William Stanley designed the first commercial transformer for Westinghouse in 1886. Very high voltages are required to transmit electricity across long distances, but are quite dangerous and not suitable in homes. A transformer makes it possible to step up (increase) the voltage of a current in order to transmit it, then to step it down (decrease) to power lights, appliances, etc. Transformers only work with alternating current and are typically formed from coupled coils of wire wound around a metallic core. Stanley built the core of his transformer from a series of E-shaped plates of iron linked together.
Michael Faraday discovered the principle of mutual inductance, upon which the transformer is based, in the 1830s. Nearly half a century passed, however, before the principle was applied to commercial purposes, rather than just scientific research. In the late 1870s, Pavel Yablochkov built a system of electric candles that used induction coils that functioned as transformers. A few years later, Frenchman Lucien Gaulard and John Dixon Gibbs of England demonstrated a transformer, which they called a “secondary generator,” in London. The device roused the attention of an American entrepreneur, George Westinghouse, who bought the patent rights. While the Gaulard-Gibbs transformer demonstrated significant promise, Westinghouse asked the chief engineer in his Pittsburgh factory, William Stanley, to improve its design.
A native of Brooklyn, New York, Stanley studied at Yale University, where he abandoned plans for a legal career to pursue a dream of electrical invention. After getting his feet wet as an electrician, he worked as an assistant to inventor Hiram Maxim, whose electrical innovations made him a rival of Thomas Edison. With Maxim, Stanley helped implement an electrical system to provide power to a shop on New York’s Fifth Avenue, one of the first of its kind. His achievements distinguished Stanley among others in the burgeoning electric industry and gained him the important position with Westinghouse.
While working on his transformer design in 1885, Stanley fell ill. On his doctor’s advice, he moved from the city to live with family in Great Barrington, Massachusetts. The slower pace of life allowed him time to transform his dream into a reality. By 1886, Stanley completed a prototype of a new parallel-connected transformer (the transformers built by Gaulard and Gibbs were connected in series). On March 20 of that year, he publicly demonstrated its use as part of an AC electric system that provided power to the businesses along Great Barrington’s Main Street. To light the shops and offices, he ran wires between them along the tops of trees that lined the street and linked them to a central station featuring a Siemens generator. He then used his transformers to step up the generator’s voltage for transmission, and then stepped the current back down with transformers placed in the basements of several of the businesses.
Stanley’s feat proved that high voltage transmission was practical and safe. Also, the parallel linkage of the transformers ensured that performance was relatively stable; any changes in load on one transformer did not affect the others. Westinghouse began commercially producing Stanley transformers less than a year after the Great Barrington demonstration. Stanley’s invention, along with additional AC advancements made by Nikola Tesla and others, gradually diminished the call for the direct current (DC) power that Edison had been championing. DC could not be safely transmitted very far because there was no way to increase or decrease voltages. In an ironic twist of history, Stanley was awarded the Edison Medal (named in honor of the great inventor) by the American Institute of Electrical Engineers in 1912 for work that helped cement the defeat of Edison’s DC system. Today AC systems and transformers that follow the same basic design as Stanley’s continue to supply almost all the world’s power.
In 1890, Stanley ventured out on his own to form the Stanley Electric Manufacturing Company. Working with John J. Kelley and Cummings Chesney, he developed an advanced AC transmission system known as the “SKC system.” The company’s early success led to its purchase in 1893 by General Electric, an enduring giant in the electric industry.