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0:00
what is going on my friends this is Dustin with electrician you and today we are gonna talk about transformers
0:24
[Music] so why do we even use transformers what are they well transformers really are are useful for a number of reasons but the most common usage is that you need to take a high voltage and change it into a lower voltage this can be for a specific piece of equipment so say you have a building that's 480 volts the whole service everything in the building has to 77 lighting and 480 you know
0:49
appliances but you have something that is a 208 rated motor or a piece of equipment that shows up and you're like [ __ ] we just paid a hundred thousand dollars for this piece of equipment and it doesn't match the voltage well ahead of time somebody's gonna know that and have been like all right we'll just take this transformer will transform the voltage we'll get this voltage at whatever this equipment is rated at so you just drop a transformer in place and you say okay well
1:17
I'm gonna take that 480 I'm gonna change it into 208 through this device and feed this thing 208 that's essentially why they're used most of the time it can be inverse I mean you could take a whole building that's 208 and you have no need for anything 480 but then you get this big-ass piece of equipment that's rated to around 480 well the only way to do that I mean you don't have 480 run to your building so you just take one of those 208 panels come off of a breaker and you
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feed this transformer in 208 and you can get 480 out of it what you're doing when you're changing the voltage you're also changing the amperage so if you look at Ohm's law volts times amps equals watts well that means to get watts or to get VA you can change the relationship between the V and the a so if you raise your voltage you're gonna lower your amperage to get the same number on the other side of that equation or inversely you can lower your voltage raise your amperage to
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get that same number so a transformer is kind of a constant power device or a constant wattage device not really wattage and get a whole different video about why transformers are rated in VA instead of watts it's kind of the same thing but really not but anyways it the whole idea is that you can get a constant amount of power through this device by feeding a different voltage through and getting a
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different voltage out because when you do that each one of those circuits is going to draw a different amount of current based off of the resistance or the reactance of the windings inside of there so a transformer typically if we say like a 480 volt Delta to a 240 volt Delta transformer on one side you're gonna have a whole crapload of windings and that's your 480 volt primary side and then on your secondary side you're gonna have a lot less whining you're gonna have thicker
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wire because what's happening is you're feeding a high voltage at a low current through the primary but since the wattage has to stay the same on the secondary side automatically what happens you've less of windings around the coil and you have thicker wire so you're gonna end up having a different resistance or reactance because of that which is going to produce a different voltage add a different amperage and it's going to be inverse so if we have a transformer that's
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got a two-to-one turns ratio means that on the primary side we've got twice as many turns as we do on the secondary side that means if we feed any voltage in we're gonna get half the voltage out just because of the number of turns so what that also means since this thing keeps the wattage the same that means that automatically it's going to figure out the current that can run through it and it's gonna change so if we're feeding a 480 volt circuit into the primary that draws a
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hundred amps well four hundred four hundred and eighty times 100 equals forty eight thousand VA so we're feeding that much power into this thing well coming out of it because we have less turns around the coil we're gonna get out 240 volts but in doing so we're gonna raise the amperage of that circuit but it's still the same forty-eight thousand watts or forty eight thousand VA through
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the device so what that means is that we have 480 coming in 240 coming out hundred amps coming in two hundred amps going out 480 volts times 100 amps equals 48 thousand two hundred and forty times two hundred amps equals 48 thousand so these devices are always just trying to balance and keep the same amount of power but it's really just based off of how many windings how many times they've won the primary versus the secondary inside of this thing transformers are also really
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helpful in isolating the primary side from the secondary side so if you have some sort of fault or something happen on the primary side it doesn't jump across to the secondary side because they're they're completely isolated you have a one winding and another winding that don't touch a good example of this would be an isolation transformer where we have the same voltage in and out so we
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feed 120 volts in we get 120 volts out so if the 120 volt primary is really dirty power you have 120 volts second area which is really clean power and you kind of have a fresh start really because you're isolating the two circuits the typical dry type transformers that you're gonna see out on a job site are going to be a delta primary and a whi secondary so you have Delta in and primary and
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you have secondary out that's why configuration there may be times where you have something that is a listed back feed transformer a back feed transformer you can actually flip those and you can feed Y in and get Delta out but I'm not gonna go into all of the different types there's zigzag transformers and there's Delta Delta and there's y Delta Delta y YY there's a lot of different
