Explanation of the phase relationship between the two transformer secondary windings, or two halves of the winding, feeding a 120/240 V Single-Phase system.
At 74 years old and been working in an electrical environment for more than 50 years I have never seen a good explanation like this. Would have loved to have you as my tutor. Keep the videos coming.
the biggest issue is arrogant electricians.. the teachers (typically former electricians int he field) will want to "skip" over stuff, to appear to be "macho" to the guys from the union or for those working in industrial. He will say stuff like "I know you guys know this stuff so we can run through this part, but if you dont raise your hand". therefore making it a matter of ONE guy looking "less of a man" for raising his hand. AND DONT LET that man be a minority among a bunch of white men.. because then theres a DOUBLE whammy feeling. the white guys looking upon you as if youre stupid. this is why teachers need to be TEACHERS ... like this man is doing.
A most unusual video where the explanation was unique and a credit to the Dave Gordon. I have never seen the concept of vectors addressed to the non maths audience in this fashion with attention to detail . You sir are a credit to your profession.
But wrong conclusion.. . He failed to identify the correct Reference point, which is and has to be the Zero or Neutral point. . . . Looks as if he sort of used the paper as his reference. . . . Paper does not carry electrical current, wires do, so you have to use the correct electrical point, which is the Zero or Neutral point.
*THANK YOU* for this! I have been trying to explain this to people for a while, and this demonstration perfectly outlines everything I've envisioned and understood. The principle of number of turns is key, as that not only directly relates to voltage (transformer ratio), it also means that if "180° out of phase" were true, then 240V could never be made. Again, thank you for this fantastic complete demonstration and explanation!
Let me try to come to your page since our previous attempt went nowhere. You make the claim several times in these comments that it is utter folly to use the center tap (neutral) as a constant reference. I have one simple question I am hoping you will humor me by answering: Why is it folly to do as such in a split phase scenario, yet it is common-- standard in fact-- to use a common reference when determining phase angles in 3 phase? If you disagree that it is the standard to measure 3 phase relationships off a common neutral, please work with me on that. That would be our sticking point. If you agree with that but think there is some fundamental difference in the way split and 3 phase are measured, help me understand what that fundamental difference is.
Perfect explanation and demonstration, thank you Dave! I have tried to explain what single phase means and that split phase is like a center tap transformer used in electronic power supplies. Most people just po-po me saying "it has always been 180 degrees out of phase" and they won't change their thinking.
Brilliant Dave. Absolutely the best instruction I have ever seen in any venue on any subject, and I've seen a lot. I'm going to watch every one. Much thanks, what a gift you have.
Brilliant, but WRONG Conclusion. . . He is not even looking correctly at his Own drawing. . . The Reference point is the Grounded Neutral point. . . All should be referenced to the Zero or Neutral point.
Thank you, I am a curious, jack of all trades, master of none type of person who has always just accepted the split phase / out of phase concept without fully understanding. I understand it now. Once again, thank you.
I assumed that it was 180 degree out of face, but when tried to analize vs the center tap.. I got a short circuit in my head.... but never had the opportunity to see it through an Oscilloscope to reveal how current flows between phases and the neutral at the same time..... wonderful explanation... greatly appreciated!!
Your videos are wonderful. I have degrees in EE and CS but I have been a programmer in medical imaging research for most of 25+ year career (did a little engineering work in the early days). I am interested in relearning at least some of the information I have sadly forgotten over this period of time.
I'm on about the same track. EE the worked in architectural engineering for a couple years then got into comp sci (had a comp sci minor in college, and programmed during high school). I've been doing mostly line of business applications with some public facing sites. I'd like to get into something a little different though. How did you get into medical imaging?
Thanks Dave. I'm in my mid 60s, have a physics background (I understand electricity from Maxwell to Feynman), over-the-top experience in res. wiring and, until now, have never fully understood "split phase"! THANKYOU.
Dave, at the beginning of the video you explained if the turns were reversed at the neutral point that it would be out of phase. It would not be out of phase, but instead it would be reversed polarity. Reversing the polarity would give you two 120 circuits and a net zero for full tap. It is how a regulator works with using reverse polarity and using the same winding to be able to raise or lower the voltage, but any single winding coming off a highline single phase will always be in phase of each other.
@@I_SuperHiro_I Yeah. Reversing the polarity is essentially multiplying the sine wave by negative one, which is the same as being 180 degrees out of phase.
Amazing tutorial.This just clarified all of my confusion about how 120/240 single-phase and 240 3-phase can all operate on 3-phase 4-wire systems. Your ability to communicate this is amazing!!!
You can't choose two different reference points for two signals to determine if they are in phase or not. You need a common reference point. Why not use ground? Oscilloscopes use ground as the reference point. If you do that then you find that you will see two sine waves that are 180 degrees out of phase on the oscilloscope screen. If you want to call that "in phase" then go ahead, but it's clearly inverted.
I've been trying to make a similar argument here and the naysayers have zwro answers in return for me. If someone wants to call a straight line (0 or 180 degrees, either) in phase by virtue of there being no 'angle' that's fine, but as you say, phase relationships require common reference points. Same in geometry to draw an angle: it needs a vertice.
@@spruce_goose5169 it's like some people have already decided to call this "in phase" and they are trying to find analogies to attempt to justify their belief. They aren't really trying to address the elephant in the room which is that with ground as your reference point, the two sine waves are in fact 180 degrees out of phase. They get annoyed when anybody who went to engineering school sees the waveforms and says "those are 180 degrees out of phase" because, well, they are. Just get over it. It doesn't matter, it doesn't change anything. Electricity still works.
I appreciate your attempts, but I don't see *_ANY_* of your other comments. It is somewhat of a "slight of hand" trick to move the reference between measurements. If you're allowed to do that, I can show you how the primary winding is out of phase with itself.
@@MartinVandepas when generators operate its my understanding that phase one starts at the north pole of a magnet while phase two starts at the south pole of the magnet which would always keep them 180 degrees apart from each other. having a tough time taking this guy seriously.
They are out of phase only on the osciloscope screen. In reality they are in phase and are ADDING UP!!!! If they were truly out of phase 180 degrees then the voltage between the two legs would be ZERO!!!!
