Transformers - Understanding Delta/Wye Connections [250.4(A)] (12min:11sec)

[@kimmer6]

I supervised installs on General Electric gas turbine generators all over the world in the 1970's and 80's. Almost all were Wye connected with generator ouput voltage at 13,800 Volts. In the 90's my 10 year old nephew became fascinated with transformers. For months I heard about this and figured the guy was like me....had to tear things apart and reassemble to make them work better while the other kids were reading comic books. So I bought him a big book on transformers and distribution yards for his birthday. Stupid me. I found out that ''Transformers'' were toys that were vehicles that unfolded into robots as featured in comic books.

[@mikeholt3717]

Lol, that is a great story!

[@shanegee6165]

It’s very necessary mike. It separates electricians from installers. Anyone can bend pipe or run rope. This is what separates men from boys

[@TheTrainstation]

One of my mates is a qualified electrician, domestic work. Hes great at wiring houses because you dont need to know much apart from pulling wires around. Last week he connected up the machines in my mates carpentry shop..the bandsaw ran backward so they switched the polarity, fine. Nrxt machine they connected a big motor with star delta switching and it arced and blew. Then...they switched the polarity on this one too and boom. SMH

[@davidanderson911]

I was amazed the first time I worked in a large substation, in the now closed Castle Air Force Base at Atwater, CA, to see these huge transformers had an XO terminal that went to straight to earth ground right off the side. My grandfather worked on the original construction of Grand Cooley Dam. He told stories about it that I was way too young to understand, other than it was a great source of pride to him. Thanks, Mike!

[@MikeHoltNEC]

I was personally at the Grand Cooley Dam and there are three "HUGE" transformers on each side of the dam. Mark A, B, and C. Then if you following the overhead buss (which I did) one terminal from each transformer tied together (Wye Secondary) and it went into the earth and it was marked "XO". Blew me a way... So I know the feeling.

[@bertgh]

This video explains everything so well and states it so simply that all the info that I tried to understand in other sites seems to be unnecessarily complicated. Mike, your videos are GOLD, thank you so much for uploading them.

[@chardysmile]

Leonardo Moreno the ground and neutral. .are they really connected inside of the transformer??

[@abebegezahegn9436]

@Mike Holt a

[@carultch]

@@chardysmile Ground and neutral are either connected inside the transformer, or inside the secondary protection disconnect immediately adjacent to it. The transformer secondary circuit is called a separately-derived system (SDS) in the NEC. This means that it needs to have its own connection to the grounding electrode, and its own establishment of the neutral at ground voltage, otherwise the three phases would float. Transformers isolate the two sides, as they only transmit change in voltage, rather than absolute voltage. From the perspective of physics, it makes the most sense sense to make your neutral-to-ground bond inside the transformer. But because there is precedent from how we bond neutral and ground in service disconnects that are on the secondary of utility-owned service transformers, the NEC gives you the option of treating the secondary conductors like service conductors, and bonding neutral to ground in the secondary disconnect. In any case, you only want to make this connection once for the SDS, and you connect to the GEC and grounding electrode, whereever it happens.

[@chardysmile]

@@carultch thanks

[@davehasenford3985]

I'm really glad you explained at the end that geometrically, the distance between the ends of the two legs, if the two legs being a length of 12 'units' from center, is 20.8. It takes some of the mystery out.

[@WhosthatTeamAFC]

When I see a tie like that I know I'm about to learn. And learn good.

[@jf8461]

I noticed the tie right away, because I happen to own the same one!

[@WhosthatTeamAFC]

@@jf8461 You probably have a lot to teach me.

[@markamber1480]

7:41 casually recommends shorting out a 12 AWG extension cord. Definitely a talk tailored for electricians...

[@jf8461]

Finally somebody who explains this where I can understand well! I am not an electrical engineer, but sometimes I have to do some electrical work and I found this video extremely helpful. I will definitely watch some of his others.

[@dutcher517]

Mr. Holt, I have watched numerous videos of yours, multiple times. I have learned an enormous amount from you and your team. Just wanted to say thank you.

