A brief history of the power transformer

Around 130 years ago a technical revolution took place that was to be a vital step in the development of modern society

History is marked by a series of great inventions that have swept across society, acting as stepping stones in the emergence of the modern world. Most people would agree that fire, the wheel, modern transportation and communication systems, culminating with the Internet all have a place on this list. Maybe less obvious but equally pivotal is the large-scale transmission and delivery of electrical energy over long distances. This breakthrough that would not have been possible without the transformer. In the first of three posts I will take a brief tour of the history behind the transformer.

A look back in time

Around 130 years ago a technical revolution took place that was to be a vital step in the development of modern society. That revolution was the commercial generation, transmission and usage of electrical energy. Nobody today can imagine a world without electricity. However, I will start by taking you back to the early days when pioneers like Thomas Edison and George Westinghouse – and their ideas were competing for the transmission system of the future: Should it be DC or should it be AC?

Very early electrical installations were local: The sites of generation and consumption were at most a handful of kilometers apart: Direct connections from the steam or hydro generators to the consumers were in the range of hundreds of volts. In the early 1880s, for example, the “Edison Illuminating Company” supplied 59 customers in Lower Manhattan with electricity at 110 V DC. But the energy demand of the fast growing cities and industrial centers called for an increase in power transmission capability.

The world’s largest transformer in 1942 (220kV / 120 MVA) at the Vartan substation Stockholm

The small steam and hydro generators were no longer sufficient and larger power plants were erected more remotely from the cities. Voltage levels had to be increased to keep nominal currents on the power lines moderate and reduce losses and voltage drops. This was the time of the birth of a new component: the power transformer.

In a transformer, two coils are arranged concentrically so that the magnetic field generated by the current in one coil induces a voltage in the other. This physical principle can only be applied in AC systems, as only a time-varying magnetic field is able to induce a voltage. By using a different number of winding turns in the two coils, a higher or lower voltage can be obtained.

The ability to transform from one voltage level to another one was the main reason for the breakthrough of AC three-phase transmission and distribution systems. These AC systems operate at a frequency high enough that human short perception does not see the time variation (“flickering”) and low enough that switching equipment can be operated safely. The best compromise was the well-known 50 or 60Hz of the today’s mains supplies.

Join me in my next post where I delve into transformer technology and its applications

*Editor’s note: The original article was written by Max Claessens and published in the special report on Transformers





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Gregory Hollings

Working every day to produce stories that highlight ABB's innovations!
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