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Page 3

| 1 Theory of Operation.. |

| Introduction: The Transformer |

| The invention of the transformer in 1884, overcoming the technical and economic limitations associated with the original dc (direct current) commercial system, made practical the eventual availability of electric power to almost every home, farm, office, store, and factory. The first commercial ac (alternating current) distribution system using transformers was put in operation two years later in Great Barrington, Mass. In the same year, 1886, ac power was transmitted at 2000 volts over 30 kilometers of line built at Cerchi, Italy. From these small beginnings, the electric power industry has grown to the giant, almost universal, force for the good of mankind the world has ever seen. For all practical purposes, this industry today is entirely a supplier of alternating current; and its development is entirely due to the transformer. |

| Figure 1-1 (on page 4), showing typical facilities required to supply electric service, vividly indicates the many places in the supply system where transformers are used. |

| What It Does |

| The transformer is a device, having no moving parts, which transfers electric power form one circuit to another by electromagnetic means, usually with changes in values of both voltage and current. A step-up transformer receives electrical power at one voltage and delivers it at a higher voltage; conversely, a step-down transformer receives electrical power at one voltage and delivers it at a lower voltage. |

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