Patent Description:
A conventional commercial aircraft generally includes a fuselage, a pair of wings, and a propulsion system that provides thrust. The propulsion system typically includes at least two aircraft engines, such as turbofan jet engines. Each turbofan jet engine is mounted to a respective one of the wings of the aircraft, such as in a suspended position beneath the wing, separated from the wing and fuselage.

More recently, propulsion systems have been proposed of a hybrid-electric design. With these propulsion systems, an electric power source may provide electric power to an electric fan to power the electric fan. Electric power systems capable of providing this electric power while maintaining a robustness and a redundancy in design would be beneficial.

<CIT> discloses a hybrid aircraft propulsion system that includes a plurality of power units configured to output electrical energy onto one or more electrical busses.

<CIT> discloses systems and methods relating to an electrical system on an aircraft. The electrical system can be for an aircraft having a turbine engine. The turbine engine has a high pressure (HP) spool and a low pressure (LP) spool. which includes a first generator in communication with a first engine, a second generator in communication with a second engine, a first rectifier and a second rectifier. Each generator has a main winding, each main winding being independently excitable and generating an alternating current (AC) output. A main AC output of the main winding of the first generator is in communication with the first rectifier, and a main AC output of the main winding of the second generator is in communication with the second rectifier.

<CIT> discloses rotor and stator segments for a generator and motor apparatus. The apparatus includes: a pair of parallel, spaced apart stator segments, each stator segment comprising a stator winding set; and a rotor segment slidably coupled to the pair of stator segments, the rotor segment comprising a magnet and being dimensioned to fit between the parallel, spaced apart stator segments. The apparatus may include a support structure, the rotor segment being slidably coupled to the support structure and the stator segment being attached to the support structure. The apparatus may be a rim generator, wind turbine generator or other electrical machine. The stator winding set includes a stator winding, and may include other electrical or electronic components, including possibly a power factor capacitor, direct current filtering capacitor, supercapacitor, and one or more diodes. The stator winding set may be encapsulated within the stator segment.

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description.

Claim <NUM> defines a vehicle electric power system and claim <NUM> defines a method. In the following, apparatus and/or methods referred to as embodiments that nevertheless do not fall within the scope of the claims should be understood as examples useful for understanding the invention.

The advantages of the present invention will become better understood with reference to the following description and appended claims.

The terms "upstream" and "downstream" refer to the relative direction with respect to a flow in a pathway. For example, with respect to a fluid flow, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows. However, the terms "upstream" and "downstream" as used herein may also refer to a flow of electricity.

For example, the approximating language may refer to a value being within a +/- <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> percent margin in either individual values, range(s) of values and/or endpoints defining range(s) of values.

The subject technology is generally directed to various architectures for an electric power system, such as an electric power system configured to supply power in an aircraft. For instance, power can be reliably generated and supplied during normal steady-state operation as well as under fault conditions in order to generate thrust in a propulsion assembly of an aircraft. Power generation can employ two electric machines (e.g., an LP generator and an HP generator) to supply engine and aircraft loads, one rotatable with an LP shaft/spool and one rotatable with an HP shaft/spool. The various configurations can be adapted to provide for high power density packaging within an aircraft engine at different voltage levels of a DC bus (e.g., ±<NUM> V, ±<NUM> V or other high voltage levels (e.g., in a bipolar voltage range of between about +/- <NUM> and about +/- <NUM>,<NUM> volts, or in a unipolar voltage range of between about <NUM> volts and <NUM> volts)), in order to optimize overall system weight, size, efficiency, and reliability. In some embodiments the voltage levels for the DC bus may be a unipolar or bipolar voltage and between <NUM> and <NUM>, below <NUM>, between <NUM> and <NUM>, about <NUM>, about <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, about <NUM>, about <NUM>, about <NUM>, between <NUM> and <NUM>, about <NUM>, between <NUM> and <NUM>, and/or above <NUM> in order to optimize overall system weight, size, efficiency, and reliability.

The ability to advantageously balance power density and performance with weight, size, efficiency, and reliability can be especially advantageous for applications including but not limited to narrow body aircraft engines. Notably, as used herein, the term "LP generator" and "HP generator" simply refers to the components of an engine the generator is associated with, and does not necessarily imply any specific characteristics of the electric machine.

