Community Research and Development Information Service - CORDIS

FP7

FUSES 2014 Report Summary

Project ID: 641336
Funded under: FP7-JTI
Country: France

Final Report Summary - FUSES 2014 (CURRENT LIMITING DEVICE TO ADDRESS DC AERONAUTICS POWER DISTRIBUTION SYSTEMS)

Executive Summary:
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 prerequisite for the CleanSky 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 leading fuses and protection devices manufacturer, and two research groups, FUSES 2014 aims 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 will be adapted to fuses and SiC technologies and optimized to make them a practical reality.
The main targets are study, optimize 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 is to demonstrate the innovative character of our proposal by studying technologies that can meet the bill of requirements base 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 believe that for example SiC brings the plus that move 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 is no existing product available on the market and specific development must be carried out to reach the objectives. The nearest fuse available is a NA UL Class T fuse, A3TX, X been the current fuse rating. The rating has been determined by taking into account the application bill of requirements.

As no obvious solution is available, we have studied two of the previously mentioned technologies, mainly Fuses and Hybrid current limiters. For this purpose, we have adapted the existing Mersen fuse technology to develop a new fuse in accordance with the specifications or part of the specifications. In parallel, we have 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 resides 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 have been closely studied. For example during the ON state the voltage drop has to be minimized, clearing state the energy dissipated by the device has been considered and for the off state leakage current has been taken into account. The specificities of aircraft applications have been taken into account, especially regarding altitude working conditions (51000ft).

Then, the main objectives can be summarized as follow:
1. Study and optimize a Silver fuse with specs as much as required and specific package for aircraft working conditions.
2. Study and optimize a SiC current limiter using existing SiC FET technologies
3. Study an optimal packaging configuration for hybrid solution fitting with altitude working conditions among others
4. Test of fuse and hybrid solutions and main parameters extraction
5. Validation of the optimal module following DO160 standard

Project Context and Objectives:
Summary description of the project context and the main objectives

1 WP1. Fuse module optimization and fabrication
The objectives of this work package are the dedication of the design and optimization of a fuse module fitting as much as possible with starting specifications. The base technology used has been the Mersen silver technology. New dimensions and geometries have been considered to fit with the required current.
1.1 Task 1.1 State of the art review and analysis of specification
As starting point, a state of the art review of existing aeronautics fuses and current limiting solutions has performed. On state specification, fault current available in the DC circuit, time current curve needed to meet bill of requirement has been studied to draft a technical solution. The strategy to be used for the study has been set-up. This strategy has impact in both WP1 and WP2.
1.2 Task 1.2 Geometry design and optimization of the fuse
The consortium experience in the fuse element design permits to shape the time current curve in order to meet certain gates. The goal is to design a fuse element with a new reduce sections area that allows to test the new design against the bill of requirement. Simulation means, as well as testing means, have been used to verify the fuse design.
1.3 Task 1.3 Fuse module fabrication
In the previous report, we have seen the design of a fuse against the bill of requirement. MERSEN experience in the fuse element design allows shaping the time current curve in order to meet certain gates. Simulation has been used to verify the fuse design. After test analysis of the first fuses batch, a redesign will be considered for the second production batch.

2 WP2. Semiconductor fuse design and fabrication
The objectives of this work package are the dedication of the design and optimisation of a SiC semiconductor current limiter fitting as much as possible with starting specifications. The base technology used has been the CSIC JFET technology, previously developed and tested by the project partners. New devices dimensions and geometries have been considered to fit with the required specifications. Some process technology adjustments have also been necessary.
2.1 Task 2.1 Analysis of specification
The starting specifications have been analysed and compared with the performances of existing SiC current limiter developed by the 3 project partners in previous works. From this initial analysis, several optimisation axes have been defined for the next phase of design and optimisation of the targeted device. This analysis has been done by all 3 partners.
2.2 Task 2.2 Geometry design and optimization of the current limiter
In this task, 2D simulation work with numerical simulator has done by INSA Lyon in order to adjust the device basic cell geometry of the device to the specs. The possibility to change some doping or etching profiles in the technology has been consulted to CSIC partner. Once defined the basic cell geometry, both INSA Lyon and CSIC have drawn the photolithography masks set using common software. Current limiter as well as technological and electrical test structures is included on the mask set.

