I've been doing service and maintenance work for over 35 years (mostly industrial, but a lot of commercial and institutional mixed in), with a lot of that being strongly related to the electrical power side of things, and I learned quite a bit from this video. That said, when it comes to whatever the standard of the day is today for what terminal and what color the high leg is, I don't really sweat that very much since I don't do installations. What I DO sweat is what my meter tells me. I do contract service work all over the place and sometimes when I roll up on a job I know that the building is pretty old. I don't know how old or when the service I'm working on was put in, or by whom. Many times, the wires to a service are all black with no phasing tape, so what used to be done and how it was supposed to be done and what color or terminal is what may be interesting to me, but Mr. Fluke is who tells me what the damn deal is in that one particular job. The history of all that stuff is really interesting, and now I understand why some of the high legs I have seen were ~ 190 something, but are almost all over 200 now, but at the end of the day - just put a meter on the thing. Also, I carry a Sharpie with me all the time, and when I open a panel with a high leg that isn't labeled with regards to that high leg, I write it across the top in bold letters for the next guy that might go into that panel. Not because I have to, but just because I'm a nice guy.
You're my favorite type of guy to follow and I always do the same thing. And if I find something that's marked with as a high leg or a Delta and it is no longer the case I also update the markings
I love these videos explains what i am reading... im a future apprentice electrician getting a step ahead
4 года назад+1
I always thought 3 phase transformers were pretty simple to understand, had to explain to a young guy today why we hook motors, 200HP in a delta, and not a WYE to a soft starter, WYE start Delta run is before we had soft starters, and we had other good tricks, lots to learn about transformers, learn when, and how to tie XO to ground, and when you don't do that. Find a local IBEW apprentice place, use google
tyler tyler . ALWAYS ALWAYS ALWAYS. Use a tester before energizing (even plugging in) ANY device. What the narrator said about all the empty spaces in the (Delta) panel is a real scenario. Unfortunately for me , as an apprentice, I failed to heed that warning and fried an old refrigerator and copier at a friends place of business. As stated in other replies to Your comment , it would behoove You to go with IBEW. Tremendous knowledge. Free Education. Tools issued upon completion of First-year apprenticeship (that's the way it was back in '96 when I started .Not sure of Your locale , but worth looking into) Should that be the route you decide , a vocational test will be given . Theirs plenty of vocational preparation tests , even some phone apps. Brush up on Algebra. Remember PEMDAS or : P lease (P arentheses) E xcuse (E xponents) M y (M ultiplication) D ear (D ivision) A unt (A ddition) S ally (S ubtraction) The way it worked back then was 11 weeks for 1st year. During that time , they didn't provide an income so make sure to prepare accordingly . Best wishes to You "Sparky" in your future endeavors whichever route you choose.
I love this stuff, and it is so important, to keep the knowledge out there and keep the guys alive. One call in your career maybe the old school odd duck system, and it can prove fatal if you don't get out the meter and confirm your assumptions.
Another way to calculate the High Leg is to take 240V(voltage from first winding)+120V(voltage from tapped winding)=360V, then 360V/1.732(squared root of 3, because it's 3 phase)= 208V
Thanks for another great video!! I've worked at utility company for 15 years and never heard anyone talking about the explanation behind how these voltages come about. Thanks for making sense out of this! :)
Since that is a 30-60-90 triangle then the short leg of the C transformer is the 120V (half of the 240 between C1 & C2), the long leg is the connection between the A and B Transformer connection and the C neutral. Any High School Geometry student (at least those I teach) will tell you that the long leg of a 30-60-90 triangle is always the square root of three times the short leg; the square root of 3 is 1.732050807... and multiplying that by the short leg of 120 gives you 207.846V--to the nearest volt that is 208! Likewise, the B transformer is the hypotenuse of that triangle and the hypotenuse of a 30-60-90 triangle is always twice the measure of the short leg so 2(120)=240! The rules for a 30-60-90 triangle are derived from trigonometric functions but the Pythagorean formula does also work for any 90 degree triangle, so (12^2 + B^2 = 24^2) (dropped the zeros for simplicity). That works out to 144 +b^2 = 576 then b^2 = 576-144, and b=square root of 432, and lastly, b=20.78. Move the decimal over one to the right to put out significant zero back and you get 207.8 or 208V! Q.E.D.
In my 50 years as a sparky only came across this once. Think in school they told us to never place too much load on the nuetral due to it might cause voltage imbalance on 3 phase loads. If you can get by with 208 volts on the 3 phase loads way better off with the Y secondary that is every where .
I love this stuff. While on the subject of changing and unusual voltages regarding delta high leg systems, there also exists a very unusual voltage, a 480 volt, high leg, 240 volts A to Neutral, 240 volts C to Neutral, and 415 volts B (high leg) to Neutral, the master electrical I am working with, ran into that, only once in his 39 year career, in the early 1990s when he was on a maintenance job to a large wood working shop near Louisville Kentucky, they had mostly 480 volt 3 phase motors , but they had the high bay meter halide fixtures running off the 240 volts. They also had 480-120 volt transformers in the facility so they could run ordinary stuff as well. I thought I'd share this and wonder, has anyone else heard of a 480 volt, high leg delta?