Electric power systems as described herein can include first and second electric machines as well as a power distribution system (PDU) that is configured as a dual bus system including first and second independent electrical power buses. Each electrical power bus can electrically connect and provide an independent source of DC power to a separate aircraft engine or other load (e.g. to an electric propulsion assembly). The dual bus system is designed to add a level of redundancy to the electric power system. If a fault occurs within an electric machine connection, internal to an electric machine, in electrical cables, in a power converter, or in another location, one of the electrical power buses (or one inverter channel associated with a single bus) can be taken offline while the other inverter channels or electrical power bus(es) continue to operate. Such electric power system configurations afford the capability of running full aircraft load with one of the inverter channels or electrical power buses being offline. Power flow thus can be advantageously managed within an electric power system without causing disruption to the system.

In addition to providing two independent electrical channels, the channels are configured to be magnetically balanced to avoid mechanical forces that would otherwise occur in the event of unbalanced magnetic pull caused by magnetic flux being generated in only a portion of an electric machine. Magnetic balancing can be achieved by providing first and second independent inverter channels within each electrical channel of an electric power system, along with specific configurations within the winding-inverter connections of an electric machine. These features can be designed so that the electric channels within the electric power systems remain magnetically balanced and mechanically stable.

In some embodiments, additional improvements can be made to the size, weight and efficiency of an electric power system. One option for achieving such additional improvements is by co-locating converters with a power distribution unit. For instance, providing an LP converter, HP converter, and first and second electrical power buses within the same PDU assembly can substantially reduce or eliminate the amount and number of cables and DC common-mode filtering that might otherwise be needed within an electric power system. Another option for achieving such additional improvements is to eliminate an LP converter by including a diode-rectifier configuration at the LP machine. A capacitor configuration can also be included at the LP machine for generating reactive power. Elimination of an LP converter by including a capacitor-diode rectifier at the LP machine is possible when power flow occurs only from the LP machine to the HP machine and not from the HP machine to the LP machine. Such option helps provide high power quality, low stress on the LP generator insulation, and reduced/eliminated need for common mode filtering on the DC cable(s) from an LP generator without oversizing the machine.

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures, <FIG> provides a top view of an exemplary aircraft <NUM> as may incorporate various embodiments of the present disclosure. As shown in <FIG>, the aircraft <NUM> defines a longitudinal centerline <NUM> that extends therethrough, a lateral direction L, a forward end <NUM>, and an aft end <NUM>. Moreover, the aircraft <NUM> includes a fuselage <NUM>, extending longitudinally from the forward end <NUM> of the aircraft <NUM> to the aft end <NUM> of the aircraft <NUM>, and a wing assembly including a port side and a starboard side. More specifically, the port side of the wing assembly is a first, port side wing <NUM>, and the starboard side of the wing assembly is a second, starboard side wing <NUM>. The first and second wings <NUM>, <NUM> each extend laterally outward with respect to the longitudinal centerline <NUM>. The first wing <NUM> and a portion of the fuselage <NUM> together define a first side <NUM> of the aircraft <NUM>, and the second wing <NUM> and another portion of the fuselage <NUM> together define a second side <NUM> of the aircraft <NUM>. For the embodiment depicted, the first side <NUM> of the aircraft <NUM> is configured as the port side of the aircraft <NUM>, and the second side <NUM> of the aircraft <NUM> is configured as the starboard side of the aircraft <NUM>.

Each of the wings <NUM>, <NUM> for the exemplary embodiment depicted includes one or more leading edge flaps <NUM> and one or more trailing edge flaps <NUM>. The aircraft <NUM> further includes a vertical stabilizer <NUM> having a rudder flap (not shown) for yaw control, and a pair of horizontal stabilizers <NUM>, each having an elevator flap <NUM> for pitch control. The fuselage <NUM> additionally includes an outer surface or skin <NUM>. It should be appreciated however, that in other exemplary embodiments of the present disclosure, the aircraft <NUM> may additionally or alternatively include any other suitable configuration. For example, in other embodiments, the aircraft <NUM> may include any other configuration of stabilizer.

Referring now also to <FIG> and <FIG>, the exemplary aircraft <NUM> of <FIG> additionally includes a propulsion system <NUM> having a first propulsor assembly <NUM> and a second propulsor assembly <NUM>. <FIG> provides a schematic, cross-sectional view of the first propulsor assembly <NUM>, and <FIG> provides a schematic, cross-sectional view of the second propulsor assembly <NUM>. As is depicted, each of the first propulsor assembly <NUM> and second propulsor assembly <NUM> are configured as under-wing mounted propulsor assemblies.

