The magnetic core of a transformer provides a flux path to facilitate flux linkage.
Soft core materials are generally used as transformer cores as these materials have higher permeability and lower coercivity, meaning they can be easily magnetized and demagnetized.
Permeability is often used to evaluate the magnetic performance of a core.
It is a measure of how much magnetic induction is generated by the magnetic material in a given magnetic field.
Permeability depends on temperature, material composition, frequency of the excitation current etc.
The material used exclusively for PFCT cores is grain oriented silicon-iron. This material contains about 3-4%
silicon to reduce conductivity and eddy current losses.
These materials work well at power frequencies, but become less effective at high frequencies [10].
Metallic oxide materials,known as ferrites, are essentially ceramics which are used as core material in HFCTs due to their relatively high resistivity and high usable frequency range.
For high frequency applications, core material with a higher initial permeability is preferred.
In addition to the material composition, the magnetic efficiency of a ferrite based CT depends on the
design, e.g. shape of core, uniformity of core cross sectional area and air gap [11].