Performance comparison of copper and aluminum conductors in transformer windings

The difference between copper and aluminum transformers is also determined by the difference in materials, which is specifically reflected in the following aspects:

1) The resistivity of copper conductors is only about 60% of that of aluminum conductors. In order to achieve the same loss and temperature rise requirements, the cross-sectional area of aluminum conductors needs to be more than 60% larger than that of copper conductors. Therefore, under the same capacity and parameters, the volume of aluminum conductor transformers is usually larger than that of copper conductor transformers. However, the heat dissipation area of the transformer also increases at this time, so it has less impact on the oil temperature rise; 2) The density of aluminum is only about 30% of copper, so aluminum conductor distribution transformers are lighter than copper conductor distribution transformers;

3) The melting point of aluminum conductors is much lower than that of copper conductors, so its short-circuit current temperature rise limit is 250°C, which is lower than the 350°C of copper conductors. Therefore, their design electrical density should be lower than that of copper conductors, and the cross-sectional area of the transformer conductors should be larger, resulting in a larger volume than a copper conductor transformer;

4) Aluminum conductors have lower hardness and are easier to eliminate surface burrs. Therefore, after making the transformer, the probability of short circuit between turns or layers caused by burrs is reduced; 5) Due to the lower tensile and compressive strength and poor mechanical strength of aluminum conductors, the short-circuit resistance of aluminum conductor transformers is not as good as that of copper conductor transformers. When performing dynamic stability calculations, the stress of the aluminum conductor should be less than 450kg/cm2, while the stress limit of the copper conductor is 1600kg/cm2, which greatly improves its load-bearing capacity;

6) The welding process of aluminum conductors and copper conductors is poor, and the quality of joint welding is difficult to guarantee, which affects the reliability of aluminum conductors to a certain extent.

7) The specific heat of aluminum conductors is 239% of that of copper conductors, but considering the difference in density and design electrical density, the actual difference in thermal time constants between the two is not as big as the difference in specific heat. Therefore, it has little impact on the short-term overload capacity of aluminum conductor dry-type transformers.