Hey there guys, Paul here from TheEngineeringMindset.com. In this video, we're going to be looking
at how transformers work. Now this follows on from our series on electrical engineering, so do check out the other videos if you've not done so already. Links are in the video description below. Coming up, we'll be looking at how
to create a magnetic field with electricity, and why only an alternating
current can be used in transformers. How a basic transformer works, then we'll look at step up
and step down transformers, and finally, we'll finish on three phase transformers. Now there are two types of electricity, AC and DC. But transformers can only work using AC, or Alternating Current. And if you don't know the
difference between these two, then please, first of all, watch the video on electricity basics first. Again, you can find links to these videos, and other useful videos, in the video description below. When we connect an AC generator to a closed loop of cable, a current will able to
flow through this cable, and the direction of the
current will alternate backwards and forwards, with the rotation of the generator. The alternation means that the
current reaches it's maximum and minimum point during the cycle, which gives it its sine wave pattern when connected to an oscilloscope. Now you can think of this
as the tide of the sea as it changes direction, and reaches its maximum and minimum point. As the current flows through the cable, it will emit a magnetic field. If we pass DC current through the cable, the magnetic field will remain constant. But, if we pass AC
current through the cable, then the magnetic field will increase and decrease in strength, and changes polarity as the current changes direction. If we place multiple cables together and pass current through them, then the magnetic fields will combine to create a stronger magnetic field. If we then wrap the cable into a coil, the magnetic field will
become even stronger. If we then place a second
coil in close proximity to the first coil, and then we pass AC, alternating current, through the the first coil, then the magnetic field it creates will induce a current
into the second coil. And this magnetic force will push and pull on the free electrons
forcing them to move. The key component here is
that the magnetic field is changing polarity as well as intensity. This change in intensity and direction of the magnetic field constantly disturbs the free
electrons in a secondary coil, and this forces them to move. This movement is known as
electromotive force or EMF. Electromotive force does not occur when we pass DC current
through the primary coil, and that's because the
magnetic field is constant, so the electrons are not
being forced to move. The only time it will
cause EMF is very briefly when the primary circuit
is open and closed or when the voltage is
increased or decreased. And that's because these
actions result in a change to the magnetic field. Therefore, we use alternating current as this change occurs constantly. Now, the problem with this setup is that a lot of the magnetic
field from the primary side is being wasted because it's not in range
of the secondary coil. So, to fix this engineers place a core of ferromagnetic material such as iron, in a loop between the primary and secondary coils. Now, this loop guides the
magnetic field along a path to the secondary coil, so that they will share the magnetic field and this makes the transformer
much more efficient. Now, the use of an iron core
is not a perfect solution, some energy will be lost through something known as Eddy currents, where the current swells around the core and this heats up the transformer, and this means that the
energy is lost as heat. To reduce this engineers
use laminated sheets of iron to form the core, and this greatly reduces
the Eddy currents. Transformers are
manufactured to be step up or step down transformers, and these are used to increase or decrease the voltage simply by using a
different number of turns within the coil on a secondary side. In a step up transformer the voltage is increased
in the secondary coil, and this will mean that
the current will decrease. But don't worry too much right now about why that occurs. We'll look at this in a later
electrical engineering video. To increase the voltage
in a step up transformer, we just need to add more turns to the coil on the secondary side than the primary side. In a step down transformer, the voltage is decreased
in the secondary coil which means that the current increases. To do this we just use
less turns in the coil on the secondary side
compared to the primary side. For example, a power station needs to
transport the electricity it is generated, over to a city some distance away. The power station will
use a step up transformer to increase the voltage and reduce the current, as this will reduce the losses for the long transmission cables. Then, once it reaches a city, this will need to be reduced to make it safe and usable by buildings and homes, so there will need to be
a step down transformer. The Transformers for commercial buildings and power stations are usually in a three
phase configuration. You'll see this placed
around your cities and towns, and they'll look something like this. These three phase transformers
can be made from either three separate transformers
that are wired together, or they can be built into one large unit with a shared iron core. In this set up, the coils will typically
sit concentrically within one another with a higher voltage coil on the outside and the lower voltage coil
sitting on the inside. Now these coils are
insulated from one another, so that only the magnetic field will pass between the two coils. To connect the two sides there are many different configurations, but one of the most commonly used, is to connect the coils in a configuration known as Delta Wye, sometimes referred to as delta star. This refers to the
primary side being wired in the Delta configuration and the secondary side being wired in a wire configuration. The centre point of the wye side where all three connectors meet, is often grounded which allows for neutral
line to also be connected. we'll cover transformer connections and calculations in other
more advanced videos as this can get quite complex, so for now, simply focus on how they work to build your base knowledge. Okay, that's it for this video. Thank you very much for watching. I hope you've enjoyed this and it has helped you. If so then please don't
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