Abstract: Reconfigurable permanent magnet electrical machines and aircraft power and propulsion systems including the electrical machines. An aircraft power and propulsion system includes: a gas turbine engine; DC electrical network; permanent magnet electrical machine including a rotor drivingly coupled to a spool of the engine, and a stator including windings controllably switchable between a star and a delta configuration; an AC-DC power electronics converter, an AC side is connected to terminals of the stator windings and a DC side is connected to the DC electrical network; an additional electrical power source connected to and controllable to supply electrical power to the DC electrical network; and a control system configured to control the switching of the stator windings between the configurations and to control the additional electrical power source to supply electrical power to the DC electrical network during a time interval when the stator is being switched between the configurations.

Abstract: Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.

Abstract: An aircraft gas turbine engine includes a heat exchanger module, and a core engine. The core engine includes an intermediate-pressure compressor, high-pressure compressor, and high and low-pressure turbines. The high-pressure compressor rotationally connects to the high-pressure turbine by a first shaft, and the intermediate-pressure compressor rotationally connects to the low-pressure turbine by a second shaft. The heat exchanger module fluidly communicates with the core engine by an inlet duct. The heat exchanger module includes a central hub and multiple heat transfer elements extending radially from the hub and spaced in a circumferential array, for heat energy transfer from a first fluid within the elements to an inlet airflow passing over a surface of the elements prior to airflow entry into an inlet to the core engine. The gas turbine engine further includes a first electric machine rotationally connected to the first shaft, and positioned downstream of the heat exchanger module.

Abstract: The disclosure relates to an electrical power system for providing a stabilised DC voltage to a power bus. Example embodiments include an electrical power system comprising: a DC power bus having first and second DC power bus terminals; an electrical storage unit having first and second terminals, the second terminal connected to the second DC power bus terminal; a DC:DC converter having first and second DC:AC converters and a transformer connected between the first and second DC:AC converters, the first DC:AC converter connected between the first terminal of the electrical storage unit and the first DC power bus terminal; and a controller connected to control a switching operation of one or both of the first and second DC:AC converters.

Abstract: The disclosure relates to an electrical power system for connecting an electrical machine to first and second DC networks operating at different voltages. In an embodiment, an electrical power system comprises: an electrical machine having first, second, third and fourth windings; first, second, third and fourth AC:DC power electronics converters each connected to receive an input AC supply from the respective first, second, third and fourth windings, each AC:DC power electronics converter having first and second DC output terminals connecting the AC:DC power electronics converters to first, second and third DC supply output terminals, wherein the first and second windings are arranged to provide an AC supply to the respective first and second AC:DC power electronics converters in quadrature to each other and the third and fourth windings are arranged to provide an AC supply to the respective third and fourth AC:DC power electronics converters in quadrature to each other.

Abstract: The disclosure relates to an electrical power system for connecting an electrical machine to first and second DC networks operating at different voltages. Example embodiments include an electrical power system comprising: an electrical machine having first and second pluralities of windings; a first AC:DC power electronics converter connected to the first plurality of windings; a second AC:DC power electronics converter connected to the second plurality of windings; a switching controller configured to provide switching signals to the first and second AC:DC power electronics converters to provide a first DC supply at a DC side of the first AC:DC power electronics converter and a second DC supply at a DC side of the second AC:DC power electronics converter.

Abstract: A power conversion circuitry configured to transition between modes of operation during an electrical fault, including: switching circuitry configured to control currents flowing along a plurality of current paths between respective pairs of nodes, wherein the paths include first and second transistor-diode pairs; and control circuitry connected to the switching circuitry configured to: configure the switching circuitry to transition, when an electrical fault is detected, to a first mode of operation by configuring the transistors to switch to a non-conducting state so currents flow through the diodes, determine when current begins to flow through a diode, and configure the switching circuitry to transition from the first mode to a fault mode of operation by configuring the transistors to sequentially switch to a conducting state so currents flow through the configured transistors. Also, a method of controlling power conversion circuitry to transition between modes of operation during an electrical fault.

Abstract: A power conversion circuitry configured to detect an electrical fault, and methods of detecting an electrical fault in power conversion circuitry, the power conversion circuitry including: switching circuitry configured to control a current flowing along a current path between first and second nodes of the power conversion circuitry; a current sensor connected to the current path, the current sensor configured to measure a rate of change of the current flowing along the current path; and control circuitry connected to the current sensor and the switching circuitry, the control circuitry configured to: detect an electrical fault if a rate of change of the current measured by the current sensor exceeds a fault threshold, and configure the switching circuitry to adjust current flow in the power conversion circuitry when an electrical fault is detected.

Abstract: An electrical power system including: an electrical power source, a power electronics converter, an electrical network, a current limiting diode and a controllable circuit interruption device, wherein: the current limiting diode is configured to limit a fault current passing between the electrical power source and the electrical network in a fault condition; and the controllable circuit interruption device is configured to interrupt the fault current in response to a determination that the electrical power system is in the fault condition.

Abstract: A power electronics converter comprising: first and second input terminals; first and second DC output terminals; a branch comprising first and second semiconductor switches connected in series between the first and second DC output terminals, the first input terminal connected to a node between the first and second semiconductor switches; a DC link capacitor connected between the first and second DC output terminals; and a reverse biased DC link diode connected across the DC link capacitor.

