Stacking factor
The stacking factor (also lamination factor or space factor[1]) 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. Between the metal sheets is a non-ferro-magnetic insulator, therefore, when calculating the flux density of the iron core this non-ferromagnetic material 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.[2]
Stacking factors are typically 0.95 or higher for transformer cores[3] and machine stators.[4] However, cores made from amorphous metal have a stacking factor of 0.8, compared to 0.96 for silicon steel.[1]
References
- ^ a b Barry W. Kennedy, Energy Efficient Transformers, p. 140, McGraw Hill Professional, 1998 ISBN 0070342881.
- ^ "Laminated cores simulation", Quick Field, accessed and archived 29 September 2019.
- ^ W.G. Hurley, W.H. Wölfle, Transformers and Inductors for Power Electronics, p. 109, John Wiley & Sons, 2013 ISBN 1118544676.
- ^ Jacek F. Gieras, Rong-Jie Wang, Maarten J. Kamper, Axial Flux Permanent Magnet Brushless Machines, p. 81, Springer Science & Business Media, 2008 ISBN 1402082274.
