3 Main Types of Magnetic Cores Used in Transformers

Motors and transformers are will not properly function without a core. The cores used in step-up/step-down transformers can be composed of several different materials depending on the application. The core has a profound effect on the functionality of the transformer. The size and geometry of the core will dictate the power, the voltage and the current the transformer can provide. The core is the conduit for the magnetic flux that is flowing when an AC signal is placed on the primary coil. This core flux transfers energy from the primary coil to the secondary coil. In order to do this effectively, transformers feature laminated steel or amorphous cores. In this post, we will discuss the different materials used for the transformer cores.

Three Main Types of Steel Cores Used in Magnetic Transformers

Magnetic transformers feature cores made from the following different materials:

  • Solid Iron/ Steel:Early on, solid annealed iron or steel was the popular choice of material for the core, since it allowed for strong magnetic fields. In more recent times, it has become unpopular due to the fact that it produces eddy currents that make the transformer inefficient. They also generate large amounts of heat that affect the overall performance of the transformer.
  • Laminated Silicon Alloy/Silicon Steel:Silicon alloy laminations, which are basically thin strips of a silicon alloy, are stacked together and used as a core. These cores are commonly used in 50/60/400Hz electrical transformers. The core material in this form allows for efficient magnetic propagation with reduced eddy currents and heat dissipation.
  • Amorphous Steel:Cores comprising extremely thin strips of amorphous steel can be used in transformers that function from mid to high frequencies. Flow of eddy currents is greatly reduced when using this material at these frequencies. Hence, it is the preferred material when looking to make your medium frequency transformer extremely efficient.

Depending on the application, the proper core can be selected to support efficient operation of the transformer. For example, a transformer that is needed to convert “wall power” to the proper voltages required to run a laser power supply is very different from a transformer used to create those same voltages but in a switching power supply. Therefore, it is important to use this knowledge in making a core selection that helps your application function optimally. Choosing the right core also means lower costs and less development time.


GT Stepp - Electrical Engineer with over 20 years of dedicated experience, proficient in the research, evaluation, test & support of various technologies. Devoted to success; comprising strong analytical, organizational & technical skill. Currently working as Sales & Operations Manager at Custom Coils, developing sales and marketing strategies that increase sales to make Custom Coils more recognized and respected in the marketplace.