Apologies if this adds some confusion but just trying to add some clarity. Let’s start with the basic single winding you are showing as the voltage source and let’s look at it without any mid-tap, center-tap, neutral, or split-phase tap connection. i.e. Just the winding. In reality this is a winding as part of a transformer, possibly your home or business pole or pad mounted transformer. If we can agree that this winding is receiving its energy as a secondary winding to a primary winding, which is being fed from a generation source, then it would seem that our interest in labeling any of the downstream, secondary wiring as “in-phase” or “out-of-phase” should always be in reference to any of the other transformer primary windings. With this approach, I am looking at our common electrical power generation and distribution system, where for example, the hydro-electric plant’s generator creates voltages via 3 distinct windings and because the armature is rotating across these 3 windings at different times, we have 3 windings which are physically arranged to be producing voltages 120 degrees (1/3 of 360) from each other. These three windings are then tied together in series, or some would say in a delta connection with three tap conductors to be extended out through various control and distribution apparatus to our local pad or pole mounted transformers. And back to my point, it is these conductors that will impact on our reference to phasing, or as we commonly label - A Phase, B-Phase, and C-Phase. My own education has me of the understanding that our commonly used system of 120/240 volts is simply a secondary winding of a local utility power transformer, which is being induced with a 240 volt voltage from a primary winding being fed from 1 or 2 of these original hydro-electric source conductors. And I include the possibility of 1 source conductor simply because in some cases the primary voltage to our local transformers may just be a primary winding utilizing one source conductor and a common grounding tie with the secondary. So when I look at this discussion, I tend to disregard references to phasing within any of the secondary 120/240 volt wiring because to me the phase of this wiring is linked to whatever source conductor or conductors are used to power the local primary winding. Yes, you could have true original source phasing within the home or business system, but it would be because the 3-phase power has been brought in and is fully utilized to power a 3-phase transformer which in turn has 3-phase secondary windings, possibly delta or Y connections. Having offered this, I also acknowledge the ability to engineer electrical phasing to operate certain 3-phase equipment. But when I read the original question Dave put out there, relative to the AC sine-wave(s), I just immediately assume it is in phase due to how the 240 volt secondary winding is powered. And I am still open to being re-educated as to how to look at phasing. I do also understand that when we want to refer to either side of the 240 volt power source, we tend to say the “black phase” or the “red phase” or even the “A phase” or “B phase”. But if you work enough with actual 3-phase power wiring, it seems odd to refer to the two conductors supplying the 240 volts as individual phases themselves simply because their source winding is one single phase. And I just never liked using “split-phase” either when looking at either of the 240 volt conductors in relation to a neutral or center-tap connection because again the phasing was created up stream. You can tap that 240 volt winding anywhere and create a myriad of different voltages but to refer to them as phases doesn’t seem to really relate to the true rotational phase of the AC voltage. And reversing wire connections in an attempt to create polarity is just simply reversing the the way in which the magnetic fields interact to boost or buck voltages reactive resistances.
pretty much all you said is correct. You glossed over the fact that your clamp ammeter in DC would have given opposite signs if turned the other way around but that did not matter much for the point. Altogether, very clear if not exactly surprising for folks familiar with meters and scopes. Thank you. However, for safety reasons, I feel that you should have made a strong point at the end when discussing results from the ground lead of the scope to L2, that this should NOT be done in real life. It WILL BLOW UP your lead and/or scope because that would essentially be a dead short between L2 at 120V and mains ground through the scope's ground lead. As it stands, a curious person not familiar with scopes may just try that to verify your (correct) assertions and be in for a bad and dangerous surprise.
I always looked at it intuitively from the center point as the reference, where the difference between the two waves accounts for the greater amplitude. There is more area between the lines. A three phase system is truly out of phase, and from the difference between them at any point of time we can extract current. But of course one full winding has to be continuous.
I believe my plain concept on current leading the voltage on distribution lines vs the voltage leads the current after the circuit breaker box in our homes is very great . Relating that to a city of service panels at different current (amperage) ratings we can see how much a town is using in current. And also how many circuit breakers we use in a breaker panel , 200 amp service can handle a quantity of 10 20 amp breakers at 120 / 240 volts each!
Dave, you have it all right (as far as I can tell) except when you say the two halves are in phase. By definition and convention we measure phase with respect to ground. So, while I sort of understand where you are going I feel it is misleading and to that there are some semantic issues. (I apologize)...With regard to AC to the house: It is important to note that L1 to L2 is "one" leg or phase, we don't talk about it as "in-phase" or "out of phase". We say in phase and out of phase with "respect to something". When you split L1 to L2 by center tapping it -- we get: L1 to N is OUT OF PHASE with L2 to N. So the problem I have with your explanation and conclusion is that by "definition and convention"... we measure phase with "Reference" to Ground. More specifically, that means that you don't swap the probes... one probe (the Neutral) probe stays on the Neutral. So, yes, you are right that it depends on how you "measure it:", but the "Proper" way to measure phase is with the reference to ground. So, yea, it is going to be "wrong" when you do it the other way... and it will show up as "In Phase" because you are no longer measuring L1 to N with respect to L2 to N. To summarize, yes, you are correct that if you measure it "wrong", it will appear "In Phase"... but it is NOT in phase (Unless you have a really good reason to change the conventional definition of "in phase" and manage to convince the entire EE world.)
In the end that what it comes to IMHO. Both of you know how it works so the "in phase", "out of phase" argument seems like one of those debates that will never be settled. But I thought the same, how can you make a comparison while shifting the reference? Notice this debate does not exist when the phases are shifted by 90 degrees or 120 degrees. 😇 Cheers!
Great video to explain this! My only suggestion is that in the lower graph, you show red as the combined 240v wave but this is slightly confusing as you also use the red to also show just the half 120v wave in the other graph. Perhaps make the center tap green, then have black/green and green/red for the two 120v, and black/red for the “combined” 240?
Physician from India. Heartiest congratulations on your excellent teaching video. I have a question. Rather than unbalancing the load, will the same effect on intensity of lights be obtained by adding an another stack of batteries 'in parallel' to one set of 4 batteries in your illustration? This has some implication in my research on diabetes. The question is open to all members too. Thanks.
Worth noting that a scope plugged into a wall will see out of phase because the "negative" lead is actually connected directly to the earth/group pin going into the wall. That's a warning for anyone who might want to scope their AC. Don't connect the little alligator clip to live. You're going to have a bad time. Ultimately earth is the base reference that people are using when discussing the phase of the two secondary coils (or two sides of the secondary coil). When you use that reference, they're out of phase. If you reference one end of the transformer for one measurement and then *_move that reference_* to the center for the other measurement, they're in phase. Actually, if you move your reference, you can make them in phase or out of phase as you please.
That's a good disclaimer. Best case scenario, your scope will meet an untimely end. Best to find a decent quality CAT rated differential probe for such measurements.
You can't actually make them in or out of phase arbitrarily, though you can create the illusion by incorrectly handling and discarding of art of the information. There was also major mistake in the video. Basically he conflated true signed potentials with useful absolute potentials. in otherwords -3v can do the same work as +3v but they are not the same when it comes to measuring and graphing phase separation.
I'm looking at solar panels. In the US, the inverter is connected line to line. In Europe, the inverter is connected line to neutral. Both result in about 240 volts. With three-phase power, the three inverters in the US are connected as delta. In Europe, the inverters are connected as Wye.
At 11:35 The unbalanced portion uses the neutral. That sounds like, it is its property to do so., We caused an unbalance to that split system is more meaningful. Is it not? By the way, a very informative well put together video. Loved it. Thank you.
I teach automotive basic electrical, so while i come as a learner I also watch with my teacher hat on. You have a great style of delivery! Nicely done explanations. Also, since i'm used to working with some pretty large DC circuits (starters, alternators, and my house also has large 12 and 48v inverter circuits) I experienced an subconscious discomfort at how hard you were working those D cells. Lol
Great video and I agree with everything you said except the terminology. L1 will always be 180° out of phase when compare to L2 and vice versa. If L1 is at +120 then L2 is -120. The in phase, out of phase terminology is really just a comparison to 3 phase to depict that L1 and L2 are always in sync with each other where in 3 phase power L1, L2 and and L3 are 120° apart
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
I feel like this unlocked something in my brain.. What still confuses me still is when it's "balanced" Dave makes it sound like the electricity is flowing all the way from one side of the "transformer" to the other, like the light at the very end does. Therefore there's no load on the neutral. BUT wouldn't that mean the "half" circuits are now being powered by "220" instead of "110". They are using the entire transformer not just one half of it? My limited understanding, wants to say when loads are balanced, each half is still just seeing the halved voltage, but since the polarity is opposing they cancel out on the neutral. But is power still flowing if it reads 0 amps on the neutral?! Haha.. this is so fascinating to me!
