Dimensioning components installed in electrical panels with respect to operational temperature

Circuit breakers, disconnectors, fuse disconnectors and fuse holders installed in LV electric panels sometimes suffer overheating, mainly due to inadequate dissipation of the heat generated. A theoretical and experimental investigation is attempted of the mechanisms that can affect heat transfer to a component-conductor system, as well the mass and the external surface area of the component. The resulting system of differential equations is solved using the Laplace transform in the s-plane. The time-dependent temperature distribution in the component-conductor system is provided by an analytical expression, and a simple formula is given for the component´s stabilised temperature. Results from the models are compared with experimental measurements performed on a fuse holder and are shown to be consistent. The model accuracy is also investigated. It is convincingly shown that excessive (or additional) external surface area of the component´s metallic parts reduces the component temperature. Above a certain level, this can make the component act as a cooler of the conductor. In addition, an increase of the component´s mass slows temperature stabilisation. The proposed model could effectively support component design as it involves all the technical characteristics of the system, so that the requirements of international standards are fulfilled in relation to the prevention of overheating