Abstract: The disclosure relates to an electric aircraft propulsion assembly comprising: an electric storage unit; a first electric motor connected to power a first propulsor; a first converter configured as a DC:AC converter having input connections connectable to the electric storage unit and output connections connected across the first electric motor, the first converter configured as a DC:AC converter; a second electric motor connected to power a second propulsor; a second converter connected between the first converter input connections and the second electric motor; and a controller configured to control operation of the first and second converters, wherein the second converter is operable as a DC:AC converter to convert the DC supply from the electric storage unit to an AC supply across the second electric motor and as a DC:DC converter to convert the DC supply from the electric storage unit at a first DC level to a DC supply at the input connections of the first converter at a second DC level.

Abstract: The disclosure relates to an electric aircraft propulsion assembly for an electric vertical takeoff and landing, eVTOL, aircraft, the assembly comprising: an electric storage unit; a first electric motor connected to power a first propulsor; a first converter configured as a DC:AC converter for driving the first electric motor and a second electric motor connected to power a second propulsor, a second converter. A controller is connected to control operation of the first and second converters and is configured to operate in a first mode in which the first and second converters are operated as DC:AC converters to drive the first and second electric motors and a second mode in which the first converter is operated to drive the first electric motor to power the first propulsor and the second converter is operated to drive the second electric motor to provide a braking torque on the second propulsor.

Abstract: A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module. The gas turbine engine further comprises a first electric machine that is rotationally connected to the turbine module, and an electrical energy storage unit. The gas turbine engine is configured to generate a maximum dry thrust T (N). The first electric machine is configured to generate a maximum electrical power PEM1 (W). The electrical energy storage unit has an energy storage capacity E (Wh), a maximum charge rate C (h?1), and a maximum discharge rate D (h?1). The electrical energy storage unit is configured to store electrical energy that may be generated by the first electric machine.

Abstract: A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module, with a first electric machine being rotationally connected to the turbine module. The first electrical machine is configured to generate a maximum electrical power PEM1 (W), and the gas turbine engine is configured to generate a maximum shaft power PSHAFT (W); and a ratio R of: R = ( Maximum ? Electrical ? Power ? Generated = P E ? M ? 1 ) ( Maximum ? Shaft ? Power = P S ? H ? A ? F ? T ) is in a range of between 0.005 and 0.020.

Abstract: Aircraft power and propulsion systems and methods of operating the systems, one method includes: operating electric machines of gas turbine engines as generators to extract mechanical power from spools and generating electrical power therefrom; meeting an electrical power demand of a plurality of electrical loads connected with an electrical system by supplying the plurality of electrical loads with electrical power generated by the electric machines; determining when there is an electrical system and/or the gas turbine engine fault and an amount of electrical power generated by the power and propulsion system is reduced to a lower level; and responsive to the determination: during a time period ?T, controlling the plurality of electrical loads reducing the electrical power demand; and during the time period ?T, meeting at least part of the electrical power demand of the plurality of electrical loads by discharging the electrical energy storage system.

Abstract: Aircraft power and propulsion systems, aircraft comprising such power and propulsion systems, and methods of restarting a gas turbine engine of such power and propulsion systems during flight are provided. One such aircraft power and propulsion system comprises: a propulsive gas turbine engine comprising a plurality of spools, combustion equipment, one or more electric machines mechanically coupled with one or more of the spools and an electrically-powered fuel pump for delivering fuel to the combustion equipment; an electrical system connected with the one or more electric machines and the electrically-powered fuel pump, the electrical system comprising an energy storage system; and a control system configured to: responsive to a determination to the effect that a flame in the combustion equipment has been extinguished, control the electrical system to supply electrical power from the energy storage system to the fuel pump during an engine restart attempt.

Abstract: Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.

Abstract: A twin-engine aircraft power and propulsion system including first and second propulsive gas turbine engines, each having combustion equipment and a first and second spool; first, second, third, and fourth electrical power generation sub-systems including electric machines respectively mechanically coupled with the first spool of the first propulsive gas turbine engine, the second spool of the first propulsive gas turbine engine, the first spool of the second propulsive gas turbine engine, and the second spool of the second propulsive gas turbine engine; and first, second, third, and fourth power channels respectively connected with distribution sides of the first electric machine, second electric machine, third electric machine, and fourth electric machine.

Abstract: Multi-engine aircraft power and propulsion systems and methods of starting the engines of multi-engine aircraft disclosed, including supplying electrical power from an electrical power source to electric machines of the a first gas turbine engine and operating electric machines as motors to drive rotation of spools of the first gas turbine engine; starting the first gas turbine engine by lighting combustion equipment of the first gas turbine engine; operating the electric machines of the first gas turbine engine as generators to extract mechanical power and generate electrical power from spools of the first gas turbine engine; transferring the electrical power to electric machines of a second gas turbine engine and operating the electric machines as motors to drive rotation of spools of the second gas turbine engine; and starting the second gas turbine engine by lighting combustion equipment of the second gas turbine engine.

Abstract: A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module, with a first electric machine being rotationally connected to the turbine module. The first electrical machine is configured to generate a maximum electrical power PEM1 (W), and the gas turbine engine is configured to generate a maximum dry thrust T (N); and a ratio S of: S=(Maximum Electrical Power Generated=PEM1)/(Maximum Dry Thrust=T) is in a range of between 2.0 and 10.0.