warning the Transformers in this video
are powered by mains voltage mishandling
of such a high voltage can lead to fatal
injuries
whenever you plug an electrical device
into an outlets you probably use them no
matter whether you just want to charge
your phone or power your laptop a
transformer will always be used their
job is to like the name implies
transform voltages in your everyday life
they transform the high mains AC voltage
into lower AC voltage that can safely be
used by common low voltage devices well
that was easy
but why are some transformers smaller
than other ones even though they are
used to output more power and what
specifications does a transformer design
it needs to come with to achieve which
output voltage and power well hang on
because in this video I will be
conducting a couple of tests in order to
not only explain how transformer works
but also to answer the question whether
it is easy to create one on your own
let's get started this video is
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understand how a transformer works let's
firstly open up this one as you can see
it's build up is not hard to grasp at
all we got a metal core which is made up
of electrical steel sheets and two coils
which are wrapped around the core to
keep it easy to understand though we can
simplify its structure to diagram like
this with the mains voltage primary coil
on the Left sides until our voltage
secondary coil on the right sides now as
a practical example I will be using this
transformer which takes AC 230 volts 50
Hertz
as in inputs which not coincidentally is
the mains voltage here in Germany and
outputs a CA 13.5 foods with a maximum
of 1600 milliamps so by connecting mains
voltage to the primary coil which you
can pretty much always identify by its
high resistance compared to the
secondary coil we can measure around 15
point 4 volts AC RMS at the secondary
coil the way this works is that after
applying the mains voltage to the
primary coil as sine current starts
flowing through the coil as you might
know when current flows through a
conductor it creates a magnetic fields
with a magnetic field strength magnetic
flux density and magnetic flux if you
don't believe me then feel free to
create your own coil with lots of
windings and power it's with a DC
voltage source which basically turns it
into an electromagnet
but anyway the formulas for all the
three important magnetic values look
like this with the magnetic flux being
the end results this flux flows through
our iron core which means it reaches our
secondary coil and since we applied an
AC voltage to the primary our flux also
changes polarity with the same frequency
and shape now the missing final piece of
this functional principle is the
induction law which says that a voltage
is induced into a conductor if the
magnetic flux changes over time which it
does so the induced voltage into the
secondary coil is our output voltage
which can ideally be calculated through
the number of turns of the primary and
secondary coil those were the absolute
basics of how a transformer works but we
want to dig deeper to start off I
measured the resistance and inductance
of the primary coil which were around 97
ohm and 5.1 Henry if we turn those two
values into the magnitude of a complex
impedance which I showed you how to do
in a previous video
then we end up with a value of 1605 ohm
that means by applying mains voltage we
should get a current flow of around 143
milliamps but after measuring the
current the practical way we can see
that we only got a current flow of 41
million s the reason is that the
magnetic flux also induces a voltage
into the primary coil which opposes the
mains voltage and thus lowers the
overall voltage at the primary and thus
also the current you can pretty much say
the transformer self regulates itself
because if the current on the input side
would be higher and thus would create a
faster changing magnetic flux we would
have a higher induced voltage which once
again regulates down the input voltage
and thus the current next we can also
find out that the transformer uses quite
a bit of real input power even though
there's no load connected on the outputs
the reason can be found if we look at
the equivalent circuit diagram of a
transformer with no loads or current
flows through the cross path and real
power losses only occur at those two
resistances the first one is the couple
resistance of the primary coil which
according to our previous measurements
should be a pretty small most power gets
wasted through the iron losses which
includes the eddy currents and
hysteresis losses
eddy currents are created by the
induction of a voltage into the iron
core and to keep them as small as
possible
iron cores are created with separated
laminated steel sheets hysteresis losses
occur while the iron core gets
alternatingly magnetized and can easily
be spotted in the corresponding pH
diagram of the use material and with
that being said let's hook up this 10
ohm resistor to the secondary coil the
load draws around 1.4 m/s at 14 volts at
the outputs while the input
and increased to 110 milliamps what
happens is that the secondary current
now also creates a magnetic flux which
not only induces a voltage into its own
coil and thus lowers the output voltage
but also into the primary coil which
thus increases its overall voltage and
therefore lets more current flow on the
primary sites the secondary current with
its 1.4 m/s is still within the legal
limits of the transformer and this
transformation came with an efficiency
of around 82 percent but if I add L 3.3
ohm resistor to the outputs we cannot
only see that the output current is
beyond the transformers limits but also
that the output voltage broke down quite
a bit and that the efficiency got
lowered to 72 percent the reason for the
lower output voltage could once again be
the increased induced voltage of the
secondary current but as we draw more
and more current on the input side of
the transformer we could also easily
reach the magnetic saturation region of
the material there the change of the
magnetic flux density is very small in
relation to the changing current which
means way less induced voltages that
means the output voltage breaks down
while the input current increases since
there's way less voltage opposing the
mains voltage and thus we get more real
power losses more heats and possibly the
destruction of our transformer to avoid
this problem we can once again have a
look at our induction voltage formula
which we want to be high the first
solution is to increase the cross
section area of the ayran core which is
why mains voltage transformers who have
a big iron core will always be able to
push more power than smaller ones the
other practical solution is to decrease
the time or in other words increase the
frequency which is why I switch mode
power supplies which use a frequency of
for example 30 kilo Hertz can be bullets
with
a small cross-section area but then
again the hysteresis and eddy current
losses increased proportional with the
frequency which is why the material is
made up of ferrets which are less
conductive a disadvantage of ferrets
though is they're smaller maximum
magnetic flux density around 0.5 Tesla
while electrical steel sheets can reach
values of around 1.5 to 2 Tesla the last
important property of a transformer we
have to talk about is the leakage flux
which if too high can lower the output
voltage of a transformer substantially
that is also why we use ayran or ferrite
cores with a high magnetic permeability
to basically keep the magnetic
resistance low in order to force most of
the magnetic flux through them but you
can learn much more about this topic if
you watch my wireless power videos and
with that being sense you are now
familiar with pretty much all the theory
and formulas you need to design a basic
transformer which leads to the question
whether it is easy to make your own well
if you can get your hands on electrical
steel sheets that come with proper
documentation then they're handy
formulas to calculate all important
parameters of a transformer which means
it is pretty easy but since the core
material is often not that easy to find
it can be quite hard to reuse an old
transformer core which I had to
experience by myself while creating this
video but I will be talking about
creating a DIY transformer and even a 3d
printed one with ferromagnetic filaments
in the second part of this transformer
adventure video series until then don't
forget to Like share subscribe and
hitting the notification bell stay
creative and I will see you next time