There is no such think as a 480V high-let system, but there are 480Y/277V systems, corner grounded 480V systems, ungrounded 480V systems, and 480 grounded systems.
We always referred to it as the high leg, every time I’ve encountered a service with the delta high leg the voltage was over 200V. I remember when I first started doing service work I’d think it was my lucky day! I got a few empty/spare breakers only to find out it’s a high leg 😂😂
I will say that waching you guy's ( shareing knawlage ), is like waching A Very Choreographed dance 💃!!! LOLO LOLOL. However, it's very refreshing to see, one dancer" giving the same answers "That I Was Thinking" ONLY SECONDS Before.,!!! LOL CARY-ON,..
dear mr.mike holt it is very good to understand grounding-safety fundamental from your lecture, thank you very much to mr.mike holt. i shall follow up your other lectures. one importance word that i will remember from that is " if you false understanding and did wrong, you start killing some body. thanks and best regards mr.salacheep yusabai bangkok, thailand
There is an easier way to calculate the high leg voltage. simply multiply the phase to phase voltage by sin(60 degrees) or 0.86623. Which is the square root of 3 (1.7321) divided by 2.
If I were to power a warehouse or a factory with lots of motors and lighting, I would use the 480Y277 volt system as indicated in your diagram. Most 3 please motors are dual voltage and use the 277 volts to run the Lights ( most hard wired LED light fixtures have universal voltage drivers in them already). In this situation, I would not bother using the Delta- Delta transformer in the first place.
At 25:00, this is why they make buck- boost transformers. So you can run a 240 volt load at its full voltage from a 208 volt Wye system.(the wimpy Wye)
With a delta high leg system, if you want to add more 120 volt loads, you can buy a transformer with a 240 volt delta primary 208Y/120 volt secondary. By putting all your 120 volt loads on the secondary of this transformer you will maintain a more balanced load on your delta service.
In my experience, I have observed that most of the electrical guys work with the observational experience without knowing and understanding the fundamentals. The basic in electrical engineering is vector representation of voltages. If you master this and know how to apply this you will understand and can explain 90% electrical engineering related analysis. I will come out with a video on this for the sake of all electrical engineers.
Please don't forget current flow, not with respect to current vs election flow (no offense to the theoretical guys) but so far as "ground loops" and multiple paths go. I spent years focused on this aspect and was a better troubleshooter because of it. Mr Holt does an excellent job touching on it's importance in the few videos I have watched.
Probably one of the few educational videos even bothering to mention delta breakers. I've personally never seen then I've heard of them, and believe they were banned in the mid 1970s, either '75 or '78 NEC, the theory was even if the main breaker was turned off, 208V from the high leg could backfeed from the load to the panel posing a shock hazard. Delta breakers were somewhat common in the 1950s until the early '70s, in some parts of the country, for a 5 ton air conditioning unit, when central air became popular and affordable post WWII, some of the larger units were not always available in single phase. I'm sure there are many older systems still in use, that have a delta breaker. Some panels, particularly residential panels from this era, were spit buss panels, which were legal until the 1981 NEC.
Using your example of applying Pythagorean's Theorem I don't get the 20.8, as the gentleman mentions. To confirm my math, I drew the actual right triangle in AutoCAD and it showed my result correct. I am not being petty, I am learning all I can about this and want to make sure I have a clear understanding of what is happening. But your video is awesome Sir! Thank you.
The interior angles of the delta are 60 degrees. The line drawn from the high leg to the neutral point bisects the triangle. The point that is the high leg is now divided into two angles, each 30 degrees.Let’s look at this a couple of different ways. 1. The rules of a 30-60-90 triangle are these. The short leg is 1/2 the hypotenuse. The long leg is sort(3) times the short leg. Using these rules, the short leg is 120 volts and the long leg is 120 * sort(3) = 208 2. A^2 + B^2 = C^2 where C is the hypotenuse. Hypotenuse^2 - (short leg)^2 = (long leg)^2 240^2 - 120^2 = (long leg)^2 57,600 - 14,400 = 43,200 Long leg = sort(43,200) long leg = 208
MikeHoltNEC I was a broadcast video tech for 20 years, I now work at a farm that absorbed the original Habbersett sausage factory and the associated museum of electrical distribution networks. As a troubleshooter who doesn't know how to say "I don't know" I am extremely grateful for this particular 26 minute video as well as the rest of them as I am currently going through them. Thank you so very much. One of the biggest lessons for me is how much I miss the beauty of a classroom. Again, thank you sir.
There are many uses for the 208 volt high leg. Most modern hard wired L.E.D. light fixtures have universal voltage drivers in them (100-277volt 50/60HZ). You can run them between the high leg and the neutral. Treat it as though it is a 277 volt system. Use 3 pole breakers which are straight rated.
You area 'smart' guy! Not many understand this concept. Answer: Yep this is perfectly fine. By the way, they do make 'straight' rated 2-pole breakers, but these are special order and cost about the same as a 3-pole breaker.
It's more effective to use wye tap to avoid a high leg on the secondary to get even voltage on all phases like 120/208 instead of 208 on B phase to neutral . Instead its 120 to neutral on A, B ,or C phases
There are many good reasons to use the Delta High-Leg, any other system besides a Wye 120/208V system. Visit MikeHolt.TV, click on Live link and learn more about voltage systems.
