What is meant by Stacking Factor of the Core in Electric Machines ?

The Stacking factor of the core refers to the thickness of the laminations in the core.  In Electric Machines, particularly AC machines, the core of the machine is made of a number of laminated steel sheets.  This is to prevent losses due to eddy current.

The stacking factor depends on the thickness of the lamination of the steel sheets which comprise the core.

The stacking factor is usually 0.9.  The stacking factor is always less than 1.

The Net Area of the core which forms the magnetic path can be calculated from the gross area by the following relation

The Net Area of the Core = Stacking factor x Gross Area of the Core