Explain why the soft iron core in a
transformer is made up of insulated laminas, sheets.
Now, if we sketch out a basic
transformer, we see it consists of three parts. There is the core of the
transformer and then on either side the primary coil and the secondary coil. When alternating current runs
through the primary coil, this creates a changing magnetic field through the
windings of this coil.
The purpose of the core is to
transmit this changing magnetic field through the windings of the secondary
coil. When it does this, EMF is induced
in the secondary coil and current begins to flow. Now, we’ve said that this
alternating current that runs through the primary coil sets up a changing magnetic
field to the windings of this coil. And that’s true.
Unfortunately, from the perspective
of the efficiency of the transformer, it also has another effect which is the setup
of potential differences across different parts of the core itself. When this happens, current starts
to flow not in the wires as we want them to but through the core material itself in
small loops, called eddy currents.
These eddy currents are responsible
for energy loss due to heat and an overall loss in efficiency for the
transformer. Let’s say we were to change our
perspective so we’re looking at the transformer core from the side. If the core was manufactured from
one single chunk of iron, then that would mean that the eddy currents that form in
the core are fairly unrestricted in where they can go. They can be as small as in one
small part of the core or they can run all through out of it in.
And as we said, it’s these eddy
currents which create efficiency losses for our transformer. In order to combat these losses, a
new design for the core was developed. In this new construction, the core
instead of being made of one piece of material is made of many electrically
insulated laminas or sheets of iron. We can imagine each lamina almost
as a slice of the core with many slices again electrically insulated stacked one on
top of another.
Here is the impact of this
redesigned core. When eddy currents do form in one
of the isolated laminas within the core, they don’t have very far to go. They’re forced to stay within that
particular sheet and can’t jump and spread throughout the rest of the core. This has the overall effect of
minimizing energy lost due to unintended current flow. In our transformer then, more of
the energy from the primary coil is able to be carried over to the secondary coil;
that is, the transformer efficiency goes up.
Here is how we can explain the
reason for this redesigned core. We can say that the transformer
core is made up of insulated laminas in order to decrease the energy dissipated due
to eddy currents. That’s the effect of constructing
the core this way.