Rated power of semi-flexible cables

Semi-flexible cables use resin sheathing for the insulation of the outer conductor. The material of the resin sheathing is selected based on factors such as the cable’s heat resistance temperature, flexibility, and environmental resistance. The rated power of the cable is limited by the heat resistance temperature of the sheathing.
·Rated power at ambient temperature of 25°C and natural cooling

 
·Rated power at ambient temperature 25°C with forced air cooling

 
·Rated power calculation model
The internal conductor, insulator, and external conductor of the semi-flexible cable are treated as a single heat-generating body, and all losses due to RF signal attenuation are converted into heat. This heat is conducted from the external conductor to the surface of the resin sheath and dissipated into the air from the resin sheath surface. The temperature at which heat transfer and heat radiation from the sheath surface and heat generation inside the cable are in equilibrium is calculated. The power at which this equilibrium temperature equals the heat resistance temperature of the sheath material is defined as the rated power.
·Physical properties used in the calculation
ETFE material thermal conductivity: 0.25 W/mK
PVC material thermal conductivity: 0.2 W/mK
Natural cooling convective heat transfer coefficient: 5 W/m²K
Forced air cooling convective heat transfer coefficient: 25 W/m²K
Sheath surface emissivity: 0.9
Forced air cooling air velocity: 0.5 m/s
These values are general representative values and may vary significantly depending on the actual installation environment of the cable. When selecting a cable, please allow for sufficient margin.