Proper transformer sizing and copper windings

By E Swanepoel, Copper Development Association Africa (CDAA)


Published in:

Electricity+Control, August 2013 (pages 46 – 48)

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The full article on Proper transformer sizing and copper windings can be downloaded in PDF format.


Transformers are essential for the transmission, distribution and utilisation of electrical energy. They are used in virtually every commercial and industrial building, from the service transformer that reduces distribution voltage, to a more usable voltage for buildings and step-down transformers that serve individual floors, and to small transformers for individual equipment. Transformers can typically be expected to operate for 20 to 30 years or more.

Over such a long lifespan, the operating cost of a transformer can greatly exceed its initial price, so the selection of the right transformer for economic performance involves examining the unit’s capacity (size) and efficiency. In this context, efficiency means looking at both the core steel and the winding material.


Take note

  • Where there is a transformer, there are losses.
  • The long term cost of the losses is now a real consideration.
  • Copper, used appropriately, remains the conductor of choice.