120/240 and 120/208 Volt Transformer Secondaries
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- Опубліковано 1 жов 2024
- Explanation of how we derive 120/240 V and 120/208 V from various Transformer Secondaries.
Additional video of interest: "120/240 V In-Phase or Out-of-Phase" • 120/240 V In-Phase or...
PLEASE NOTE: The arrows above the left schematic show that this is one winding that has simply been tapped in the center. The waveforms below it in the lower left can give the wrong impression that the "halves" of the winding are out-of-phase with each other. This is because I'm using the neutral as a reference and as I mention in the video, from the perspective of the neutral you look "up-arrow" to one end and "down-arrow" to the other end of the winding. BUT, from either end (i.e: black wire to red wire, or vice-versa) you will be looking "up-arrow" or "down-arrow" for the entire length of the winding (i.e: in-phase).
You can dig through the comments for further discussion on this. I have made a video addressing the phase relationship within 120/240 V systems, and I hope to create other videos focusing on current flow in each of the scenarios that will further our understanding of these transformer configurations.
Thank you,
Dave
This man is a master at teaching... so clear. his body movements, his eye movements , hands all work in coordination with each other. his voice, easy on the ears... His brain the conductor of the whole operation. A pleasure to learn from...Thank you Dave.
Yes sir!! 🧑🏻🏫
Rolling my eyes
Dave taught at my JATC for a couple years. He’s literally the only reason about 40 of us made it past our second year.
I get the same vibe. This man knows how to teach well.
Sheesh .....get a room 😆
30, 60, 90 degrees and you get 208. Wow, I never realized that trigonometry and electricity were connected!
As a EE, I have to commend you on a well diagrammed and spoken lesson. Good job!
Nice work Dave. This is one of the most thorough and understandable descriptions on 120/240 and 120/208....excellent.
I was so lucky to be in his classes. Dave, you rock, man.
Truly a master in explaining, makes it easier to understand the concepts
13:47 "They ended up blowin' up a bunch of stuff because they were Russian"?
In other words, they connected to the wrong Pole?
@@ivanzapata396 😑 ::whooshh::
Other than you kept referring to the peak voltages as 120V which would be confusing to a beginner when actually Vp ≈ 170Vac or Vp-p ≈ 340Vac hence the need for capacitors with 370V or 440V ratings.
Root Mean Square is just the DC equivalent hence there would be a straight line drawn through the sine wave to represent that average. Vrms = Vpeak/√(2). RMS is the only way to average a sine wave in case your wondering. It's also used to take an average in statistics to minimum the effects of outliers 😉
- 1st drawing - Single Phase
- 2nd drawing - Three Phase (Wye)
- 3rd drawing - Three Phase (Delta)
I suggest adding "Ugly's Electrical References" book to your toolbox because it covers all this and much more in case you forget.
Great video 😊
The 120/240V thing was actually a late 19th century thing - all derived from the Great Fire of Chicago. Edison lamps were made out of carbon, and used 110V, however, other companies figured out how to make lamps using tungsten, a much more resilient metal and could work at 240V (carbon lamps burn up at 240V). Since adoption of electricity was much slower in Europe, the European utilities went with 240V as it saved money on copper and is more efficient. Our 110V system was derived as a split-phase system, because Edison noticed that some people's lights were brighter than others. So he designed the system as two 110V generators (this was DC, mind you) and connected them together to form a third neutral line. He realized by monitoring the current flowing on the neutral line, he could determine how bad the imbalance was and rebalance the grid so the same number of lamps were on each half so everyone's lights were the same brightness. In addition, if you needed more power, you had 240V (DC) available.
Now, electrification was huge in the US - especially after the Great Fire of Chicago which meant everyone started from scratch, and skyscrapers were a thing. Gas lamps couldn't be lit more than a few stories up, and everyone wanted electric lighting. So much so that demand for light builbs was so big even though carbon lamps were obsolete, Edison was still making millions of them as the tungsten lamp makers couldn't keep up (in the late 19th century, they made around 10 million tungsten lamps, and Edison made nearly 60M carbon lamps. This changed about 20 years later in the early 20th century when carbon lamps were finally obsolete and replaced with tungsten lamps. However, by now the die has been cast - 110V had been around for so long, there was no appetite to change over to 240V..
In Europe, electric lamps were seen as a novelty, and very few people had it. The rich folks refused to install it in their castles, so when it came time, it was trivial to switch over.
