't pretend to chastise a member for condescension while at the same time your own message is doing the same. Don't trifle with me. My threats are not idle.

 

[iwire]

Don't trifle with me. My threats are not idle.

Now that is funny.

 

[jwelectric]

This thread has taught me one thing if nothing else.

Stupidity is gained with education. The more we learn the more stupid we get.

The easy way to solve this question is to forget all about the phase angles and time wraps and go to a simple lab experiment that we all can do.

Take a two cell flash light and insert the power supply first in line and then 180 degrees out of line and record what happens.

 

[kwired]

Limited to extremely low amperage 120Vac is only technically safer because you require a minimum current to supply enough power to trigger fibrillation. Strictly speaking this occurs at half the amperage for a 240Vac circuit. However, if we're using amperages that low we typically use 24VDC or less. Therefore for fibrillation it's practical to assume they're the same level of danger.

At higher levels of amperage we leave the fibrillation zone and move into the cooking or burn zone. Technically speaking the 240Vac will reach this zone first. But again the difference is very modest. And you're already above the fibrillation and muscle lock-on requirements. So again, in a practical sense the 120Vac is just as dangerous.

Double may seem significant to the lay person but electrically the difference between 120Vac and 240Vac safety is only of scholastic interest.

Unless you are talking about power supplies that are only capable of delivering current in the microamp ranges, I don't see what you are getting at. 24VDC likely can deliver enough current for fibrillation, if applied to the right place. Most people have high enough resistance that 24 volts will not be a problem with external body contact.

 

[weressl]

View attachment 5894

Ok in the above diagram of a single phase transformer with two secondaries that are connected together at center point we can notice the polarity dots, so with this in mind if I connected a dual trace scope in this manner trace 1 input = red to 3 black to 4 trace 2 input red to 5 black to 6 I should get two identical wave forms that will trace in the same path across the screen in step with each other and positive at the same time and visa versa, I would try this but I would have to use an input isolator for my quad trace as the inputs are common on the shield and I don't have an isolator.

...and this is a repeat what I've posted before to try to get through some thick skulls.:lol:

 

[weressl]

If you wish to send this message, then your own posting should not display what you ask to be restrained.

Don't pretend to chastise a member for condescension while at the same time your own message is doing the same. Don't trifle with me. My threats are not idle.

Let's see how far you get Rucio. I suggest that you will be banned LOOOONG before that happens, which would be sad because seldom do we get petulant children around here who provides endless entertainment.:lol::lol::lol::lol::lol::lol:

 

[pfalcon]

Unless you are talking about power supplies that are only capable of delivering current in the microamp ranges, I don't see what you are getting at. 24VDC likely can deliver enough current for fibrillation, if applied to the right place. Most people have high enough resistance that 24 volts will not be a problem with external body contact.

The OP was only discussing 120Vac and 240Vac. So yes, for the voltage to matter regarding fibrillation you would have to be in the microamp range or below. In which case you're not going to use either cause you're probably on a 3.3V circuit board that would otherwise fry.

 

[pfalcon]

If you wish to send this message, then your own posting should not display what you ask to be restrained.

Don't pretend to chastise a member for condescension while at the same time your own message is doing the same. Don't trifle with me. My threats are not idle.

Let's see how far you get Rucio. I suggest that you will be banned LOOOONG before that happens, which would be sad because seldom do we get petulant children around here who provides endless entertainment.:lol:

:lol:

Thanks for the laughs.

You all unofficially have your hands slapped. :rant: :weeping: Deep breaths. Deep breaths.

Is this all because if I put a probe on the neutral and move the other probe back and forth on the hots that I get opposite readings?

 

[iwire]

Is this all because if I put a probe on the neutral and move the other probe back and forth on the hots that I get opposite readings?

Yes, as a mater of fact it is all your fault.