Referring particularly to <FIG> and <FIG>, the first propulsor assembly <NUM> is mounted, or configured to be mounted, to the first side <NUM> of the aircraft <NUM>, or more particularly, to the first wing <NUM> of the aircraft <NUM>. The first propulsor assembly <NUM> generally includes a turbomachine <NUM> and a primary fan (referred to simply as "fan <NUM>" with reference to <FIG>). More specifically, for the embodiment depicted the first propulsor assembly <NUM> is configured as a turbofan engine <NUM> (i.e., the turbomachine <NUM> and the fan <NUM> are configured as part of the turbofan engine <NUM>).

As shown in <FIG>, the turbofan engine <NUM> defines an axial direction A1 (extending parallel to a longitudinal centerline <NUM> provided for reference), a radial direction R1, and a circumferential direction C (extending about the axial direction A1; not depicted in <FIG>). In general, the turbofan engine <NUM> includes a fan section <NUM> and a core turbine engine <NUM> disposed downstream from the fan section <NUM>.

The exemplary core turbine engine <NUM> depicted generally includes a substantially tubular outer casing <NUM> that defines an annular inlet <NUM>. The outer casing <NUM> encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor <NUM> and a high pressure (HP) compressor <NUM>; a combustion section <NUM>; a turbine section including a high pressure (HP) turbine <NUM> and a low pressure (LP) turbine <NUM>; and a jet exhaust nozzle section <NUM>. The compressor section, combustion section <NUM>, and turbine section together define a core air flowpath <NUM> extending from the annular inlet <NUM> through the LP compressor <NUM>, HP compressor <NUM>, combustion section <NUM>, HP turbine section <NUM>, LP turbine section <NUM> and jet nozzle exhaust section <NUM>. A high pressure (HP) shaft or spool <NUM> drivingly connects the HP turbine <NUM> to the HP compressor <NUM>. A low pressure (LP) shaft or spool <NUM> drivingly connects the LP turbine <NUM> to the LP compressor <NUM>.

For the embodiment depicted, the fan section <NUM> may include a fixed or variable pitch fan <NUM> having a plurality of fan blades <NUM> coupled to a disk <NUM> in a spaced apart manner. As depicted, the fan blades <NUM> extend outwardly from disk <NUM> generally along the radial direction R. For the variable pitch fan embodiment, each fan blade <NUM> is rotatable relative to the disk <NUM> about a pitch axis P1 by virtue of the fan blades <NUM> being operatively coupled to a suitable actuation member <NUM> configured to collectively vary the pitch of the fan blades <NUM> in unison. The fan blades <NUM>, disk <NUM>, and actuation member <NUM> are together rotatable about the longitudinal axis <NUM> by LP shaft <NUM>.

Referring still to the exemplary embodiment of <FIG>, the disk <NUM> is covered by rotatable front hub <NUM> aerodynamically contoured to promote an airflow through the plurality of fan blades <NUM>. Additionally, the exemplary fan section <NUM> includes an annular fan casing or outer nacelle <NUM> that circumferentially surrounds the fan <NUM> and/or at least a portion of the core turbine engine <NUM>. The nacelle <NUM> is supported relative to the core turbine engine <NUM> by a plurality of circumferentially-spaced outlet guide vanes <NUM>. A downstream section <NUM> of the nacelle <NUM> extends over an outer portion of the core turbine engine <NUM> so as to define a bypass airflow passage <NUM> therebetween.

Additionally, the exemplary turbofan engine <NUM> depicted includes a first electric machine and a second electric machine. For the embodiment shown, the first electric machine is rotatable with the LP shaft <NUM> and fan <NUM>, and the second electric machine is rotatable with the HP shaft <NUM>. In such a manner, it will be appreciated that for the embodiment shown, the first electric machine is an LP electric machine <NUM> and the second electric machine is an HP electric machine <NUM>.

Specifically, for the embodiment depicted, the LP electric machine <NUM> is configured as an electric generator co-axially mounted to and rotatable with the LP shaft <NUM>. As used herein, "co-axially" refers to the axes being aligned. Moreover, for the embodiment shown, the LP electric machine <NUM> is positioned inward of the core air flowpath <NUM> within or aft of the turbine section of the turbofan engine <NUM>, and as such may be referred to as an embedded electric machine.

Similarly, for the embodiment depicted, the HP electric machine <NUM> is configured as an electric generator co-axially mounted to and rotatable with the HP shaft <NUM>. The HP electric machine <NUM> is also positioned inward of the core air flowpath <NUM>, but within compressor section of the turbofan engine <NUM>, and as such may also be referred to as an embedded electric machine.

