Solid State Fuses for Commercial Vehicles - Limitations and Possibilities

Abstract: This thesis, written at Scania CV AB in Södertälje, Sweden, during the spring of 2015, treats the subject of Solid State Fuses and the possibility to use these in heavy vehicles. A Solid State Fuse is a device containing only solid state components, implementing a function to protect wiring harness and connectors from damage caused by electrical faults. The device should contain circuit breakers able of breaking a worst case fault current, which have been found to be inductive currents. Other challenges are regenerative currents, over voltage and voltage transients. Solutions for these challenges are suggested. One challenge that remains to be solved is heat dissipation. Due to high ambient temperatures, a method to divert heat remains to be investigated. When these challenges are overcome, the Solid State Fuse offers a wide range of advantages. These include, but are not limited to, advanced fault detection, automatic reset, diagnostics and relay functionality. Most important, it is found that today’s technology, particularly the MOSFET, is sufficient for implementing Solid State Fuses meeting standards and requirements. In addition, a study of load and fault characteristics is made, the Smart Power Switch is investigated and a concept using MOSFETs for breaking regenerative currents is realized with successful results.