Stacking factor
The stacking factor is used in electrical transformer design. Since transformers are made up of metal sheets, almost always iron, they are laminated so they do not contact each other. This is done to reduce the intensity of eddy current losses in the core, while keeping a high flux carrying capacity. The lamination is not a ferro-magnetic material, therefore, when calculating the flux density of the iron core this must be taken into account. The stacking factor gives an approximate number to how much of the core is effective when calculating flux.
Flux and Flux Density are related by area. The apparent area of the core is the measured area, where the lamination is included in the measurement. The effective area of the core is the area that actually affects the flux density calculation. The effective area can be found using the following relationship.
Aeffective=ksAapparent
The stacking factor will always be less than 1, this is because a stacking factor of 1 means that there is no laminate on the metal sheets. From this equation one can also calculate the stacking factor through algebraic manipulation given that the effective area is known.
The stacking factor is also known as the lamination factor or the space factor.
The stacking factor is usually known before the actual manufacturing of the transformer since calculation after the transformer is assembled would be wrought with measurements errors. Therefore, information for any particular transformer should be collected directly from the manufacturer before performing any kind of test to avoid serious damage.