jwelectric
Senior Member
- Location
- North Carolina
why not just a plain old single phase center tap transformer
240v debate....
- Thread starter stickboy1375
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why not just a plain old single phase center tap transformer
Rick Christopherson
Senior Member
By the way, with the heavy black arrow (triangle) some people will confuse this for a flow direction on the pump and not realize that your pumps are simply pulsating back and forth. It's this pulsating that messes up the concept you wanted to show by putting your check valves where you did.
mivey
Senior Member
Well now I'm confused and curious. I love to learn new things and I am hoping you would be able to enlighten me. I have models for inductors using large paddlewheels with inertia, models for capacitors using bladders, and I would like to get the diode right.
mivey
Senior Member
Thanks for the input. I'll look at that and see about refining my hydraulic model.
Not at all. Just that you are invoking irrelevant rules when you bring in Flemming's left and right hand rules.
mivey
Senior Member
I tried that and it did not seem to work for some because they are confusing direction with polarity.
To get to the center-tap, there must be an understanding that you can indeed have a single-phase, three-wire circuit fed by two voltages that really are displaced by 180?. If you can't understand that, then you will never understand the rest. I tried to clarify that in my post #98 and some still did not get it.
Rick at least agrees that you can have two real voltages with 180? displacements serving a single-phase three-wire circuit. His problem is with me saying that there are actually voltages in the center-tap winding that have a 180? difference. I understand that is his issue with what I have said.
Is that your issue as well or do you also have issues with the voltages from two sources having a 180? difference, as in my post #98?
Conventionally, it's the other way round but not important. The significant point is that the current and voltage from each end is displaced from the other.
Without that, the circuit would/could not produce full-wave rectification. Yet it does.
It beggars belief that such a simple circuit is still being disputed.
mivey
Senior Member
As long as we are being irrelevant, a complementary right hand rule is:
Hold out your hand with your thumb pointing up and fingers extended, with your hand oriented like your were going to catch the flux in the palm of your hand. Then the flux goes perpendicular through your hand, hitting your palm first.
When you are "catching the flux", with your right hand, motion is in the direction of your thumb and your outstretched fingers point in the direction of the current. Gives you fewer finger cramps than Fleming's rule.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Why are they irrelevant? Aren't they used to demonstrate an interrelationship between flux and voltage?
I am trying to point out that there are fundamentals that our industry uses when constructing and interconnecting electro-magnetic devices. Have you tried to build any of your mutli-pulse rectifier circuits by ignoring the relationship of the different transformer windings and the fluxes?
And least we forget, in the real world: Van<180? = -Van<0
Rick Christopherson
Senior Member
I don't think anyone will automatically contest the concept that you could have two independent sources that are physically 180? out of phase, but you have to be extremely careful with your wording of it in the process. Forgive me for not taking the time to find a specific example for you, but that's because I am not trying to argue this, only point it out to you as the author. That being said, there have been times when a single word in a sentence has been enough to flag the entire sentence as incorrect. In other words, be careful with the "absolutes" that result from a single misplaced word.
mivey
Senior Member
Well, I had a 50/50 shot at it.
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.
Nature is not so strange as to have circuits really work by breaking its own laws. It really is simple. I am thinking of a different approach that may will help turn on the lightbulb for some. I am hoping to get some fundamental understandings of how things work out of the way first, or we will just be reduced to arguing over basic theory like we have been.
mivey
Senior Member
No doubt about that and we have burned a lot of posts for that very reason.
This would be so much easier and faster in person. The problem here is what you mean, what you write, what someone reads, and what they comprehend can all be different and it makes a forum like this an interesting exercise in communication. These discussions have really helped me in writing things at work because I find myself reading things back and wondering how many different ways it could be taken.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
You are clearly stating that the direction of the flux directly 'impacts' the direction of current.
Previously you stated in post #487,
.mivey said:
Then explain how, in the real world of electro-magnetism, the direction of flux does not impact the direction of the voltage, or at least the high potential and low potential ends of a conductor.
mivey
Senior Member
It goes back to the basic definition of what a voltage is. I'll work on some wording for a post that hopefully will help you understand what I mean.
jwelectric
Senior Member
- Location
- North Carolina
First the 120 voltages that are formed from a center tap single phase transformer is not two sources but only one source, the transformer
Second these two voltages are not 180 degrees apart but instead all of one accord. 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.
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.
mivey
Senior Member
There again is the problem. When I try to get some fundamental understandings about voltages out of the way, you completely ignore that and jump right ahead to the main course. How about you finish the appetizer first then we'll move on to the main course? If you do not understand the part about the two separate sources, you will not be able to follow along in the next part of the discussion and we will constantly be going back and forth to discuss voltage fundamentals.
If you want to contest what I say after the appetizer, great, but don't fight that battle before you get there. If you don't follow what I am saying about the other, you will be fighting windmills instead of what I plan to present.
Perfect example of why you need to finish the appitizer first or you will never be able to move forward. Go back and read my post #98. You will see that the polarity markings of the two transformers would be on opposite sides of the three-wire circuit. Also look at how I applied these two separate sources, with 180? displaced voltages and fed Rick's example circuit in post #290. Can you follow those two posts and do you agree that these are real voltages and not just math tricks?
I know this is two separate sources and the real battle begins with the single core, but can't we move past the fundamentals of individual sources, voltages, and separate cores?
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
If I remember right (like I can do that:roll
much depends upon how a transformer is wound, if we look at the primary coil and H1 would indicate that the coil is wound over the top then and H2 would come out from underneath so with H1 is to your left then you would place your fingers over the top and you thumb would point to your left.
Now again on the secondaries if the X1 is wound over the top then X2 returns from underneath and placing your fingers over the top would place your thumb to the left, now reverse this and X1 becomes X2 and by placing your finger underneath will place your thumb to the right.
I'm not sure if I'm right about this but it seems to come to mind:?
I know this has to do with transformers that have the polarity dot at opposite ends of the core instead of on the same end?
Rick Christopherson
Senior Member
Polarity dots at opposite ends of the core comes from the minus sign in Faraday's Law of Induction.
jwelectric
Senior Member
- Location
- North Carolina
The only thing I am interested in discussing is a single phase 120/240 transformer such as the original question was.
Not two power sources, not fluid power, just a plain old single phase 120/240 volt transformer
They mention flux, current and motion. Not voltage.
Look back at post #431. Look at both the primary and secondary connections. It gives 24-pulse operation. From a three phase supply. The main objective of what might seem like a complex arrangement is to minimise harmonic content on the supply.
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.
And, unless I have missed it, I think I am the only poster here who has put up actual circuit diagrams of real stuff we have made and photographs of it.
Here's another taken during the build phase.
It clearly shows the physical arrangement of the circuit that Rick claims I got wrong - yet failed to provide his "corrected" version.
Made around 1992 and still operational.
Designed and supplied any such systems yourself?
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