ELECTRICAL & ELECTRONICS
POWER CORE PARADIGM SHIFT
REO
WHY MODERN ELECTRICAL APPLICATIONS
DEMAND NEW CORE MATERIALS
Modern electrical systems that use inductors,
such as on-site renewable energy generation,
rely on efficient electronics for power
conversion and switching. Here, Steve
Hughes, managing director of power quality
specialist REO UK, explains how the choice of
electromagnetic core materials — particularly
new ones like amorphous cores — can make
all the difference to electrical applications.
According to the Fundamentals of Electric
Circuits by Charles Alexander and Matthew
Sadiku, “An inductor is a passive element
designed to store energy in its magnetic
field. They are used in power supplies,
transformers, radios, TVs, radars and electric
motors”.
An inductor is one of the three types of
passive linear elements, along with capacitors
and resistors, that make up a circuit. The
main difference between a capacitor and
an inductor is that, where a capacitor stores
charge in an electrical field, an inductor
stores the energy in a magnetic field.
Because an inductor opposes any change in
the direction of current flowing through it, it
is particularly suited to blocking AC current
and only letting DC through.
Although any material that conducts
electrical current has inductive properties,
to produce a practical inductor, a coil of
conductive wire is wrapped around a core.
More commonly known as a choke, coil or
reactor, an inductor generates a magnetic
field to store electrical energy when an
electric current flows through it.
Storing energy is necessary in a variety
of electrical applications. As the need to
produce clean energy becomes increasingly
important, high frequency switching and
power transformation necessitates the need
for energy-efficient components that can
switch faster and exhibit fewer conduction
losses. Fifty years ago, for example, the high
frequency inverters that make renewable
generation possible today simply did not
exist.
There are a few factors that can affect the
strength of the inductive force generated
in an inductor. These include the magnetic
field flux density and the permeability of the
core, which are affected by variables such
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as the number of turns of the coil, the cross
sectional core-area covered by the coil, the
length of the coil and the core material.
As electric current flows through the
inductor’s coil, it generates a magnetic field.
The number of magnetic field lines passing
through the surface of the conductive
material (the magnetic intensity) affects the
density of the resulting field, which is why
the geometry and shape of the inductor is
important to maximise the flux density.
Steve Hughes - managing director of REO UK
CORE MATERIAL
Once the coil variables have been optimised,
the next variable is the permeability of the
core. Permeability is the measure of how
well a material can support a magnetic field
within itself. Using a ferromagnetic core with
a high permeability — usually made of iron,
but can also be made from nickel, cobalt or
other iron alloys — significantly increases
inductance compared to using a coil made
from air or steel.
While a high permeability is preferable, the
core’s material affects its saturation limit.
This is when an increase in the applied
magnetic field intensity does not continue to
magnetise the core material, leading to flux
density levelling off. This effectively means
the inductor stops acting as an inductor,
potentially leading to excessive current
waveforms damaging components such as
sensitive semiconductor materials.