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kinds of transformers that I can make several more videos about but just know that there is different wiring configurations that they wire the coils in one side than they do on the second side and it allows for some unique things to happen in doing that [Music] all right so without going too crazy into depth I just wanted to illustrate a little bit what the difference between Delta and Y is
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so say we've got this transformer out there right and we keep saying that we've got Delta primary and that we've got Y secondary really what that means is incoming we've got Delta outgoing we've got Y so what Delta and Y means is that there's three coils inside of a transformer so say we've got a coil one you've got coil - we've got coil three this is our secondary so we'll just write
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secondary that means that these coils together are wired a specific way so that they get a certain amount of voltage out of them so that they have a certain relationship and that we can provide a neutral when we get power out of it to our load so if you look this coil would be representative of this one X - L would be a representative of that one x3 would be this one so this is our low voltage output this is our Y so what they do is first obvious thing is every single one of the
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coils is tapped together right like at one end of every coil they're all combined so what we could do is just take like this one this one and this one boom so that is our EXO that is this point the center point where all three coils come together well then each one of them has another end of the coil that's not hooked up to anything well that's what we actually hook up our three phase load to you inside of a panel so you know we'd have conductors that go out from this thing and
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hook into a panel and do a breaker somewhere and that's the secondary side and that's how you're getting a neutral is you're just taking the center point just like they do up in the streets you know we got the transformers are up on pole the point where all three of them come together is where we put our grounded conductor and actually ground that part of the transformer so now let's talk about the primary side of this same exact device so transformers on the inside they actually
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have one coil on the inside and another coil that goes around them on the outside so the primary is always the one on the outside the primary is gonna have twice as many windings as the secondary will and the primary is going to be a smaller wire than the secondary because when you're stepping down your voltage you're going to be increasing your amperage coming out so the Delta is wire a little
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bit different you still have three points one two three but instead of taking all of the coils and putting them together in the center they're taking each coil and going end-to-end with them and then we just tap off of each one of these points all right so we've got h1 to h2 well this is our h1 and we have to connect that to h2 and then we take h2 and go to H 3 H 2 to H 3 and then from H 3 we
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go back to H 1 so it's kind of getting sloppy sorry but at each one of these points then we have a jumper that comes out and these are the terminals that you would put your high voltage on so these would be--you're your in in in and these would be out out out probably should it just represent a temp like I drew them right you got X 1 X 2 X 3 and we've got X o up there we've got H 1 H 2 and H 3 so that's how they're wound really there they're wounded twice as much on the
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primary half as much on the secondary that's how you would get you know if it is the turret two to one turns ratio sometimes transformers that like 4 to 1 turns ratios or whatever a lot of there's so many different kinds of Transformers that have so many different reasons to them but that's just to show you it's the same coil of wire you know there's one on the inside and one on the outside
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they put them inside of each other but depending on how you wire them if you wire 3 ends together or if you wire end to end in series you're gonna get a different amount of voltage different ratio of amperage there's a whole whole last video I can do on that what's the difference I'll put on a delta versus output on a why why you would have 240 volts coming out versus 208 coming out but I'll get into that later I just wanted to show you guys it's kind of the relationship to the
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windings and how all of that works inside [Music] now let's open up the guts of a transformer and see what it looks like there's a couple of things to take note of inside of a transformer now this is a really old transformer you've got all your taps here you can tell on a transformer that the Y secondary is this point usually the actual strap that everything hooks up to is thicker than all
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of the rest of the taps are but also you've got these bands that all three come off to the same point and the only place on a transformer where that's going to be the case is at the neutral so that's something just to kind of take note of another thing is notice that you've got these thin conductors and you've got these thick conductors there's another one thin thick thin thick and then
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all the neutrals are thick everything that's on the secondary side since the secondary is the low voltage in our case is going to need to be thicker because the secondary is less voltage but more amperage so that thicker conductor can handle more amperage the thin conductor is on the primary side so usually when a coils wrapped the high-voltage primary is going to be a thin conductor so you
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can tell that this is like number 10 you know th H n without any insulation on it whereas the inside is your secondary and that is that really really thick conductor so you can tell what your secondary versus your primary is just you know if none of these are labeled like in this transformer not a single one of these is labeled so it's like well [ __ ] how do I know where my primary wires go or how do I know where my secondary go you could sit and tone all of that out or you could
