Transformers - Understanding Delta/Wye Connections, NEC 2014 - [12.3], (12min:11sec)

all right let's go to what's the primary wiring system today in configuration which is a Wye connected transformers why connect the transfers have one lead from each of the windings connected to a common point the lead from each winding is connected to the line conductors so we're not worried about the Delta primary it's not an issue let's talk about the Delta Wye connected let's focus on the white connection here the voltage of this winding here is going to be 120 and then 120 and 120 and see what you taught us earlier that means that the number of windings on the primary on this primary compared to the windings on the secondary is there's four times more windings on the primary than there is in a secondary so this this transformer ratio turns ratio is four to one not that it's a big deal but just so you understand how that numbers work out now you bring here's the transformer three different physical transformers you connect them all together here this one spot then you run one wire over on the load second wire over third wire over and then the centerpoint and people say will you derive a neutral new neutral you're not deriving anything that just happens to be a point you're connecting to and that's 120 now let's talk about a Wye configuration what does the advantages of a Wye system well the advantage to a Wye system is that if you have a lot of 120 volt loads you can distribute those loads over three different windings where if you go back to the Delta Delta configuration look what the problem is here you only have one transformer that you can connect 120 volt loads on here which means you can't have this as a pad mount of transferrin you'd have to have three physical different size transformers you'd have two smaller transformers and then one larger transformer because of all the 120 volt loads being restricted on to that one winding but the advantage that a delta is higher voltage not really the best system you want to have you have a bunch of 120 volt loads but when you go into a Wye system well yeah you know the voltage is a little lower which means what if you were having a bunch of line the line loads higher current but if you have a whole bunch of lighting loads you can distribute the loads over and now you can get what a built-in transformer that's already constructed as a pad mounted transfer is a lot more convenient than screwing around with a bunch of three separate different transformers so advantages of a Y system is you get lined to neutral loads and you can distribute those loads and you still get line the line loads full it's a little lower here's another way looking at it oh I was looking at the primary line way that looks like Delta you know that is that is a delta configuration so I'm not worried about that I'm on the Y we probably need to describe this as Delta yeah but I rather have this word Delta here and then Y configuration here so I can see that look quicker okay so now let's look at here we get this winding is connected x0 connects to X Oh connects to X oh and then this is x1 x2 x3 line the line voltage is 208 and line the neutral volt is 120 let me tell you a story about this type of graphic here I did a seminar for Grand Coulee Dam I did a few of those up at the Spokane I think north of Spokane Washington Grand Coulee kind of interesting area up there and I get up there and I'm learning all about I went into the penstock the penstock is where the water comes down and goes all the way down and it goes and it comes around and it spins around and it goes to a turbine now it's only like about a six foot diameter where it actually gets to the turbine so I'm now physically in the penstock and it's very cold because you're in the bottom of the dam the temperatures in the bottom the water's probably in the low 40s and so the concrete over the generations of time it's gotten very cold so I'm freezing the penstock and I'm thinking to myself man I hope somebody doesn't press that button you know what I mean because I don't be Chum coming out the other end there so I'm in there and I'm seeing how this water comes in it looking at the turbine I'm like man that is so cool it's a little tiny thing I can't believe that and it's turning ok Eric is it turning magnets or is it turning the winding I think it's can't remember which attorney if I don't there are no permanent magnets on a generator like that it's a nice machine but determining is it it's what effectively it's turning a magnet because it's a synchronous machine okay so it's it's turning the magnetic field okay then you have the conductors on the outside so you have the magnetic field that's being moving through the conductors which is inducing voltage and it produces thirteen thousand eight volts okay 13 8 well maybe it's 14 for now whatever it is but at that time it was thirteen eight that was Grand Coulee there right so now I go outside the dam and there's this huge green thing and I run up to it I don't know what any of this stuff is working I mean I'm here in a power plant I mean this is one of you know this is a famous power prime Grand Coulee Dam and I walk around and look at that and I see a sign it says phase a my name I'm stunned because I'm used to seeing a transformer right I mean it's a transformer and I'm thinking it is a transformer but this is phase a and I look up and I realize what in this three of them and I look up and guess what there's two staffs coming out of line side and I'm looking at them so now I'm looking at the two staffs of each of those and I see there's a bar from one bus on each face that connects to each one and if you have one bar on each one connected together then there was three wires one from each transformer going up I looked at the guy I'm like - are you kind of why secondary he goes yeah and I'm like wow no matter how big it is we still had the fundamentals it was a wise secondary five hundred thousand volts and each of those transformer over five hundred thousand VA 500 