This is the conductor temperature rise above ambient temperature.

$\Delta\theta_R(t)$: Conductor temperature rise above ambient at time t after application of current $I_{c2}$, neglecting variation in conductor resistance.

$\Delta\theta_R(i)$: Conductor temperature rise above ambient, when the magnitude fo the step function current is the sustained rated current, and $i$ is expressed in hours.

$\Delta\theta_R(\infty)$: Conductor temperature rise above ambient in the steady state, i.e. the standard maximum permissible temperature rise.

Symbol
$\Delta \theta_{\mathrm{R}}$
Unit
K
Related
$M$