Oh, and the first war of the currents was between Edison and Westinghouse, not Tesla. The second war of the currents was between GE and Westinghouse which dictated if we'd use two-phase (Westinghouse, via Tesla's patents) or three-phase (GE, Edison had been kicked out) AC. Tesla is confused in these because Westinghouse bought Tesla's AC motor patent (and later all of Tesla's patents). That patent showed how a motor would work at 60Hz two-phase. You have to remember though, that just because of this, power was still not quite standardized as you could get DC, 60Hz, or 133Hz AC power (133Hz because Westinghouse managed to find a design for an electric meter but that required 133Hz to run properly).
133Hz from my understanding, was more commonly used with carbon arc lamps common for streetlights and in factories and large retail stores from the early 1880s until the early 1900s, because it flickered less than 60Hz. You also had very oddball frequencies such as 25, 33.3 & 40Hz, to name a few. The early days of electrification must have been a very intriguing time to live through. And all this was in major US cities, many farms and homes in rural areas didn't have electricity until after WWII, my grandmother recalled not having electricity until merely a few months before she married in 1947, born in a farmhouse in 1925 and lived to be 96.
Give me a 240/120 volt delta system anytime. Forget the wimpy Wye.
My favorite term for the high leg of a delta transformer for 120/240 is the "bastard leg."
I am electromechanical engineer, your explanation is very very clear. THANKS a lot teacher.
Dave your videos are so immensely understated. You're an absolute hidden gem and I can't thank you enough for making this material available. I'm an IBEW electrician apprentice in my 3rd year and I constantly supplement my school work with your videos.
High-leg delta is a bad system. Symmetrical load is almost impossible and it´s complicated to use. Here in Europe, every household gets 230/400V three-phase power. 230V 1p for normal appliances and 400V 3p for every device above 4kW.
Stupid question time. Are the line 280 wires Brown, Orange Yellow and the black, red and blue the outputs? Would you be running the Neutral for 120v in white? You probably have a wire color code video, I'll look. You do amazing videos. Some airhead talks about stringing beads and gets 100K subscribers, but real , well presented videos don't. Life isn't fair. Thank you for taking the time, the videos are great.
Fantastic video. However, the one thing I disagree with is at 13:47 and people blowing up a bunch of stuff because they were Russian. I think any electrician in the industry long enough has blown up a few things and they aren't all Russian... Yes I had to
i feel lucky that people like dave are on youtube and shares their knowledge, great info!
You have simplified months of frustration in trying to understand these concepts. I cannot wait to check out the rest of your videos. I so appreciate the clarity you deliver. THANK YOU!
Best explanation ever. I finally understand!!!!!!!!!!
Thank you.
At 13:47 it sounded like he said people were blowing up a bunch of stuff cause they were Russian 🤣
wronnnnnnnnnnnnng.... this is just wronnnnnnnnnnnng!
Amazing explanation, very good job 👏
Great people share their knowledge!!! God bless you!
I like the idea of the radius of a circle in terms of a generator, starting from west or zero axis , like a radar from west , north , east , south and to west. !
Radar or radius is from center point to the inner circumference of the circle ⭕️ . Diameter is from west to east or north to south, that is why a radius really is interesting like radar !
i recently installed 3 phase in my building, they would not give me 240 delta so i had to go with 208. do you know why they won't install 240 delta anymore? is it just because people don't know how a dmm works?
You'd probably have to argue that with your utility provider. Although here are the reasons I can tell. In a delta configuration with a center grounded transformer, maintaining a balanced system is nearly impossible, since all the 120 volt loads come off one transformer. 240 volt, single phase loads strategically placed in the panel can help, but there is a catch. The two pole breaker must be rated 240V, not 120/240V if placed on the high leg, and 240V double pole breakers are not as common and more costly than the 120/240V and will likely need to be special ordered. And most, but not all 240V equipment will run fine on 208V, for instance many larger window AC units and outdoor condensers mention 208V and 240V on the nameplate. So to sum it up the 240/120V three phase system although still useful in very specific applications, is something a lot of utilities no longer install, although other's will install one upon request, and electricians therefore must be aware of this system because you will run into it at some point in your career.
This is one of the best videos I have watched out of a lot out there that explains with this much clarity and expertise. Thanks for passing your knowledge how it should be with all.
Wow I wish I had a teacher like you when I was in trade school, nice job explaining and simplify something so complicated, please continue uploading videos!!!
Thank you for helping me understand the wye out of phase 208 and the delta ! My teacher could use some lessons from you on explaining things better!
Wow you are amazing! Thank you so much for making this video. I will share this to all my friends.
Dave, I was looking for the definition of a great teacher, and now I got it on this UA-cam video. You are beyond excellent and keep up doing this amazing teaching style.
