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Inductor Core Material: The Heart of an InductorWhat Does a Magnetic Core Do?
Functionally, an inductor's magnetic core stores recoverable energy. Circuit designers specify inductors that are capable of receiving and returning energy in prescribed intervals. Mechanically, an inductor's core provides support for its windings. Magnetically, an inductor's core provides the medium to concentrate and contain magnetic flux. The combination of winding turns and volume of magnetic material sets an upper limit on the maximum allowable magnetic flux a core can sustain. Flux density is important because it's related to energy. Higher flux densities imply greater amounts of stored energy. Magnetic flux is analogous to electrical current in a purely resistive electrical circuit. Magnetic reluctance is analogous to resistance. A core with low reluctance can support a relatively high flux density. The same size core with high reluctance can support a lower flux density.
Another important core parameter is called permeability. Permeability is inversely related to reluctance. A core with high reluctance has low permeability and vice versa. Permeability is an important parameter because it can be thought of as a flux multiplier. For reference, consider the flux multiplier of free space to be unity (cgs system). Core permeability is always relative to the permeability of free space. Thus, the relative permeability of useful magnetic materials ranges from 10 to 10,000. More practical values of relative permeability are in the range of 100 to 1000. An inductor transforms electrical energy into magnetic energy. That magnetic energy is stored in the inductor's magnetic field. Consequently, energy stored at one instant in time can be retained in the core until it's needed later. By controlling the rate at which energy is stored and removed from the magnetic field, designers can implement switched-mode power supplies. For example, switching power supplies may operate in the range of tens of kilohertz to a few megahertz. Slower switching supplies must store more energy per cycle than higher frequency switchers. The result is that core size is larger for lower switching frequencies and smaller for higher switching frequencies.
For a given winding configuration and core size, an inductor's value of inductance will be higher for a core with higher permeability. For the same electrical conditions, an inductor with a higher value of inductance can store more energy than an inductor with a lower value of inductance. Table 2 illustrates a few of the applications where magnetic cores are required.
Behavior of Different Core MaterialsInductor Core Material: The Heart of an Inductor
Functionally, an inductor's magnetic core stores recoverable energy. Circuit designers specify inductors that are capable of receiving and returning energy in prescribed intervals. Mechanically, an inductor's core provides support for its windings. Magnetically, an inductor's core provides the medium to concentrate and contain magnetic flux. The combination of winding turns and volume of magnetic material sets an upper limit on the maximum allowable magnetic flux a core can sustain. Flux density is important because it's related to energy. Higher flux densities imply greater amounts of stored energy. Magnetic flux is analogous to electrical current in a purely resistive electrical circuit. Magnetic reluctance is analogous to resistance. A core with low reluctance can support a relatively high flux density. The same size core with high reluctance can support a lower flux density.
Another important core parameter is called permeability. Permeability is inversely related to reluctance. A core with high reluctance has low permeability and vice versa. Permeability is an important parameter because it can be thought of as a flux multiplier. For reference, consider the flux multiplier of free space to be unity (cgs system). Core permeability is always relative to the permeability of free space. Thus, the relative permeability of useful magnetic materials ranges from 10 to 10,000. More practical values of relative permeability are in the range of 100 to 1000. An inductor transforms electrical energy into magnetic energy. That magnetic energy is stored in the inductor's magnetic field. Consequently, energy stored at one instant in time can be retained in the core until it's needed later. By controlling the rate at which energy is stored and removed from the magnetic field, designers can implement switched-mode power supplies. For example, switching power supplies may operate in the range of tens of kilohertz to a few megahertz. Slower switching supplies must store more energy per cycle than higher frequency switchers. The result is that core size is larger for lower switching frequencies and smaller for higher switching frequencies.
For a given winding configuration and core size, an inductor's value of inductance will be higher for a core with higher permeability. For the same electrical conditions, an inductor with a higher value of inductance can store more energy than an inductor with a lower value of inductance. Table 2 illustrates a few of the applications where magnetic cores are required.
Behavior of Different Core MaterialsInductor Core Material: The Heart of an Inductor
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