ABSTRACT
Power transformers are selected based on the application, with the emphasis toward custom design being more apparent the larger the unit. Power transformers are available for step-up operation, primarily used at the generator and referred to as generator step-up transformers, and for step-down operation, mainly used to feed distribution circuits. In the United States, transformers are rated based on the power output they are capable of delivering continuously at a specified rated voltage and frequency under “usual” operating conditions without exceeding prescribed internal temperature limitations. The normal life expectancy of a power transformer is generally assumed to be about 30 years of service when operated within its rating. The conductors used in power transformers are typically stranded with a rectangular cross section, although some transformers at the lowest ratings may use sheet or foil conductors. Rectangular cores are used for smaller ratings and as auxiliary transformers used within a power transformer.
