ASTM A-719 standard defines the lamination factor, S, of a stacked laminated core as the ratio of solid volume of steel stack (calculated from weight and density) to the actual volume of the compressed stack (determined from its dimension).

S = 100 x ( Solid Volume by wt and density ) / ( Measured Volume )

Lamination factor which is also termed space factor or stacking factor (SF) is a measure of bulk density or compactness of the core.

Lamination Factor:

Thus the stacking factor could be used to calculate approximate core cross-sectional area AC by:

AC = w x h x S

Since the stacking factor can vary from .90 to .99 depending on the fabrication method and other factors, the exact core cross-sectional area can be calculated by core weight as;

AC = (m / d ) x (w / As)

Lamination factors are a very important consideration in transformers and motors core design because they indicate the deficiency of effective steel volume. Ideally a core should be 100% magnetic lamination. This permits more flux carrying material in a given core volume, increasing effective magnetic permeability. This minimizes exciting current, can reduce size, winding weight (copper) and could reduce audible noise. Practically, this goal can only be approached because of spaces between laminations. The lamination factor is effective by: