I2Rhäviö

I2Rhäviö, commonly written I^2R-häviö, refers to the heat losses in electrical conductors and components that arise from the resistance encountered by electric current. The term is used especially in power engineering and electronics to describe the portion of electrical power that is dissipated as heat due to ohmic resistance.

The loss power is given by P = I^2 R, where I is the root-mean-square current and R is the electrical resistance of the path at the operating temperature. Since resistance increases with temperature for most conductors, I^2R-häviö can grow as devices operate, creating a feedback that must be managed by cooling and thermal design.

In power systems such as transformers, motors, cables and transmission lines, I^2R-häviö accounts for a substantial part of copper losses. In AC operation, skin effect and proximity effects can raise the effective resistance at higher frequencies, increasing I^2R losses beyond the DC value.

Reducing I^2R-häviö involves lowering current for a given power (for example by increasing system voltage), using conductors with larger cross-sectional area or lower resistivity, and improving cooling to keep resistance lower. In high-frequency or high-current applications, stranded conductors or litz wire and careful distribution design help mitigate skin and proximity effects. In specialized systems, superconductors offer near-zero resistance, but require cryogenic cooling.

Because I^2R-häviö is temperature-dependent and accumulates as heat, it is a central consideration in efficiency calculations and thermal management of electrical equipment. Accurate modeling often treats I^2R losses separately from core and stray losses to optimize performance.