Overview
Aluminum and copper have many similarities, for example, both oxidize over time. They suffer similar losses in performance, depending on how they are coiled or wound. These factors are part of the reason why there is an ongoing debate about which metal is superior for alternator winding performance.
Advantages of aluminum windings
- The cost of aluminum is much lower than that of copper, thus providing commercial advantages.
- Aluminum has a very thin layer of oxide on its surface that prevents air and water from entering the metal, thus resisting corrosion.
- Although copper is more conductive, the same weight of aluminum has proven to be almost twice as effective a conductor.
- Aluminum is more flexible than copper and therefore easier to wrap during production.
- The higher resistivity of aluminum inherently results in lower eddy current losses in the windings. This reduces the risk of hot spots.
Disadvantages of aluminum windings
- Aluminum connections are susceptible to oxidation. The connection must pierce the aluminum oxide layer so that it remains airtight
- An aluminum wound coil is larger than an equivalent copper coil, meaning it requires approximately 1.8 times the cross-section to carry the same amount of current.
Advantages of copper windings
- Copper is stronger than aluminum. It expands less, but both materials have similar maintenance schedules.
- Copper can carry almost twice the current capacity of aluminum, making them slightly smaller than aluminum wound alternators.
- In rare cases, generators with copper windings are less expensive to manufacture because they are smaller. But it is open to copper price fluctuations.
- The smaller size of copper alternators reduces the cost of the magnets used, but this does not make them more competitive than aluminum wound alternators.
Advantages of copper windings
- Copper is much more expensive than aluminum.
- Copper is more difficult to wind into a core than the softer aluminum.
- Copper is becoming increasingly scarce, with most supplies going to China.
Conclusion
It looks like this fight will last a full twelve rounds, ultimately coming down to the judges’ scorecards. No doubt there will be a rematch in the near future.
The fact is that an alternator wound with aluminum or copper coils may have similar losses and performance, depending on its actual design. Because both aluminum and copper alternators use the same insulation system and have similar temperature rises, they have similar rated lifespans. However, in the cost-conscious era, aluminum is proving to be the most admirable choice.