Copper windings and aluminum windings of distribution transformers are the core differentiating factors that affect their performance, cost, and service life. There are significant differences between the two in terms of material properties, electrical performance, economy, and operation and maintenance requirements. This article will analyze from multiple perspectives to provide a comprehensive understanding of their distinctions.
Losses and Efficiency
Copper windings have high electrical conductivity, resulting in lower copper losses under the same current. For example, a 1000kVA transformer with copper windings has copper losses 15%-25% lower than one with aluminum windings when operating at full load. It saves electricity during long-term operation and meets energy-saving design requirements.
Aluminum windings have low electrical conductivity, so their cross-sectional area needs to be increased to reduce resistance. However, copper losses are still slightly higher, and the efficiency is 1%-3% lower.
Overload Capacity
Copper windings have a high melting point (1083℃) and excellent thermal stability. When overloaded, the temperature rises slowly, and the insulation is not easily damaged. They can withstand overload for 1-2 hours.
Aluminum windings have a low melting point (660℃). When overloaded, the temperature rises rapidly, which easily leads to insulation aging or short circuits. They can only withstand overload for less than 30 minutes, so the load rate must be strictly controlled.
Temperature Rise and Heat Dissipation
Copper windings have high thermal conductivity (401 W/(m·K)), enabling fast heat transfer and lower temperature rise (5-10K lower than that of aluminum windings).
Aluminum windings have low thermal conductivity (237 W/(m·K)), which makes heat easy to accumulate. Larger radiators or enhanced structures need to be designed; otherwise, the service life of the insulation will be shortened.
| Parameter | Copper Winding | Aluminum Winding |
| Electrical Conductivity(20℃) | 58 MS/m | 37 MS/m |
| Cross-sectional Requirement | datum | 1.6 |
| Density | 8.9 g/cm³ | 2.7 g/cm³ |
| Tensile Strength | 200–250 MPa | 70–140 MPa |
| Melting Point | 1083℃ | 660℃ |
| Thermal Conductivity | 401 W/m·K | 237 W/m·K |
Material Cost LME 3M Cu/Al Avg (Mar–Aug 2025) | US$ 9,785/ton | US$ 2,610/ton |
Initial Purchase Cost
For example, for a 2500kVA oil-immersed transformer, the material cost of the aluminum-core version is approximately 40%-60% lower than that of the copper-core version, and the overall price difference ranges from 30% to 50%. Using an aluminum-core transformer can significantly reduce the initial investment.
Long-term Operating Cost
Copper windings have low copper losses, so the electricity cost saved during long-term operation can cover the initial price difference. Additionally, their maintenance cycle is longer, resulting in lower maintenance costs.
Aluminum windings have high copper losses, leading to 5%-10% higher electricity costs. Moreover, their insulation ages faster, requiring frequent inspections and resulting in higher maintenance costs.
Service Life Difference
Copper windings have good chemical stability and high-temperature resistance, with a designed service life of 25-30 years.
Aluminum windings are prone to oxidation and have high temperature rise, with a designed service life of 15-20 years.
In China, where the Huawei factory is located, the State Grid and the mainstream market mainly use copper-core transformers. The use of aluminum-core transformers in China's State Grid is regarded as a serious act of cutting corners by suppliers and will result in severe penalties. However, considering the return on investment, most new energy power plants use aluminum-core transformers in their packaged substations to reduce construction costs.
Globally, 80% of distribution transformers are aluminum-core. Countries such as those in the Middle East and Russia use aluminum-core transformers. The main reason is the significant cost advantage, which highly aligns with the core needs of large-scale infrastructure construction in the Middle East and the wide-area power grid coverage in Russia (especially in remote areas) for "low-cost and lightweight equipment". At the same time, it can also reduce reliance on imported copper resources, balancing economy and supply chain stability.
Copper Windings are Suitable for:
1.Areas with long-term full load / frequent overload (e.g., urban core areas, industrial parks)
2.Projects with high energy-saving requirements and pursuit of long service life (e.g., municipal engineering, large enterprises)
3.Harsh environments such as high temperature and humidity (e.g., coastal areas)
Aluminum Windings are Suitable for:
1.Rural low-load areas (low load rate, small fluctuations)
2.Temporary infrastructure projects (e.g., construction sites, temporary housing quarters)
3.Scenarios sensitive to initial costs and accepting regular maintenance
Q: What are the core performance differences between copper-wound and aluminum-wound transformers? Which scenarios are they suitable for respectively?
A: The core differences focus on 3 key dimensions:
Energy Efficiency: The conductivity of copper windings (58 MS/m) is much higher than that of aluminum (37 MS/m). For 1000kVA models, the full-load copper loss is 15%-25% lower, and the efficiency is 1%-3% higher;
Overload Capacity & Heat Resistance: Copper has a melting point of 1083℃ and can withstand overload for 1-2 hours, while aluminum (melting point 660℃) can only withstand overload for up to 30 minutes;
Service Life & Stability: The design life of copper windings is 25-30 years, compared with 15-20 years for aluminum windings.
Q: The initial purchase cost of aluminum-wound transformers is 30%-50% lower than that of copper-wound ones. Which is more cost-effective for long-term use?
A: The decision should be based on "service cycle + load factor":
Short-term & Low-load Scenarios (e.g., temporary construction sites, rural power distribution areas): Aluminum windings have a 30%-50% lower initial cost (taking 2500kVA oil-immersed models as an example). When the load factor is low, the difference in copper loss is small, making aluminum windings more cost-effective;
Long-term & Full-load Scenarios (e.g., industrial parks, municipal engineering): Although copper windings have a higher initial cost, they save 5%-10% in annual electricity fees, and the initial price difference can be recovered within 2-5 years. With a service life about 10 years longer and lower operation and maintenance costs, copper windings are more economical throughout the entire life cycle.
Q: What problems are aluminum-wound transformers prone to in high-temperature, humid environments or under frequent overload? How to avoid them?
A: The core shortcomings of aluminum windings are "easy oxidation + high temperature rise": In high-temperature and humid environments, the oxidation rate of aluminum wires accelerates, leading to increased contact resistance and accelerated insulation aging; under frequent overload, the temperature rises rapidly, which may easily cause short-circuit faults. Avoidance Solutions:
If aluminum windings must be selected, optimize the radiator design (increase heat dissipation area) and strictly control the load factor (avoid long-term operation exceeding 50% of the rated load);
For high-temperature, humid, and frequent overload scenarios (e.g., coastal industrial parks), prioritize copper windings — their thermal conductivity (401 W/m·K) is 1.7 times that of aluminum, with a temperature rise 5-10K lower and stronger chemical stability, which can avoid the above problems.
Q: What are the selection preferences in different regions around the world?
A: 80% of distribution transformers worldwide are aluminum-core. Russia (85%) and the Middle East (70%) have the highest proportion due to demands for low cost and light weight, followed by Europe (60%) and Asia-Pacific (70%). Only 20% of transformers in Europe and North America use aluminum cores, with a greater focus on energy saving and long service life.
Q: What targeted support can be obtained by choosing Huawan's copper/aluminum-wound transformers? How to get a scenario-adapted selection plan and quotation?
A: Huawan provides 2 core guarantees:
Compliance Guarantee: The transformers comply with international universal standards and meet mainstream global technical specifications, adapting to new energy and overseas infrastructure needs;
After-sales Guarantee: 1-2 years warranty, with special operation and maintenance guidance to reduce inspection costs.
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