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AC arc welders, as the most widely used welding equipment in the welding industry, hold a quite important position in the minds of users. For a long time, the huge market size has made AC arc welders a highly competitive area in the welding industry, which has directly led to a mixed quality of products available in this market. As a result, users are inevitably led into various misunderstandings: one is the belief that the heavier the AC welding machine, the better it is, and the other is the belief that AC welding machines made of copper are superior to those made of aluminum. Regarding the **standards** for AC arc welders, there are no standards regarding the weight or material of the welders; the main criteria for assessing their quality are their electrical performance and safety features. Users hold such views because AC arc welders have always been regarded as labor-intensive products with low technical complexity, and the majority of AC arc welders in the 20th century were made using copper coils. However, as people’s awareness of energy issues continues to grow and their concepts of reform evolve, the materials used in arc welding machines have been improved, and domestic researchers have clearly highlighted the advantages of using aluminum in place of copper. 1. High-purity imported aluminum is used to replace copper in the construction of the primary and secondary coils of transformers. Since copper is currently in short supply, while aluminum is abundant, metal price markets show that the price of copper is 32 yuan per kilogram, whereas the price of aluminum ranges from 23 to 27 yuan per kilogram. Moreover, aluminum, as a lightweight metal material known as the \"flying metal,\" will be widely used in various fields such as industry and daily life, both today and in the future. Although aluminum has slightly poorer electrical conductivity than copper for the same cross-sectional area, that is, its resistivity is higher than that of copper (aluminum’s resistivity β_alum ≈ 0.027, while copper’s resistivity β_copper ≈ 0.017). However, its electrical conductivity can be improved by increasing the cross-sectional area of the aluminum wire (i.e., the current-carrying area). If the cross-sectional area of aluminum wire reaches approximately 1.6 times that of copper wire (0.027/0.017), its electrical conductivity will be comparable to that of copper. Moreover, the density of aluminum is lower than that of copper (the density of copper is 8.9, while that of aluminum is 2.7). Therefore, when using aluminum instead of copper in transformers, to achieve the same level of electrical conductivity, the weight ratio of copper to aluminum is 8.9/2.7, which is approximately 1.9 times. In other words, although aluminum does not have as good electrical conductivity as copper, this deficiency can be overcome by increasing its cross-sectional area; furthermore, this approach also helps to reduce the weight of the transformer. Aluminum has a much better thermal conductivity than copper; therefore, it can dissipate more heat in the same amount of time. Moreover, since the cross-sectional area of aluminum wires is 1.6 times larger than that of copper wires, their circumference is also greater, which increases the heat dissipation area. As a result, the temperature rise of the transformer in the welding machine is lower when aluminum wires are used, and this also **increases the service life of its surface insulation layer**. Of course, the manufacturing process for aluminum is more complex than that for copper. In particular, the resistance of aluminum wires is related to the manufacturing process used to produce them as well as the purity of the aluminum, and the level of expertise in manufacturing aluminum wires in China is not high. At present, only a few welding machine manufacturers in China (such as the Sino-Japanese joint venture Tangshan Panasonic and the Sino-French joint venture St. Louis) have successfully mastered the core technology for producing welding machine transformer coils using aluminum wire on par with or even better than copper wire. They are generally made using aluminum wires with a purity of over 99.8% imported, and their surfaces are insulated with imported special transformer insulating oil; the other components are the same as those in standard welding machines. II. Silicon steel sheets: Most of the AC welding machines available on the market today are rather bulky, and the main reason for this is the unreliable quality of the silicon steel sheets used in them. By using 0.5mm imported silicon steel sheets, it is possible to **reduce the heat generation of these sheets; under the same temperature rise, this allows for a smaller size of the transformer and a reduced weight. III. Melting and solid bonding process for aluminum and copper: Since, at the same heating temperature, aluminum has a higher coefficient of expansion than copper, and aluminum’s surface oxidizes to form aluminum oxide when heated; moreover, aluminum oxide has very poor electrical conductivity. If aluminum wires and copper wires (copper terminals) are fastened together using fasteners such as bolts and nuts, the aluminum oxide on the surface of the aluminum wire will prevent proper fastening, resulting in increased resistance at the connection point, heat generation, and problems with current flow. To address this technical flaw, some domestic manufacturers (such as the ones mentioned above) employ an aluminum and copper melting and solidification process, which allows the aluminum wires at the primary and secondary output terminals to be directly bonded to the copper wires through melted metal, thereby reducing the machine’s temperature rise and losses. In summary, by adopting these three new technologies and processes, the AC arc welding machine **reduces its weight and volume, saves resources, and its reliability as well as various operational parameters meet** the standard requirements. The use of aluminum to replace copper will surely become the trend in the development of AC arc welders.