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Loss factor magnetic duct

The loss in duct made of (ferro)magnetic steel is calculated in the same fashion as the loss in steel pipes of pipe-type cables.

Symbol
$\lambda_{4}$
Formulas
${10}^{-5}\frac{0.0115s_{c}-0.001485Di_{d}}{R_{c}}$three single-core cables in trefoil in magnetic steel pipe
${10}^{-5}\frac{0.00438s_{c}+0.00226Di_{d}}{R_{c}}$three single-core cables in cradled formation in magnetic steel pipe
$\lambda_{4} \left(\frac{f}{60}\right)^2 \sqrt{\frac{60}{f}}$other frequencies than 60 Hz
$0$steel pipe is non-magnetic or a pipe-type cable with flat-wire armour over all three cores after they are laid up is used
Related
$Di_{d}$
Inner diameter duct [mm]
$e$
Constant $e$ [m/s$^2$]
$f$
System frequency [Hz]
$\lambda_{3}$
Loss factor steel pipe pipe-type cable
$R_{c}$
Electrical resistance conductor [$\Omega$/m]
$s_{c}$
Separation of conductors in a system [mm]
Used in
$I_{c}$
Conductor current [A]
$q_{4}$
Ratio of losses environment
$T_{eq}$
Thermal resistance, equivalent [K.m/W]
$W_{duct}$
Duct losses [W/m]
$W_{h}$
Heat generated by external object [W/m]
$W_{I}$
Ohmic losses (phase) [W/m]