Rights. What up? Everybody? Welcome to another episode of Let's Ask Paul,
the podcast where you can ask me any question you want on the National
Electrical Code or electrical topics in general. Maybe you want to ask questions about
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was asked over on a TikTok a live stream that I did recently, and
they said, Paul, won't you explain a delta high leg when it comes
to the configuration of a delta high leg? And I said, well,
while I'm at it, why don't I just playing Delta high legs Delta transformers,
and then why not go on and explain a three phase why transformer as
well? Okay, and again this is a topic that some electricians, you
know, like dude, I just hook it up, right, I just
I just hook it up to the terminals. I don't get into the nuances
of why I'm going to get two a weight out of a one twenty two
forty vote delta high leg. How I'm going to get two eight votes vectorially,
they don't care about that, or they go, well, you know
what, I use a three phase why transformer, and maybe I'll explain why
one is an advantage over the other a little bit, I guess, since
we're here, and you might say, well, what do I do to
get two a eight and how do I get one twenty out of a why
configure a transformer? Okay, so we can kind of we'll kind of look
at all those little things today and maybe it'll help you out a little bit,
and if I confuse you, I'm sorry. Again. It's a podcast
platform, so sometimes it is easier to get confused. Okay, but let's
start off talking a little bit about three phase. So if you're familiar with
commercial electrical and you've been doing that for a while, and it's not to
say that you won't have single phase in it, but a lot of times
in the commercial industrial because of the motors, you're gonna have three phase,
and it's much more economical to have three phase to a building. And then
if you need single phase, you can just tap for example, the winding
between phase and phase B I'm excuse me, phase and phase C, let's
say, and then you tap it and then you can get single phase one
twenty two forty. But at the end of the day, it's it's just
more economical to bring three phase and bring down it's much harder to take a
single phase to a building. Let's say you're in a commercial building and you
need you have some loads that need to have single phase. It's it's I
mean that need three phase, but you only have single phase in the building.
It's much more costly to go from from single phase to three phase.
And the equipment that's necessary than it is to go from three phase down to
single phase. So again, for the same level of voltage, it's much
more cost effective. Now, another thing that I usually tell people just to
go look at it and see the difference in the amps when you're dealing with,
for example, motors single phase versus a three phase motors. So if
you go to four thirty two forty eight and four thirty dot two fifty and
you're looking at motors in the FLC the full load current, you're going to
notice for the same level of horsepower and voltage, your amps are going to
be less under three phase than it would be for single phase. Okay.
So economically, it's just makes more sense to do three phase and drop it
down to single wind necessary, okay, And that's what the utility people do
for generation. It's much more economical for them to do that as well.
Now, one of the things that people ask is the principles behind three phase.
Okay, whether it's a Y transformer or delta configure transformer, the principles
behind three phase is that it has three separate AC voltages and they're all offset
by one hundred and twenty degrees Okay, and by doing so again, all
of the voltages of a three phase are always at zero. Now you measure
phase to phase, you'll get a certain certain level. Okay, phase to
phase, phase phase, it's very consistent throughout each one of them. Okay,
it maintains that that consistency. So that's kind of the the one hundred
and twenty degrees from each other's the configuration of the phase or creates it that
way. Now, let's let's kind of talk about a delta. So that
delta looks like a triangle, each winding, each transformer could be made up
of three single phase transformers, just one winding connected end to end in a
series format in a closed loop scenario, and that creates your delta. And
there are, of course, there's applications for what's an open delta. Basically,
just one of the windings is removed. You have an open delta configuration.
But we're just going to talk delta rather than confused people. Maybe on
another episode, well we'll talk open deltas and stuff like that. But just
a normal delta triangular configuration. You have an A, B and a C,
and so it's separate windings from A to B B two C and A
two C. Okay, Now, typically you're here folks talk about B being
the high leg. Now, typically on the utility side, it's usually C
is a high leg, and then when it comes down into your meter,
it gets changed in it has to go in as B. But but at
the end of the day, we're just talking that high leg, that one
leg, wild leg, bastard leg, high leg. How do we get
that out of a delta transformer? Okay, so let's just talk in general
a delta transformer, not a high leg yet, just pure delta transformer.
