What Up? What Up? What Up? Everybody? Welcome to another episode
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So part of this ongoing series that we've had that was based on a
question that came in through the Let's Ask Paul that asked me to do all
these things series parallels Olms law combination, and I just couldn't do them all
in one, so I decided to break these up. So it's starting it
like episode one seventy one, and it goes through one seventy one, one
seventy two, one seventy three, one seventy four, So there's quite a
few of those episodes. Hopefully they'll be titled right so it's not confusing,
but make sure you listen to them because I go over series and parallels,
I go over ohms law, I go over combination series and parallels and kind
of try to paint you a mental picture because again it's podcasts are difficult,
and but that's one of the reasons why I love podcasting is because it forces
me to And some people don't understand this. They say, Paul, just
get to the point. You're long winded, dude. What I'm trying to
do is convey a mental picture, and it's just a method that I use.
So my podcasts and my videos are not for everybody. If I if
I've already, if you've watched my stuff for five minutes or two minutes and
you're like, dude, this guy just rambles on, then you might as
well just not follow me, click off of me, go to somebody else,
because that's my teaching, is approach, and I'm not changing for anybody.
I've been doing this for thirty four years, so you love it or
hate it, it is what it is. So you can decide whether you
want to follow them here or not. That's up to you. I don't
care one way or the other. Okay, So let's look at some things
here. So I have some question. This episode today is not going to
be a real long one. This one is focusing on how to find the
horsepower. So if you're given a certain variable when it comes to single phase
or even three phase, and you need to find out what the horsepower is
if you don't happen to know, now, if you're on an exam,
they're going to be giving you and a certain kind of a question. And
there's certain things you need to know to find the horsepower. Right. I
need to know what the voltage is. I need to know what the efficiency
is of the motor. I need to know what the power factor is of
the motor. All these things I have to have in order to be able
to calculate the horsepower. Right. So that's one of those things that we
have to remember that wattage wise, one horsepower is seven hundred and forty six
watts. So when we're trying to think about what happens with the efficiency scenario,
then we have to make sure that we follow these formulas. Now,
I'm not expecting you to remember these formulas. But it is something that you
can pause and jot down in your codebook if you're preparing for an exam.
If they let you write in your codebook, write them in there. If
they do not, and I can't tell you that your state does, don't
ask me. Go to the whatever the testing agency is for your state.
If it's PSI, they'll have a bulletin that'll tell you what you can and
can't do in your codebook. If it's ICC, they'll have a guide to
tell you what you can and what you can't do. That's not my responsibility,
that's your responsibility. Okay, so let's just make sure we're all square
on that. All right, Let's get into the first one that we might
encounter. And then this is the first time that I'm going to talk about
DC current direct current, because typically on an exam, the only time that
I really ever see them talk about DC current is when they're trying to find
the horsepower of a motor. So that's why in previous episodes I really didn't
get into direct current. But here I am, and it's not a more
overly confusing calculation. The only real difference here is that there's really, typically,
uh, there's no power factor involved. There's the amperage, there's efficiency,
there's the voltage, YadA, YadA, but there's really no efficiency,
I mean, excuse me, there is no power factor involved in that.
Okay. So that's really the key difference. Okay, So let's look at
a first equation. So the formula that you're going to use to determine power
factor for a direct current is again remember we're going to talk about it in
terms of numerator and denominator, So kind of like a one quarter or one
over four. The top is a numerator, the bottom is the denominator.
That way I can kind of pint that mental picture for you about the formula.
