Among the many components of a transformer, the winding is undoubtedly one of the key components, and its performance directly affects the overall performance of the transformer. Foil winding in transformer commonly chooses aluminum foil or copper coil.
Cost and weight advantages
Aluminum is abundant in the earth's crust and is cheaper than copper. In transformer production, using aluminum foil as a winding material can significantly reduce the cost of raw materials. For example, if an aluminum foil winding is used for a transformer with a capacity of 1000kVA, the material cost can be reduced by about 20% - 30%. Moreover, the density of aluminum is only about one-third of that of copper, which greatly reduces the weight of transformers using aluminum foil winding.
For some application scenarios with strict weight requirements, such as mobile substations and transformers in the aviation field, the lightweight advantages of aluminum foil windings are particularly prominent, which is convenient for transportation and installation, and can reduce energy consumption during equipment operation.
Good electrical conductivity and heat dissipation performance
Although the electrical conductivity of aluminum is slightly lower than that of copper, the electrical conductivity requirements of the transformer can be met by rationally designing the cross-sectional area of the aluminum foil. At the same time, the aluminum foil has good thermal conductivity and can quickly dissipate the heat generated by the winding.
In actual operation, the transformer winding will generate heat due to the passage of current. If the heat cannot be dissipated in time, the winding temperature will rise, affecting the performance and life of the transformer. The heat dissipation advantage of aluminum foil winding can effectively suppress the generation of hot spot temperature of the winding. For example, in the high temperature environment in summer, the winding temperature of the transformer using aluminum foil winding can be 5-10℃ lower than that of the copper foil winding, which greatly improves the stability and reliability of the transformer operation.
Mechanical strength and short-circuit resistance
After proper processing, aluminum foil has good mechanical strength and is not easy to deform. During the operation of the transformer, especially when a short circuit occurs, the winding will be subjected to strong electromagnetic force. Aluminum foil winding can withstand large short-circuit forces and reduce the risk of winding deformation and damage due to their mechanical strength and structural characteristics.
Relevant experiments show that in simulated short-circuit tests, the winding integrity rate of aluminum foil winding transformers is 15% - 20% higher than that of ordinary winding transformers, effectively ensuring the safety of the transformer in the event of a fault.
In developed countries such as Europe, America, and Japan, the application of aluminum foil for transformer is very common. Take Fuji Electric of Japan as an example. Its dry-type transformers widely use aluminum foil with high-tech physical properties containing rare earth metals as conductors for high and low voltage coils.
This kind of aluminum foil not only maintains good conductivity, but also improves mechanical strength, has a bright surface and is not easy to oxidize. The transformer using this aluminum foil winding has achieved miniaturization and lightness, and has excellent cracking and aging resistance, and the product service life has been increased to more than 40 years.
Although aluminum foil has many advantages in transformer foil windings, it also faces some challenges. Among them, the copper-aluminum connection problem is a more prominent one. To solve this problem, special welding processes and transition connection materials are often used.
In addition, the control of the oxide layer on the surface of the aluminum foil is also a key link. Although the natural oxide layer on the surface of the aluminum foil has a certain insulation effect, it may affect the electrical performance of the winding in some cases. By adopting surface treatment technologies such as anodizing, the thickness and quality of the oxide layer can be accurately controlled to better meet the insulation requirements of the winding.