If you are getting 240V AC when you test voltage between Phase A and Phase B, then they are reversed polarity. There is no other way that computing the voltage difference between the two 60Hz (or 50Hz) wave functions will produce any reading. If they were in-phase and the same function in the time domain there would be barely any voltage difference between the two phases, so no current will flow in such a test unless your phase legs are very unbalanced.
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
I wanted to explain better my concepts to customers as English is not my native language and this video was absolutely outstanding. Beyond your evident electrical knowledge, it's your ability to explain and transmit that knowledge, plus the nice quick practical setup, your whiteboard and the camera job, it's what makes this truly remarkable and creates huge impact. I will be recommending your channel. Kudos, Dave. I am subscribing to keep learning ,refresh my knowledge and pick up your words & sentences!
If you look from the load (no load shown in your white board diagram) to the source, you must chose the neutral as the common reference for both 120 VAC legs (L1, L2). This is forced by the fact that 120 VAC outlets are polarized so you can't reverse the sense of L1 and L2.. What is really going on here is, with respect to the neutral, L1 and L2 have opposite polarity. For half-wave, symmetric periodic signals, V(wt + π) = -V(wt). Thus a 180 phase shift is indistinguishable from a polarity reversal. Your error is your perspective. You should be looking from loads to source rather from source to load. From the load perspective, moving the common reference is not valid - your black wire must remain on the neutral.
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
So, boys and girls - what is the terminology that we should be using? Do we have *single phase, split phase electric service...* or what should we call it here in the U.S.?
We commonly call it split phase, but most of us don't need to call the overall structure anything. We just need to know that some receptacles are 120 VAC and others are 240 VAC. The latter take different plugs, so it's easy. We don't even need to know that much. If the receptacle mates with the plug on our electric clothes dryer, then it's the dryer receptacle.
Thank you for that explanation. It cleared up in my mind how the phases work. Why it's called single phase power but we can get 2 different phases with respect to the neutral.
What do we call that phase cancellation in electronics? Common mode rejection? That sounds about right. There WAS 2 phase power that was usually 25 Hz, and always 90 degrees out of phase. Some of it was 60 Hz, and possibly 50 in Europe or Russia. We got our 60 Hz from Russia or Tesla got equipment for 60 Hz. At the time, it was the only thing available. I think it was a watt hour meter. Remember Westinghouse & Edison wanted to SELL electricity for profit, so they needed meters. Tesla did NOT want to sell electricity. He wanted to give it away, for free. (Nikolai Tesla, not the car company!)
Beautiful explanation Dave, helped me to visualize what's happening. Your explanation about the transformer coil winding direction really helped me a lot.
@@davegordon6819 Thank you so very much for this video. It even surpasses your fantastic Open Neutral video. This video should be considered to conclusively shoot-down the "180° out of phase" belief once and for all. I reasoned this all out myself a while ago and have been trying to explain this (the two legs can't be additive if they're out of phase) to people, but this demonstrates it better than I can explain by far!
Thank you for the video, great explanation. I do have a question on the center tap that has a lug added to the winding midway neutral. I understand having the potential difference between L1 and your neutral and having 120, and having 220 between L1 and L2. I understand the in phase and out of phase. When I'm working on a machine ( 120v / 220v ) I can grab the neutral at any time and never be shocked ( though you shouldn't ) because there are 0 volts on the neutral always, no matter the load being powered ( as long as everything is working and wired correctly) . All the voltage is used in powering the load. Neutral is also bonded to ground. In your drawing, it looks like if I took your neutral and bonded it to ground it would be a short to ground. I'm sure I'm missing something and not understanding it fully. Thank you.
I honestly can’t tell if your joking, if this is a spoof video. It’s very well done, for a spoof. It’s kinda funny and kinda dangerous with so many people getting UA-cam certified and using videos like this as an educational system. Just to be completely clear, when you ground the center tap, both phases are completely 180 degrees out of phase. The fact that you can hook your leads up incorrectly to a scope doesn’t change the fact that they’re 180 out
"When you ground the center tap" ... so before you ground it, they are not 180 degrees out of phase? What magic happens when you ground it, to reverse the flow of current in one half?
If they are in phase with each other then there is no difference of potential between phases. And yes when you provide a ground reference current flow actually changes. Once you ground it, ground is your reference, it’s a universal reference. This is elementary electrical theory and a basic education not based off UA-cam would do you all well
very nice presentation. Now, if the 240V AC is a pure sine wave, does that mean that the two 120V AC waves are not pure sine? I am thinking that since they switch at the same rate and the amplitude is different, only one of the voltages is pure sine. If that is correct, which is pure sine?
Mike holt says the opposite or maybe I’m misunderstanding. He says phases must be out of phase for the neutral to carry the difference, if they are in phase then the neutral will carry the sum
It sounds like Mike is using incorrect terminology, like many people. For the neutral to carry the difference, the total current must be coming from opposite legs or poles of the transformer with reference to the neutral or 0v point.
Neither Upper drawing nor Lower drawings indicate a reference connection. By indicating the the refrence as GROUND the top drawing becomes understandable...the "OR ?" notation becomes irrelevant
It's absolutely basic and so obvious ... I've worked with split secondaries all my life ... having 4 connections... parallel the windings for double the current and series for twice the voltage and half the current ... just make damn good sure the sec windings are IN phase with each other ( when you parallel the windings ) or you will soon have a burnt out transformer..!!
@@Falcrist Yes, thank you. I come from the old school, fixing televisions and using an isolation transformer. The old oscilloscopes have a common return on the probes and are grounded. If you attempt to look at the 240 voltage, you clip your two probe grounds on the neutral and the probe tips on the two hots. It shows up as 180 out of phase if you forget to invert the second channel. I now have an isolated scope, but had old school habits. I know how to correctly reference the probes, I just had a brain fart. Brain farts can be dangerous. I have watched people blow up their leads because they didn't isolate the probe return. Viewing 3 phase is a perfect example. Thank you for your excellent videos!
If I pull 600V off 2 poles of a 3-phase system and derive a 120/240 split using a TFMR like the one you are describing, how will the primary 600V being 120deg out of phase translate into the 120/240 secondary? Will I measure 240V, or 208V? Do they wind it in a way to compensate? Why doesn't it harm my loads? Awesome video--thanks!
So if the red wire and black wire are in phase, if you were to touch them together you should get a negligible spark, right? (i.e., if they are in phase no to little spark; out of phase BIG ARC) I don't suggest doing this as you will get a BIG BLINDING ARC which implies they must be OUT OF PHASE)
Thank you for this videos! I appreciate all of your material! You have a great gift of putting the subject into terms that can be understood. I look forward to more videos in the future.
Let's say I have a device designed for EU standards (230 V 1-phase, Neutral, and Ground) and I connect this device to the split-phase system to the "hots" L1 and L2 (240 V), I will get no problem with the device and it will work fine? or no? The difference of 10 V can be neglected. Who had the same experience please help.