@@MR-nl8xr Squaring is the namesake of multiplying a number by itself, because the area of squares is the application of this operation where it was discovered. There are plenty of applications of squaring numbers that have nothing to do with actual squares. You can find plenty of geometric proofs on how squaring sides of a triangle will find the relationship among the sides of the triangle.
Very good and clear explanation. At the beginning you asked what does "Delta" actually mean. In Greek, it is just the way to day the letter which sounds like "d". In a similar way that z is pronounced zee in English.
Διαφορά (diaphora) = difference in Greek. Leibniz was using Latin lowercase d for infinitesimal differential in his Calculus notation. The Latin letter being spoken for already, Greek Delta also standing for a Greek word meaning difference, would stand for finite change.
Delta as the name of the transformer topology has nothing to do with the concept of difference. It is named as such, due to the arrangement of voltage vectors in real/imaginary number space, looking like the triangle letter Delta.
Yea but primary to secondary mutual induction. Does it actually stack together like a hexagon ? Yeah, gosh FINALLY the age old question of 230, 115, and 199, and 110.
Jeff, The original triangle is an equilateral. When a line is drawn from the tip of the triangle to the neutral point on the other side, the equilateral triangle is cut into two triangles, each of which is a 30 60 90. If you look at the 30 60 90, the line that was just drawn is the long leg. The line from the neutral point to the point on the triangle is the short leg. These two legs have a 90 degree angle between them. The side of the equilateral that has not been bisected is the hypotenuse. The hypotenuse is 240 volts. This is given because it is a 240 volt delta system. The short leg is 120. This is given because the neutral point is the midpoint of a 240 volt winding. The long leg is sqrt(240^2 - 120^2) Eric
Hey mike very informative vid. But i have a question. How do i know if to use a Star input or Delta input transformer? Does this go according to the voltage? Now am just sayin here if the voltage is 480/277 volts do use a Star input transformer or if the voltage is 240/120/208 the high leg do i use a Delta input transformer. Or if its 208/120 do i use a Star input transformer. Thanks will be much appreciated.
Isn't that an equilateral triangle? not a 30-60-90 as there is not right angle. Thus the degrees of the angles and length of the sides giving us the relationship for establishing the 208v can only be calculated using the only known existing portion of the equilateral angle of 60degrees and using the cosine rule to solve. What am I missing? I love your vids.
H most likely stands for high side. I'm not sure why they selected X, of all possible letters for the low side. My guess is that it has to do with X being the de-facto choice for variable names in Algebra, and the X/Y/Z trio, or X/Y duo, is used when there are multiple sets of secondary terminals. Multi-winding transformers label winding set #1 secondaries as X1/X2/X3/X0, and set #2 secondaries as Y1/Y2/Y3/Y0.
Man, mike that is a very professional way to handle an individual who took a blow at your intelligence. Criticism? Yes. But he could have worded it more constructively opposed to the way he did. You know that though.
James Lee? Is it not referred to as the Pythagorean theorem? (spoiler: It is). It can be called Pythagoras' theorem, or Pythagorean theorem. Ado about nothing. (and actually if we're being picky here, notice his name is actually not PythagorUs but PythagorAs.)
Pythagoras is his name. Pythagoras', is the possessive form of his name. "Pythagorean" is the adjective referring to his work. Just like "Newtonian" and "Gaussian" are adjectives describing the work of Newton and Gauss respectively.
The national Electric code mandates that the phase rotation be clockwise ABC in panels (Left to right, top to bottom, and front to back). Article 408.3E(1) and 409.102B of the 2014 NEC.
In the slide at the 23 minute mark, the wild leg is moved to the B phase by swapping the B and C phases. This reverses the phase order in violation of the code sections Jolyon mentioned. The connection from meter to panel should have rotated the phases: C to B, B to A, and A to C.
Brian London interesting observation, and I think good that you pointed it out. Perhaps this is why sequence at any given point is a crap shoot, folks who simply put the high leg in B slot are focused on moving all associated loads and not blowing equipment up. Although when motors start spinning backwards you'd think they'd come to what you just pointed out. I have so many three phase panels at work I thought it would be a good idea to scope them out for sequence. It was frustrating when after several panels each was different within the same drop.
I will be installing a 75 kva 3 phase s/u xfmr, 240 hi-leg primary to 480/277 secondary. it will supply power for a glycol chiller located 60 feet from xfmr equip. Do I need both pri and sec protection and what size fuses and wire?
Hello mike! where can i buy you program? to study. im a 20 year old taking electrician 2 code and wiring! looking to become a journeyman later in the future! what do you recommend to me?
+Chapin001 It sounds like you are on the right path. Please call the office at 888.632.2633 and we will take care of you. So happy that we are going to be a part of your journey.
What a disrespectful sexist post. Clearly this post was not necessary other than to be hurtful. I'm sure your mother and father would be disappointed in your public display of sexism. It would be wonderful if you responded in a positive way so that we don’t think poorly of your upbringing. How old are you by the way?
