What is a variac, and how does it work? - Simple Explanation

Uploaded by Hassasin195 on 14.10.2011

Hi, and welcome to this video on how a variac works, and also what a variac is.
So, this is a variac, and the definition of a variac is something that
had a variable
alternating current, hence Vari - AC
Variac is actually a trademarked name,
but it's been used by
so many different
companies that it's just basically the name that has been adopted by the device in general
Now, what it is is an auto-transformer, I'll get more into that a little bit later on
So basically what does it do?
Once we turn it on,
right now i have
it hooked up
and as you can see, there is a large knob on the top
and as I turn it up,
you can see
the brightness is going up
on the lightbulb.
The lightbulb is connected directly,
and as I go up and up
And there we have
the full voltage.
Right there
So I can go anywhere from the normal wall voltage which is being plugged in,
I can even go above it, but that would burn the bulb out faster,
I can
go lower as well
so what this allows me to do is smoothly
select a variable voltage
now the indicators on the top
there is an arrow on the knob
and it's numbered
around it so I can figure out how much it's outputting
just to double check, there is an analogue gauge there,
although some of the newer units have digital guages
so you can be more accurate with your output measurements
Now, let's take it apart and see how it works!
first of all remember
you gotta unplug it.
make sure it's off,
always a good safety precaution
and find your screwdriver, and get to work!
Now, you have to remember
that this does run on
mains, or line voltage
(means the same thing)
This does have the potential to
kill you
if you touch it while it's on, if you touch the hot side.
so i'd recommend
to not take apart your variac, and rather have
uh... an electrician or somebody that knows what they're doing so that you don't get shocked.
so now you can actually
lift the case right off
so as you can see in a closer view,
you can see how it's numbered and then when I have the knob
it has an arrow on it
and then I can go
and I can select my voltage
all right
so basically what happens when I turn the variac
as you can see
there is this brush
that spins
on this copper winding
this is just one copper winding
and you'd think that a transformer normally has a primary and a secondary winding,
well, since this is an autotransformer
what an autotransformer is is a transformer where the primary and the
secondary windings
are basically just one winding
so you don't have two, you just have one
so as you can see here I have the hot side connected right there
and then around on the other side
i have the
neutral connected to that first winding
so, what this allows me to do is so that I can have
there is neutral (zero)
and there I have one hundred percent
and what i can do
is I can select anywhere in between there
so basically my primary winding
is here to here
and then with my secondary winding i select how long it is using this,
how many windings that is
so if it is a one to one ratio i get a one to one output
if it's a two to one ratio
or a one to zero point five (0.5) as it would be in this case because
that's what the ratio would be half the voltage
quarter of the voltage so and so forth and because it slides across
I am able to get a smoothing continuous
non-stop updating voltage. So here's one hundred percent, some variacs
like mine
can go all the way up, mine goes up to two hundred percent i know some of them
that can go up to three hundred percent
of their value
now this variac is off, so it's safe to touch but if this variac was
plugged in
then this would
if you touch this this would hurt you pretty badly so please do not take it
apart, please have somebody that knows what they're doing do that for you
alright so that in essence how it works, nice and simple,
Alright, so if you have any questions, comments, or complaints (hopefully not),
on this video, please post a comment
in the section below
um... I have quite a few other fun electrical doo-dads
around here including a neon sign transformer
which will probably be my next video
which will be
some nice high-voltage displays
So, look forward to that video coming out sometime
in the next week or so
and yeah, thank you for watching the video
and if you enjoyed watching it and if you enjoyed watching me,
I recommend that you subscribe to see all the videos that I am producing.
Thank you,
have a good day, night or whatever it is wherever you are. Bye!