Electrical Power Distribution Systems (EPDS) employed among others in Aeronautics are usually protected by active electronic driven switching components. In order to reduce response time and simplify protection driving, fuses are being considered as one of the prerequisites for the Clean Sky HVDC network.
The development of a new generation of hybrid and/or full static current limiter solutions, able to operate above 51000ft, is crucial for specificities of aircraft applications. From one side fuses technologies could be adapted to parts of the requirements but may not fully comply. On the other side, the material properties of Silicon Carbide as semiconductor, clearly superior to those of Si, should lead to enhanced hybrid current limiters with much better performance than conventional fuses or Si based solutions.
Pooling a leading fuses and protection devices manufacturer, and two research groups, FUSES 2014 aimed at a breakthrough in current protection technology to build either a hybrid and/or a full static current limiter solution with different benefits than existing solutions. Well stablished and new methodologies were adapted to fuses and SiC technologies and optimised to make them a practical reality.
The main targets were to study, optimise two solutions and validate the optical module following DO160 standard adapted to high DC voltage networks to be integrated into aircraft EPDS:
- A required specs Silver fuse and specific package.
- A SiC current limiter using existing SiC FET technologies plus its optimal packaging configuration.
Our goal was to demonstrate the innovative character of our proposal by studying technologies that can meet the bill of requirements based on 60 years plus of current limiting device by Mersen with the support of 2 well-known universities that have demonstrated a thinking out-of-the-box in the field of current limiting devices.
We believed that for example, SiC brings the plus that moves current limiting device to hybrid and/or full static current limiting device. Taking into account the initial specifications listed in the call for proposal SP1-JTI-CS-2013-03-SGO-02-066, there was no existing product available on the market and specific development must be carried out to reach the objectives. The nearest fuse available was a NA UL Class T fuse, A3TX, X been the current fuse rating. The rating had been determined by taking into account the application bill of requirements.
As no obvious solution was available, we had studied two of the previously mentioned technologies, mainly Fuses and Hybrid current limiters. For this purpose, we adapted the existing Mersen fuse technology to develop a new fuse in accordance with the specifications or part of the specifications. In parallel, we studied and developed a Silicon Carbide current limiter based on a power FET technology with two (ACCUMOS) or three electrodes (JFET).
The innovative character of this project proposal resided in the association of this current limiter with the developed fuse to build a hybrid current limiter solution. For the 2 types of technologies, the ON state, the clearing state and the OFF state had been closely studied. For example, during the ON state the voltage drop had to be minimised, clearing state the energy dissipated by the device had been considered and for the OFF state leakage current had been taken into account. The specificities of aircraft applications had been taken into account, especially regarding altitude working conditions (51000ft).