No if you have a lot of mschinery portable cinveyors & welders. Only cavemen do not phase out all of the 3 phase receptacles. Easy peesey using the BOY Brown orange yellow color on all 480 volt receptacles. At my first job we had 50 refrigerted trucks that had to be plugged into 3 phase receptacles every night. At next job me and another young sparky phased out all of the portable welders conveyors that got rearranged several times a week along with packing machines that had to be moved several times a week. Cracked me up when I saw reversing drum switches on 5 portable welders and at least 25 packing/ wrapping machines. For conveyors caveman had short reversing cords. We would spend an entire shift just phasing out 3 phase receptacles. Most from a cord drop off a 20' ceiling. It paid for itself quickly.
@@possibility28able 3 phase secondary power using only 2 primary phases. It is most likely a money issue. No need to run 3 primaries when 2 will do the job. From what I have been told....
@@possibility28able cheaper and if you add a third transformer can increase KVA by I think 50%. ( been over 50 years since I had class in this ). Have to be carefull with open delta in that you do not get as good voltage regulation then a closed delta.
Your comment is 100% wrong; it is NOT safe. I'm going to assum your post was intended to be annoying. Please watch the following video it it was sincer; studio.ruclips.net/user/videompgAVE4UwFw/comments
@@MikeHoltNEC Sorry Mike but it's just that I don't get why is neutral necessary Foloowing your explanation we could just use the ground wire both to create a voltage between it and phase and to ground the whole building couldn't we? You says that neutral is not driven, and ground wire's function is not giving a path to free the excess of electrons, so it's like we need just two wires and we can leave all the security on a breaker.
@@MikeHoltNEC I watched it, I have cleared my doubts about basics but now I have a big one. If a parallel circuit has the same voltage in all the loads, why are there voltages drops? I mean, I connect the toaster, the oven, the shaker... then I take the multimeter, put the probes in the socket and I find a voltage drop, why? It is a paralel circuit wich means the same voltage and different amps
@@tvblood3550 Because there is always voltage drop on the wires supplying the individual parallel loads. When it's said the voltage of resistors are in parallel, they are assuming no voltage drop of the conductors.
Good morning , for the 3 transformers installation in Delta to have the high leg, please, can you tell me if all 3 transformers must have same Power output ?
@@ahsankabir2082 No. There are WYE to WYE transformers as well. It is common to have DELTA on the primary size, because it allows you to eliminate the neutral from the source. It also allows 2:1 (480 delta to 240 delta) or 4:1 (480 delta to 120/208V wye) as the transformer ratio, when working with 480V primaries, rather than a ratio involving the sqrt(3). It is also common for utility service transformers to have DELTA primaries, in the event that there is only consumption on the premises. Step-up applications often require (per the utility), a WYE topology on the medium voltage side.
![Transformers - Understanding Delta/Wye Connections [250.4(A)] (12min:11sec)](http://i.ytimg.com/vi/a8LjxEtd8N8/mqdefault.jpg)
![Transformers - Understanding Delta/Wye Connections [250.4(A)] (12min:11sec)](/img/tr.png)
![Grounding, Objectionable Current [250.6, 2020 NEC]](http://i.ytimg.com/vi/skX9XI3de5U/mqdefault.jpg)
![Solar Photovoltaic (PV) Systems, Scope, NEC 2020 - [690.1], (39min:21sec)](/img/1.gif)
I've been doing service and maintenance work for over 35 years (mostly industrial, but a lot of commercial and institutional mixed in), with a lot of that being strongly related to the electrical power side of things, and I learned quite a bit from this video.
That said, when it comes to whatever the standard of the day is today for what terminal and what color the high leg is, I don't really sweat that very much since I don't do installations. What I DO sweat is what my meter tells me.
I do contract service work all over the place and sometimes when I roll up on a job I know that the building is pretty old. I don't know how old or when the service I'm working on was put in, or by whom. Many times, the wires to a service are all black with no phasing tape, so what used to be done and how it was supposed to be done and what color or terminal is what may be interesting to me, but Mr. Fluke is who tells me what the damn deal is in that one particular job.
The history of all that stuff is really interesting, and now I understand why some of the high legs I have seen were ~ 190 something, but are almost all over 200 now, but at the end of the day - just put a meter on the thing.
Also, I carry a Sharpie with me all the time, and when I open a panel with a high leg that isn't labeled with regards to that high leg, I write it across the top in bold letters for the next guy that might go into that panel. Not because I have to, but just because I'm a nice guy.
You're my favorite type of guy to follow and I always do the same thing. And if I find something that's marked with as a high leg or a Delta and it is no longer the case I also update the markings
I love these videos explains what i am reading... im a future apprentice electrician getting a step ahead
I always thought 3 phase transformers were pretty simple to understand, had to explain to a young guy today why we hook motors, 200HP in a delta, and not a WYE to a soft starter, WYE start Delta run is before we had soft starters, and we had other good tricks, lots to learn about transformers, learn when, and how to tie XO to ground, and when you don't do that.
Find a local IBEW apprentice place, use google
@ dont you also get more current from a delta configuration?
tyler tyler . ALWAYS ALWAYS ALWAYS. Use a tester before energizing (even plugging in) ANY device. What the narrator said about all the empty spaces in the (Delta) panel is a real scenario. Unfortunately for me , as an apprentice, I failed to heed that warning and fried an old refrigerator and copier at a friends place of business.