The LP electric machine <NUM> and the HP electric machine <NUM> each include a rotor <NUM> and a stator <NUM>. The LP electric machine <NUM> and the HP electric machine <NUM> may be configured in accordance with one or more of the exemplary electric machines described below.

It should be appreciated, however, that in other embodiments, an axis of the LP electric machine <NUM> and/or the HP electric machine <NUM> may be offset radially from the axes of the LP shaft <NUM> and HP shaft <NUM>, respectively, and further the LP electric machine <NUM> and/or the HP electric machine <NUM> may be oblique to the axes of the LP shaft <NUM> and HP shaft <NUM>, respectively. Further, in one or more exemplary embodiments, the LP electric machine <NUM> and/or the HP electric machine <NUM> may be located outward of the core air flowpath <NUM>, e.g., within the casing <NUM> of the turbofan engine <NUM> or nacelle <NUM>. Moreover, although the LP electric machine <NUM> and the HP electric machine <NUM> are described above as electric generators, in certain exemplary embodiments one or both of the LP electric machine <NUM> and the HP electric machine <NUM> may be configured as an electric motor, or may be switched between an electric generator mode and an electric motor mode.

Further, it should also be appreciated that the exemplary turbofan engine <NUM> depicted in <FIG> is provided by way of example only, and that in other exemplary embodiments, the turbofan engine <NUM> may have any other suitable configuration. For example, in other exemplary embodiments, the turbofan engine <NUM> may be configured as a turboprop engine, a turbojet engine, a differently configured turbofan engine, an unducted turbofan engine (e.g., without the nacelle <NUM>, but including the stationary outlet guide vanes <NUM>), or any other suitable gas turbine engine. For example, the gas turbine engine may be a geared gas turbine engine (e.g., having a reduction gearbox between the LP shaft <NUM> and fan <NUM>), may have any other suitable number or configuration of shafts/ spools (e.g., may include an intermediate speed shaft/ turbine/ compressor), etc..

Referring still to <FIG> and <FIG>, although not depicted in <FIG>, the propulsion system <NUM> depicted additionally includes an electrical power connection assembly <NUM> to allow the LP and HP electric machines <NUM>, <NUM> to be in electrical communication with one or more other components of the propulsion system <NUM> and/or the aircraft <NUM>. For the embodiment depicted, the electrical power connection assembly <NUM> includes one or more electrical cables or lines <NUM> connected to the LP and HP electric machines <NUM>, <NUM>, which may extend from the LP and HP electric machines <NUM>, <NUM> through one or more of the outlet guide vanes <NUM>. As will be discussed in greater detail below, the electrical power bus is generally configured as a high-voltage electrical power bus, such that the propulsion system <NUM> may generally operate with relatively high voltages.

Additionally, the propulsion system <NUM> depicted further includes one or more energy storage devices <NUM> (such as one or more batteries or other electrical energy storage devices) electrically connected to the electrical power connection assembly <NUM> for, e.g., providing electrical power to the second propulsor assembly <NUM> and/or receiving electrical power from an electric generator. Inclusion of the one or more energy storage devices <NUM> may provide performance gains, and may increase a propulsion capability of the propulsion system <NUM> during, e.g., transient operations. More specifically, the propulsion system <NUM> including one or more energy storage devices <NUM> may be capable of responding more rapidly to speed change demands.

Referring now particularly to <FIG> and <FIG>, the exemplary propulsion system <NUM> additionally includes the second propulsor assembly <NUM> positioned, or configured to be positioned, at a location spaced apart from the first propulsor assembly <NUM>.

Referring still to the exemplary embodiment of <FIG> and <FIG>, the second propulsor assembly <NUM> is mounted to the second side <NUM> of the aircraft <NUM>, or rather to the second wing <NUM> of the aircraft <NUM>. Referring particularly to <FIG>, the second propulsor assembly <NUM> is generally configured as an electric propulsion assembly including an electric motor and a propulsor. More particularly, for the embodiment depicted, the electric propulsion assembly <NUM> includes an electric motor <NUM> and a propulsor/fan <NUM>. The electric propulsion assembly <NUM> defines an axial direction A2 extending along a longitudinal centerline axis <NUM> that extends therethrough for reference, as well as a radial direction R2. For the embodiment depicted, the fan <NUM> is rotatable about the centerline axis <NUM> by the electric motor <NUM>.

