Abstract: An electrical power system includes: an H-bridge DC:DC power converter including first and second half-bridge circuits having low-side transistors and a high-side transistors, and an inductor connected between AC sides of the first and second half-bridge circuits; a DC power source connected to a first half-bridge circuit DC side; a DC electrical network connected to a second half-bridge circuit DC side; and a control system. The control system: controls the low-side and high-side transistors' switching state of the first and second half-bridge circuits; monitors one or more electrical power system operating parameters and determines whether there is a fault in the DC electrical network; and in response, modifies a switching operation of the low-side and high-side transistors of the first and second half-bridge circuits to supply a controlled amount of current from the DC power source to the DC electrical network.

Abstract: A DC:DC converter includes: a DC:AC converter circuit having DC and AC sides; an AC:DC converter circuit having DC and sides; an AC link connecting the AC side of the DC:AC circuit and the AC side of the AC:DC converter circuit, the AC link including a transformer having a first winding connected to the AC side of the DC:AC converter circuit and a second winding connected to the AC side of the AC:DC converter; a capacitor; and a switch arrangement having a first state and a second state, wherein: in the first state, the capacitor is connected in series between the AC side of the DC:AC converter circuit and the first winding of the transformer; and in the second state, there is a current path between the AC side of the DC:AC converter circuit and the first winding of the transformer that does not include the capacitor.

Abstract: A DC:DC power electronics converter in an electrical power system includes: DC:AC and AC:DC converters; and an AC link connecting AC sides of the converters, the AC link including a transformer having first and second windings connected respectively to AC sides of the converters; a DC power source connected to the DC side of the DC:AC converter; a DC electrical network connected to the DC side of the AC:DC converter; and a control system to: control a switching operation of respective first and second pluralities of transistors of the converters, monitor one or more operating parameters of the electrical power system and determine whether there is a fault in the electrical network, and if so, modify a switching operation of the first and/or second plurality of transistors to supply a controlled amount of fault current from the DC power source to the electrical network via the DC:DC power electronics converter.

Abstract: There is provided an electrical power system comprising: a DC voltage source, a DC electrical network, a DC to AC to DC converter having a primary side connected to the DC voltage source and a secondary side connected to the DC electrical network, and a controller configured to control the DC to AC to DC converter, wherein the controller is configured to: monitor an electrical current or voltage between the DC voltage source and the DC electrical network; determine, based on the monitored electrical current or voltage, whether the DC electrical network is in a fault condition; and increase a switching frequency of the primary side of the DC to AC to DC converter in response to a positive determination that the DC electrical network is in a fault condition.

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 power electronics converters having circuit breaker protection for use in case of faults. Example embodiments include a power electronics converter for converting an input AC supply having a plurality of phases to an output DC supply, the converter comprising: a plurality of AC input terminals connectable to the plurality of phases of the AC supply; first and second DC output terminals; a capacitor connected between the first and second DC output terminals; a first MOSFET connected between each of the plurality of AC input terminals and the first DC output terminal; a second MOSFET connected between each of the plurality of AC input terminals and the second DC output terminal; and a third MOSFET reverse connected in series with the first MOSFET between the first DC output terminal and each of the plurality of AC input terminals.

Abstract: The disclosure relates to estimation of junction temperatures of transistors in a power electronics converter. Example embodiments include a method of estimating a junction temperature of a transistor in a power electronics converter configured to convert between first and second supply voltages, the method comprising: providing a gate switching signal to the transistor; measuring a rate of change of current through the converter during a switching period of the transistor; and outputting an estimated junction temperature of the transistor based on the measured rate of change of current, wherein the rate of change of current is measured while a gate voltage of the transistor is above a gate threshold voltage and a drain-source voltage across the transistor is above a predetermined fraction of the first or second supply voltage whereby the rate of change of current is measured in a linear region.

Abstract: An estimation of junction temperatures of transistors in power electronics converter.

Abstract: There is provided a current limiting diode 200 comprising a gate 206, a source 202, a drain 204 electrically connected to the source by an n-channel or p-channel 220 and a thermoelectric generator 208; wherein the source and the gate are electrically connected by a fill structure 210, and wherein the thermoelectric generator is configured to: generate a thermoelectric voltage by absorbing heat from the n-channel or p-channel and rejecting heat to a heat sink in a current limiting condition; and apply the thermoelectric voltage between the gate and the source.

Abstract: An AC to DC conversion device has first and second AC input terminals arranged to be coupled respectively to first and second terminals of a phase of an AC current generator, an H-bridge rectification device comprising two pairs of diodes, each pair being coupled to a respective one of the AC terminals to produce a DC output comprising a rectified back EMF waveform, and a waveform generator. The waveform generator comprises an output coupled to the DC output of the H-bridge rectification device, and is configured to input a unidirectional waveform to the DC output having the same magnitude and fundamental frequency as the rectified back EMF, phase shifted by a predetermined angle relative to the rectified back EMF waveform.

Abstract: Reconfigurable permanent magnet electrical machines and aircraft power and propulsion systems comprising such electrical machines are described. In one aspect, an aircraft power and propulsion system comprises: a gas turbine engine; a permanent magnet electrical machine comprising a rotor drivingly coupled to a spool of the gas turbine engine, and a stator comprising windings controllably switchable between a star configuration and a delta configuration; a DC electrical network; an AC:DC power electronics converter, an AC side of which is connected to terminals of the stator windings of the electrical machine and a DC side of which is connected to the DC electrical network; and a control system. The control system is configured to monitor at least one operating condition of the power and propulsion system and to control the switching of the stator windings between the star configuration and the delta configuration based on the at least one operating condition.

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 = P E ? M ? 1 ) ( Maximum ? Dry ? Thrust = T ) is in a range of between 2.0 and 10.0.

Abstract: The disclosure relates to an electrical power system with current fault protection provided by current limiting diodes. Example embodiments include an electrical power system comprising: an electrical machine; an AC:DC power electronics converter connected to receive an input AC supply from the electrical machine and provide an output DC supply across first and second output terminals; a DC bus connected to first and second output terminals of the AC:DC power electronics converter; a load connected across the DC bus; a first circuit breaker switch and a first current limiting diode connected in series between the AC:DC power electronics converter and the DC bus; and a second circuit breaker switch and a second current limiting diode connected in series between the DC bus and the load, wherein the first current limiting diode is configured to limit current to a higher level than the second current limiting diode.

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. 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: 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: 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.