As stated in other replies to Your comment , it would behoove You to go with IBEW. Tremendous knowledge. Free Education. Tools issued upon completion of First-year apprenticeship (that's the way it was back in '96 when I started .Not sure of Your locale , but worth looking into) Should that be the route you decide , a vocational test will be given . Theirs plenty of vocational preparation tests , even some phone apps. Brush up on Algebra. Remember PEMDAS or :
P lease (P arentheses)
E xcuse (E xponents)
M y (M ultiplication)
D ear (D ivision)
A unt (A ddition)
S ally (S ubtraction)
The way it worked back then was 11 weeks for 1st year. During that time , they didn't provide an income so make sure to prepare accordingly .
Best wishes to You "Sparky" in your future endeavors whichever route you choose.
I love this stuff, and it is so important, to keep the knowledge out there and keep the guys alive. One call in your career maybe the old school odd duck system, and it can prove fatal if you don't get out the meter and confirm your assumptions.
Folding my kiddos clothes and learning at the same time! Another great video
That's cool!
Another way to calculate the High Leg is to take 240V(voltage from first winding)+120V(voltage from tapped winding)=360V, then 360V/1.732(squared root of 3, because it's 3 phase)= 208V
Good point, never considered that option!
Or, tan 60 degrees = 1.732
Thanks Mejia, Mike, and Sparky!
Brilliant
Yes, also you can just multiply the phase-ground voltage by root 3 to get the high leg voltage, ie 120v x 1.732 = 208
Thanks for another great video!! I've worked at utility company for 15 years and never heard anyone talking about the explanation behind how these voltages come about. Thanks for making sense out of this! :)
How are there only 175k views - Mike holt is spitting pure knowledge. VS DIY video on how "wire" a house has millions of views. smh
I think because I'm focused on the electrical profession, and not the general public.💕
Since that is a 30-60-90 triangle then the short leg of the C transformer is the 120V (half of the 240 between C1 & C2), the long leg is the connection between the A and B Transformer connection and the C neutral. Any High School Geometry student (at least those I teach) will tell you that the long leg of a 30-60-90 triangle is always the square root of three times the short leg; the square root of 3 is 1.732050807... and multiplying that by the short leg of 120 gives you 207.846V--to the nearest volt that is 208! Likewise, the B transformer is the hypotenuse of that triangle and the hypotenuse of a 30-60-90 triangle is always twice the measure of the short leg so 2(120)=240! The rules for a 30-60-90 triangle are derived from trigonometric functions but the Pythagorean formula does also work for any 90 degree triangle, so (12^2 + B^2 = 24^2) (dropped the zeros for simplicity). That works out to 144 +b^2 = 576 then b^2 = 576-144, and b=square root of 432, and lastly, b=20.78. Move the decimal over one to the right to put out significant zero back and you get 207.8 or 208V! Q.E.D.
I will say that having the panel of 4 other guys is nice for sharing knowledge
In my 50 years as a sparky only came across this once. Think in school they told us to never place too much load on the nuetral due to it might cause voltage imbalance on 3 phase loads. If you can get by with 208 volts on the 3 phase loads way better off with the Y secondary that is every where .
I love this stuff. While on the subject of changing and unusual voltages regarding delta high leg systems, there also exists a very unusual voltage, a 480 volt, high leg, 240 volts A to Neutral, 240 volts C to Neutral, and 415 volts B (high leg) to Neutral, the master electrical I am working with, ran into that, only once in his 39 year career, in the early 1990s when he was on a maintenance job to a large wood working shop near Louisville Kentucky, they had mostly 480 volt 3 phase motors , but they had the high bay meter halide fixtures running off the 240 volts. They also had 480-120 volt transformers in the facility so they could run ordinary stuff as well. I thought I'd share this and wonder, has anyone else heard of a 480 volt, high leg delta?
There is no such think as a 480V high-let system, but there are 480Y/277V systems, corner grounded 480V systems, ungrounded 480V systems, and 480 grounded systems.
Great work. ✔️💯🏆
Thanks so much for sharing. 😉👌🏼
We always referred to it as the high leg, every time I’ve encountered a service with the delta high leg the voltage was over 200V. I remember when I first started doing service work I’d think it was my lucky day! I got a few empty/spare breakers only to find out it’s a high leg 😂😂
I will say that waching you guy's
( shareing knawlage ), is like waching
A Very Choreographed dance 💃!!! LOLO
LOLOL. However, it's very refreshing to see, one dancer" giving the same answers "That I Was Thinking" ONLY SECONDS Before.,!!! LOL CARY-ON,..
dear mr.mike holt
it is very good to understand grounding-safety fundamental from your lecture, thank you very much to mr.mike holt. i shall follow up your other lectures. one importance word that i will remember from that is " if you false understanding and did wrong, you start killing some body.
thanks and best regards
mr.salacheep yusabai
bangkok, thailand
Man this is just gold.
Thank you.
Pythagorean theorem. That's right Eric.
There is an easier way to calculate the high leg voltage. simply multiply the phase to phase voltage by sin(60 degrees) or 0.86623. Which is the square root of 3 (1.7321) divided by 2.
Always look out for that triangle I worked with a guy that burnt up a few computers and TVs because he didn't understand a delta in a machine shop
If I were to power a warehouse or a factory with lots of motors and lighting, I would use the 480Y277 volt system as indicated in your diagram. Most 3 please motors are dual voltage and use the 277 volts to run the Lights ( most hard wired LED light fixtures have universal voltage drivers in them already). In this situation, I would not bother using the Delta- Delta transformer in the first place.
