The ferrite cores used for signals have a range of applications from 1В kHz to many MHz, perhaps as much as 300В MHz, and have found their main application in electronics, such as in AM radios and RFID tags. They are useful in all kinds of electronic switching devices вЂ“ especially power supplies from 1В Watt to 1000В Watts maximum, since more powerful applications are usually out of range of ferritic single core and require grain oriented lamination cores. The ferrite cores used for power transformers work in the low frequency range (1 to 200В kHz usually ) and are fairly large in size, can be toroidal, shell, or shaped like the letters вЂCвЂ™, вЂDвЂ™, or вЂEвЂ™. Cores can also be classified by shape, such as toroidal cores, shell cores or cylindrical cores. There are two broad applications for ferrite cores which differ in size and frequency of operation: signal transformers, which are of small size and higher frequencies, and power transformers, which are of large size and lower frequencies. It is important to select the right material for the application, as the correct ferrite for a 100В kHz switching supply (high inductance, low loss, low frequency) is quite different from that for an RF transformer or ferrite rod antenna, (high frequency, low loss, but lower inductance), and different again from a suppression ferrite (high loss, broadband) ДЄs any given blend has a trade off of maximum usable frequency, versus a higher mu value, within each of these sub-groups manufacturers produce a wide range materials for different applications blended to give either a high initial (low frequency) inductance, or lower inductance and higher maximum frequency, or for interference suppression ferrites, a very wide frequency range, but often with a very high loss factor (low Q). The exception is with common mode inductors, where the threshold of choice is at 70В MHz. NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1В MHz.ДЇor applications below 5В MHz, MnZn ferrites are used above that, NiZn is the usual choice. Nickel-zinc ferrite ( NiZn, with the formula Ni aZn (1в€’a)Fe 2O 4).MnZn have higher permeability and saturation levels than NiZn. Manganese-zinc ferrite ( MnZn, with the formula Mn aZn (1в€’a)Fe 2O 4).The low coercivity means the material's magnetization can easily reverse direction while dissipating very little energy ( hysteresis losses), at the same time the material's high resistivity prevents eddy currents in the core, another source of energy loss.

They have a low coercivity and are called ' soft ferrites' to distinguish them from ' hard ferrites', which have a high coercivity and are used to make ferrite magnets. Ferrites that are used in transformer or electromagnetic cores contain iron oxides combined with nickel, zinc, and/or manganese compounds. Ferrites are ceramic compounds of the transition metals with oxygen, which are ferrimagnetic but nonconductive.

Ferrite core inductor 470