The formulae to calculate the loss factor for screen and sheath $\lambda_1$ use the resistance of the sheath $R_{sh}$ or screen $R_{sc}$ at its maximum operating temperature. Because the temperature of the sheath or screen is a function of the current, $I_c$, an iterative method is used for the calculation.

Symbol
$\theta_{\mathrm{s}}$
Unit
°C
Formulae
$- T_{\mathrm{1}} \left(W_{\mathrm{c}} + \frac{W_{\mathrm{d}}}{2}\right) + \theta_{\mathrm{c}}$
$\theta_{\mathrm{c}}$
$W_{\mathrm{c}}$
$W_{\mathrm{d}}$