For example, switching power supplies may operate in the range of tens of kilohertz to a few megahertz. By controlling the rate at which energy is stored and removed from the magnetic field, designers can implement switched-mode power supplies. Consequently, energy stored at one instant in time can be retained in the core until it's needed later. That magnetic energy is stored in the inductor's magnetic field. More practical values of relative permeability are in the range of 100 to 1000.Īn inductor transforms electrical energy into magnetic energy. Thus, the relative permeability of useful magnetic materials ranges from 10 to 10,000.
#Heating effect on ferrite core inductor free
Core permeability is always relative to the permeability of free space. For reference, consider the flux multiplier of free space to be unity (cgs system). Permeability is an important parameter because it can be thought of as a flux multiplier. A core with high reluctance has low permeability and vice versa. Permeability is inversely related to reluctance. The same size core with high reluctance can support a lower flux density.Īnother important core parameter is called permeability. A core with low reluctance can support a relatively high flux density.
Magnetic reluctance is analogous to resistance. Magnetic flux is analogous to electrical current in a purely resistive electrical circuit. Higher flux densities imply greater amounts of stored energy.
Flux density is important because it's related to energy. The combination of winding turns and volume of magnetic material sets an upper limit on the maximum allowable magnetic flux a core can sustain. Magnetically, an inductor's core provides the medium to concentrate and contain magnetic flux. Mechanically, an inductor's core provides support for its windings. Circuit designers specify inductors that are capable of receiving and returning energy in prescribed intervals. Table 1 illustrates the variety of core materials.įunctionally, an inductor's magnetic core stores recoverable energy. Material cost may become a significant factor for larger, higher power cores. Cores can be fashioned by casting, machining or pressing. Each of these different materials has different properties at different frequencies, temperatures and power levels. If appropriate, the core will provide a corner radius.Įxamples of core materials for inductors include silicon steel, iron powder and ferrites. To accommodate direct windings, a well-designed magnetic core will have a smooth winding surface. When wound directly on the core, the magnetic material must not subject the thinly insulated wire to rough surfaces or sharp edges that could cut through insulation. Note that the wire used for the inductor windings is usually insulated, because when closely wound, adjacent turns would short out. Other times, the windings may be wound on a sleeve that is slipped over the core. Sometimes, windings are wound directly around the core. Multi-piece cores, each piece made of the same magnetic material, are sometimes used for extremely complex shapes or larger inductors.Ĭores must be constructed and finished with an understanding of how windings will be installed. In addition, an inductor's magnetic core doesn't have to be made in one piece. Consequently, a core's geometrical shape can take the form of a cylinder, bobbin, toroid or several other complex shapes. A core's geometry depends on various factors, including the application the available mounting area and volume the allowable radiation the limitations on windings the operating temperature and how the inductor will be mounted. There are many possible inductor core geometries.
#Heating effect on ferrite core inductor plus
Magnetic cores plus their windings can be thought of as miniature electromagnets. There are various types of “soft” magnetic materials as well as different types and shapes of magnetic cores. The combination of magnetic core and windings results in a measurable property called inductance. A magnetic core is usually surrounded by carefully arranged windings of wire. Although physically hard, a magnetic core is said to be “soft” when it doesn't retain significant magnetism. We'll also focus on understanding the properties of inductor core material - the heart of an inductor.Īn inductor's magnetic core is made of specially formed material with “soft” magnetic properties. How else can you explain the many types of core materials, types of windings, sizes, geometries and wide range of applications? This article will discuss three examples of the numerous types of material: silicon steel, soft iron powder and ferrites. However, a closer look reveals underlying complexity.