Stacking factor

The stacking factor is the ratio of electrical steel along the axial length of the iron core.

The magnetic core of electrical machines is often made up of thin iron laminations in order to reduce eddy-current losses and improve the performance. These lamination sheets are slightly insulated with a coating and are oriented in parallel with the direction of the magnetic flux. Laminating a core increases its volume not only due to the applied coating, but also since the stacked laminations are not perfectly flat due to manufacturing or processing, e.g. punching.

It is important to account for the stacking factor when designing an electrical machine, since a stacking factor of less than 1.0 reduces the flux carrying capacity of the iron core accordingly. The stacking factor is low for very thin iron laminations and is approaching unity as the lamination thickness increases. The stacking factor is sometimes also called lamination factor or space factor.

In the electric machine design software Emetor, you can provide a stacking factor for both the stator and rotor laminations (0.1 <= stacking factor <= 1). You can find the corresponding inputs in the preprocessor under the section "Axial parameters". In such a way, it is possible to simulate machine designs with different iron lamination materials in the stator and rotor. In order to get a reasonable estimate of the stacking factor, check the materials library for your specific material or use the rule of thumb that Emetor uses in order to estimate the stacking factor when there is no value available from the manufacturer.

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