2.3 Task 2.3 Technology optimization and device fabrication
Some preliminary processing tests have performed in order to adjust possible doping or etching profiles changes defined in task 2.2. Once the photolithography mask set available from task 2.2, device fabrication have started in the CSIC clean room.

2.4 Task 2.4 On-wafer characterisation of the current limiter
Once completed the clean room processing, a basic on-wafer characterisation of the fabricated devices will be performed. From this characterisation phase, good dies will be identified for packaging.

2.5 Task 2.5 Devices packaging
Dicing and die selection will be done by the partners. Taking into account the specific requirement of the application in term of pressure, temperature, humidity and mechanical stress, part of the packaging of the SiC device will be subcontracted, and part will be done by the partners

3 WP3. Module characterization and validation
The objective of this work package is to validate one of the 2 proposed solutions for the module, which are fuse or current limiter hybrid module. For this purpose, the consortium are working since M10 on a standalone characterization and engineering tests of each 2 solutions before selecting the most adequate.
3.1 Task 3.1 Fuse module standalone testing
Mersen DC labs in Europe and US allow the consortium to speed up the testing. Due to the availability of the lab different fuse solutions are tested and the results will be evaluated against the bill of requirements. Mersen is already supplying products qualified with DO160 standard to aeronautics industries and own the facilities to perform electrical and environmental engineering tests.
3.2 Task 3.2 SiC current limiter hybrid module testing

The labs of the three partners will be used to make a full testing, including engineering DO160 testing, of the SiC current limiter hybrid module. Most electrical testing will be done by INSA Lyon and CSIC while the environmental testing will be performed by Mersen.

3.3 Task 3.3 Final optimal module testing

In a similar way to task 3.1 and 3.2, the final module selected as optimal solution will be tested to extract the main parameters and to demonstrate DO160 standard validation.

3.4 Task 3.4 TRL validation and support to integration in EPDS demonstrator

The final modules will be produced and delivered by Mersen to the clean Sky partners in charge of EPDS demonstrator. Mersen will support the integration of the modules in the final demonstrator.
All the partners will assess the Clean Sky partners on the testing of the modules.

4 WP4. Management, exploitation and dissemination
The objective of this work package is to efficiently execute legal, contractual, ethical, financial and administrative management of the project, the grant and consortium, so as to facilitate R&D, validation and dissemination activities by allowing researchers and industrial partners to focus on adding S/T and market value.
4.1 Task 4.1 Management
This task covers activities related to the overall organization, planning and control of the project. It addresses liaison with the Commission and the Clean Sky platform, ensures timely delivery of deliverables as well as any other contractually relevant document and includes:
• The overall legal, contractual, ethical, financial and administrative management;
• Management of all financial aspects, including European contribution and auditing and also will monitor and assure the timely and quality project reporting (Periodic Reports).
• The scientific and technical co-ordinator will also be responsible for the technical coordination of the management & technical tasks of the project
• Coordination of knowledge management and other innovation-related activities
Management includes effective decision-making procedures, optimum internal communication, conflict resolution and active promotion of collaborative work among researchers’ teams.

4.2 Task 4.2 Explotation

The results from this project will be used to expand partners´ product portfolio to include new fuses and limiting systems for aircraft application. Concerning Standardization, devices will be tested following DO160 standard within the project. However, the project partners will also consider if new test methods for the product qualification need to be developed as complement to the existing standards. In case of positive answer, a report on such possible alternative testing methods would be generated. To strengthen the project IPR strategy, early activities will be dedicated to a patent mapping review. The mapping activity will identify existing patents that match closest to the project innovations, thereby: (1) enabling the innovative claims of the project to be strengthened (better defined); (2) helping to identify competitive technologies and free patent space; ensuring protection of the project results; and (3) helping to identify wider opportunities for exploitation. It is important to note that the partners already share common patents in the field.