Visitor from Norway. From Europe we have for a long time wondered about the strange US split phase low voltage, high current distribution system. In most of Europe we now use 230/400V 3 phase TN - network for private homes. With 3phase the motors are simpler with no capacitors that often fails after some years. With a rotating magnetic field, the rotation direction can easily be reversed too. Very practical to open garage doors.
Great video! But I still have a question: do electrical companies generate single phase (180deg out of phase) AND 3 phase (120deg oop)? Or how do they do to provide single phase households and 3 phase commercial clients?
when he says "flatten" look at it this way. theres FORCE in between the humps. as you PUSH one hump to to "flatten" it, you also PUSH that dotted line AND the RED line also will push that same amount...Thats where he's claiming that the wire would look as it does.
How does transformer works for 120/240 input and 120/240 1kva output, i'd seen transformer that the input used was 120 Volts and output used was 240 volts. How this system works? It would be great if you added actual demonstration, still confused me if the transformer is a boost transformer. Thank you!
Thak God we don't have this foolishness in 240V countries. With a 240/415 volt system we have 240v between any active and neutral or ground in every case. In typical household installations we take 1 active to the house, neutral is bonded to ground at multiple points (MEN) . In an industrlai and commercial systems we take all three phases into the building we have 240 volt single phase ciruits from the neutral to the actives. we have 415V, supply between any two phases and either star, delta or triple phase connections for three phase appliances. . putting a neutral half way up a phase is potentillay problematic where there are mixed single and three phase installations. Because in three phase distribution the star pont must be grounded. . Unless it is a very large or high demand installation, we do not have supply transformers in buildings a 240/415 4 wire supply runs up the street. If there is a transformer for the building or complex it will come in as 11KV . having a neutral half way up a phase also makes a variety of circuit protections more complicated. . there are very rare situations where we will hva 240 volt floating dual active or 240 volt split phase installations
In the North American system, with a so called split-phase, which is simply two phases, it is not possible @15:15 to get a 240V swing relative to the SAME reference as the default reference. The 120V and 240V are not in phase, that would happen if the secondary was referenced at one end, instead of the middle. I appreciate that this is for electricians, but the 120/240V is easily contrasted to the original Edison's circuit. Two batteries, in series, referenced in the middle. It's that simple.
Like 95% of the way there and you jump to the opposite conclusion because the last graph in the upper right was drawn incorrectly. What you drew was effectively two measurment leads connected to a single pair of power conductors. The black-neutral and neutral-red should be vertically separated, because there is also a black-red differential in the system which is essential information that should not have been discarded. I believe your focus on the internals of the power source is what led you off course. Pretend you have no knowledge of the power source transformer/generator/battery of cells/inverter, just three mystery wires. Remember we are concerned with power phase here, not the internals of the power sources. (There could be multiple sources of power and claiming in phase or out of phase within a coil becomes rather misleading and pedantic to define. Also consider that defining the anode and cathode in a cell is both irrelevent to the overall circuit and that they actually swap depending on charge or discharge state, despite only a small non-reversing change in general circuit voltage.) Remember that while effective/useful potential is measured as the absolute differential(~RMS), the phase separation is signed(positive and negative) and non-arbitrary(more electros is always more negative). If the sources are in phase (both at positive peak at the same time), then they will have a constant voltage across them and will effectively become a DC voltage. In other words they start with a 3v difference and as one rises or falls the other also rises or falls so 30⁰, 60⁰, 90⁰, 180⁰ later they will still have a 3v difference.
Three comments. One and foremost is this is a great presentation, well done sir. Two, electricians measure from the neutral to phase, and the first graph illustrates that best. In that graph, the two sine wave are clearly 180 degrees out of phase with respect to the neutral. Three, the opposing phase demonstration is more of a parallel circuit. Just go ahead and fold it in half, the batteries are now aligned with one another. Connect the leads that were on opposite ends. I’m claiming the batteries are in phase in phase, same current out, same in. Being in phase, the bottom light has no voltage to work and remains off. All that being said, you are really spot on by defining the reference point. As an old sparky, I’m standing by my neutral and claiming 180 degrees out of phase…
I very much enjoyed this video and its explanation of the output of a center tapped transformer. I particularly liked the example of flattening one sine wave to demonstrate a single phase of twice the amplitude. I understand that the output differs from say a three phase generator where the coils and rotation cause the phases to be physically sepearated by 120 degrees along the time axis, but I find arguing about the "in phase" of "out of phase" argument about household current about as useful as agruing whether a Zebra is white with black stripes or the reverse. Once you understand how it works and what is happening I think the distinction is meaningless. The output of the center tapped transformer when referenced to neutral behaves exactly as two seperate mechanically produced phases would. I have always thought as the wave as "flipped" as opposed to shifted 180 degrees. I would like to see an experiment where someone built a two phase generator running 180 degrees out of phase rather than the conventional 90 deg and hooked that output to three test points and then hooked the output of a center tapped to three others. With the sources of the power hidden. I wonder if it would be possible to identify which was which. Thanks for a great video. I always find that thinking of things like this in as many ways, with as many examples as possible really helps to visualize what's actually going on.
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This is so simple if you have a right teacher, managed to understand it after YEARS!
At 74 years old and been working in an electrical environment for more than 50 years I have never seen a good explanation like this. Would have loved to have you as my tutor. Keep the videos coming.
Choose better environment 😅
@@K1-1can’t just move where you want with liberals scalping and raising the costs of living in all electrical concentrated areas
@@K1-1 rude
This has never made complete sense to me until now. 9 years in the trade and 5 licensed and now I get it. Thank you!
the biggest issue is arrogant electricians.. the teachers (typically former electricians int he field) will want to "skip" over stuff, to appear to be "macho" to the guys from the union or for those working in industrial. He will say stuff like "I know you guys know this stuff so we can run through this part, but if you dont raise your hand". therefore making it a matter of ONE guy looking "less of a man" for raising his hand. AND DONT LET that man be a minority among a bunch of white men.. because then theres a DOUBLE whammy feeling. the white guys looking upon you as if youre stupid.
this is why teachers need to be TEACHERS ... like this man is doing.
Mr. Dave, you are the Biggie Smalls of the electrical world. Your elegance with words and understanding of the hood is amazing!
A most unusual video where the explanation was unique and a credit to the Dave Gordon.
I have never seen the concept of vectors addressed to the non maths audience in this fashion with attention to detail . You sir are a credit to your profession.
But wrong conclusion.. . He failed to identify the correct Reference point, which is and has to be the Zero or Neutral point. . . . Looks as if he sort of used the paper as his reference. . . . Paper does not carry electrical current, wires do, so you have to use the correct electrical point, which is the Zero or Neutral point.
wow I almost cried during this video. looks like i am going to have to deep dive all of your content ty
This is kind of people/profesor we need to have in schools. Amazin
Brilliant, guys like Dave are the type people that I study to level up.
This is the most helpful explanation that I have heard on 120/240 phasing...looking at dc voltage was the key to me.
Please make more videos. By far these have been the most helpful I have come across. Easy to follow and clearly explained. Truly a great instructor.
Unfortunately Wrong. . . He failed to use the correct Reference point, which is simply the Zero or Neutral point.
*THANK YOU* for this! I have been trying to explain this to people for a while, and this demonstration perfectly outlines everything I've envisioned and understood. The principle of number of turns is key, as that not only directly relates to voltage (transformer ratio), it also means that if "180° out of phase" were true, then 240V could never be made. Again, thank you for this fantastic complete demonstration and explanation!
