Power Transformer

A static electromagnetic device that transfers electrical energy between two or more circuits through mutual induction, simultaneously changing voltage and current levels while keeping power nearly constant (P_in ≈ P_out, S_in = S_out). Transformers enable bulk power to be transmitted at high voltages — reducing current and therefore I²R losses — then stepped down for distribution and end-use. A large power transformer is rated in MVA with a nameplate voltage ratio (e.g., 500/230 kV); it is typically the single most expensive and critical piece of equipment in a transmission substation, with lead times of 12–24 months for large units.

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