4.3 Task 4.3 Dissemination

Dissemination of the project results will be carried out using the following channels: participation to Clean Sky events and in topic related conferences, production of papers/articles and press release. The presence of two academic partners will help the dissemination at scientific journals and conference levels. Reference to Clean Sky project will be done in the acknowledgments. The coordinator will be in charge of dissemination in Industrial forums (PCIM...), in free specialized journals such as Bodo Power or EPE journals, and through press release.

Project Results:
The objective of the Clean Sky project is to implement a power distribution in aircraft instead of hydraulic and thermal systems. This change will allow reducing volume and weight. In this project, the electrical system is a continuous transmission line. MERSEN expertise involves in the current limiter protection.
Whose specifications are the following ones:
• Nominal bus voltage = 540V with Vbus max= 900V
• Maximum voltage drop at 90°C Vdrop=125mV

• Nominal current In = 83A
• Maximum leakage current Ileakage= 100 uA

• Overshoot : Iover= 120 A et Vover= 650V during 60s

• Melting time :
o 250A → 3s
o 830A → 10 ms

• L/R < 5ms

• Temperature:
o Device = 95°C (between -40°C and 130°C)
o 130°C during 1h without degradation
o -40° C during 1h without degradation
o 150°C during 5 min without degradation
o -50°C during 5 min without degradation

• The lifetime should be superior to 10 000 cycles
The goal is to design a fuse element with a new reduce sections area that will allow testing the new design against the bill of requirement. The fuse is the most reliable breaker. It is a pure thermal device that will clear the circuit when the fault current has created enough energy to melt its conductive element. Large power fuses use conductive elements made of silver, copper or tin to provide stable and predictable performance. The structure of the fuse is shared in four elements: electrical connection, fuse element (conductive element), extern isolation (ceramic) and sand.
The simulation of the new fuse has been established and the optimization of the reduced section allows shaping the time current curve in order to meet certain gates.
Prototypes have been realized and the presentation of the manufacturing process control and test will be written in the following deliverable.
The delivrable 3.1 presents the Fuse gen II overcurrent protection device for DC applications. The conduction path made by the pyroswitch and the clearing path made by a fuse bring the best of the 2 products, i.e. low voltage drop, high inrush current capability, high cycling performance, fast cutting of the busbar. Moreover the fuse presents an excellent capacity to clear high DC current. Tailored to the final application, these 2 devices bring the best performances for the More Electrical Aircraft.

For the WP2: Even if the processed devices are operating, these samples are too resistive in forward mode for the SSCB prototype. The devices are almost all normally off or have a very low threshold voltage (-1V), which would be good if the on-resistance would not be so high.

The observed behavior is due to a thinner channel thickness that targeted. The effective channel thickness has been estimated to (~500nm). This can be caused by either an epi-layer parameter deviation or to fabrication process variations.

Correction actions taken
Some physical analysis have been performed (SIMS, FIB) and several validation done with the epitaxy provider.
SIMS analysis allowed certifying the delivered epilayer are in accordance with the specified parameters. Then, various options are possible to optimize the device fabrication process:
• To Increase of epitaxial layer thickness and tuning the doping value
• To modify the P+ implantation parameters to better control the final channel thickness
• To modify some of the process steps parameters in order to reduce the gate leakage current

A new fabrication batch has been launched in order to correct the processing parameters and reach the targeted specs for the devices.
Even if the processed SiC current limiting devices fabricated in WP2 are operating, the samples are too resistive in forward mode for the SSCB prototype. The devices are almost all normally off or have a very low threshold voltage (-1V), which would be good if the on-resistance would not be so high.
An alternative solution has been chosen for the fabrication and the characterization of the SiC current limiter: implement commercial SiC devices. One issue is the fabrication yield of power module. Indeed, using commercial devices implies to increase the number of die to connect in parallel. We end up with 3 functional modules for 5 modules fabricated.
The experimental measurements performed on delivered modules allows to validate:
• The control board able to drive 16 MOSFET connected in parallel
• The compatibility of the modules with the BOR (I(t) tripping curve (low on resistance, current sensing).