Thank you, as a mechanical engineer I’ve always struggled with electrical concepts and this helped me understand much more about how the different windings affect voltage.
Thank you! Really gonna help me with school
Fantastic video! I recently took over management of a 160 year old theatre that has a high leg delta panel in the projection room. Wanted to get familiar with the system. This video was incredible informative. Don't be worried. It did not give me the the confidence to monkey with the panel. I'll call a pro anytime this panel needs works.
Hi guy some one please tell me the different between home depot 2 gauge thhn copper wire and Lowes wire. They both made by southwire but why does lowe list it can only carry max 110 amp while home depot listed on their site 125 amp max. If I don't remember wrong, I think in store even said 130 amp. I plan to run 25-28 feet inside conduit over head inside garrage ceiling. 125 circuit breaker box. Thanks
Thank you so much for the video 🙌😂🙌🙏🏻🙏🏻🙏🏻🙏🏻 it helps me to understand many dots 🫡🙌🙌🙌🤜
While 208 volts is a 3 phase voltage produced by 3 phase transformer bank, it is commonly used as a network voltage by utilities as a leg to leg voltage for single phase residential loads instead of 240.
So is it safe to use the 208v along with with neutral or earth?
another system worth an honorable mention, is, an open delta, typically 120/240, but occasionally corner grounded 240. I've seen this in rual areas, almost always on a farm setting, when most of the loads are single phase 120/240, with a smaller amount of 3 phase motors, typically a grain drier, augers and conveyer. The capacity of a full delta is not warranted, and the system can be easily recognized, by the two transformers, one being significantly larger, in terms of KVA, because all your 120V loads come off that one. the smaller transformer is the power transformer, this provide the high leg. Much like the full delta, open delta suffers from the same limitations, very difficult if not impossible to balance, along with the possibility of mistakenly connecting a single pole breaker to the high leg when 120 volts is needed. As such these systems are rarely encountered in new installations.
I was wondering if someone would spot this. I actually did a job at a water treatment plant in Pueblo, Colorado that used an open delta service.
Thanks for explaining a different method to calculate the HIGH LEG to ground. I did not know using Pythagorean theorem gives you 208AVC. I've always use Vector addition.
I did the HW chum
rms = root means square
center neutral opposing and pushing relativity of product
Bus wiring
Voltage = Points if differential potential of to points (Check out angle theta!!)
as well as from which 120 degrees of the exact moment of the circuit became energized comparing the constant peaks per delegated cycle (Alternating Current and it's Value) while subbing out impedance with greater use of Volts and VA (Volt Ampere) to mediate or use the Load (What the conductors are connected two and their rating) for treatment of the new simulated
resistance from use of Center Tapped Neutral
Connecting within the center if the Wye Connect will split...not only the windings but the voltage.
Equaling=B phase To High leg is 208V
Make Sure You label!
Searched for this explanation for way too long. Very well done Dave.
@dev Gordon 1 question.... I din't got that why center tap is grounded instead they (who made this ckt firstly) can keed either side of it can be connected to ground.... Idea is when we running 240 volt appliance.... If ground fault occurs then PROBABILITY will be 50% that wire will be live and 50% will be neutral wire
So that during neutral connects to ground... Damage will be almost equal to zero and in other hand if live touches ground fault current will more and immediately clears out fuses in path , i know someone will say potential with respect to ground will less in center tap configuration, but either you get electrocuted by 120 or 240 you will get electrocuted....!!!
Also in 240 volt system without center tap to ground connection wire sizing will also reduced for 240 volts for same kilowatts while center tapped live wire and neutral will be the same as before
I understand everything perfectly the only issue im having is the right triangle reference where he says c2 - b2 = a2 , so in normal its A2 + B2 = C2 , so 120^2 + B2 = 240^2 , divide by both sides to isolate the unknown B^2=57600/14400 B^2=4 , root both sides B=2 is my math wrong , i havent taken algebra in years so i might be missing something
Question: Where would a wye transformer like this one be used? It seems like the only place it would be good for would be structures requiring only 120V services. Are there any instances where straight hot leg to hot leg 208V would be needed? Aren't most devices 120V or straight 240V? I understand 3 phase where you have a high 208V leg, but I've never seen that high leg used on a single pole by itself, it's always used in conjunction with the other 2 phases to produce +240V at 3 points during the cycle.
10:54
I'm an electrician, and never understanded why the neutral ( X0 ) has to be " grounded " ?!
I know what happens when it's not, but dont understand the reason...
Is it only in case of unbalanced 120v loads in a star 120/208v ?
But what if its 3 phases 208v star configuration, and we only put a load on phase A and B ( 208v single phase ) , and the X0 is not grounded, what happens?
