Cable Bundle Protection and Cross-Section Reduction by using a centralized Smart Fusing Strategy

Thermal fuses are very commonly used for wire protection in several technical fields due to their low cost and robust design. However, as another possibility within future automotive electrical distribution systems (EDS), smart fuses based on solid-state switches and current sensing are being considered. A smart fuse uses a software tripping characteristic, which can be implemented in many different ways by separating the fuse design from electrothermic respectively physical limits. This kind of fusing has several benefits, e.g. resetability, diagnoses, smaller tolerances and reduced dependencies on ambient temperature and arcing.One way is a model-based approach as smart fuse characteristic, where the heating of the conductor is calculated. An isolated conductor is often assumed to be the worst case scenario with respect to its thermal behaviour. However, depending on load conditions and conductor positions within a wire bundle, a single conductor can be exposed to more challenging thermal conditions and reach higher temperatures. Under certain conditions, it might also be better cooled if surrounded by enough signal wires within the bundle.The equivalent to a fusing box with smart fuses is a smart load controller. This device measures the current in every fused channel and could estimate the bundle load and heating. Thus, an appropriate protection approach can be deployed depending on load conditions and bundle setup. This paper describes the wire and bundle models, shows the validation with measurements and a procedure to adjust the wire model depending on the bundle configuration.