Understanding Cores, Chokes, And Losses

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Understanding Cores, Chokes, And Losses
Electric current, when flowing through a
conductive material, generates a magnetic field,
that which is strongest at the conductors
surface, and weak farther from the conductor.
Magnetizing a core material wont stop it from
having a magnetic charge when you stop
magnetizing it. Instead, if you want to get it
back to zero magnetization, you will have to
reverse the magnetization. This is what is
called the hysteresis loop, which occurs when
alternating positive and negative magnetic
fields are applied to the material. Understanding
the hysteresis loop The magnetization force
depicted by the symbol H is the magnetic field
that is applied on the magnetic core material.
And, the magnetic flux, depicted by the symbol
B, is the total magnetic field flowing through
an area, the intensity being referred to as flux
density. The hysteresis loop is this B-H curve,
analyzing which is very important when designing
transformers, inductors, and chokes. What
elements alter the magnetic flux? The area of the
core, the number of turns, and the switching
frequency are all important factors that alter
the magnetic flux. If the core area, number of
turns, and switching frequency are increased, the
flux will decrease. Also, greater the core
materials permeability, greater is the flux
density.
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Designing a transformer, inductor, and
choke While designing an inductor or choke, you
dont want to cause saturation of the core by
increasing the AC or DC current. The DC current
is what generally saturates the core, as its
constant and moves the core to a certain flux
level. Yet, you need to always ensure that the
maximum AC current is also well below the
saturation point. Saturation can also be reached
by increasing the flux density, normally by
increasing the voltage. The core materials
permeability also impacts the saturation. High
permeability saturates the core faster, and low
permeability saturates the core at a higher flux
density. Core losses Transformers transfer power,
so you want minimum losses when transferring
power from the primary to the secondary. This is
the main reason why ferrite cores are commonly
used for high frequency designs, and
high-permeability grain-oriented silicon steel
cores are used for low frequency transformers. On
the other hand, inductors and chokes store
energy, which is why you want high flux cores in
them. Transformers, inductors, and chokes always
encounter power losses, which generates heat,
causing thermal issues. Toroidal core losses can
result from the following When the flux is
moved from positive to negative, and the area is
enclosed by the loop, it results in hysteresis
loss. This loss can be lowered by using more
expensive materials. When there is difference in
flux voltage in the cores causing circulating
currents in the magnetic material, it results in
eddy current loss. A higher switching frequency
results in greater eddy current loss. Miracle
Electronics chokes are designed to provide the
highest common mode impedance over the widest
frequency range. This is the reason why they are
considered as the most reliable toroidal chokes
manufacturers in India, when clients are looking
for chokes that are effective in filtering supply
and return conductors with in-phase signals of
equal amplitude.