At 25:00, this is why they make buck- boost transformers. So you can run a 240 volt load at its full voltage from a 208 volt Wye system.(the wimpy Wye)
Pythagorian's is a malapropism. It's the Greek mathematician Pythagoras, therefore it is called "The Pythagorean Theorem".
With a delta high leg system, if you want to add more 120 volt loads, you can buy a transformer with a 240 volt delta primary 208Y/120 volt secondary. By putting all your 120 volt loads on the secondary of this transformer you will maintain a more balanced load on your delta service.
In my experience, I have observed that most of the electrical guys work with the observational experience without knowing and understanding the fundamentals. The basic in electrical engineering is vector representation of voltages. If you master this and know how to apply this you will understand and can explain 90% electrical engineering related analysis. I will come out with a video on this for the sake of all electrical engineers.
Perfect! Post the link to your video in a reply.
Please don't forget current flow, not with respect to current vs election flow (no offense to the theoretical guys) but so far as "ground loops" and multiple paths go. I spent years focused on this aspect and was a better troubleshooter because of it. Mr Holt does an excellent job touching on it's importance in the few videos I have watched.
The power triangle, impedance triangle, etc. all are the same concept. Trig. These all give you a better understanding of what's going on.
In san Diego we had some 277 volt high leg
Probably one of the few educational videos even bothering to mention delta breakers. I've personally never seen then I've heard of them, and believe they were banned in the mid 1970s, either '75 or '78 NEC, the theory was even if the main breaker was turned off, 208V from the high leg could backfeed from the load to the panel posing a shock hazard. Delta breakers were somewhat common in the 1950s until the early '70s, in some parts of the country, for a 5 ton air conditioning unit, when central air became popular and affordable post WWII, some of the larger units were not always available in single phase. I'm sure there are many older systems still in use, that have a delta breaker. Some panels, particularly residential panels from this era, were spit buss panels, which were legal until the 1981 NEC.
ive seen issues arise with 240 volt equiptment that also use a neutral, like an RV outlet, which could not be on the high leg.
Using your example of applying Pythagorean's Theorem I don't get the 20.8, as the gentleman mentions. To confirm my math, I drew the actual right triangle in AutoCAD and it showed my result correct. I am not being petty, I am learning all I can about this and want to make sure I have a clear understanding of what is happening. But your video is awesome Sir! Thank you.
The interior angles of the delta are 60 degrees. The line drawn from the high leg to the neutral point bisects the triangle. The point that is the high leg is now divided into two angles, each 30 degrees.Let’s look at this a couple of different ways.
1. The rules of a 30-60-90 triangle are these. The short leg is 1/2 the hypotenuse. The long leg is sort(3) times the short leg. Using these rules, the short leg is 120 volts and the long leg is 120 * sort(3) = 208
2. A^2 + B^2 = C^2 where C is the hypotenuse. Hypotenuse^2 - (short leg)^2 = (long leg)^2 240^2 - 120^2 = (long leg)^2 57,600 - 14,400 = 43,200 Long leg = sort(43,200) long leg = 208
MikeHoltNEC thank you for taking your time to explain that for me.
You are most welcome.
MikeHoltNEC I was a broadcast video tech for 20 years, I now work at a farm that absorbed the original Habbersett sausage factory and the associated museum of electrical distribution networks. As a troubleshooter who doesn't know how to say "I don't know" I am extremely grateful for this particular 26 minute video as well as the rest of them as I am currently going through them. Thank you so very much. One of the biggest lessons for me is how much I miss the beauty of a classroom. Again, thank you sir.
There are many uses for the 208 volt high leg. Most modern hard wired L.E.D.
light fixtures have universal voltage drivers in them (100-277volt 50/60HZ). You can run them between the high leg and the neutral. Treat it as though it is a 277 volt system. Use 3 pole breakers which are straight rated.
The high-leg is not permitted to be terminated on to a 1-pole or 2-pole breaker (slash rated breakers) per 240.85.
That is correct. But what if you use the high leg from a 3 pole circuit breaker, which is already straight rated any way?
You area 'smart' guy! Not many understand this concept. Answer: Yep this is perfectly fine. By the way, they do make 'straight' rated 2-pole breakers, but these are special order and cost about the same as a 3-pole breaker.
Excellent video!
I feel so smart now
Exactly what makes me work so hard!
It's more effective to use wye tap to avoid a high leg on the secondary to get even voltage on all phases like 120/208 instead of 208 on B phase to neutral . Instead its 120 to neutral on A, B ,or C phases
There are many good reasons to use the Delta High-Leg, any other system besides a Wye 120/208V system. Visit MikeHolt.TV, click on Live link and learn more about voltage systems.
Great video. How dumb am I, so much to learn.. thanks a lot.
Me too...
You the man. Do on the primary delta, you have twice the number of wraps of the wire in each transformer coil yea?
Primary voltage is 2x the secondary voltage.
Great video
I bought one of the alarm gfi's at Lowe's
A , is unknown length .. so 240 squared - 120 squared equals a number, then u square that number will give u A ..
@@MR-nl8xr Squaring is the namesake of multiplying a number by itself, because the area of squares is the application of this operation where it was discovered.