So you'll have an A and B and a C, and again you'll have
a winding between each so terminal points B to A. You'll have a winding
which is two hundred and forty volts between A and B, and then you'll
have a A to C the windings between that, and if you were to
measure from A to C, then you're gonna get what two hundred forty volts.
And again, let's keep it simple. We're not talking four eight in
two seventy seven, which would be this kind of the same principle. Let's
keep it simple. A two forty volte delta to keep so that everybody stays
on track. Okay, the volta is changed, but the principles are the
same. Okay. So in this scenario, when we have a delta configuration,
there is no high leg. It's just a delta. Now, you
can have a corner grounded delta where you tap one of the corners right and
that makes a connection right, So you get a corner corner grounded delta.
But we'll talk about that in a different episode. To keep it, you
know, keep focus. We're just talking about a normal delta configuration. So
when I measure my measurements from B to A, I'm gonna get two forty
A two C two forty B two C two forty. So it means I
bring conductors off of those terminal points down to my panel. That's what I'm
gonna get. Okay, Readings Now, in order to be able to take
a delta transformer three phase and get single phase from it, then what we
have to do is we have to tap the center point of one of those
windings and typically not always, but typically it's done between the A and C,
and what we'll get is a midpoint tap. And so from A to
midpoint tap, and this is also you know, typically a transformer that can
do this, we'll have those taps built into it or have that configuration tap
points available. So between A and the midpoint, you're gonna get a hund
twenty volts because that's half of a winding, right, and of course if
you go to C to the midpoint, then you're going to get one hundred
and twenty volts as well, and half of the winding. Now, a
lot of people ask, so when would I do this? So in a
delta transformer is very common in buildings that have a lot of motor loads but
have very little lighting loads or very few loads that need one hundred and twenty
volts because you are going to be loading up that winding or that that that
phase. You're gonna be loading that up with your one hundred and twenty volts.
Okay, But if you have a lot of motors, you want to
take advantage of the to forty volt configuration. Okay. So typically the delta
transformer or you know, the delta when you have the mid tap is used
in configurations like this where you have a bunch of motors and limited one twenty
volt loads. Okay, Now when you do that now and you tap that
center point that winding between let's say the A and the C winding. Because
you're trying to achieve a one twenty two forty volt point, you then have
the BEE phase. Now, the B phase is vectorially where you do the
math, it is not only seeing a full two hundred forty volt winding between
let's say B and C, but it's also getting half of the winding between
C and the midpoint. So vectorially, that creates the voltage that gives us
the two to eight. Now, people say, now, how does that
actually work? Well, given that each winding produces sine use sotal voltage.
Okay, the voltage from the high leg to that neutral it's vectorially, and
if you measure it in a victorial triangle, it's vectorially the sum across one
entire winding. Okay, that entire two forty volte winding, and it's taking
half of basically one hundred and twenty volts of the other winding to get to
that midpoint. So and it's basically referred to as two forty volts through the
main winding and then negative one twenty volts through that half portion of the seed
to let's say midpoint of the other winding. Well, in order to determine
that mathematically and to develop that vectorial value, we take one hundred and twenty
volts, okay, and we multiply that by the square root of three.
Okay. So if you take your calculator and you do one hundred and twenty
volts, I got one with me times one point seventy three two, which
is square root of three. It's three phase. That gives me two hundred
and seven point eight. And again do it again just to make sure.
Yep, two O seven point eight four. We know that point eight rounds
up to two O eight. So that's how we get the two one hundred
and eight volts. Now, the reason for this is vectorially, it is
thirty degrees phase shift between the two voltages, about a thirty degrees shift in
phase, and so that's what ends up happening to it. Right. So
at the at the end of the day, you're thinking, okay, how
does that happen? Well, two hundred and forty volts, and you basically
phase shift it thirty degrees. That gets it down to about the two O
eight And of course you work it out using the formula one hundred twenty times
one point seventy three two, which is a square root of three. That's
how you get the two eight. But again it's it's a Victoria process.
