Learn More about Ferrite Cores

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Learn More about Ferrite Cores
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Overview

• Ferrite cores are dense, homogeneous ceramic
  structures composed of iron oxide (Fe2O3) mixed
  with oxides or carbonates of one or more metals
  such as manganese, zinc, nickel, or magnesium.
  They are pressed, then fired in a kiln to 1300o C
  before being machined to meet various operational
  requirements. Because of their high electrical
  resistivity and low eddy current losses over a
  wide frequency range, ferrites have an advantage
  over other types of magnetic materials. These
  properties, combined with high permeability, make
  ferrite ideal for use in high frequency
  transformers, wide band transformers, adjustable
  inductors, and other high frequency circuitry
  starting at 10 kHz to 50kHz.

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Importance of permeability in power materials?

• Permeability is calculated as flux density (B)
  divided by drive level (H). Power materials are
  typically used in high frequency transformer
  applications thus, high flux density and/or low
  core losses are important characteristics.
  Permeability is less important due to its
  variability across an operating flux range.

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Disaccommodation

• Disaccommodation occurs in ferrites and is
  defined as a decrease in permeability over time
  after a core has been demagnetized. This
  demagnetization can be caused by heating above
  the Curie point with a decreasing amplitude
  alternating current or by mechanically shocking
  the core. The permeability increases towards its
  original value in this phenomenon, then begins to
  decrease exponentially. If no extreme conditions
  are expected in the application, permeability
  changes will be minor because the majority of the
  change will have occurred within the first few
  months of the core's manufacture. The decrease in
  permeability is accelerated by high temperatures.

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Difference between nickel-zinc and manganese-zinc
ferrites

• The permeability of MnZn materials is high,
  whereas that of NiZn ferrites is low.
  Manganese-zinc ferrites are used in applications
  with a frequency of operation less than 5 MHz.
  Nickel-zinc ferrites have a higher resistivity
  and are used at frequencies ranging from 2 MHz to
  hundreds of megahertz. The exception is common
  mode inductors, where the impedance of MnZn
  material makes it the best choice up to 70 MHz
  and NiZn from 70 MHz to several hundred GHz.

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Ferrite Applications

• Ferrite cores have two broad applications that
  differ in size and frequency of operation signal
  transformers (small size and higher frequencies)
  and power transformers (large size and lower
  frequencies). Cores can also be classified based
  on their shape, such as toroidal, shell, or
  cylindrical cores.
• Power transformer ferrite cores operate in the
  low frequency range (1 to 200 kHz2) and are
  fairly large in size. They can be toroidal,
  shell, or shaped like the letters C', D', or
  E'. They are useful in all types of electronic
  switching devices, particularly power supplies
  ranging from 1 Watt to 1000 Watts. because more
  powerful applications are usually beyond the
  capabilities of ferritic single cores and
  necessitate grain oriented laminated cores
• The ferrite cores used for signals have
  applications ranging from 1 kHz to many MHz,
  possibly as much as 300 MHz, and have found their
  primary application in electronics, such as AM
  radios and RFID tags.

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Ferrite Applications(Properties, materials and
shapes)

Applications Desired Properties Preferred Materials Available Shapes
Broadband Transformers Low loss, High µ (permeability), Good frequency response J, W, M Pot cores, Toroids, E, U I cores, RM, EP cores
Common Mode Chokes Very high µ J, W, M Toroids, E cores
Converter and Inverter Transformers Low losses, High saturation F, L, P, R, T Toroids, E, U I cores, Pot cores, RS cores, Planar cores
Differential Mode Inductors Low losses, High temperature stability, Good stability across load conditions F, P, R, T Gapped pot cores, EP cores, E cores, RM cores, Planar cores, PQ cores
Narrow Band Transformers Moderate Q, High µ, High stability F, J Pot cores, Toroids, RM cores, EP cores
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Continued.
Applications Desired Properties Preferred Materials Available Shapes
Noise Filters High µ, Good frequency response J, W, M Toroids
Power Inductors Low losses at high flux densities and temperatures, High saturation, Good stability across load conditions F, L, P, R Pot cores, E cores, PQ cores, RM cores, Planar cores
Power Transformers High µ and low losses at high flux densities and temperatures, High saturation, Low exciting currents F, L, P, R, T Ungapped pot cores, E, U I cores, Toroids, EP cores, RS cores, DS cores, PQ cores, Planar cores
Pulse Transformers High µ, Low loss, High B saturation J, W, M Toroids
Telecom Inductors Low losses, High temperature stability, Good stability across load conditions F, P, R, T Pot cores, EP cores, E cores, RM cores, Planar cores
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Address
Cosmo Ferrites Limited,
517, 5th Floor, DLF Tower-A, Jasola
New District Centre, Jasola,
New Delhi - 110025. India.
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