Full rated power characterization wasn’t possible. Indeed the low number of functional modules don’t makes possible to test modules at high current levels.
The module assembly process is quite challenging. The fabrication failure (3modules functional over 5) points out the necessity to reduce the straight inductances within the power module, as well as the number of SiC devices to parallel. Having SiC custom devices, we should be able to reduce the number of parallelized MOSFET, increasing thereby the fabrication yield of the sub-modules.
Performance analysis and perspectives.

To achieve a high level of reliability and performances for a SiC current limiter module, it would be necessary:
- To stabilize the SiC current limiter power device fabrication
- To reduce the fabrication delay of the boards,
- To reduce the number of parallelized devices.

A new fabrication batch has been launched in order to correct the processing parameters and reach the targeted specs for the devices. Devices would be delivered after the end of the project. However, the preliminary measurements point out the possibility to address the Cleansky objective.
The cost estimation of such a solution will be higher than 5k€, assuming that SiC Die cost could be around 35€ /unit, and considering the high cost of a custom packaging.

For the WP3: Our experience in the fuse element design allows us to shape the time current curve in order to meet certain gates. This deliverable presents the work done to design a fuse element and test it. The reduce section area allows us to test the new design against the bill of requirement. Simulation has been used to verify the fuse design. After test analysis of the first fuses batch, a redesign will be considered for the second production batch.

Potential Impact:
4.1 Technical objectives
Simulation has been used to verify the fuse design. After test analysis of the first fuses batch, a redesign has been considered for the second production batch. The second batch is an hybrid solution based on fuse and pyroswitch technologies. The conduction path made by the pyroswitch and the clearing path made by a fuse bring the best of the 2 products, i.e. low voltage drop, high inrush current capability, high cycling performance, fast cutting of the busbar. Moreover the fuse presents an excellent capacity to clear high DC current. Tailored to the final application, the final device brings the best performances for the More Electrical Aircraft. We have launched the building of 200 devices to qualify the DO160. Today the situation is at follow: the ‘‘hybrid fuse” developed by Mersen fit the early protection/clearing requirement of the project. We were expecting to test our device at Airbus before engaging any DO160 certification/testing. Our prototypes are ready for this test but the testing at airbus has been delayed to unknown date. More urgent testing at Airbus have taken priority. Mersen have made the decision not to engage any DO160 testing/certification before the testing at Airbus. No need to do DO160 if we fail the testing at Airbus, it would have been spending money too early. Current situation is complicated since we don’t know when the testing at Airbus will occur and we need to close the project. Since we cannot any longer keep the project open Mersen proposed to close it without DO160 standard Eng. Tests. Nevertheless, since samples are ready to test, Mersen will perform the testing at Airbus once their lab becomes available. Of course Mersen will not seek any EU funding for this deliverable/task not completed. Mersen estimates at 3pm the load that would has been used to carry on D0160 Eng. testing.
Concerning the SiC demonstrator, even if the processed SiC current limiting devices fabricated in WP2 are operating, the samples are too resistive in forward mode for the SSCB prototype. The devices are almost all normally off or have a very low threshold voltage (-1V), which would be good if the on-resistance would not be so high.
An alternative solution has been chosen for the fabrication and the characterization of the SiC current limiter: implement commercial SiC devices. One issue is the fabrication yield of power module. Indeed, using commercial devices implies to increase the number of die to connect in parallel. We end up with 3 functional modules for 5 modules fabricated.
The experimental measurements performed on delivered modules allows to validate:
• The control board able to drive 16 MOSFET connected in parallel
• The compatibility of the modules with the BOR (I(t) tripping curve (low on resistance, current sensing).

Full rated power characterization wasn’t possible. Indeed the low number of functional modules don’t makes possible to test modules at high current levels.
The module assembly process is quite challenging. The fabrication failure (3modules functional over 5) points out the necessity to reduce the straight inductances within the power module, as well as the number of SiC devices to parallel. Having SiC custom devices, we should be able to reduce the number of parallelized MOSFET, increasing thereby the fabrication yield of the sub-modules.