There are plenty of applications of squaring numbers that have nothing to do with actual squares. You can find plenty of geometric proofs on how squaring sides of a triangle will find the relationship among the sides of the triangle.
Delta is simply named delta because it looks like the Greek symbol that’s it believe it or not.
Very good and clear explanation. At the beginning you asked what does "Delta" actually mean. In Greek, it is just the way to day the letter which sounds like "d". In a similar way that z is pronounced zee in English.
Διαφορά (diaphora) = difference in Greek. Leibniz was using Latin lowercase d for infinitesimal differential in his Calculus notation. The Latin letter being spoken for already, Greek Delta also standing for a Greek word meaning difference, would stand for finite change.
Delta as the name of the transformer topology has nothing to do with the concept of difference. It is named as such, due to the arrangement of voltage vectors in real/imaginary number space, looking like the triangle letter Delta.
machines don't all run the same direction, black ,red , blue won't work
VERY CAREFULYY WHITH THE CONECTION THE EQUIMENT THAS WHY THE WARNING IS mandatory IN THIS SYSTEM
What?
Yea but primary to secondary mutual induction. Does it actually stack together like a hexagon ? Yeah, gosh FINALLY the age old question of 230, 115, and 199, and 110.
Stack like a hexagon? I have no clue, let me know what you find out.
awesome..
So the bottom line is, your meter can be your best friend.
It's not a 30/60/90 (as drawn) and the 208 is the hypotenuse, not the 240. He spoke incorrectly. It is an equilateral triangle.
Jeff, The original triangle is an equilateral.
When a line is drawn from the tip of the triangle to the neutral point on the other side, the equilateral triangle is cut into two triangles, each of which is a 30 60 90.
If you look at the 30 60 90, the line that was just drawn is the long leg. The line from the neutral point to the point on the triangle is the short leg. These two legs have a 90 degree angle between them. The side of the equilateral that has not been bisected is the hypotenuse.
The hypotenuse is 240 volts. This is given because it is a 240 volt delta system.
The short leg is 120. This is given because the neutral point is the midpoint of a 240 volt winding.
The long leg is sqrt(240^2 - 120^2)
Eric
Hey mike very informative vid. But i have a question. How do i know if to use a Star input or Delta input transformer? Does this go according to the voltage?
Now am just sayin here if the voltage is 480/277 volts do use a Star input transformer or if the voltage is 240/120/208 the high leg do i use a Delta input transformer.
Or if its 208/120 do i use a Star input transformer.
Thanks will be much appreciated.
Isn't that an equilateral triangle? not a 30-60-90 as there is not right angle. Thus the degrees of the angles and length of the sides giving us the relationship for establishing the 208v can only be calculated using the only known existing portion of the equilateral angle of 60degrees and using the cosine rule to solve. What am I missing? I love your vids.
the 30,60,90 has a right angle and you can use tan or cosine to solve for it.
wrong triangle, he was talking about the one drawn in to calculate the high leg voltage, not the delta itself.
Pythagoras!
👍
Question? On the secondary delta (between C1 & C2) is 120 volts 180 degrees out of phase with each other on this set up?
Thank you for this. Why are the letters H and X used?
I'll try to find out...
H most likely stands for high side.
I'm not sure why they selected X, of all possible letters for the low side. My guess is that it has to do with X being the de-facto choice for variable names in Algebra, and the X/Y/Z trio, or X/Y duo, is used when there are multiple sets of secondary terminals.
Multi-winding transformers label winding set #1 secondaries as X1/X2/X3/X0, and set #2 secondaries as Y1/Y2/Y3/Y0.
Your friend should have moved the breakers in the panel when the high leg was moved from the C phase to the B phase.
LOL. Mistakes happen to the best of us at some time or another!
@@MikeHoltNEC Expensive ones at that.
Please ! The guy's name was Pythagorus, not "Pythagorian" (15:42/26.35)
We'll work on that, thank you.
Man, mike that is a very professional way to handle an individual who took a blow at your intelligence. Criticism? Yes. But he could have worded it more constructively opposed to the way he did. You know that though.
James Lee? Is it not referred to as the Pythagorean theorem? (spoiler: It is). It can be called Pythagoras' theorem, or Pythagorean theorem. Ado about nothing. (and actually if we're being picky here, notice his name is actually not PythagorUs but PythagorAs.)
PythagorAs! 😁
Pythagoras is his name. Pythagoras', is the possessive form of his name. "Pythagorean" is the adjective referring to his work. Just like "Newtonian" and "Gaussian" are adjectives describing the work of Newton and Gauss respectively.
The national Electric code mandates that the phase rotation be clockwise ABC in panels (Left to right, top to bottom, and front to back). Article 408.3E(1) and 409.102B of the 2014 NEC.
That is true, but why are you making this comment? What am I missing.
Because you brought up the subject. So It was for anyone's information. You are not missing anything.
In the slide at the 23 minute mark, the wild leg is moved to the B phase by swapping the B and C phases. This reverses the phase order in violation of the code sections Jolyon mentioned. The connection from meter to panel should have rotated the phases: C to B, B to A, and A to C.
