Thermal Analysis of Power Cables Installed in Solid Bottom Trays Using an Equivalent Circuit

Cables in ventilated and ladder-Type trays have been extensively studied and are rated according to ANSI/NEMA standards. The National Electric Code (NEC) provides guidelines on ampacity for cables installed in ventilated and ladder-Type trays. However, for solid bottom trays, there is very little published material; there are neither standards nor guidelines. This paper proposes a methodological approach for the thermal rating of power cables installed in solid bottom trays with and without cover. An analog thermal-electrical circuit is derived from first thermodynamic principles. The circuit parameters are easy to compute. The method is completely general and is applicable to trays with any number of cables (not only to integer fill depths). The validity of the method is corroborated with numerous finite-element method simulations and laboratory experiments. A hand-worked example is given for illustration.