- Requirement Definition and Design -
A collaboratively defined requirement set for the electric machine and power electronics intended for the NextGENCTR application was performed in the early stage of the HVDCGEN project. This activity provided functional and constraint requirements which formed the baseline for the justification work developed throughout the project to demonstrate system compliance.
The design phases of the project consisted of extensive trades covering the following main topics:
• Electric Machine Trade Study - focusing on machine topology, pole/slot combination, materials, winding configuration, and geometry
• Mechanical Design Study - focussing on housing construction, interfaces, cooling, and mechanical disconnection options
• Power Electronics Design Study - focussing on monitoring and protection, control system, signal I/O, interfaces, cooling
The end result was a design definition and associated documentation to allow for the manufacture of:
A state-of-the-art electric machine consisting of:
• Laminations: NO10
• Windings: Distributed round wire, 200°C rated
• Rotor: Surface mount magnets with carbon fibre wrap
• Speed: 24,000rpm
• Power: 95kW continuous
• Cooling: Air cooled from shaft mounted mixed flow fan
• Mechanical disconnection: Pneumatic shaft retraction
A bespoke power electronics and control system consisting of:
• Architecture: Three SiC MOSFET Inverter
• Safety: Dual controller architecture with monitoring & protection and dedicated power controller
• Cooling: Air cooled heat sink
• PCBs: Power board, control board, gate driver boards
- Testing and High-level Results -
Two HVDCGEN prototypes have been manufactured (motor and GCU electronics). An extensive testing campaign has been performed on these prototypes using a ‘back-to-back’ motor/generator test arrangement.
Summary of the project objectives and results achieved:
• Provision of power: 90kW. 270VDC Voltage: ± 1%, Current ripple: ± 5A. EN 2282 and/or Mil standard 704F - Partially achieved: Uncontrolled generator output approx. 80kW, with control system tuning controlled generation would be achieved.
• Safety objectives met for CAT events < 1 x 10^-10/FH - Achieved: Justification by analysis, implemented in the architecture and tested successfully mechanical/electrical disconnect, dedicated monitoring and protection controller.
• Efficiency > 90% - Partially achieved: Approx. 88% in motor mode / 92% in generator mode (uncontrolled operation). Expected that with minor control system tuning higher efficiency could be achieved.
• Reduced mass: < 23 kg - Not achieved: System mass 31.4kg – with further optimisation 23kg is believed to be achievable but would come with significant cost impact.
• Easier maintainability: LRU < 16kg. Change out times < 1 hour - Achieved: Motor/Generator 15.8kg and GCU 15.6kg.
• Provide mechanical power 5 kW - Achieved: Mechanical power up to 90kW achieved.
- Communication and Dissemination, Exploitation, IP -
When possible, opportunities to publicly highlight the success of the HVDCGEN project have been taken. The HVDCGEN motor/generator was displayed in Cardiff in Oct 2021 at the Autolink conference, an initiative arranged by the Welsh Automotive Forum. Feedback from this event was very positive.
Exploitation and lessons learnt from the HVDCGEN project has been initiated. Initial discussions with a EU helicopter manufacturer closely linked with the HVDCGEN project on how the outputs of project (technology and knowledge gained), or other DFG technology and capabilities, may fit with their electrification/hybridisation strategies have been very positive. Further discussions and provisional planning for a future site-visit to explore relevant topics is ongoing. Globally the drive for electrification/hybridisation of VTOL, rotary, and fixed wing aircraft is increasing - these future vehicles/platforms may be potential opportunities to exploit the HVDCGEN technology. Attracting interest will be achieved through attendance at high profile conferences/events, new funded project sources (e.g. EU Clean Aviation), or directly through OEMs.
Three main areas of the HVDCGEN project have been identified as having potentially valuable IP:
• System air cooling architecture
• Mechanical disconnection system
• Power electronics architecture and hardware protection