And I don't want people to, you know, lose their mind in this
because you basically only need to understand the principles. Now, if you're an
electrician, it does this every day. You don't even give a damn about
that concept. Right, But in a delta high leg, you're gonna get
one hundred and twenty volts from the center tap of one side of one winding,
and you're gonna get two hundred and forty volts across any two of the
phases. And then you're gonna get approximately two o eight volts from the high
leg, which in our cases that b to the neutral center point or the
center point of the winding that's been tapped, right, And that's basically how
they're all configured that way. Hopefully you understand, you know, kind of
I've made that mental picture and how you do it. Now when it comes
to a Y type transformer, how do you get two o eight volts?
Again, they're one hundred and twenty. The phase ors or the ways that
configured is the phases are one hundred and twenty degrees out of phase and from
phase A to B, for example, it's going to be two o eight.
From B to C. Now we're gonna we're talking to WHY transformer,
it's going to be two o eight. But from any one of those phases
to the center tap point, okay, or the neutral point of this WHY
configuration, whereas all of these separate single phase transformers come together at one common
point in the center, okay. And then the other end of the of
those windings is which you connect your conductor to that ends up coming down to
your panels. For example. So if we were to take any one of
the A, B or C and can and test it from the neutral point
over to the B right, then you're gonna get one twenty. If I
do the neutral point to A, you're gonna get one twenty. If I
do neutral point to SEE, you're gonna get one twenty. People saying,
no, dubb, Paul, that's common sense. Now when would I use
a Y panel over a delta panel. Well, a lot of office buildings
that have the majority of their loads are one twenty vote loads or one twenty
vote lighting. Then you need more capacity on that transformer to handle the one
twenty vote loads, Whereas, remember on the delta you have a center tap,
so you have very limited windings, so it's limited capacity. Whereas in
a why if you know that building is going to have a lot of one
twenty vote loads and very few motor loads, very minimum motor loads, even
though you could have two to eight, but very minimum, then at the
end of the day, you're gonna want to go with a y transformer just
makes more sense for the loads. But if you have a building, let's
say that that has very limited maybe the lighting and very few receptacles can remember
receptacles are not required in a commercial building. The engineer designs where they go.
So if you have more lighting, but ultimately you have larger motors or
more to forty volt loads, then you want to go with a delta.
Whereas you're only contributing one of the windings for those one twenty vote loads or
two forty volt single phase loads, and you need more capacity in the three
phase configuration for the delta, then that's what you're going to go with.
So again you get to make your choices. A lot of people will come
in and be able delta primary and then it chains over to a why maybe
you have delta configuration coming to the building where it's just a B and C,
and now it's going to derive a Y secondary because we want to get
that two to eight, one twenty and that's the loads that we're going to
be using that type of thing. Okay, so it depends on the configuration
of your transformer. But but hopefully they answered the question. I'm sure it's
not going to answer it deep enough for those people out there that are the
haters. And that's fine because usually the people that are haters don't know how
to do their own videos and wouldn't know how to educate anybody anyway. So
that if you've got all this amazing knowledge, then why aren't you sharing it
with people? Okay, I'm just saying some of us out there at least
trying to share some knowledge with folks. And again, it's a podcast,
so I did my best at trying to explain the differences or where you might
see one over the other and that type of thing. All right, Okay,
well that's it, folks. That's all I've got for today's episode.
Hopefully that answered a little bit of question about the why versus Delta. Obviously
we could go deeper talk about open Delta's cornerground at Delta's zigzag configuration transformers.
Yeah, we could go in all that, but do we really need to
on this episode? I think not. All right, folks, appreciate you.
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Tell next time, folks, stay safe, God bless boo ookey boo
boo boo, donkey bo