Transformers feature primary, secondary and tertiary windings, whose working depends on the flux that is produced between these windings. Magnetic cores in the transformers serve as the pathway of the flux. These cores are magnetic materials with high magnetic permeability used to guide magnetic fields in transformers and other electrical or magnetic devices. They are made of ferromagnetic metals or compounds. There are a variety of materials that can be used to manufacture these magnetic cores, the most common ones mentioned in this blog post.
Solid iron cores serve as an excellent pathway to provide magnetic flux and retain high magnetic fields without saturating the iron. However, these cores are not recommended for transformers that operate in AC applications because its magnetic field produces large eddy currents, which in turn produce lots of heat at high frequency.
Carbonyl iron is a highly pure iron that has stability across a wide range of temperatures and magnetic flux levels. Carbonyl iron powder comprises of micrometer-sized iron spheres coated with a thin insulating layer that reduces the eddy current at high temperature. Often known as RF cores, these carbonyl iron cores have lower losses, but lower permeability too.
Magnetic cores that use amorphous steel are made of many layers of paper-thin metallic tapes that help to reduce the flow of eddy currents. These cores have fewer losses than other magnetic cores, which help them to easily operate at high temperatures as compared to standard lamination stacks. However, amorphous steel is too brittle to be used in motors, which is why they are used in high efficiency transformers that operate at medium frequencies.
Silicon steel has high electrical resistivity and offers high saturation flux density. It also has high permeability and low losses, which enables silicon steel cores to be used in high-performance applications. To reduce eddy current losses, most low frequency transformers use laminated cores made of stacks of thin silicon steel to provide current with space only enough to flow through narrow loops between every lamination layer. (You can learn more about laminated magnetic cores below in the blog.)
Amorphous or vitreous metals are glassy and non-crystalline, thus can be used to create high-efficiency and high-performance transformers. The low conductivity of these materials helps to reduce eddy currents. These amorphous metals can be highly responsive to magnetic fields for low hysteresis losses, and can have low conductivity to reduce eddy current losses.
Ferrite ceramics are made from iron oxide and one or multiple metallic elements, which are made in different specifications to meet diverse electrical requirements. Ferrite ceramics magnetic cores are used in high-frequency applications and serve as efficient insulators to prevent eddy currents. However, losses like hysteresis loss can still occur with these ceramics.
Laminated magnetic cores
Laminated magnetic cores are made of stacks of thin iron sheets coated with an insulated layer, which lie parallel to the lines of flux. These insulation layers serve as barriers to prevent eddy current so that it can flow only through the narrow loops within each single lamination layer. This technique prevents major of the current from flowing and reduces eddy current to a very low level. Moreover, narrow laminations can reduce power losses to a great extent too. Thus, thinner the laminations, lower the eddy current loss will be.
As you can see above, every material has its own pros and cons. This is why you need to consult an electrical expert to know which core will be the most suited for your transformer. And to rely on experts for providing you with transformers that can be customized as per your requirement, the name is Miracle Electronics, the leading name as a transformer manufacturer in India since more than 20 long years now!