Why use copper rather than aluminium in power transformers?

servo-blog-aluminium-for-power-transformersPower transformers are at the heart of all modern systems. Without electricity, the world can’t run, and without transformers, the electrical system can’t be thought of.

Do you know what’s in the heart of these transformers?

Yes, you got it right! It’s the windings of the transformers, without which they can’t work. These windings are either of Copper or Aluminium. However, copper windings are preferred over the Aluminium windings as they are better and superior in many respects than them. Let’s discuss them one by one what makes the copper preferred choice than Aluminium exclusively when it comes to the transformers.

Why do we Prefer Copper over Aluminium in transformers?

1. Lower Creep Level – Copper has much lower creep than that of aluminium. The creep rate of aluminium goes up to 25 times under the extreme loading and high-temperature conditions and this makes the aluminium wounded transformers more vulnerable to failures than that of copper wound transformers.

2. Durable and long-lasting terminations – The copper terminations are durable and long-lasting than that of aluminium because of the difference in the formation of the oxides which forms during their life span. Copper oxide is soft and electrically conductive. It easily breaks down also. Whereas, the aluminium oxide is just opposite of it that it’s tough as it got strongly clanged to the terminals and is hard to dislodge ones get formed and accumulated. Above all the aluminium oxide formed on the terminals are electrically insulating also. Aluminium requires a layer of tin, copper or nickel in case you are going for non-mechanical connections as soldering, etc.

3. No galvanic action – There is no galvanic action in case of copper to copper terminations. Therefore, in the case of copper windings, the terminations made from the transformers allow for copper to copper terminations at the transformer terminals. The connectors are normally made up of copper or copper alloys such as brass etc. therefore, there is no danger of galvanic action during their terminations. Whereas, Aluminium when in touch with copper or copper alloys during termination loses material through galvanic action and leads to loosening of contacts or complete loss of contacts.

4. Harder, stronger and ductile – Copper is much harder, stronger and ductile than aluminium and all this let copper expand less and does not let it flow at termination points, thus preventing regular inspections and other maintenance as tightening connections or checking terminations. Aluminium being weaker flows away from the terminals when tightened and if not tightened properly, it leads to loose connections, sparking or maybe fire in the installations, if left unchecked for longer durations.

5. High Short-Circuit withstands capability – Copper, when compared to aluminium, has marvellous mechanical properties, such as yield strength or modulus of elasticity. This leads to exclusively going for copper wounded transformers when it comes to transformers where short-circuits probability is higher, in such as arc furnaces. The frequent short-circuits deteriorate the systems and leads to the significant weakening of transformers and their terminations, in turn reducing the reliability of transformers and the entire system as such.

6. Smaller and lighter – Copper wound transformers are smaller, lighter and compact than aluminium transformers of the same rating. The copper has low resistivity in comparison to that of aluminium. It’s just 0.6 times that of aluminium and in case of going for the aluminium wound transformer than the cross-section of the conductor required is of 1.66 times higher than that of copper. This results in overall larger size of everything whatever is used in the manufacturing of the transformers such as transformer tanks, oil, core, contacts, insulation, etc. And all this led to a heavier and larger transformer which requires a larger and stronger area for being installed.

7. Less Metal fatigue – The High Voltage windings in case they are made up of copper they are less susceptible to metal fatigue than that of aluminium windings, as the fatigue life of the aluminium conductor is much less in comparison to that of copper. This made the aluminium transformers more prone to failures once the windings get loose over a period of operation

8. High performance – The copper wounded transformers have higher performance, better efficiency and lower lifecycle cost as they have lower energy losses and are dear to the consumers pocket rather than drilling a hole, as it happens in the case of aluminium transformers, where the maintenance cost, operational cost, installation cost and other running expenses are much higher than that of copper wounded transformers.

9. Better current distribution – The current distribution in copper conductors is better than that of aluminium due to its higher conductivity and metallurgical properties. This prevents non-linear loads from causing additional losses as they do in the aluminium wounded transformers, thus making copper wounded transformers a better choice.

10. Less expensive to manufacture – The copper wounded transformers are less expensive while manufacturing in comparison to that of aluminium ones because of less material and cross-section of the conductor required. It requires smaller machines and other facilities such as smaller powder coating set-up, smaller quality control labs, less storage area, etc. required during manufacturing, making it more viable to manufacture than that of aluminium wounded transformers.


By now you would have realized that the best choice while selecting the right transformer for your set up would be the copper wounded transformer rather than aluminium wounded transformers because of their plethora of benefits and other advantages over the aluminium ones.

Servostar is the renowned manufacturers and suppliers of transformers and stabilizers for more than the last two decades throughout PAN India.