The future of air travel is evolving beyond fossil fuels with hybrid electric and all-electric aircraft leading the way. The growing need for low emissions and carbon neutrality has created a new focus on more electric aircraft (MEA), as aircraft original equipment manufacturers (OEMs) look to satisfy the growing needs of travelers while achieving the environmental goals being mandated around the world.
Power for all systems on conventional aircraft today is derived primarily from jet engines, fueled, of course, by fossil fuels. Engine gearbox-driven generators provide power for standard electrical equipment like avionics, lighting, and general cabin power. High-pressure engine bleed air is used to drive pneumatic systems such as cabin pressurization, anti-icing, and air conditioning. The engine gear box also drives hydraulic pumps for flight controls, landing gear, braking systems and door actuation as well as mechanical systems such as oil and fuel pumps. Parker Aerospace has a deep pedigree stretching back decades with sub-systems and components in conventional engines.
Moving towards more electric aircraft
The evolution to MEA changes the way these systems are implemented. Whether it’s a more electric aircraft with jet engines, a hybrid electric, or a fully electric aircraft, mechanically-driven pumps for hydraulics, pneumatics, oil, and fuel will be replaced with fully electric pumps and actuators for everything including flight surface controls, environmental systems, and braking.
Initially, gas-powered engines will still drive the electric generators for these systems. Ultimately, gas turbine engines may be replaced entirely with fully electric motors and batteries. This migration will start small, with commuter transports and urban air mobility platforms first reaching the market.
Migration from hydraulic and pneumatic energy to electric energy requires improved power-handling capability and efficiency. System voltages for MEA will climb from 28VDC and 115VAC to upwards of 1,000VDC. This power will be delivered by a complex combination of generators and batteries and requires a highly advanced and flexible electrical distribution system capable of managing system needs.
Developing improved solutions for new demands
Along with the increase in demand and capacity, the potential for significant damage during short or overload conditions must be recognized. For example, a 270V Li-Ion battery can deliver more than 2,000 amps into a short in a matter of microseconds. The typical electrical interfaces on today’s aircraft consist of mechanical relays and contactors, which are not fast enough to prevent fault propagation, and may even fuse during a fault event. This drives a need for an effective solution for high voltage, high-power buses with enhanced capability.
To answer that call, Parker Aerospace’s Fluid Systems Division has been developing a modular solid-state power controller (SSPC) for use as a standalone unit that is an electronic replacement for a relay or contactor. As part of a larger electrical distribution system, multiple SSPCs can be configured into a solid-state electrical distribution unit (SSEDU). Think of an SSPC as an individual circuit breaker whereas the SSEDU would be the entire circuit breaker box containing multiple breakers. An SSEDU can be configured with two or more SSPCs, with each SSPC being an individually controlled channel.
Utilizing advanced silicon carbide technology, Parker’s SSPC design is a modular architecture that yields the potential to accommodate multiple platform applications without costly redesigns and qualifications. Some features include:
- High-speed, high-efficiency, high-power density per channel.
- High-speed fault mitigation and bus reconfiguration.
- Programmable I2T fault protection.
- Inrush current mitigation (for high capacitive input loads).
- Low RDSon to maximize efficiency.
- Bi-directional and bi-polar SSPC options.
- Discrete input or communication bus control.
- Support for ARINC 429, Mil-Std-1553, CAN bus & others.
Multiplying the benefit from solid-state power controllers
An individual SSPC can be programmed and coordinated with other SSPCs to provide staggered power on/off configurations when used in a multi-channel configuration. Power sequencing, source and load isolation, power routing, and bi-directional flow for battery charge/discharge, can all be configured in the same SSEDU. Voltage, current, temperature and other performance and fault data is available for each SSPC.
The Parker Aerospace modular SSPC design provides benefits beyond the technical specifications. The initial concept was to provide the protection and control in a format that would allow scalability and flexibility in an electrical distribution system implementation. Taking advantage of the common SSPC design allows for:
- Reduced application non-recurring engineering (NRE) and development time
- Reduced platform certification cost and time.
- Certification by similarity of sub-components across applications and platforms.
- Reduced reliance on key components/suppliers.
- Increased flexibility to integrate new technologies.
- Ability to use the same part number across multiple applications.
Parker has completed testing of a first-generation, eight-channel SSEDU, with each channel configured for 270VDC and handling loads from 20 amps to 150 amps. The capability demonstrated included programmed and manual switch control, bolted short fault mitigation, startup and operational overcurrent protection, thermal efficiency with continuous loads, and bi-directional power flow on individual channels.
Current development on the second-generation SSPC will culminate with a two-channel unit in a more compact, thermally efficient, and lighter unit. This fully capable demonstrator will provide an example of how the Parker Aerospace SSPC and SSEDU can be utilized for multiple applications and configurations requiring the control, protection, and flexibility required to satisfy the needs of the new generation of more electric aircraft.
This blog was contributed by electronics engineering manager Andrew Walsh from the Fluid Systems Division of Parker Aerospace.