Brian London interesting observation, and I think good that you pointed it out. Perhaps this is why sequence at any given point is a crap shoot, folks who simply put the high leg in B slot are focused on moving all associated loads and not blowing equipment up. Although when motors start spinning backwards you'd think they'd come to what you just pointed out. I have so many three phase panels at work I thought it would be a good idea to scope them out for sequence. It was frustrating when after several panels each was different within the same drop.
@@brianlondon4695 Very interesting indeed!
I will be installing a 75 kva 3 phase s/u xfmr, 240 hi-leg primary to 480/277 secondary. it will supply power for a glycol chiller located 60 feet from xfmr equip. Do I need both pri and sec protection and what size fuses and wire?
Please get my transformer app at MikeHolt.com/App
Hello mike! where can i buy you program? to study. im a 20 year old taking electrician 2 code and wiring! looking to become a journeyman later in the future! what do you recommend to me?
+Chapin001 It sounds like you are on the right path. Please call the office at 888.632.2633 and we will take care of you. So happy that we are going to be a part of your journey.
Ora chapin
What is up with all these guys and their horrible ties? I can't believe their wife let them out of the house like that.
What a disrespectful sexist post. Clearly this post was not necessary other than to be hurtful. I'm sure your mother and father would be disappointed in your public display of sexism. It would be wonderful if you responded in a positive way so that we don’t think poorly of your upbringing. How old are you by the way?
Synchronizing phase rotation thru out an entire facility would be too good to be true. Now your just spoiling electricians if you do that.
We can dream can't we?
No if you have a lot of mschinery portable cinveyors & welders. Only cavemen do not phase out all of the 3 phase receptacles. Easy peesey using the BOY Brown orange yellow color on all 480 volt receptacles. At my first job we had 50 refrigerted trucks that had to be plugged into 3 phase receptacles every night. At next job me and another young sparky phased out all of the portable welders conveyors that got rearranged several times a week along with packing machines that had to be moved several times a week. Cracked me up when I saw reversing drum switches on 5 portable welders and at least 25 packing/ wrapping machines. For conveyors caveman had short reversing cords. We would spend an entire shift just phasing out 3 phase receptacles. Most from a cord drop off a 20' ceiling. It paid for itself quickly.
im in michigan and sometimes i see only 2 transformers on a pole for a 3 phase hook up. hows that work?
Look up an open delta phase system
It is an open delta configuration. I am a utility high voltage crew leader. We build them all the time.
@@CHICAGOHAND What's the point of an open delta?
@@possibility28able 3 phase secondary power using only 2 primary phases. It is most likely a money issue. No need to run 3 primaries when 2 will do the job. From what I have been told....
@@possibility28able cheaper and if you add a third transformer can increase KVA by I think 50%. ( been over 50 years since I had class in this ). Have to be carefull with open delta in that you do not get as good voltage regulation then a closed delta.
So in conclusion It's safe to touch a phase wire barefoot and wet right?
Your comment is 100% wrong; it is NOT safe. I'm going to assum your post was intended to be annoying. Please watch the following video it it was sincer; studio.ruclips.net/user/videompgAVE4UwFw/comments
@@MikeHoltNEC Sorry Mike but it's just that I don't get why is neutral necessary Foloowing your explanation we could just use the ground wire both to create a voltage between it and phase and to ground the whole building couldn't we? You says that neutral is not driven, and ground wire's function is not giving a path to free the excess of electrons, so it's like we need just two wires and we can leave all the security on a breaker.
@@tvblood3550 Watch - ruclips.net/video/mpgAVE4UwFw/видео.html
@@MikeHoltNEC I watched it, I have cleared my doubts about basics but now I have a big one.
If a parallel circuit has the same voltage in all the loads, why are there voltages drops? I mean, I connect the toaster, the oven, the shaker... then I take the multimeter, put the probes in the socket and I find a voltage drop, why? It is a paralel circuit wich means the same voltage and different amps
@@tvblood3550 Because there is always voltage drop on the wires supplying the individual parallel loads. When it's said the voltage of resistors are in parallel, they are assuming no voltage drop of the conductors.
A 3:26 - 3:30 you mean to say 240v but you say 480v.
How about a Ghost phase
A Delta with a C phase grounded
I'll add that to the updated video next year.
Not a ghost phase. It's a corner grounded delta
Good morning , for the 3 transformers installation in Delta to have the high leg, please, can you tell me if all 3 transformers must have same Power output ?
No, the power output is not a factor for voltage, and as a matter of fact, the three transformer typically would not all be the same kVA rating.
3:27, is this a typo?
Isn't the voltage between line 1 and line 2 in your secondary windings 240, not 480?
You are correct, I did say 480V, and I should have said 240V. Sorry and thank you.
basic trig and vectors
What a mess, that's why Y systems are superior
Is delta connected always at high voltage side?
so,such type of questions are illegal?
Do you mean is there always a high leg? Then no
@@ahsankabir2082 No. There are WYE to WYE transformers as well.
It is common to have DELTA on the primary size, because it allows you to eliminate the neutral from the source. It also allows 2:1 (480 delta to 240 delta) or 4:1 (480 delta to 120/208V wye) as the transformer ratio, when working with 480V primaries, rather than a ratio involving the sqrt(3).
It is also common for utility service transformers to have DELTA primaries, in the event that there is only consumption on the premises. Step-up applications often require (per the utility), a WYE topology on the medium voltage side.
🖒🖒🖒!