The aluminium foil used for transformer winding is required high-quality pure aluminum as raw materials which has high conductivity, soft characteristics, smooth surface, is an ideal material for the production of dry-type transformers, and the key raw material for transformer winding.
In dry type transformers, aluminium–aluminium windings have been commonly used nowday. Aluminium foil strip can replace copper conductors in distribution transformers. Aluminum foil and sheet in appropriate strip widths and lengths have widely replaced wire in electrical transformers.
Aluminum foil transformers
| Grade | Al(%) MIN |
Si(%) Max |
Fe(%) Max |
Cu(%) Max |
MN(%) Max |
Zn(%) Max |
Mg(%) Max |
Ti(%) Max |
Other elements(%) |
| 1050 | 99.5 | 0.25 | 0.4 | 0.05 | 0.05 | 0.05 | 0.05 | 0.03 | 0.03 |
| 1060 | 99.6 | 0.25 | 0.35 | 0.05 | 0.03 | 0.05 | 0.03 | 0.03 | 0.03 |
| 1070 | 99.7 | 0.25 | 0.04 | 0.03 | 0.04 | 0.04 | 0.03 | 0.03 | |
| 1350 | 99.5 | 0.1 | 0.05 | 0.01 | 0.01 | — | — | 0.03 |
Foil winding transformers
| Grade & Temper | Thickness | Width |
| 1050/1060/1070/1350-HO(O) | 0.2-3.0 mm | 20-1350 mm |
| Inner Diameter | Conductivity Number (% IACS) |
Reisitivity number (Ω·mm² /m) |
| 150/300/400/500 mm | ≥61 | ≤0.027548 |
| Elongation (%) | Tensile strength(Mpa) | Density in 20°C |
| 20 | >60 | 2.7kg/cm3 |
How do aluminum foil for transformer designs work?
Basic construction consists of electrical grade aluminum or copper foil, temperature-suitable interwinding insulation, fiberglass and nomex sheet insulation. The unit is then vacuum pressure impregnated (VPI) with a specially formulated epoxy resin designed to assist in heat transfer and to bond the components into a stable, dense unit.
Designers of transformer manufacturer usually select 1050,1060,1070,1350 grade, the aluminum content is min 95% but commonly above 99.6%-99.7 %. Aluminium sheet foils are mainly used in dry-type transformers of high and low voltage winding as a conductive material. As aluminum transformers tend to be less costly than copper transformers, therefore, aluminium strip is the most popular material for transformer strip.
Aluminum foil for transformer winding application
Transformers are designed and built with copper or aluminium windings. But transformers using aluminum foil winding have advantage of small size, light weight, good insulation properties, flame retardant, non-polluting, partial discharge, resistant to moisture, smooth and reliable operation, low noise, and low maintenance cost.