Grain orientated electrical steel is used for the manufacture of magnetic cores within transformers.
The best magnetic properties are only found in the rolling direction due to the nature of the manufacturing process. If the material is magnetised outside the rolling direction the core losses increase significantly. The extent of this increase varies from a factor of three times at 90 degrees and four times at 60 degrees.
It is therefore essential that the material is magnetised as precisely as possible along the rolling direction throughout the magnetic circuit.