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just look and be like okay well this is a tiny little wire that that goes to this coil so I know that this is a primary this is thick so that's gonna be a secondary that's a primary that's a secondary that's a primary that's a secondary the order the phasing you know from a phase B phase C phase none of that really matters essentially as long as you are in the same coil for everything so
13:57
you know if you have an a phase primary this is going to be your a phase secondary because they both go down into the same place now another thing to look at these are the taps for the transformer so you notice every one of these is tapped on the left side second post down same thing here and same thing here so each one of these represents a different a different post or different voltage if
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you have to make minor adjustments so if you need 208 but you're getting like 273 or something like that you can actually move these around this is changing the primary windings so instead of you being all the way at the highest potential you can lower it slightly and you can tell each of these these bands there's like individual bands it's all one solid conductor but what they did is they they
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wrapped that conductor all the way around this coil and at a certain point they twist it out a little bit and then they just kept going and then they twist it out a little bit twisted out a little bit and they kept doing that so wherever you tap this it's going to change the difference in potential just slightly so it's going to bring it from a higher to a lower potential and that's how you can make small little adjustments in your voltage when you have a higher or lower secondary
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voltage coming out now another thing to take note of is the neutral so a lot of people say that you derive a neutral when you're talking about a delta to Weiss transformer so you're bringing Delta in you're getting a Y out well this is the common point or the center point for that Y configuration so you see this conductor is going down it's wrapping the inside of that coil and it's coming back out to this common point same thing with the next winding you've got a
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phase conductor that you hook up here it goes down wraps are on that coil and it comes back to the same exact point same thing for the third one so all three of your secondary windings are coming back to a common point and that is where we get our neutral from that's where we hook up neutral right here that goes out to our load and then you'll notice that there is a bonding jumper that goes all the way down to ground so in this transformer it's really really important in all
16:18
transformers to bond this is called your EXO terminal this is where your neutral and your ground need to be bonded together so you bond to EXO that's all your neutrals are gonna hook your load neutral to it you're gonna make sure that you run a bonding jumper all the way down to the can itself you know the metal of this enclosure and then any other grounds that come in or out of the transformer also have to bond to that plus if you have building steel that you're trying to bond to
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you're gonna have a jumper that goes out and then goes up somewhere to building steel and you might even have a ground rod that's coming out same thing that ground rod is going to come so all of those things all those grounds equipment grounds grounding electrodes building steel and neutral all of them need to be bonded together in the same exact place at the centre point of that secondary and that is always on the EXO terminal most of the Transformers you're going to come across
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newer ones at least are gonna say like h1 h2 h3 X 1 X 2 X 3 and X 0 they're going to label what each thing is but it's just kind of cool that I have this one that is really really old and shows how all of its wound [Music] now let's talk a little bit about sizing transformers so there's a pretty easy calculation that we need to go by to size one of them it's for single-phase at least it's just
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voltage times amperage equals your VA that's what the transformer is going to be rated in that's the power rating the three-phase it's the same thing I just wrote these threes so that you knew we were talking about three-phase there's nothing to do with the calculation but you're going to take your voltage times your amperage times the square root of 3 which is 1.73 - just a good number to
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memorize anytime you're dealing with three-phase loads you need to use this talk an efficiency horsepower anything like that you always need to use a square root of 3 or 1.73 - that'll give you your three-phase VA for the transformer so let's start out with single things we're going to use the secondary so reason I use the secondary is the load that you're trying to feed is coming out of
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the secondary side of that transformer so you need to know what the the voltage of that equipment is and what the amperage is and then you can figure out what the primary side is based off of that so we've got voltage and amperage of our load let's say that we have a 208 volt single phase load that is a 200 amp piece of equipment so we know we have 208 for our voltage we've got 200 amps so what is
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the VA so we've got 208 times 200 which is going to equal 40 1,600 VA so transformers are always rated in kV a which just means thousands of VA so it's really gonna be a 41.6 kVA transformer now you're gonna always upsize like they only make just a 41.6 v8 right here kVA transformer so they do make a 45 though so you can round up to 45 KVA and have that be your the size of your transformer that's pretty easy right so you know 45 kV a is gonna handle the load coming out of
