aluminum foil strip


Aluminum Conductor in Resin Cast Dry-Type Transformer

Source:Original Editing:frank Time:2022-04-25 18:03
The use of aluminum instead of copper as the raw material for making transformer windings began in my country in the 1970s, but it was not long before transformers that replaced copper with aluminum were no longer advocated and manufactured. The reason is that the resistivity of aluminum is higher, and the conductivity is only 60% of that of copper. Under the same voltage level, capacity and loss, the volume of the Aluminum Conductor in Resin Cast Dry-Type Transformer is larger; It is believed that the mechanical strength of aluminum and the ability to withstand thermal shock are far inferior to that of copper, so it is believed that the dynamic and thermal stability of aluminum-based copper transformers is poor; in addition, the problem of copper-aluminum welding has not been well solved, which also restricts the development of aluminum winding transformers. . However, since the production of copper has been difficult to meet the increasing demand, aluminum winding transformers have been gradually developed all over the world. At present, in foreign countries, the production technology of Aluminum Conductor in Resin Cast Dry-Type Transformer is very mature and is widely used. At the same time, due to the violent fluctuation of copper prices in recent years, the development of aluminum winding epoxy resin cast dry-type transformers has gradually formed a consensus among domestic dry-type transformer manufacturers, and has been manufactured in large quantities.

Aluminum foil in resin cast dry type transformer is a kind of resin cast dry-type transformer that entered China earlier. In the early 1990s, this kind of transformer experienced a period of high accident incidence. Through analysis, the main causes of the accident are the quality, process and tooling of aluminum foil. With the development of raw material industry and the continuous improvement of dry-type transformer pouring equipment, the product quality produced by some domestic manufacturers after appropriate process improvement of this technology has been very stable. Compared with other types of resin cast dry-type transformer, this type of product has the following advantages.
(1) Compared with wire wound winding, the production efficiency of foil wound winding is significantly improved, and the tooling and die are simple, which is conducive to organizing large-scale production.
(2) When wire winding is used for high and low voltage, the reactance height of the two windings often varies greatly, especially for products with large capacity. Due to the large low-voltage current, multiple wires need to be wound together, and the ampere turn distribution between high and low voltage is uneven, which will produce great transverse magnetic leakage during transformer operation, which is not conducive to the dynamic and thermal stability of the transformer. The winding made of foil conductor can easily solve this problem.
(3) The interlaminar voltage of foil winding is the turn to turn voltage, and the interlaminar voltage of wire wound winding is equal to the product of turn voltage and number of turns. From the perspective of electric field strength, the interlaminar field strength of wire wound winding is much higher, and it is much simpler to deal with the interlaminar insulation of foil wound winding.
(4) The eddy current loss of transformer winding is directly proportional to the fourth power of the radial thickness of the conductor, while the foil wound winding, especially the low-voltage winding, can effectively reduce the eddy current loss of the winding due to the thin foil. Compared with wire wound winding, the eddy current loss of foil wound winding is reduced by about 40%
(5) When the high-voltage winding adopts multi-stage foil winding, due to the large longitudinal series capacitance of the winding, the lightning impulse resistance of the dry-type transformer is greatly improved.
The voltage gradient distribution has strong lightning impulse resistance. It is precisely because the resin cast dry-type transformer with aluminum foil wound high and low voltage has the above five advantages that this type of transformer has been greatly recognized and developed well in Europe. At the same time, this type of resin cast dry-type transformer also occupies a considerable market share in China. The author believes that domestic manufacturers can give priority to this type of aluminum winding transformer when manufacturing aluminum conductor transformer.
Aluminum foil wound in resin cast dry type transformer, especially the one used aluminum foil is adopted for high and low voltage windings. The technical performance, dynamic and thermal stability of the products are no worse than that of copper winding dry-type transformer. At the same time, the excellent economic and technical indexes of aluminum winding transformer are energy-saving products that need to be developed in China. In fact, due to the increasingly prominent contradiction between supply and demand of copper materials and the violent fluctuation of copper price in recent years, many transformer manufacturers have to use aluminum conductor to replace copper conductor. These aluminum winding transformers that have operated safely for several years have well proved the reliability of aluminum winding transformers, indicating that aluminum winding resin cast dry-type transformers are worthy of vigorous promotion.