Ferrites are one of the principal middle materials utilized in inductors and transformers.

Inductor ferrite is used to offer an growth withinside the permeability of the medium across the coil to growth the inductance of the inductor.

Ferrites are broadly used inside inductor generation to enhance the overall performance of the inductor.

Ferrite Overview

Ferrites are iron-based magnetic materials that take the shape of a ceramic. 

Because ferrites are comprised of powder, the ferrite cores used in inductors and other applications may be created in a variety of forms to meet the needs of the application. 

Ferrites, commonly known as ferromagnetic materials, are categorised into two types depending on magnetic coercivity, or the persistence of internal magnetism:

Soft Ferrites: Soft ferrites are ferrite materials that may readily switch the polarity of their magnetisation without requiring a large amount of energy to do so. This indicates that there is just a minor loss of energy. 

Soft ferrites have a high electrical resistance and hence minimal eddy current losses when used in inductors and transformers. 

Soft ferrites are frequently formed from a combination of iron, nickel, zinc, and manganese oxides. The most common soft ferrite magnets are manganese-zinc and nickel-zinc magnets. Soft ferrites are commonly employed in the cores of inductors and transformers due to their high resistance, which results in minimum energy loss.

Generally soft ferrites are accepted as those having a coercivity of less than 1 kA.m.

Hard ferrites: Permanent magnets are another name for hard ferrites. They retain the polarity of their magnetisation even after the magnetising field is withdrawn, indicating that they have a high remanance level. 

Hard ferrite magnets are often formed of oxides of barium, iron, or strontium. They are inexpensive to create and are the magnets that are used in a variety of applications, but are most typically seen as basic home magnets (e.g., kitchen magnets). 

Hard ferrites are defined as those having coercivity values more than 10 kA/m.

Ferrites are ceramic iron-based compounds that are chemically inert. They usually have the chemical formula XFe2O4, where X is a transition material.

To make the ferrites used in inductors and other applications, the metal powers are mixed in proportions, milled to get the desired grain size, and then pressed into form. 

Sintering involves heating the material to temperatures ranging from 1150°C to 1300°C. 

Sintering is a process in which a powdered ceramic material is held in a mould to give it the desired shape and then heated to a temperature below the melting point of the material. It is discovered that the atoms in the powder particles seep over the particle boundaries, fusing the particles together. In this manner, a single solid thing is formed.

The sintered core of the inductor ferrite may still need to be finished; for example, it may need to be ground to create a very flat surface in circumstances when matching halves of a core are required. Flat surfaces are required here to guarantee that air gaps in inductors or transformers, for example, are as little as feasible. 

Thousands of small crystals or grains make up the final ferrite substance. These are typically roughly 10m across. There are many more tiny magnetic domains within each grain or crystal that can have a random orientation after heating. When an external field is applied, these domains will tend to orientate in the same direction.

Ferrite core permeability

When a ferrite is utilised in an inductor, there are several parameters that must be considered. The permeability of an inductor ferrite, on the other hand, is the most important property. The permeability of the inductor ferrite allows the inductor to have a substantially higher inductance than if simply an air core was utilised. 

The permeability of ferrites used in inductors varies greatly depending on the kind of ferrite. They can have permeability levels ranging from 20 to more than 15,000, while some extremely specialised ones may have greater values. 

Inductor ferrite core losses

The core losses and frequency dependency of ferrites in inductors are two significant parameters of interest to electronic engineers who use ferrites in inductors. 

A ferrite core's core losses can be stated in terms of following manner

Where:

 Pe = eddy current loss 

 Pr = residual loss   

 Pc = total core loss 

 Ph = hysteresis loss 


The hysteresis loss is observed to increase linearly with increasing frequency and flux. With rising frequency and flux, the eddy current loss grows exponentially. However, it is discovered that the hysteresis loss is the main core loss up to a frequency dictated by the core's performance. Above this, eddy current loss takes precedence. 

To optimise high frequency performance, the grain size of the ferrite used in the inductor must be small, and the mixture must be free from impurities.

If you are looking for Mnzn based soft ferrite cores for your transformers or other Application, you will want to source them from a well-established and ISO 9001 certified manufacturer. Cosmo Ferrites Limited has been manufacturing quality Soft Ferrites of various types for many years. The company can provide you with a soft ferrite core in various sizes to help you meet your application requirements.