The creation of power transformers

Power transformers: from design to delivery

ABB designs and manufactures some 1300 power transformers a year, for all voltages and applications, at 22 focused factories all over the world.


1945: Made to run for 40 years.

2003: Transformers are tailor-made solutions.

ABB power transformers are engineered to run for a long time, 40 years or more, non-stop and with minimal maintenance. They are tailor-made to meet the exact specifications of the customer and the transmission system in which it is to function.


ABB designs and optimizes a transformer from the customer’s specifications. The design is then verified using advanced simulation software to ensure that the transformer meets customer requirements and international standards, and that it will withstand all forms of natural, mechanical and electrical stress.


Power transformers are made from high-grade materials – a very special type of electrical steel for the core (the steel is made at only a handful of mills in the world), high-grade copper for the windings, and cellulose-based paper for insulation.


It takes three months to make a medium-sized power transformer of 200-300 MVA. Much of the work is highly skilled and done by hand.

A transformer requires between 1,000 and 3,000 laminations of electrical steel, each of which is laid by hand.

The copper windings are wound by hand. Precision is vital, as are craftsmanship, knowledge and experience, and testing cannot take place until the transformer is finished. If a mistake is made during construction, the transformer has to be rebuilt at great cost.

Curing and immersion

The coils of windings and cellulose are cured to remove all traces of air and moisture. After drying and vacuum processing, the coils and the transformer core are immersed in oil, which has a better dielectric strength than air. All power transformers are oil-filled.


A medium-sized power transformer of 200-300 MVA measures approximately 3 x 4.5 x 6 meters and weighs about 100 tons. Transport is by road or rail, or even by air in special cases. Rail transport is most common.


An advanced acceptance test is performed before the transformer leaves the factory. ABB engineers make or supervise the installation to ABB standards; commissioning is performed by the buying utility.

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    The evolution of Power transformer

    • ABB built one of the first power transformers in 1893 and remains market leader – in terms of market share, installed base and technological innovation – to this day.

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