Cableizer
Log in

Conductor to surface attainment factor

This is the attainment factor for the temperature rise of the conductor above the outside surface of the cable according to the IEC 60853-2 standard. This factor takes the thermal capacitance of the cable into account and approaches a value of 1.0 if the transient time periods are sufficiently long compared to the thermal time constant of the cable.

The applied formula is equivalent to the following formula: $\Delta\theta_{c_t}/(n_{c}W_{c}(T_A+T_B))$

Symbol
$\alpha_t$
Formulae
$\frac{T_{a0} \left(1-e^{-a_0 \tau}\right)+T_{b0} \left(1-e^{-b_0 \tau}\right)}{T_A+T_B}$
Related
$a_0$
Coefficient a for partial transient temperature rise [1/s]
$b_0$
Coefficient b for partial transient temperature rise [1/s]
$T_A$
Element A of equivalent thermal circuit [K.m/W]
$T_{a0}$
Apparent thermal resistance a [K.m/W]
$T_B$
Element B of equivalent thermal circuit [K.m/W]
$T_{b0}$
Apparent thermal resistance b [K.m/W]
$\tau$
Transient load period [s]
Used in
$\Delta \theta_{c,t}$
Transient temperature rise of conductor [K]
$\theta_R$
Rated current transient to steady-state ratio