This is not how I understood the 120/240 transformer works… I thought it was a single phase 240V transformer it’s a neutral midpoint… so only a SINGLE wave not two… it measures peak to peak not wave peak to wave peak…
I received dumpling machine from China and they made 220v single phase thinking it's good for using in the USA. There are five wires coming out of the machine. Electrician said its 3 phase, but he was afraid to make the connection because on my circuit breaker cabinet said 120v/208v. Can I use this machine without transformer?
A complete transformer's teaching wideo❤
@davegordon6819
Dave, I absolutely enjoy your topics and teaching method.
I have a question I’d love to see you do a video on.
There’s a debate in the RV industry about the use of voltage stabilizers. Some say not to use them, as they will drop the voltage for the rest of the RV users, as the stabilizers sacrifice current for voltage, therefore pulling more current and lowering the voltage at the post.
My take is that if there is low voltage at the RV post, say 104V, instead of 120 per leg, the appliances, Air Con, refrigerator, etc.,inside the RV are going to pull more current, as they maintain their power requirements. Therefore, boosting the voltage with an autoformer, will reduce current consumption at the RV, but will consume more current at the post, making the current equal to that without the autoformer, minus some inefficiencies. Am I off base here?
Hi dave, thanks for sharing, for the wye connection. in single phase 208V. How do we calculate the current for each phase.
since the single phase 208vac running on two phases (L1&L2) . Does it means current in L1= L2 ?
like single phase to neutral 120Vac. Current flow in neutral = current flow in L? or any other calculation.
need it to calculate total load at each phase.
thanks in advance
So what happens with the sin waves when you change 208 (2hot legs) to 120/240 via a transformer. I'm perplexed because you still keep 120 volts
"Ended up blowing up a bunch of stuff, cause they were RUSSIAN". - context😅
13:45 "They were Russian. They had to stay behind and fix everything"
Looool
I know he said "rushing" but it sounded like "Russian"
On the 3rd drawing, is the 208 volts also called grounded B-phase?
You are giving me information that the maintenance guy I use to work with wouldn't give me because it would have taken to long to explain.
Excellent video. I'm pretty sure that this was explained in trade school, but definitely not this clearly.
I need help! Lol im trying to get 208 single phase and need 32 amps. What is the transfromer ill need? Supply voltage would be 240 v
13:45 "Ended up blowing up a bunch of stuff, because they were Russian." This video aged well.
Thank you, Dave! I've just discovered your videos while looking for some information about transformers. You combine two of my favorite subjects: electricity and math. Fifty years ago I was an electrician in the Navy. At that time, we were trained in single phase and three-phase delta and wye transformers. I understood it completely at the time, but never had experience with them since then and lost my knowledge of them. Now I understand them a whole lot better.
Nice tutorial. But can you use the delta center tapped high leg 208v for single phase 208v appliance? Thanks in advance
Under x2 there’s a tank ground bushing right underneath it. The green ground wire. How do I hook that up? Do I connect to only tank ground or both x2 bushing and tank ground bushing? I’ve seen people do both. Don’t know which one to do.
This man is a truly gifted teacher!!!!
He just schooled me so good!
Thanks sir
We love ur videos
His diagrams are perfectly simple
Here the batteries did not blow up when he changed the direction. How come with 480vac if you do this you'll blow things blow up.
You may find instanes where you are given either a 3 wire cord or 4 wire cord and youre told the voltage supply is single phase, finding a starting point isnt always so easy, I kindly ask that you clarify slightly more so that we get a better understanding of your informative lecture. Thanks a lot, i hope to hear from you.
At 2:20 you point with your finger the direction of current flow for the RED-half of the inductor. Is this correct or wrong? Appears to be a mistake. Are you using conventional current or electron current?
They ended up blowing up a bunch of stuff because they were Russian....
That drives me nuts..."Hot Water Heater". You don't heat hot water. Nor is it a heater operating using hot water.
You "plus them"?
Dude, you are way too smart to say these things....way smarter than me.
In 1910-1920 era houses only had 30 amp 110 volt service. the way i remember it.
Hello.i have a problem with a neutral of secondary coil of single phase transformers .the question is how I can make a difference between the neutral and the phase . thanks to everyone reply to my question
There are plenty of uses for the high leg. Many modern LED light fixtures are rated for voltages between 100 and 277 volts 50 or 60 Hz. If you use the high leg, make sure that you use a straight rated 240 volt breaker.
So you're saying there are single pole, straight 240V breakers manufacturered ??? If so they're about as rare as a royal flush.
