Power losses arise from core (iron) losses, copper (winding) losses, stray losses, and dielectric losses. Core losses include hysteresis and eddy currents due to alternating flux in the core. Copper losses are I²R heating in windings under load. Stray losses occur when leakage flux induces currents in structural parts, clamps, and tank walls. Dielectric losses occur in insulation and oil under electric stress. Together they reduce efficiency and generate heat that must be removed by the cooling system.