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the secondary and then coming out of the primary you would just may have to make sure that you're running for a 480 to it and then your breaker size conductor size and everything's gonna be based off of whatever that's going to draw so that's pretty easy to figure that out as well now let's do three phase so three phase is the same deal say that we've got 208 three-phase instead of 208 single-phase like we had in this one 208 we'll say that we still have a 200 amp load
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times 1.73 - which is the square root of 3 and that's going to give us our VA and the total is 72 thousand 51 which would be our VA so then our que VA would be 72 kPa again you're gonna want to round up so there's a seventy-five kVA transformer then that's the one that you're gonna want to use so pretty easy right like it's not that difficult to figure out what the transformer size should be
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what the load is you you just need to know it's Ohm's law it's you know your your e times I equals P it's your power same thing over here e times five times square root of 3 equals power now when I said that a 45k VA would be the next size up for a single phase transformer that's technically not correct so the 45k VA is a three-phase transformer sighs so within single-phase usually you're going
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to be working with like 15 kV a 25 kV a 37 half 50 75 and a hundred those are the typical sizes they go above that three-phase you're usually working with like the fifteen twenty five forty five seventy five hundred and twelve point five but those are the typical sizes within three-phase so just understand when you're sizing the transformer and you get your calculation to go look up single transformer sizes or three-phase transformer sizes or damn chart to remind you what
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all of them are but if you order a 45 kV a single for his transformer it's gonna show up three-phase so understand what you're getting into before you order one [Music] some really important things to consider when working with transformers is make sure that you look in the transformer to see if it comes with lugs or not a lot of transformers out there don't come with lugs they just come with holes that you can bolt your own lugs on some of them do come with lugs another thing to
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pay attention to is the actual positioning of the lugs so that way you're not screwing yourself and then out in the field you don't have enough wire because you didn't plan for how those conductors were going to come in another important thing to do because this is a vibrating piece of equipment is to make sure that you you tighten everything to the torque specs of the equipment this is
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something important to do on all big equipment on all lugs at services it's something that I do all the time because our code here we actually have to mark our torque settings so an inspector can look at them but with especially with vibrating equipment it's really important to torque all of your lugs down get a torque wrench out look at what the specs of the equipment call out for and and torque everything to spec another important thing to think about is once you've hooked up a
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transformer and you've turned everything on check your voltage and make sure that you have the right voltage for the piece of equipment that you're going to be running out to you if it calls for 208 and you have like 222 for your voltage but it's still connected in Y configuration you can go into the primary taps where it'll say like 500 volts 460 volts you know like 340 volts you can actually change the taps on the primary to get a different voltage out if you need to kind
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of bump your voltage up a little bit or bump your voltage down a little bit there's a lot of equipment out there that cannot be hooked up you know there's certain tolerances of voltages so if the voltage you're getting is plus or minus 5% or plus or minus 10% you may ruin that piece of equipment or the equipment down the line that you're feeding so make sure that you check your voltage check the equipment to see if you're within your values and if there's any question
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about it you can always call the manufacturer of the equipment and make sure and say this is the voltage I'm getting out do you do I need to change these taps or am I good within the warranty they'll be able to tell you that but just know that you can change the taps on these transformers on the primary side another thing to pay attention to you is vibration so taking pads and putting them underneath the transformer when a metal transformer is sitting on concrete
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it's gonna vibrate it's gonna be loud so putting transformer pads underneath your transformers even if it's something that you're hanging from a ceiling on a strut rack put transformer or put a put rubber pads underneath the transformer that way it's not vibrating metal on metal it'll just make it a little bit quieter the last thing to note when ordering a transformer is pay attention
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to the actual physical size of the transformer not every 75 kVA transformer is going to be the exact same size some of them are taller some of them are wider you know make sure that you pay attention to the size measure if you're trying to replace a transformer especially measure the dimensions of everything take a picture of the nameplate of that transformer get as much information as you can so
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that you can match it exactly for what was there alright so that's pretty much it I could have done like 13 videos in 20 different directions covering a lot of this stuff way more in-depth there's so much to know with transformers but I just wanted to get like give you guys kind of a basic flow understanding how to size them how to change them out things to think about how to know what is on the nameplate somehow to just understand all of it so let me know if you guys have any
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other questions appreciate your attention thank you so much I'll see you the next one [Music]
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