[@MikeHoltNEC]

I'm so glad that God has blessed me so that I can provided this service to the industry. Thank you for the message, God Bless, Mike Holt

[@dutcher517]

MikeHoltNEC I start an Electrical Power Technology with an AAS this month. I am currently an electrician apprentice and have worked on Siemens 2.3 mW wind turbines. When I have more disposable income, I will buy your DVDs. Until then, your videos are absolutely top notch. Seriously, I've watched hundreds, and yours are so clear and concise. Wish I could sit down with you and ask questions. You and that panel in the video, obviously know your stuff. Have a great weekend.

[@MikeHoltNEC]

Thank you, have a wonderful day and look forward to meeting you one day at one of my seminars.

[@vince6829]

Thanks for sharing your knowledge.

[@Top5DeadOrAlive]

Mike you are a monster, see? A monster of electricity.

[@esjel9804]

Out here we call him a beast!

[@mino-kw1oh]

mike, another great video. thank you for your dedication to the craft.

[@MikeHoltNEC]

Mino, thank you, have a wonderful day.

[@guitarhvac]

Thanks! This finally makes sense out of something many people work with all the time, but have no idea how or why it exists.

[@KartiacKID]

I would have loved having as one of my professors in college

[@MikeHoltNEC]

Thanks for the kind words, God Bless.

[@commercialsparky7776]

Good video as usual, great video actually.

[@lendavidhart9710]

Thank you for this, i love this stuff, i should have gotten into this earlier in life Edit- thanks again i learned alot watching this.

[@MikeHoltNEC]

You are most welcome.

[@AM-dj5nv]

Hello Mr. Holt, can you please explain 3phase delta with a corner ground? I ran into this at an oilfield in southeastern New Mexico. What’s the advantage/purpose. Could this cause step potential? Thank you very much Mr. Holt!

[@mdhaskins1]

I love this stuff!!

[@user-mz7hb1dq5x]

thanks for uploading

[@MikeHoltNEC]

You are welcome.

[@jamescaraway6191]

Mike: As a point of information. I would like to point out the following. A delta transformer is an isosceles triangle. All triangles have a total of 180 degrees. Because it is an isosceles triangle the angles are all equal. Therefore the angle between all angles in a delta transformer are 60 degrees. If one takes the sine of 60 degrees multiplied by 240 volts one will get 207.8 volts. In addition Y transformer is arranged in a circle. Because there are 3 equally spaced transformers the effective angle is 120 degrees. Interesting the sine of 120 = sine 60.Therefore line to neutral voltage in both delta and neutral are equal. Interesting HUH?

[@MrBrandoncreel]

James Caraway delta is an equilateral triangle and that's why all angles are equal. Thus 60-degrees.

[@carultch]

Equilateral triangles are more specific than isoceles triangles. Isoceles triangles just have two equal sides and two equal angles. Equilateral triangles have all three sides, and all three angles equal.

[@selfmade128]

Amazing teacher

[@MikeHoltNEC]

Thank you, I try to improve each day.

[@V2Guerrero]

It is absolutely necessary, lol

[@interplucky]

Really looking for WYE-DELTA configuration. Sad you didn't cover it :( The NJATC homework asks about WYE-DELTA, but doesn't explain it very well.

[@MikeHoltNEC]

Call me 352.455.0794 anytime and I’ll help! Mike Holt

[@garbo8962]

In my 50 years as an industrial electrician never came across a Y Delta. A Y primary more then likely would only be feed with 3 wires.

[@tedlahm5740]

Question; My local residential transformers are ALL Single Bushing grounded Why. Yes, only one bushing. This is multipoint grounding at each pole/transformer. Question, where is the parallel neutral going back to the power company substation? thank you

[@floogon_gameing6987]

Not lookimg for that kind of transformer but this was still very informative

[@richardbriley9377]

J

[@jolyonwelsh9834]

You can buy a 3 phase dry type transformer with a 120/240 Delta secondary all in one.

[@MikeHoltNEC]

Correct.

[@garbo8962]

Was told years ago that never use more then around 10% on a delta secondary with one of the secondary coils tapped for 120 volts. If too much power is pulled off one coil it produces a greater voltage drop in that coil. For every 1% voltage difference between 3 phase legs think it produces around 3% more heat in a 3 phase motor.

