The transformer serves many purposes in an electrical power distribution system. It can step up voltages to permit large amounts of power to be transmitted over long distances with minimum losses, and then step that voltage down to user levels. They permit parts of the electrical system to be electrically isolated from other parts for safety or convenience, and allow electrical quantities to be measured or scaled proportionally. Transformers operate at very high efficiencies, use stationary, rugged structures with no moving parts (except for some accessories on the largest units), and are well understood. The discussion here concentrates on transformers used at low and medium voltage levels.

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System Voltage Variations
Electrical Service And Distribution
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