Let me try to come to your page since our previous attempt went nowhere.
You make the claim several times in these comments that it is utter folly to use the center tap (neutral) as a constant reference. I have one simple question I am hoping you will humor me by answering:
Why is it folly to do as such in a split phase scenario, yet it is common-- standard in fact-- to use a common reference when determining phase angles in 3 phase?
If you disagree that it is the standard to measure 3 phase relationships off a common neutral, please work with me on that. That would be our sticking point. If you agree with that but think there is some fundamental difference in the way split and 3 phase are measured, help me understand what that fundamental difference is.
Geez. Me thinks Jovet swam too deep. Confidence > comprehension perhaps. Came out swinging he did.
Perfect explanation and demonstration, thank you Dave! I have tried to explain what single phase means and that split phase is like a center tap transformer used in electronic power supplies. Most people just po-po me saying "it has always been 180 degrees out of phase" and they won't change their thinking.
I really enjoy a lecture using electron flow. When studying CRT tubes, it is the electron beam moving. Great presentation. Thank you.
Brilliant Dave. Absolutely the best instruction I have ever seen in any venue on any subject, and I've seen a lot. I'm going to watch every one. Much thanks, what a gift you have.
Brilliant, but WRONG Conclusion. . . He is not even looking correctly at his Own drawing. . . The Reference point is the Grounded Neutral point. . . All should be referenced to the Zero or Neutral point.
Thank you, I am a curious, jack of all trades, master of none type of person who has always just accepted the split phase / out of phase concept without fully understanding. I understand it now. Once again, thank you.
I assumed that it was 180 degree out of face, but when tried to analize vs the center tap.. I got a short circuit in my head.... but never had the opportunity to see it through an Oscilloscope to reveal how current flows between phases and the neutral at the same time..... wonderful explanation... greatly appreciated!!
Your videos are wonderful. I have degrees in EE and CS but I have been a programmer in medical imaging research for most of 25+ year career (did a little engineering work in the early days). I am interested in relearning at least some of the information I have sadly forgotten over this period of time.
I'm on about the same track. EE the worked in architectural engineering for a couple years then got into comp sci (had a comp sci minor in college, and programmed during high school). I've been doing mostly line of business applications with some public facing sites. I'd like to get into something a little different though. How did you get into medical imaging?
This is a much better explanation of this concept than any of the other videos I've found today, most of which were scattered and incoherent.
Thank you for this clear explanation of in-phase and out-of-phase.
Almost 30years in the trade and I love your video. You keep my mind sharp thanks.
Superb AC current flow using DC batteries. You are a master indeed.
Thanks Dave. I'm in my mid 60s, have a physics background (I understand electricity from Maxwell to Feynman), over-the-top experience in res. wiring and, until now, have never fully understood "split phase"! THANKYOU.
Dave, at the beginning of the video you explained if the turns were reversed at the neutral point that it would be out of phase. It would not be out of phase, but instead it would be reversed polarity. Reversing the polarity would give you two 120 circuits and a net zero for full tap. It is how a regulator works with using reverse polarity and using the same winding to be able to raise or lower the voltage, but any single winding coming off a highline single phase will always be in phase of each other.
Practically in an AC Sine Wave, don’t they have the same effect?
@@I_SuperHiro_I Yeah. Reversing the polarity is essentially multiplying the sine wave by negative one, which is the same as being 180 degrees out of phase.
@@namejeff1050 thanks
Glad to see that you're still posting videos. Still my favorite teacher regardless I won't be able to have you as a teacher anymore :)
Thanks for your support Devan. I hope they're still giving you good opportunities to work with a variety of equipment out in the field.
Agree!!! Keep us teaching please!
Amazing tutorial.This just clarified all of my confusion about how 120/240 single-phase and 240 3-phase can all operate on 3-phase 4-wire systems. Your ability to communicate this is amazing!!!
ALL of your confusion?
Yes, this is just one of the three phases. It doesn't matter which one. That's why this is 1PH service.
Such an elegant explanation. Kudos from an EE.
You can't choose two different reference points for two signals to determine if they are in phase or not. You need a common reference point. Why not use ground? Oscilloscopes use ground as the reference point. If you do that then you find that you will see two sine waves that are 180 degrees out of phase on the oscilloscope screen. If you want to call that "in phase" then go ahead, but it's clearly inverted.
I've been trying to make a similar argument here and the naysayers have zwro answers in return for me.
If someone wants to call a straight line (0 or 180 degrees, either) in phase by virtue of there being no 'angle' that's fine, but as you say, phase relationships require common reference points. Same in geometry to draw an angle: it needs a vertice.
@@spruce_goose5169 it's like some people have already decided to call this "in phase" and they are trying to find analogies to attempt to justify their belief. They aren't really trying to address the elephant in the room which is that with ground as your reference point, the two sine waves are in fact 180 degrees out of phase. They get annoyed when anybody who went to engineering school sees the waveforms and says "those are 180 degrees out of phase" because, well, they are. Just get over it. It doesn't matter, it doesn't change anything. Electricity still works.
I appreciate your attempts, but I don't see *_ANY_* of your other comments.
It is somewhat of a "slight of hand" trick to move the reference between measurements. If you're allowed to do that, I can show you how the primary winding is out of phase with itself.
@@MartinVandepas when generators operate its my understanding that phase one starts at the north pole of a magnet while phase two starts at the south pole of the magnet which would always keep them 180 degrees apart from each other. having a tough time taking this guy seriously.
They are out of phase only on the osciloscope screen. In reality they are in phase and are ADDING UP!!!! If they were truly out of phase 180 degrees then the voltage between the two legs would be ZERO!!!!
Nice job Dave. I am proud to have you in the IBEW
Fantastic presentation. Really well explained and demonstrated. Thank you very much!
That couldn't have been explained any more clearly. Perfect!
