To transformer enterprises, the raw materials for transformer winding has several choices, the aluminum strips and the copper strips. In addition to the low cost, the aluminum strips also have other advantages than the copper strip wire, that is the thermal stress resistance, and this is one of the reasons why more and more people choose to buy transformer aluminium strip.
Aluminium strips are much more resistant to thermal stress than copper strips. The thermal expansion coefficient of the epoxy resin is 3.3×10-5 (mm/mm.h.°C), and the thermal expansion coefficient of the copper material is 1.6×10-5 (mm/mm.h.°C), which is more than doubled. The thermal expansion coefficient of the transformer aluminium strip is 2.3×10-5 (mm/mm.h.°C), which is only 1.0×10-5 (mm/mm.h.°C) smaller than the resin. In daily operation, due to the change of load, the temperature of the dry-changing coil changes, and the thermal expansion coefficient of the conductor and the resin will generate thermal stress. If the thermal stress is too large and repeated, the resin will be cracked. Compared with copper, the thermal expansion coefficient of aluminium strips is closer to epoxy resin, which reduces thermal stress, which greatly improves the crack resistance and safety of dry-type transformers and prolongs the service life of equipment. It can be seen that the dry-type transformer high-voltage coil wound with copper foil or copper wire is more likely to crack than the coil wound by the aluminum strip, and the service life is relatively short. Therefore, more and more enterprises prefer to buy transformer aluminium strip than copper strip.
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