So the numerator portion here of this formula, the top part would be
volts times amps times efficiency divided by the denominator version, which is seven forty
six, which is rounded up. That's what the wattage is for a one
horsepower motor. Okay. So that's your baseline. So if I gave you
a question and I'm trying to determine what the horse power is, and I
gave you the question, then I would say, okay, I have a
twelve volt motor. It draws a current of eight point zero nine ampiers and
it has an efficiency rating of ninety six percent, so pretty damn efficient,
okay. And again this being probably so because it's DC. It says,
determine the horsepower. Okay. So if you think of that that formula the
numerator volts times amps times efficiency divided by seven forty six, then we can
just plug in the numbers. So I got a calculator here, so it's
E, which is eve of the voltage is twelve times I which is the
amps and current okay, which is in this case is eight point zero nine,
so twelve times eight point zero nine. So we're gonna have twelve times
eight point zero nine. And then the efficiency was ninety six. And as
you've heard me in other podcasts, always take that percentage and work it down
to a decimal. So start at the right of the six and move two
spaces to the left. That makes it point ninety six, so times point
nine six. Okay. So again, so you all follow along, it's
twelve times eight point zero nine times point nine six, and that comes to
ninety three point one nine. Okay. Now at that point you're you got
the denominator at the bottom, which is the seven forty six numerator at the
top. So I'm just gonna take that ninety three point one nine ninety three
point one nine, and I'm going to divide that in seven forty six,
and that's gonna give me a point one two four nine, okay, which
equates to one eighth of a horse power. And if you see that one
two four nine, it kind of equates to that because if I were to
take that one and divide it into eight, it's one point two five,
right, So that point one two four nine is again the nine at the
end. If you're rounding it down rounding it up, that equates to one
point two five. So that is one eighth of a horse power, okay.
Or basically, you could take the one horse power one point zero divided
by point one two four nine and it gives you eight, and that's how
you know it's one eighth horse power. Okay. So anyway, one eighth
horse power based on now, so that's the DC version, okay. So
now let's move into single phase. So now single phase, the only thing
that changes here, okay, is that you're throwing in a power factor.
So if we have the same type of equation here we're gonna change the values
a little bit here. So we have a single phase one hundred and fifteen
volt ac motor with an efficiency rating of ninety two percent. Of course you
all know that I'm gonna convert that to point ninety two just right off the
bat, and a power factor of eighty percent. Also, I'm gonna convert
that start the right of the zero, move two space to the left point
eight zero, converting that into decimals. So you always want to work in
decimals, okay. So then it says, determine the horse power if the
amp load is four point four amps. So we're given the amps, we're
given the efficiency, we're given the power factor, and we're given the voltage.
Dude, this is easy pasy, right, So we simply work this
equation. So what's the equation horsepower equals E. That's the vaults times I,
which is the amps times efficiency times PF the power factor divided by what
seven forty six, which is the rounded up watts for one horse power.
Okay, so let's work the math, so it'd be one fifteen. Again,
always use what they give you in the equation. Do not say,
well, in the circuit one twenty. Don't we use one twenty, No,
you use what they give you, okay. And also, by the
way, if you go look at the tables in four thirty, two eight,
two forty nine, all that, you're going to notice that the motors
are in one fifteen, two thirty things like that. Okay, So just
use what they give you. Don't make this overly complicated, So just do
one fifteen. We're gonna work the numerator part, the top part first,
so it's gonna be one fifteen times four point four because that was the current
times point ninety two, which was the efficiency rating, times point eight zero,
which was the power factor, and that's gonna give me three hundred and
seventy two point four one six. And since we already have that in our
calculator now, we're just going to divide that by the seven forty six and
that gives us zero point four two. Okay. So when you look at
how this is rounding, you know that half of a horse power would be
point five, right, so this is point four nine nine two. Then
what we would do that this would you know, you know that this is
going to be a half horse power motor. Okay, makes sense. So
it's a half horsepower motor based on the power factor based on the efficiency rating,
which is, by the way, typically how we come up with the
name plate values. Okay, when it comes to trying to find out what
the currents and all are, and we did that previously in another episode,
Hey, how to find the amps? We did all that just so you
know. Okay, So but here we're searching for the horsepower and in this
case it was a half horsepower. Next, let's do this with three phase.
And again not to get people really like, oh god, here we
go three phase, folks, it's exactly the same. The only difference is
because it's three phase, we got to equate the square root of three.
Now, you can use one point seven three to two or you can use
one point seven three. They're both going to be close enough. It's not
going to make a difference in your equation. So if you want to keep
it simple, then you can do one point seventy three. But that's totally
up to you. Now I will tell you that because the Uglies book likes
to use one point seventy three and not the one point seventy three to two.