Sick name
Apologies if this adds some confusion but just trying to add some clarity. Let’s start with the basic single winding you are showing as the voltage source and let’s look at it without any mid-tap, center-tap, neutral, or split-phase tap connection. i.e. Just the winding. In reality this is a winding as part of a transformer, possibly your home or business pole or pad mounted transformer. If we can agree that this winding is receiving its energy as a secondary winding to a primary winding, which is being fed from a generation source, then it would seem that our interest in labeling any of the downstream, secondary wiring as “in-phase” or “out-of-phase” should always be in reference to any of the other transformer primary windings. With this approach, I am looking at our common electrical power generation and distribution system, where for example, the hydro-electric plant’s generator creates voltages via 3 distinct windings and because the armature is rotating across these 3 windings at different times, we have 3 windings which are physically arranged to be producing voltages 120 degrees (1/3 of 360) from each other. These three windings are then tied together in series, or some would say in a delta connection with three tap conductors to be extended out through various control and distribution apparatus to our local pad or pole mounted transformers. And back to my point, it is these conductors that will impact on our reference to phasing, or as we commonly label - A Phase, B-Phase, and C-Phase. My own education has me of the understanding that our commonly used system of 120/240 volts is simply a secondary winding of a local utility power transformer, which is being induced with a 240 volt voltage from a primary winding being fed from 1 or 2 of these original hydro-electric source conductors. And I include the possibility of 1 source conductor simply because in some cases the primary voltage to our local transformers may just be a primary winding utilizing one source conductor and a common grounding tie with the secondary. So when I look at this discussion, I tend to disregard references to phasing within any of the secondary 120/240 volt wiring because to me the phase of this wiring is linked to whatever source conductor or conductors are used to power the local primary winding. Yes, you could have true original source phasing within the home or business system, but it would be because the 3-phase power has been brought in and is fully utilized to power a 3-phase transformer which in turn has 3-phase secondary windings, possibly delta or Y connections. Having offered this, I also acknowledge the ability to engineer electrical phasing to operate certain 3-phase equipment. But when I read the original question Dave put out there, relative to the AC sine-wave(s), I just immediately assume it is in phase due to how the 240 volt secondary winding is powered. And I am still open to being re-educated as to how to look at phasing. I do also understand that when we want to refer to either side of the 240 volt power source, we tend to say the “black phase” or the “red phase” or even the “A phase” or “B phase”. But if you work enough with actual 3-phase power wiring, it seems odd to refer to the two conductors supplying the 240 volts as individual phases themselves simply because their source winding is one single phase. And I just never liked using “split-phase” either when looking at either of the 240 volt conductors in relation to a neutral or center-tap connection because again the phasing was created up stream. You can tap that 240 volt winding anywhere and create a myriad of different voltages but to refer to them as phases doesn’t seem to really relate to the true rotational phase of the AC voltage. And reversing wire connections in an attempt to create polarity is just simply reversing the the way in which the magnetic fields interact to boost or buck voltages reactive resistances.
Beautifully said.
pretty much all you said is correct. You glossed over the fact that your clamp ammeter in DC would have given opposite signs if turned the other way around but that did not matter much for the point. Altogether, very clear if not exactly surprising for folks familiar with meters and scopes. Thank you. However, for safety reasons, I feel that you should have made a strong point at the end when discussing results from the ground lead of the scope to L2, that this should NOT be done in real life. It WILL BLOW UP your lead and/or scope because that would essentially be a dead short between L2 at 120V and mains ground through the scope's ground lead. As it stands, a curious person not familiar with scopes may just try that to verify your (correct) assertions and be in for a bad and dangerous surprise.
Thank you for this explanation! What an eye opener.
I always looked at it intuitively from the center point as the reference, where the difference between the two waves accounts for the greater amplitude. There is more area between the lines. A three phase system is truly out of phase, and from the difference between them at any point of time we can extract current. But of course one full winding has to be continuous.
I believe my plain concept on current leading the voltage on distribution lines vs the voltage leads the current after the circuit breaker box in our homes is very great . Relating that to a city of service panels at different current (amperage) ratings we can see how much a town is using in current. And also how many circuit breakers we use in a breaker panel , 200 amp service can handle a quantity of 10 20 amp breakers at 120 / 240 volts each!
Dave, you have it all right (as far as I can tell) except when you say the two halves are in phase. By definition and convention we measure phase with respect to ground.
So, while I sort of understand where you are going I feel it is misleading and to that there are some semantic issues. (I apologize)...With regard to AC to the house: It is important to note that L1 to L2 is "one" leg or phase, we don't talk about it as "in-phase" or "out of phase". We say in phase and out of phase with "respect to something". When you split L1 to L2 by center tapping it -- we get: L1 to N is OUT OF PHASE with L2 to N. So the problem I have with your explanation and conclusion is that by "definition and convention"... we measure phase with "Reference" to Ground. More specifically, that means that you don't swap the probes... one probe (the Neutral) probe stays on the Neutral. So, yes, you are right that it depends on how you "measure it:", but the "Proper" way to measure phase is with the reference to ground. So, yea, it is going to be "wrong" when you do it the other way... and it will show up as "In Phase" because you are no longer measuring L1 to N with respect to L2 to N. To summarize, yes, you are correct that if you measure it "wrong", it will appear "In Phase"... but it is NOT in phase (Unless you have a really good reason to change the conventional definition of "in phase" and manage to convince the entire EE world.)
In the end that what it comes to IMHO. Both of you know how it works so the "in phase", "out of phase" argument seems like one of those debates that will never be settled. But I thought the same, how can you make a comparison while shifting the reference? Notice this debate does not exist when the phases are shifted by 90 degrees or 120 degrees. 😇 Cheers!
This is a magnificent video
Great video to explain this! My only suggestion is that in the lower graph, you show red as the combined 240v wave but this is slightly confusing as you also use the red to also show just the half 120v wave in the other graph. Perhaps make the center tap green, then have black/green and green/red for the two 120v, and black/red for the “combined” 240?
Blue would be better. Green could be confusing given its near-universal meaning in this context for grounding/earthing.
Bravo. What a perfect video
Physician from India. Heartiest congratulations on your excellent teaching video. I have a question. Rather than unbalancing the load, will the same effect on intensity of lights be obtained by adding an another stack of batteries 'in parallel' to one set of 4 batteries in your illustration? This has some implication in my research on diabetes. The question is open to all members too. Thanks.
Worth noting that a scope plugged into a wall will see out of phase because the "negative" lead is actually connected directly to the earth/group pin going into the wall.
That's a warning for anyone who might want to scope their AC. Don't connect the little alligator clip to live. You're going to have a bad time.
Ultimately earth is the base reference that people are using when discussing the phase of the two secondary coils (or two sides of the secondary coil). When you use that reference, they're out of phase. If you reference one end of the transformer for one measurement and then *_move that reference_* to the center for the other measurement, they're in phase. Actually, if you move your reference, you can make them in phase or out of phase as you please.
That's a good disclaimer. Best case scenario, your scope will meet an untimely end.
Best to find a decent quality CAT rated differential probe for such measurements.
No point in doing that when a 24Vac center-tap transformer will display the same results only its safely scaled down to non-lethal voltages 😊
You can't actually make them in or out of phase arbitrarily, though you can create the illusion by incorrectly handling and discarding of art of the information. There was also major mistake in the video. Basically he conflated true signed potentials with useful absolute potentials. in otherwords -3v can do the same work as +3v but they are not the same when it comes to measuring and graphing phase separation.
I'm looking at solar panels.
In the US, the inverter is connected line to line.
In Europe, the inverter is connected line to neutral. Both result in about 240 volts.
With three-phase power, the three inverters in the US are connected as delta.
In Europe, the inverters are connected as Wye.
The best explanation
Good explanation sir.
At 11:35 The unbalanced portion uses the neutral. That sounds like, it is its property to do so.,
We caused an unbalance to that split system is more meaningful. Is it not?
By the way, a very informative well put together video. Loved it.
Thank you.
Well done sir!
I teach automotive basic electrical, so while i come as a learner I also watch with my teacher hat on. You have a great style of delivery! Nicely done explanations. Also, since i'm used to working with some pretty large DC circuits (starters, alternators, and my house also has large 12 and 48v inverter circuits) I experienced an subconscious discomfort at how hard you were working those D cells. Lol
The electricity is generated in phase. But it's then split and out of phase in reference to neutral.
Dave you are an excellent teacher Keep the good work up.