[@spatzky]

At 7:00, he said faults will not cross on delta wye grounded transformers. You are wrong. SLG, DLG, LL faults do not cross delta wye ground transformers BUT a three phase fault does.

[@mikeholt3717]

That is NOT what Eric said, he said the fault doesn't go from primary winding to secondary winding becasue of the air gap between the primary and secondary.

[@DP-hy4vh]

Another way to get 208 volts line-to-line; (120 V + 120 V) * Sin 120° = 207.84 V or 208 V (rounded up)

[@MikeHoltNEC]

Thank you!

[@colt2657]

We always multiplied by 1.73

[@saifamu1989]

Phase to Phase Voltage (Vab) is √3 times the phase to neutral voltage (Van) in magnitude but Vab would lag behind Van by 30°. This is true only in case of a Wye connection...in Delta connection, its the Current which obeys this rule.

[@stoobydootoo4098]

Treat the voltages as vectors (because they are!). You can do it 2 ways using trigonometry - 1) (simplest) Split the isoceles triangle into 2 right angle triangles. 60*/30*/30* on the right side. Cos 30* (0.866) = adjacent (??? Volts) / hypoteneuse (120 Volts) Simple arithmetic shows the adjacent as almost 104 Volts. It's the same on the left side triangle. Add them together = 208Volts. QED. 2) The Sin rule - A (120 Volts)/ Sin a (30*(0.5)) = B (??? Volts)/ Sin b (120*(0.866)) Simple arithmetic shows that B is almost 208 Volts. Simples! (As we say in the UK after a long running series of TV ads.)

[@stoobydootoo4098]

Just to clarify, I'm referring to the Wye example. Sides A, B (imaginary line), & C. I'm calling A, & C 120 Volts. B on top is the 'unknown' Voltage.

[@engrjunogarte9844]

7620/13200Y---120v/240v

[@MikeHoltNEC]

Post your quesiton on MikeHolt.com/Forum.

[@SJ-hw7bx]

Wouldnt 500,000 va be 500Kva????

[@evanbrawner2414]

S J MVA would be million, so 500 million volts. Idk why he said MVA then said 500 thousand lol

[@saifamu1989]

500,000 VA = 500 KVA = 0.5 MVA Complex Power

[@rameshdathrampersad9216]

I understand but not everything. If we were to put more windings on each transformer of the secondary star side to give 240 line to line and 120 from line to neutral. Can they put that number of turns so that we can achieve those voltages out of a secondary star system or is the 208 / 120 is just how it works because i know or heard you can put a certain number of turns to get a desired voltage. Thanks

[@MikeHoltNEC]

You can't get 240/120V on the secondary of a Wye configured winding.

[@MrKadidle51]

Can I connect a delta system to the secondary of a wye transformer and just not terminate the neutral? Transformer is 4160 to 480y277. However it's a 480 delta system.

[@dhunsaker26]

I would like to find a video that explains neutrals on 2 wire power line to underground transformers.

[@G30RG13N]

Gold gold gold

[@keving1774]

So you're saying you're allowed to have an average of10% voltage drop?

[@MikeHoltNEC]

Kevin, thanks for your comment. Can you explain where you are getting 10% voltage drop from the video?

[@saifamu1989]

Voltage regulation

[@dehuifang]

the most devises allow 10% voltage drop

[@smash72cutlass30]

Unstable incoming power during peak times of the day especially during summer months. Brown outs ? Or does that not happen at 480v My concern is this is a 180K saw sold to my client with the understanding that at 208V will run fine given it’s 10% power allowance. Manufactured in China to run at 200V

[@garbo8962]

Good luck with any electrical product made in cheating lack of quality control communist china.. Several China motors that I connected ran hotter then others. Company ordered a spare 100 HP plain Jane normal Nema frame motor. cheating China motor states to only use wire rated for 110degrees C. Asked my inspector & several sparkies if they ever came across this. All said no.

[@smash72cutlass30]

@@garbo8962 actually my mistake there from Japan. There whole power grid is 3phase 200V I’ve been running these saws from 3 phase 240V delta high leg so far no problems. There were initial software problems but not sure if that was power related. And this 240V is more like 253V so with a step up transformer it’s making 490V on 460V machines. Fingers have been crossed for a couple years now.