To achieve a high level of reliability and performances for a SiC current limiter module, it would be necessary:
- To stabilize the SiC current limiter power device fabrication
- To reduce the fabrication delay of the boards,
- To reduce the number of parallelized devices.

A new fabrication batch has been launched in order to correct the processing parameters and reach the targeted specs for the devices. Devices would be delivered after the end of the project. However, the preliminary measurements point out the possibility to address the Cleansky objective.

The cost estimation of such a solution will be higher than 5k€, assuming that SiC Die cost could be around 35€ /unit, and considering the high cost of a custom packaging.
The cost estimation of the hybrid fuse solution is estimated as 300€, which is much lower but this device isn't ressetable.

4.2 Management objectives
The management organization comprises three levels: the global management, the administrative management of the project, and the management of WPs. The management system has been set up at the beginning of the project life and has been coordinated by Mersen that implemented and deployed the necessary management procedures (costs, people, facilities, communication, knowledge, legal aspects and IPR and risks). The management has been simple as there are only 3 partners, used to work together since many years.
The work package managers have been designed for each WP. The work package leader is involved in the detailed coordination, planning, monitoring and reporting of the work package and for the detailed communication with other work packages. More specifically, the work package leaders are responsible for:
• Leading the WP including technical and management activities, continuously monitoring the progress of the participant tasks, controlling its efficiency
• Reporting WP/task activity to the whole consortium in four-month reports
• Ensuring that milestones and deliverables of the WPs are fulfilled, organizing, if needed, special meetings to determine suitable measures to be taken

4.3 Dissemination.
The results from this project will be used to expand partners´ product portfolio to include new fuses and limiting systems for aircraft application, considering specific package for altitude working conditions. This is clearly a market segment that will increase in importance over time. The challenge of introducing these new products to the global market will be easier and less risky as they have been specified, developed and tested in open co-operation with Clean Sky platform.

In addition, the results of this project may clearly have applications in other industrial fields. With the growth in DC renewable energy like PV linked with the need of energy storage for smart grid applications and DC energy distribution come the need of DC protection. This study will not only answer a particular application demand like aircraft DC distribution protection but also all future DC networks like, but not limited to, DC data center working at higher DC voltage, Capacitor bank for large to medium application for smart grid and private DC energy production. We can foresee the use of DC circuit protection in for example battery bank or supercapacitor bank. In traction applications full EV or hybrid HV and for large vehicles, trucks, trams, busses, shipboard... this device will answer and demand not yet or partially fulfil. Also smart DC protection will be needed, controllable protection from high fault current to low fault current will be a plus and will be attractive to all future DC distribution network. 1 to 1.5 MW batteries bank for smart grid application use standard DC breakers that not really fulfil the need of customers.
The early adopters of these hybrid fuses are clearly the EV car manufacturers. We have been testing this market with the hybrid fuse and we have strong demand for the performance is breaking to this field of applications. We are able now to cover application up to 1000 VDC, fault current up to 15 kA with a device rated up to 800 A RMS.
We foresee as well application in AC, where the fault current is too low to melt standard fuse. The hybrid fuse can be turned off with an external triggering signal. Top of it with the self-trigger function added to our design we foresee the utilization of this device as a backup device for standard breakers. For low fault current the breaker open the circuit, for high fault current our device will open the circuit. This approach will simplify the design of the breaker therefor the its cost.
As far as quantities the aircraft applications will represent only small quantities of devices versus the need in PV for example. We foresee the need of new DC current limiting device in PV sting, in PV sub array and main DC fuse. If we use the currently sold quantities in PV and/or EV applications we can foresee annual quantities in millions of pieces. Even though we could not finalize the testing with our SiC design we still believe that the SiC design will address a niche like current limiting/clamping for Li-Ion battery cell application. This will boost the use of SiC, therefore will beneficiate European SiC component manufacturer. This will certainly create a need to SiC European manufacturer i.e. creating high tech jobs. Same analysis can be done with new DC distribution network, same quantities but this is still a growing application.

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Contact

JEAN-FRANCOIS DE PALMA, (MERSEN VP R&D)
Tel.: +33241961540
E-mail
Record Number: 193619 / Last updated on: 2017-01-13