Great video and I agree with everything you said except the terminology. L1 will always be 180° out of phase when compare to L2 and vice versa. If L1 is at +120 then L2 is -120. The in phase, out of phase terminology is really just a comparison to 3 phase to depict that L1 and L2 are always in sync with each other where in 3 phase power L1, L2 and and L3 are 120° apart
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
I feel like this unlocked something in my brain.. What still confuses me still is when it's "balanced" Dave makes it sound like the electricity is flowing all the way from one side of the "transformer" to the other, like the light at the very end does. Therefore there's no load on the neutral. BUT wouldn't that mean the "half" circuits are now being powered by "220" instead of "110". They are using the entire transformer not just one half of it?
My limited understanding, wants to say when loads are balanced, each half is still just seeing the halved voltage, but since the polarity is opposing they cancel out on the neutral. But is power still flowing if it reads 0 amps on the neutral?! Haha.. this is so fascinating to me!
This man makes these concepts very understandable. Visual learning is a must for many. Great iob sir.
If you are getting 240V AC when you test voltage between Phase A and Phase B, then they are reversed polarity. There is no other way that computing the voltage difference between the two 60Hz (or 50Hz) wave functions will produce any reading. If they were in-phase and the same function in the time domain there would be barely any voltage difference between the two phases, so no current will flow in such a test unless your phase legs are very unbalanced.
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
Just missing the dot on the schematic symbol to indicate the polarity of the magnetic field for the windings.
I wanted to explain better my concepts to customers as English is not my native language and this video was absolutely outstanding. Beyond your evident electrical knowledge, it's your ability to explain and transmit that knowledge, plus the nice quick practical setup, your whiteboard and the camera job, it's what makes this truly remarkable and creates huge impact. I will be recommending your channel. Kudos, Dave. I am subscribing to keep learning ,refresh my knowledge and pick up your words & sentences!
Excellent explanation! Most scopes would have to have isolated probes if really testing AC.
If you look from the load (no load shown in your white board diagram) to the source, you must chose the neutral as the common reference for both 120 VAC legs (L1, L2). This is forced by the fact that 120 VAC outlets are polarized so you can't reverse the sense of L1 and L2.. What is really going on here is, with respect to the neutral, L1 and L2 have opposite polarity. For half-wave, symmetric periodic signals, V(wt + π) = -V(wt). Thus a 180 phase shift is indistinguishable from a polarity reversal. Your error is your perspective. You should be looking from loads to source rather from source to load. From the load perspective, moving the common reference is not valid - your black wire must remain on the neutral.
I agree with you. L1 and L2 have to be out of phase with one another would respect to their sine waves otherwise how would you measure any voltage between them.
So, boys and girls - what is the terminology that we should be using? Do we have *single phase, split phase electric service...* or what should we call it here in the U.S.?
We commonly call it split phase, but most of us don't need to call the overall structure anything. We just need to know that some receptacles are 120 VAC and others are 240 VAC. The latter take different plugs, so it's easy. We don't even need to know that much. If the receptacle mates with the plug on our electric clothes dryer, then it's the dryer receptacle.
Thank you for that explanation. It cleared up in my mind how the phases work. Why it's called single phase power but we can get 2 different phases with respect to the neutral.
Very fantastic Explaination😊
What do we call that phase cancellation in electronics? Common mode rejection? That sounds about right. There WAS 2 phase power that was usually 25 Hz, and always 90 degrees out of phase. Some of it was 60 Hz, and possibly 50 in Europe or Russia. We got our 60 Hz from Russia or Tesla got equipment for 60 Hz. At the time, it was the only thing available. I think it was a watt hour meter. Remember Westinghouse & Edison wanted to SELL electricity for profit, so they needed meters. Tesla did NOT want to sell electricity. He wanted to give it away, for free. (Nikolai Tesla, not the car company!)
Well done!!!
Beautiful explanation Dave, helped me to visualize what's happening. Your explanation about the transformer coil winding direction really helped me a lot.
The lightbulb setup really helps it click for me. Thanks for the education.
You're very welcome Joe. I'm glad the lights light it up for you :)
@@davegordon6819 Thank you so very much for this video. It even surpasses your fantastic Open Neutral video. This video should be considered to conclusively shoot-down the "180° out of phase" belief once and for all. I reasoned this all out myself a while ago and have been trying to explain this (the two legs can't be additive if they're out of phase) to people, but this demonstrates it better than I can explain by far!
Thank you for the video, great explanation. I do have a question on the center tap that has a lug added to the winding midway neutral. I understand having the potential difference between L1 and your neutral and having 120, and having 220 between L1 and L2. I understand the in phase and out of phase. When I'm working on a machine ( 120v / 220v ) I can grab the neutral at any time and never be shocked ( though you shouldn't ) because there are 0 volts on the neutral always, no matter the load being powered ( as long as everything is working and wired correctly) . All the voltage is used in powering the load. Neutral is also bonded to ground. In your drawing, it looks like if I took your neutral and bonded it to ground it would be a short to ground. I'm sure I'm missing something and not understanding it fully. Thank you.
Thank you very nice explain
I honestly can’t tell if your joking, if this is a spoof video. It’s very well done, for a spoof. It’s kinda funny and kinda dangerous with so many people getting UA-cam certified and using videos like this as an educational system. Just to be completely clear, when you ground the center tap, both phases are completely 180 degrees out of phase. The fact that you can hook your leads up incorrectly to a scope doesn’t change the fact that they’re 180 out
"When you ground the center tap" ... so before you ground it, they are not 180 degrees out of phase? What magic happens when you ground it, to reverse the flow of current in one half?
If they are in phase with each other then there is no difference of potential between phases. And yes when you provide a ground reference current flow actually changes. Once you ground it, ground is your reference, it’s a universal reference. This is elementary electrical theory and a basic education not based off UA-cam would do you all well
very nice presentation. Now, if the 240V AC is a pure sine wave, does that mean that the two 120V AC waves are not pure sine? I am thinking that since they switch at the same rate and the amplitude is different, only one of the voltages is pure sine. If that is correct, which is pure sine?
OMG. Thank you! I have worked in an electrical environment for 25 years and have never come across such a clear explanation.
Mike holt says the opposite or maybe I’m misunderstanding. He says phases must be out of phase for the neutral to carry the difference, if they are in phase then the neutral will carry the sum
It sounds like Mike is using incorrect terminology, like many people. For the neutral to carry the difference, the total current must be coming from opposite legs or poles of the transformer with reference to the neutral or 0v point.
WOW! I have never thought of using DC as demonstration of AC. Brilliant!
Dave, what's going on? Haven't seen any new postings. Hope you are in good health. Soli Deo Gloria my friend. Best Wishes
Great video
Thanks Roger. I appreciate the support.
@@davegordon6819 I've downloaded this video to show my fellow electricians it's surprising on how many of us get this wrong.
Thank you Dave I really appreciated you describe this in phase and out of phase it was excellent
Neither Upper drawing nor Lower drawings indicate a reference connection.
By indicating the the refrence as GROUND the top drawing becomes understandable...the "OR ?" notation becomes irrelevant
Hello Dave, your presentation is excellent! I think it could relate to Current Transformer that has reversed polarity connection.
It's absolutely basic and so obvious ... I've worked with split secondaries all my life ... having 4 connections... parallel the windings for double the current and series for twice the voltage and half the current ... just make damn good sure the sec windings are IN phase with each other ( when you parallel the windings ) or you will soon have a burnt out transformer..!!
Excellent explanation
Perfect
I'm an hvac technician and find these videos extremely useful
Great. Now people without isolated channel oscilloscopes are going to blow their leads up. Please point that out.