[@garbo8962]

@@smash72cutlass30 Think I heard or read years ago that Japan might be one of the counties that run on 50 Hertz and not the 60 Hertz here in USA. Speed of an AC induction motor is Hertz times 60 ( 60 seconds in 1 minute ) divided by pair of poles minus losses. So a 2 pole motor running on 60 Hertz will run around 3460 to 3500 RPM ( Used most often for pumps ). The most common by far the 4 pole motor running on 60 Hertz will run around 1740 to 1760 RPM. We had a pump running off a VFD ( DRIVE) that ran at 70 Hertz most of the time. I asked service tech if motor was rated to run that much over the stamped speed and how does this affect life of motor. Of course he had no ideal.

[@smash72cutlass30]

@@garbo8962 50 hertz 100% true there motors are all wound accordingly. Problem comes when you purchase a used machine most will need a independent transformer to step up or down which ever gives you the closest power to the name plate. Most are just 200V doesn’t even give you a option. Just hooked one up 480 down to 200 just to give it the power it’s used to. Big problem if your power from the poco is high to begin with.

[@engrjunogarte9844]

A banking transformer is configured to OPEN WYE/OPEN DELTA. Can this be reconfigured to OPEN WYE/OPEN WYE? What will be its secondary output voltage...Thanks and appreciate for reply.

[@MikeHoltNEC]

Order the transformer configured the way you desire it to be. But I have a question, what in the input and output voltages?

[@trevonwalker8022]

Is the neutral 120v kinda confused about the neutral in the transformer. I’m so good at electrical in the field but the book work honestly discouraged me

[@MikeHoltNEC]

Don't put yourself down, you just need to get the right book and you need to have video that explains the book. All of our products have this. I suggest you visit MikeHolt.com/Products and get our theory program.

[@jonasnewell6094]

I used Mr. Holt’s books to be able to pass my journeyman’s test and then the master electrician test. I put in an extra 30 min a day studying and it paid off, but it pays off more when there is an issue and you can troubleshoot it because you understand it or at times know what resource to use to find the answer. The book work can be very confusing at first, but eventually it will all tie together. I’m confident in saying if every electrician gave up when they became confused we wouldn’t have any electricians but men like Mike can help your career.

[@MikeHoltNEC]

@@jonasnewell6094 Thank you, that is why we do what we do,! We love the stories about how the products help people out for the long game. Congrats on all of your successes and if we can help you in any way please let us know. Not sure if you have seen any of our business or leadership products products yet but as you continue along your career you may find these helpful as well, www.mikeholt.com/product-category-list.php?id=5. Take care and thanks again.

[@jonasnewell6094]

So I decided to get the business management skills books because like you said, I want to advance in my career and being able to learn from others success and mistakes is invaluable. I appreciate all your help and thank you for being a blessing. Do you have any videos explaining the que and delta connection in motors and why they are used?

[@MikeHoltNEC]

@@jonasnewell6094 No, but I'm sure if you search the Internet you'll get your answers.

[@dane5167]

If I’m using a driver, and I want to find out the amps, do I do the watts devided by the secondary or by the primary? Let’s say I have 300 watts pulling and I devide it by the secondary 12v that’s 25 amps would that trip 20 amp breaker? And if I devide 300 by 120v it’s only 2.5. So what is the amperage actually being used on the primary

[@MikeHoltNEC]

Post your question on MikeHolt.com/Forum.

[@drawingtime2589]

If a line voltage on the primary are connected to each other wouldn't that result in an arc blast please help me to understand why these diagrams show them connected to each other

[@MikeHoltNEC]

Nope, because this is a 'winding' that has sufficient impedance' and the load on the winding will be practically zero amperes when there is no load on the secondary. I'm sorry but I can't explain the entire theory related to your answer.

[@drawingtime2589]

@@MikeHoltNEC Thanks for the reply, so- this primary winding is like a very very -very- long heating element? In theory? That's it for now, I know yall are very busy!

[@MikeHoltNEC]

@@drawingtime2589 Well.... you can't use the example of 'resistance' since this is related to induction (but you are kinda right).

[@drawingtime2589]

@@MikeHoltNEC thanks I've been pondering this for quite some time

[@walexsyfigueroa1146]

12 _3 romex

[@Espiritiv]

Why does the USA use 120V systems and not 240V like other countries?