@@Sparky-ww5re No, but all 3 pole breakers are straight rated and some double pole breakers are. You can simply use the high leg as part of a multi wire branch circuit. There's nothing in the NEC that says you can't use the high leg to neutral. You can run three (2 wire) branch circuits from a three pole breaker. You can not however run a 4 wire branch circuit with a shared neutral from three single pole breakers. NEC 210.4B.
Sir can u plz explain how current flow when we use just two line 208v wye system with neutral for one receptacle do they cancel each other the way they do in 240v split phase.
You the fuckin man bro keep up the good work I really enjoy your teachings
Can you get 120v to ground without a neutral for single phase power from a 3 phase panel?
Great video, I do have one question at 10:25 when you said that if you take any vertical point on the 3 phase graph and add it up you get 0. Are you referring to where the one phase peaks and the other 2 phases are intercepting underneath that peak? I assume you are subtracting the value of the peak from the values of the negative voltage phases underneath the neutral. Just threw me off when I heard you say that.
So there is a push and pull or alternating between the 240 lines but there never is a push from the neutral? So 120 is off and on but not back and forth between hot and neutral?
So in the “Y” system you can touch the neutral (like in a splitter) because it’s grounded and not get shocked
Thank You Dave well done! Best teacher I seen yet! Thanks again.
Very good explanation. Crystal clear tome
I've been digging to find a good explanation and now I've found it. Thank you sir!
The left drawing implies two phase which is not true. Although the presenter makes note of this in the description, it is still misleading.
For this single phase connection at 8:45 minutes, do I need a neutral? Or just the 2 live wires? It isnt so esy to comprehend
I like this channel. It's for smart people.
Thanks a lot Mr. dave, I just need some more clarity around 8:45 minutes, it does not cut across that easily.
Is there no such thing as 120 volts peak to peak or 60 vp+ and 60 vp- ?
I always have wondered what would happen if you get a center of a transformer coil and stick it in the ground
Awesome job explaining
What about if I need to install a motor of 220V in an installation of 208 V? Can I take only 2 phases
You answer the question that I been looking for I don’t know how long
What happen of voltage if one transformer not working?
I was nodding off to the debate and watched this instead, far more substance and I had an “ah-ha” moment. 🍻
Thank you Dave, easily explains the differences as well as applications. And thank you for the math lesson (brings back memories).
A single phase has 240V how comes a three phase has 415V ?
You may cover this in another video, but there is another reason to have a 240 delta system. If you already have a 120/208 Y system in your facility and need another service,NEC says the second service must be a different voltage, hence have a 120/208Y service and a 120/240 Delta service on the same building.
Can you run a single phase house on a 120/208 3 phase bank
Well done. And I actually saw the fireworks first hand at work when one of the guys installed a bunch of new 120 V fluorescent fixtures to a 208V high leg by mistake. WE also had 277 VOLT stuff that people made mistakes with. Luckily we worked for BIG OIL. They could afford it.
@dave, great job explaining the topic. I am getting a (grid-tied) solar system installed which only outputs single 240/208v connected to the Red and Black terminals on the breaker panel. Wonder how is the 240/208v transformed into split phase (2x 120v)? There is no video created on the topic, might be a great opportunity to make one.
Amazing video and explanation
I am wiring a 230volt three phase hydraulic pump from a Lincoln welder/Generator three phase Delta 240volt. My question is do I just run the three hots or do I also wire the neutral to the pump. Thank you I would really appreciate your answer.
THANK YOU, I APPRECIATE YOU. Im literally sending this to few of my classmates and couple of my electrical friends
I have a project I'm interested in to go completely off grid, I have a max 4000watt 120v and 240v generator I intend on using currently just to try it out. But so far my idea is to take it and attach it to a transformer just like the residential ones in order to get the 120/240v for my home and to keep the rpms low. I just wonder if there would be some sort of resistance that I'm just not seeing at the moment that could potentially damage the generator or appliances.
And if in the future if I upgraded to a generator that had the capability of producing kilowatts and only 1 at a time 120 or 240 or 208 without modification to the existing set up would using 208 3phase in combination with the transformer harm my home or appliances or would I be better off sticking with the 120v or 240v?
Dave I was wondering if you know where the term “single phase” comes from when referring to 2 legs of the 208 system connected to serve a load. I am constantly being asked why it isn’t referred to as 2 phase due to the fact that two of the phases are connected. I apologize if this is a silly question but I can’t seem to come up with a good answer.
Anyway thank you for all the great videos!
Hello Dave,
I watched your videos. Excellent presentation. May I copy the URL's and share with my electrical classes.
Thanks
Ron