This is why we talk about the two split "phases" being 180 degrees out of phase. The practical reference point is earth/ground.
@@Falcrist Yes, thank you. I come from the old school, fixing televisions and using an isolation transformer. The old oscilloscopes have a common return on the probes and are grounded. If you attempt to look at the 240 voltage, you clip your two probe grounds on the neutral and the probe tips on the two hots. It shows up as 180 out of phase if you forget to invert the second channel. I now have an isolated scope, but had old school habits. I know how to correctly reference the probes, I just had a brain fart. Brain farts can be dangerous. I have watched people blow up their leads because they didn't isolate the probe return. Viewing 3 phase is a perfect example. Thank you for your excellent videos!
If I pull 600V off 2 poles of a 3-phase system and derive a 120/240 split using a TFMR like the one you are describing, how will the primary 600V being 120deg out of phase translate into the 120/240 secondary? Will I measure 240V, or 208V? Do they wind it in a way to compensate? Why doesn't it harm my loads? Awesome video--thanks!
So if the red wire and black wire are in phase, if you were to touch them together you should get a negligible spark, right? (i.e., if they are in phase no to little spark; out of phase BIG ARC) I don't suggest doing this as you will get a BIG BLINDING ARC which implies they must be OUT OF PHASE)
Thank you for this videos! I appreciate all of your material! You have a great gift of putting the subject into terms that can be understood. I look forward to more videos in the future.
Let's say I have a device designed for EU standards (230 V 1-phase, Neutral, and Ground) and I connect this device to the split-phase system to the "hots" L1 and L2 (240 V), I will get no problem with the device and it will work fine? or no? The difference of 10 V can be neglected.
Who had the same experience please help.
They are both in phase, hence they are addidive.
Yes! 🥇
Visitor from Norway. From Europe we have for a long time wondered about the strange US split phase low voltage, high current distribution system. In most of Europe we now use 230/400V 3 phase TN - network for private homes. With 3phase the motors are simpler with no capacitors that often fails after some years. With a rotating magnetic field, the rotation direction can easily be reversed too. Very practical to open garage doors.
Dave, love the videos and appreciate your amazing talent of teaching.
Great video! But I still have a question: do electrical companies generate single phase (180deg out of phase) AND 3 phase (120deg oop)? Or how do they do to provide single phase households and 3 phase commercial clients?
Very nice.
when he says "flatten" look at it this way. theres FORCE in between the humps. as you PUSH one hump to to "flatten" it, you also PUSH that dotted line AND the RED line also will push that same amount...Thats where he's claiming that the wire would look as it does.
How does transformer works for 120/240 input and 120/240 1kva output, i'd seen transformer that the input used was 120 Volts and output used was 240 volts. How this system works? It would be great if you added actual demonstration, still confused me if the transformer is a boost transformer. Thank you!
How do you calculate the kW load knowing the voltage (240V or 120V)? I always get confused on the applied math between 240V and 120V
Ummm it's neither, as "hiding" the middle neutral conductor reveals, the output has always been a singular 240V.
Is your ammeter measuring Conventional current or ELECTRON current? When I google ammeters, it says they measure conventional current flow.
Thak God we don't have this foolishness in 240V countries.
With a 240/415 volt system we have 240v between any active and neutral or ground in every case.
In typical household installations we take 1 active to the house,
neutral is bonded to ground at multiple points (MEN)
.
In an industrlai and commercial systems we take all three phases into the building
we have 240 volt single phase ciruits from the neutral to the actives.
we have 415V, supply between any two phases
and either star, delta or triple phase connections for three phase appliances.
.
putting a neutral half way up a phase is potentillay problematic where there are mixed single and three phase installations.
Because in three phase distribution the star pont must be grounded.
.
Unless it is a very large or high demand installation, we do not have supply transformers in buildings
a 240/415 4 wire supply runs up the street.
If there is a transformer for the building or complex it will come in as 11KV
.
having a neutral half way up a phase also makes a variety of circuit protections more complicated.
.
there are very rare situations where we will hva 240 volt floating dual active or 240 volt split phase installations
In the North American system, with a so called split-phase, which is simply two phases, it is not possible @15:15 to get a 240V swing relative to the SAME reference as the default reference. The 120V and 240V are not in phase, that would happen if the secondary was referenced at one end, instead of the middle.
I appreciate that this is for electricians, but the 120/240V is easily contrasted to the original Edison's circuit. Two batteries, in series, referenced in the middle. It's that simple.
Like 95% of the way there and you jump to the opposite conclusion because the last graph in the upper right was drawn incorrectly. What you drew was effectively two measurment leads connected to a single pair of power conductors. The black-neutral and neutral-red should be vertically separated, because there is also a black-red differential in the system which is essential information that should not have been discarded.
I believe your focus on the internals of the power source is what led you off course.
Pretend you have no knowledge of the power source transformer/generator/battery of cells/inverter, just three mystery wires. Remember we are concerned with power phase here, not the internals of the power sources. (There could be multiple sources of power and claiming in phase or out of phase within a coil becomes rather misleading and pedantic to define. Also consider that defining the anode and cathode in a cell is both irrelevent to the overall circuit and that they actually swap depending on charge or discharge state, despite only a small non-reversing change in general circuit voltage.)
Remember that while effective/useful potential is measured as the absolute differential(~RMS), the phase separation is signed(positive and negative) and non-arbitrary(more electros is always more negative).
If the sources are in phase (both at positive peak at the same time), then they will have a constant voltage across them and will effectively become a DC voltage. In other words they start with a 3v difference and as one rises or falls the other also rises or falls so 30⁰, 60⁰, 90⁰, 180⁰ later they will still have a 3v difference.
Three comments.
One and foremost is this is a great presentation, well done sir.
Two, electricians measure from the neutral to phase, and the first graph illustrates that best. In that graph, the two sine wave are clearly 180 degrees out of phase with respect to the neutral.
Three, the opposing phase demonstration is more of a parallel circuit. Just go ahead and fold it in half, the batteries are now aligned with one another. Connect the leads that were on opposite ends. I’m claiming the batteries are in phase in phase, same current out, same in. Being in phase, the bottom light has no voltage to work and remains off.
All that being said, you are really spot on by defining the reference point. As an old sparky, I’m standing by my neutral and claiming 180 degrees out of phase…
Thank you
I very much enjoyed this video and its explanation of the output of a center tapped transformer. I particularly liked the example of flattening one sine wave to demonstrate a single phase of twice the amplitude. I understand that the output differs from say a three phase generator where the coils and rotation cause the phases to be physically sepearated by 120 degrees along the time axis, but I find arguing about the "in phase" of "out of phase" argument about household current about as useful as agruing whether a Zebra is white with black stripes or the reverse.
Once you understand how it works and what is happening I think the distinction is meaningless. The output of the center tapped transformer when referenced to neutral behaves exactly as two seperate mechanically produced phases would. I have always thought as the wave as "flipped" as opposed to shifted 180 degrees.
I would like to see an experiment where someone built a two phase generator running 180 degrees out of phase rather than the conventional 90 deg and hooked that output to three test points and then hooked the output of a center tapped to three others. With the sources of the power hidden. I wonder if it would be possible to identify which was which.
Thanks for a great video. I always find that thinking of things like this in as many ways, with as many examples as possible really helps to visualize what's actually going on.