Okay, So either way, it's going to get you to the same
result. Okay, So we'll just use the full amount this time. Make
people happy, all right, So what is this equation? So now we
have a three phase load motor and we need to find the horsepower. So
it's four hundred and sixty volt motor, okay, and it draws a current
of fifty two amp years okay. Is the motor has an efficiency rating of
ninety four percent. Eh, it's pretty low, but okay, and has
a power factor of eighty percent. What is the horsepower? Okay? This
is the kind of questions that you will be given on an exam if they
want you to tell you what the horsepower is. Again from don't confuse this
for sizing motors and things that you're going to use the FLC and everything in
four. This is only for like a general knowledge type question where it's trying
to ask you what the horsepower is? Okay, So what are all the
givens here? So the formula that you're gonna use is exactly the same as
we did with the single phase. The only difference is we're going to add
on the one point seventy three to two at the end, so it'd be
E, which is a voltage times I, which is the amphior times efficiency.
In this case, the efficiency was ninety four percent, so again it's
point ninety four. Uh, the power factor was eighty percent. You remember,
we're gonna convert that the decimal, So it's point eight zero. That's
the power factor multiplied by one point seventy three to two. And then we're
gonna take that, which is the numerator, that's the top summation, and
we're going to divide that by the denominator, which again is seven four six,
which the rounded version of the wattage for one horse power motor. Okay.
Remember seven forty six watts is the rounded up value for a one horse
power motor. Okay, So let's do that for sixty times fifty two,
which is the AMPS times point ninety four, which is the the efficiency of
the motor times point eight zero, which is the power factor times one point
seven three two. That gives me three thirty and fifty four point nine to
three. And then I'm going to divide that by seven forty six, and
that gives me forty one point seven six ampiers. I mean, excuse me,
forty one point seven six horse power, So forty one point seven horsepower.
Okay, we're not rounding. This is not an AMPS, this is
horsepower, so we're not rounding. So we can drop the six and just
keep it at forty one point seven horsepower. So this is probably no motor
is going to be a horse power forty one point seven. But the reason
you do this in the real world as you might go, okay, well,
then I need a fifty horse power motor whatever the next standard sized horse
power motor is. That's what you would get. Okay, But on an
exam, if they're asking you what the horsepower is, this is how you
would calculate it out to find out what the exact horsepower is. And then
typically you're going to go to you know, in the real world, you're
going to say, okay, well and this is the case, and that's
what my horsepower is. But maybe I need a fifty horsepower motor. Okay,
well you go to fifty horsepower. But then when you're sizing circuits and
you're sizing everything else, that's when you're going to say, screw this,
this is just for an exercise. Now you're going to go what in the
real world, You're going to start using the FLC and that's how you're going
to size the branch circuit to motors and all those type of things. Okay,
So don't get it confused. This is simply to answer a question for
an exam. That's it. So in this question four, in a sixty
volt motor that pulls fifty two amps, that has an efficiency of ninety four
percent and the power factor of eighty using the formula, the horsepower for the
question on the exam is forty one point seven horsepower. That's it. Don't
overthink it, Okay, all right. Remember these are like questions you would
get on an exam, but in the real world sizing the circuits, they're
probably gonna just already have selected a motor that it's horsepower. You're gonna just
use that. You're gonna go the FLC. You're gonna size everything in four
thirty like you normally would. The only reason we did this exercise today is
to show you how to calculate horsepower if they ask you a specific knowledge question
on an exam and they want you to be able to answer a question that
type of scenario, because in the real world, they're probably already going to
tell you the horsepower the motor to be used. They're already gonna do that,
okay, so don't get confused. All right, folks, I told
you not a long one. It's not a little bit shorter than the other
ones. But this is how to find the horsepower, whether it's DC single
phase or three phase. If you get a question on an exam, that's
simply trying to find out what the horsepower is for this specific motor based on
the information that is given. Okay, all right, folks, hopeing you
got something out of that, and thanks for listening to this whole entire series.
If you have any other that you'd like us to do, just do
me a favorite. Go to Paul Abernathy dot com. Go on and submit
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It as always, I'll never mention your name unless you tell me to.
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I do my best to answer them for you. Maybe you appreciate the content.
If you do, we appreciate you. If you don't, piss off,
go somewhere else till next time, stay safe, God bless nothing.
Ask nothing, Ask nothing.