A gas turbine engine includes a compressor section having a first compressor and a second compressor, the second compressor having a higher pressure than the first compressor, and a turbine section having a first turbine and a second turbine, the second turbine having a higher pressure than the first turbine. The first compressor is connected to the first turbine via a first shaft. The second compressor is connected to the second turbine via a second shaft. An electric motor is connected to the first shaft such that rotational energy generated by the electric motor is translated to the first shaft. A fan is connected to the first shaft via a gear system. The gas turbine engine includes at least a takeoff mode of operations, a top of climb mode of operations and a maximum cruise mode of operations. The gas turbine engine is sized to operate at peak efficiency in the maximum cruise mode of operations.

An electrical system includes: a battery; a fuel-cell pack; a load electrically coupled to the fuel-cell pack; a switching arrangement electrically coupled to the battery, the fuel-cell pack and the load; a DC-DC converter; and a control system. The switching arrangement configures the electrical system in at least one of a battery-charge mode and a combined-drive mode. In the battery-charge mode the battery is coupled in series to the fuel-cell pack and the load via the DC-DC converter for simultaneous charging of the battery and driving of the load by the fuel-cell pack. In the combined-drive mode, the battery is coupled in series to the fuel-cell pack and the load via the DC-DC converter for driving of the load by both the battery and the fuel-cell pack. The control system is configured to: monitor a parameter of an electrical power provided to the load; and control the DC-DC converter.

An electrical system includes: a battery; a fuel-cell pack; a load electrically coupled to the fuel-cell pack; a switching arrangement electrically coupled to the battery, the fuel-cell pack and the load; a DC-DC converter; and a control system. The switching arrangement configures the electrical system in at least one of a battery-charge mode and a combined-drive mode. In the battery-charge mode the battery is coupled in series to the fuel-cell pack and the load via the DC-DC converter for simultaneous charging of the battery and driving of the load by the fuel-cell pack. In the combined-drive mode, the battery is coupled in series to the fuel-cell pack and the load via the DC-DC converter for driving of the load by both the battery and the fuel-cell pack. The control system is configured to: monitor a parameter of an electrical power provided to the load; and control the DC-DC converter.

Hybrid-electric aircraft and a series hybrid powertrain configured to power the aircraft for a medium-haul flight. The series hybrid power train includes a plurality of energy storage units, at least one range extending generator, and a plurality of electric propulsors, each coupled to a distribution bus. The electric propulsors can produce a maximum thrust of at least 15 MW. During a cruise regime, the hybrid-electric aircraft can have an airspeed of at least 0.7 Mach at an altitude of less than 32000 feet, and the plurality of electric propulsors can have a fan pressure ratio of between 1.15 and 1.19. The hybrid-electric aircraft can have a degree of hybridization of at least 25% for the medium-haul flight and carbon dioxide equivalent (CO.sub.2e) well-to-wake greenhouse gas (GHG) emissions less than 0.25 lbs/Available Seat Mile (ASM).

A power generation system includes a generator configured to output alternating current (AC) power, an active rectifier configured to receive the AC power from the generator, convert the AC power to direct current (DC) power, and output the DC power. A current injector is connected to the active rectifier and is configured to provide an injection current to power flowing through the active rectifier. The injection current includes a reactive component.

A power generation system includes a generator configured to output alternating current (AC) power, an active rectifier configured to receive the AC power from the generator, convert the AC power to direct current (DC) power, and output the DC power. A current injector is connected to the active rectifier and is configured to provide an injection current to power flowing through the active rectifier. The injection current includes a reactive component.

An electrical propulsion system for an aircraft includes a central bus and a plurality of branches, each branch having at least one electrical power source, at least one electric propulsion device, and a branch bus, connected to each source and to each propulsion device of the branch. Each branch includes a DC/DC voltage converter connecting the branch bus to the central bus, said DC/DC voltage converter being configured to galvanically isolate said branch bus from the central bus.

An electrical propulsion system for an aircraft includes a central bus and a plurality of branches, each branch having at least one electrical power source, at least one electric propulsion device, and a branch bus, connected to each source and to each propulsion device of the branch. Each branch includes a DC/DC voltage converter connecting the branch bus to the central bus, said DC/DC voltage converter being configured to galvanically isolate said branch bus from the central bus.

Examples are disclosed that relate to an electric machine that achieves independent speed, variable frequency power generation and has increased power density, efficiency, reliability, and reduced complexity relative to conventional electric machines. In one example, an electric machine includes a stator, a first stationary winding coupled to the stator, a second stationary winding coupled to the stator, and a rotor. The second stationary winding includes a plurality of winding segments corresponding to a number of phases of power of the electric machine. The rotor extends through the stator and the second stationary winding. The rotor includes a plurality of rotor segments. Each rotor segment of the plurality of rotor segments includes a plurality of pole lobes that extend radially from the rotor segment. Two or more pole lobes of each rotor segment are located on opposing sides of a corresponding winding segment of the second stationary winding.

Examples are disclosed that relate to an electric machine that achieves independent speed, variable frequency power generation and has increased power density, efficiency, reliability, and reduced complexity relative to conventional electric machines. In one example, an electric machine includes a stator, a first stationary winding coupled to the stator, a second stationary winding coupled to the stator, and a rotor. The second stationary winding includes a plurality of winding segments corresponding to a number of phases of power of the electric machine. The rotor extends through the stator and the second stationary winding. The rotor includes a plurality of rotor segments. Each rotor segment of the plurality of rotor segments includes a plurality of pole lobes that extend radially from the rotor segment. Two or more pole lobes of each rotor segment are located on opposing sides of a corresponding winding segment of the second stationary winding.