[@MikeHoltNEC]

Good question, let me know what you discover.

[@Sparky-ww5re]

The reason has little to do with practicality, and 120 volts is used for historical reasons. You see, back in 1879 when Thomas Edison produced the first practical incandescent lamp, it used a carbon filament, and worked best at 100V. Edison's first electrical power plant on Pearl Street in New York City in 1882, supplied 110 volts DC. Less than a decade later, in the mid 1880s Tesla designed and patented the alternating current system which was far more efficient and could serve customers miles away instead of blocks, 110/120 Volts AC became set in stone, since it was backwards compatible with the carbon filament lamps at the time, and for decades, AC and DC mains power would coexist. Switching over to 220- 240V like much of the world uses, would obviously be very expensive and impractical, since everyone would have to buy new equipment or install step-down transformers in their homes and businesses. The 230V 50Hz system used in Europe & much of the world, is actually a more efficient system than we have in North America.

[@twn5858]

Does the neutral on the wye carry less amperage? Why are there 3 120 voltage lines and only one neutral?

[@MikeHoltNEC]

The answer is not something that can be answered via a post. I suggest you search the Internet on calculating neutral current for a three-phase system.

[@carultch]

Look at the timing of three phase balanced waveforms at once, with 120 degrees of phase separation each. When phase A is at full amperes, phases B and C are both at -50% of full amperes. One phase is at -50% and increasing, the other phase is at -50% and decreasing. The current adds up to zero, among the phase conductors alone, given balanced currents on all three phases. Phases B and C are sharing the job of carrying the return current of phase A, while they are also supplying current of their own timing. You could theoretically cut the neutral conductor (not something I would advise), and the phase conductors would carry the full round trip current on their own, given balanced current among all three phases. Worst case scenario of any imbalance, the neutral will carry a current equal to the largest current among the three phases. That is why you need only the one neutral conductor. Certain situations of extreme nonlinear loads may require a 200% sized neutral, given triplen harmonics that are multiples of 180Hz on harmonic intensive loads. These harmonics add up, rather than cancel out, on the neutral conductor. But for most loads, a 100% neutral is enough.

[@GH-oi2jf]

There is no reason to have more than one neutral, because the neutral should be at the same potential to ground (zero, ideally) for each phase.

[@ulymunoz1105]

I have three phase motor 230v3p can connect to transformer delta connection. L1-L2 & neutral is 120V neutral L3 235v

[@MikeHoltNEC]

Please post your question on the Code Forum at www.MikeHolt.com, under the Engineering Section.

[@smash72cutlass30]

I’m hooking up a large 3phase saw that was purchased overseas and ran at 200v 3phase. I’m installing a 45kva 3phase 480V primary delta to y secondary 208v is concidered within the 10% voltage allowance on he equipment. I always thought the 10% was for voltage problems from utility company provided your starting with the proper voltage. In this case I’m already higher to start. Has me concerned if there is flux in the incoming.

[@MikeHoltNEC]

What do you mean by 'flux in theincoming?' Send a link about this topic.

[@millerelex]

Lol, Spokane, sounds like cocaine.

[@MikeHoltNEC]

Thank you for the suggestion, I'm in Seattle right now and knew I was still calling it wrong.

[@carultch]

It is said as "Spo-KAN" with the stress on the end syllable. The silent E is a red herring, because the end sounds like can rather than cane.

[@millerelex]

@@carultch I graduated Shadle in 94

[@jjsh9849]

Do the experiment.

[@carultch]

Ryan Jackson did the experiment. kzbin.info/www/bejne/rYiVZaqsrcSbrMU

[@MsTommyknocker]

Wye = Star?

[@MikeHoltNEC]

This is not a term that is commonly use for 'Wye" but it's a perfectly good term to use for 'Wye.'

[@carultch]

If we had four-phase electricity, the topologies would be called Plus and Square.

[@MsTommyknocker]

@@carultch Excuse me, But What are you replying to?

[@Rico702Vegas]

TURBINE... not turban.

[@MikeHoltNEC]

Thank you! I didn't realize that I said it wrong, I'll work on doing a better job!