MBA 500 500 MBA giving you five hundred thousand volts face to face just simple basic transformer it was a delta coming out at thirteen eight going up to five hundred thousand then they transmit five hundred thousand do some magnetic coupling somewhere else at 138 thousand then they do some more magnetic coupling down to maybe sixty nine thousand magnetic coupling maybe somewhere like around 34,000 magnetic coupling some around 14,000 magnetic coupling some around 277 482 more magnetic coupling down to a 120 208 so the electrons from the power plant actually never even left the our plan they just went up to the primary and they went I mean what for the primary winding of the primary one right back down the line so it's a magnetic coupling that we're getting done here so look back at this graphic yo Eric you got to say something yeah you've brought up a brilliant principle about this this whole system and that is if you look at this transformer on the graphic you'll see that there's air between the primary and the secondary effectively it's totally totally isolated so if there's a fault on the five hundred thousand volt system it doesn't go through the air to the hundred and thirty-eight kV system so it's there's also a big safety factor here safety issues separate coupling by the way if you when you when you have this magnetic coupling that's called a separately derived system get it coil a twelve gauge wire and put another coil a 12 gauge wire on top of that put a light bulb on the second coil get a clear light bulb okay and then take the first coil of 12 gauge wire connect it to a cord set or the extension cord whatever you want say a power supply cord and plug it in a receptacle but you only have like about 45 seconds when you plug it in it'll draw about 40 amperes and then while it's drawn 40 amperes on this primary that you plugged in the coil of wire on top is going to be carrying very very little current but the light bulb would light up put an iron bar between the primary second and we talked about this in our Theory course and how about--how transfers work out so that is called a separately derived system all right let's get back here so here is your primary which is a Delta primary because it's all connected in series here's your secondary they're all connected to one point that's a Wye secondary another way to look at it here is this is all connected in series is a Delta will identify this is as a Delta configuration and then we'll identify this as they're all coming to the one point here and then line 1 line 2 line 3 this is going to be a wide configuration primary secondary line voltage on a Wye system that's the both this measure in the primary side is the primary voltage and the Volt is measured on the secondary side is pretty straightforward it's going to be the secondary voltage we talked about the primary line voltage is 480 because we're having a connected Delta now I don't know this to be the case and I don't want to spend like too much in here guys my experience is generally it's Delta Delta Delta Y there's no reason why I can't be why why why Delta okay but there are some both its considerations so I'm not going to get into why deltas unless we get maybe at the end of the DVD we can kind of review that and discuss them so we're talking Delta Delta Delta Y for right now so here's about Delta primary here's my Y secondary what's my voltage as well from line the line take a voltmeter is 208 and from line any one line the neutral is going to be 120 Stephen just a point to notice that if it is a wide connected system your line to neutral times square root of three will give you your line to line although it's that so hold on 20 well that was a just let me that let me slowly die sorry line to neutral voltage okay honey yeah times one point seven three two gives you 208 okay to seventy-seven times one point seven three two gives you 480 also you know those are wide connected systems when you have that square root of three okay so if you're saying the both the between line and neutral and line the line if line the line is one point seven three times more than the one twenty then Y configuration and not that we were even care right but but if somebody asks you question it you got to let you got a 120 208 what kind of transfer winding it is well it has to be a wife it's 120 240 it's a delta or it would be line that I'm not even afraid to go here but I'm gonna give it a shot here Eric okay this real quick what she said earlier about the the rulers the paper the drawing also holds true here if you lay out that Y with 12 inches 12 inches and 12 inches not hold on you're saying if I had show this and I should show this is 120 volts here and if I show this is 120 volts here and if we say the 120 volts were just simply measurements 12 inches and 12 inches that this distance is this a hypotenuse no I still have that snare a right triangle we still got the theorem yeah and so if you yeah if you were actually to draw a dotted line from the neutral point up you'd have two right triangles now would that be a squared plus B squared no now not in this particular case but but just if we just go back and say that a is 12 inches and B is 12 inches this is the point weak point is 20 point 8 inches okay so don't worry just it just that's how it's gonna work electrically as it works mathematic it's all Matt it's all math you're saying yeah okay again you know I realize that some of the stuff we're talking about is it isn't necessary but I believe it's a good thing to have the basis in understand theory and fundamentals because that gives you the tools I think that just to help you understand and communicate with people all right I'm done with Delta Delta I'm done with Delta Y we explain why a Delta Delta gets used not so much today Y Delta Y gets used most common because you can you can configure those and compartments already pre-built and configured

Channel: MikeHoltNEC

Views: 181,509

Keywords:

Id: a8LjxEtd8N8

Length: 12min 10sec (730 seconds)

Published: Mon Apr 14 2014