Ferrite Core

Ferrite is a magnetic material which consists of a mixed oxide of iron and other elements that are made to have crystalline molecular structure. The crystalline structure is created by firing the ferrite material at a very high temperature for a specified amount of time and profile. The general composition of ferrites is xxFe2O4 where xx represents several metals. The most popular metal combinations are manganese and zinc (MnZn), and nickel and zinc (NiZn). These metals can be easily magnetized.

Ceramic Cores

Ceramic is one of the common materials used for inductor cores. Its main purpose is to provide a form of the coil. In some designs, it also provides the structure to hold the terminals in place. Ceramic has a very low thermal coefficient of expansion. This allows for relatively high inductance stability over the operating temperature ranges. Ceramic has no magnetic properties. Thus, there is no increase in permeability due to the core material. Ceramic core inductors are often referred to as "air core" inductors. Ceramic core inductors are most often used in high-frequency applications where low inductance values, very low core losses, and high Q values are required.

Kool Mu® Core

Kool Mu® is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. Kool Mu material is an alloy that is made up of nickel and iron powder (approx. 50% of each) and is available in several permeabilities. It has a higher permeability than powdered iron and lowers core losses. Kool Mu performs well in power switching applications. The relative cost is significantly higher than powdered iron.

MPP Core

MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. The basic raw materials are nickel, iron, and molybdenum. MPP stores higher amounts of energy and has a higher permeability than Kool Mu. The core characteristics allow inductors to perform very well in switching power applications. Since higher energy can be stored by the core. The cost of MPP is significantly higher than Kool Mu, powdered irons, and most ferrite cores with similar sizes.</p>

Powdered Iron Core

Powdered iron is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. Powdered iron cores are made of nearly 100% iron. The iron particles are insulated from each other, mixed with a binder (such as phenolic or epoxy) and pressed into the final core shape. Powdered iron cores are typically the lowest cost alternative and their permeabilities typically have a more stable temperature coefficient than ferrites.

Laminated Cores

Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface which is commonly an oxide finish. Laminated cores are used in some inductor designs but are more common in a wide variety of transformer applications.