The fan <NUM> includes a plurality of fan blades <NUM> and a fan shaft <NUM>. The plurality of fan blades <NUM> are attached to/rotatable with the fan shaft <NUM> and spaced generally along a circumferential direction of the fan (not shown). In certain exemplary embodiments, the plurality of fan blades <NUM> may be attached in a fixed manner to the fan shaft <NUM>, or alternatively, the plurality of fan blades <NUM> may be rotatable relative to the fan shaft <NUM>, such as in the embodiment depicted. For example, the plurality of fan blades <NUM> each define a respective pitch axis P2, and for the embodiment depicted are attached to the fan shaft <NUM> such that a pitch of each of the plurality of fan blades <NUM> may be changed, e.g., in unison, by a pitch change mechanism <NUM>. Changing the pitch of the plurality of fan blades <NUM> may increase an efficiency of the second propulsor assembly <NUM> and/or may allow the second propulsor assembly <NUM> to achieve a desired thrust profile. With such an exemplary embodiment, the fan <NUM> may be referred to as a variable pitch fan.

Moreover, for the embodiment depicted, the electric propulsion assembly <NUM> depicted additionally includes a fan casing or outer nacelle <NUM>, attached to a core <NUM> of the fan <NUM> through one or more struts or outlet guide vanes <NUM>. For the embodiment depicted, the outer nacelle <NUM> substantially completely surrounds the fan <NUM>, and particularly the plurality of fan blades <NUM>. Accordingly, for the embodiment depicted, the fan <NUM> may be referred to as a ducted electric fan.

Referring still particularly to <FIG>, the fan shaft <NUM> is mechanically coupled to the electric motor <NUM> within the core <NUM>, such that the electric motor <NUM> drives the fan <NUM> through the fan shaft <NUM>. The fan shaft <NUM> is supported by one or more bearings <NUM>, such as one or more roller bearings, ball bearings, or any other suitable bearings. Additionally, the electric motor <NUM> may be an inrunner electric motor (i.e., including a rotor positioned radially inward of a stator), or alternatively may be an outrunner electric motor (i.e., including a stator positioned radially inward of a rotor).

As briefly noted above, the electric power source (i.e., the electric generator(s) of the first propulsor assembly <NUM> for the embodiment depicted) is electrically connected with the electric propulsion assembly (i.e., the electric motor <NUM> and the fan <NUM> of the electric propulsion assembly <NUM> for the embodiment depicted) for providing electrical power to the electric propulsion assembly. More particularly, the electric motor <NUM> of the electric propulsion assembly <NUM> is in electrical communication with the electric power system through the electrical power connection assembly <NUM>, and more particularly through the one or more electrical cables or lines <NUM> extending therebetween. Again, as will be discussed in more detail below, the electrical power connection assembly <NUM> is configured to provide relatively high-voltage electrical power to the electric propulsion assembly for driving the electric propulsion assembly.

A propulsion system in accordance with one or more of the above embodiments may be referred to as a gas-electric, or hybrid-electric propulsion system, given that a first propulsor assembly is configured as a gas turbine engine and a second propulsor assembly is configured as an electrically driven fan.

It should be appreciated, however, that in other exemplary embodiments the exemplary propulsion system may have any other suitable configuration, and further, may be integrated into an aircraft <NUM> in any other suitable manner. For example, in other exemplary embodiments, the hybrid-electric propulsion system may have any suitable number of gas turbine engines (such as one, two, three, four, etc.) distributed in any suitable manner (such as along a port side wing, a starboard side wing, a fuselage of the aircraft, an aft location, etc.), and mounted in any suitable manner (such as in an under-wing mount, an over-wing mount, integrated into a wing, mounted to a fuselage of the aircraft, mounted to a stabilizer of the engine, mounted at the aft end as a boundary layer ingestion engine, etc.). Similarly, the hybrid-electric propulsion system may have any suitable number of electric propulsion engines (such as one, two, three, four, etc.) distributed in any suitable manner (such as along a port side wing, a starboard side wing, a fuselage of the aircraft, an aft location, etc.), and mounted in any suitable manner (such as in an under-wing mount, an over-wing mount, integrated into a wing, mounted to a fuselage of the aircraft, mounted to a stabilizer of the engine, mounted at the aft end as a boundary layer ingestion engine, etc.). In the event a plurality of gas turbine engines are provided with electric machine to generate electrical power, each may be directed to a single electric propulsion engine or a single group of electric propulsion engines, or each may be in electrical communication with a common electrical bus to provide power to the electric propulsion engine(s).

Moreover, it will be appreciated that although the propulsion system described herein is depicted as having been incorporated into an aircraft <NUM>, in other exemplary embodiments, the propulsion system may additionally or alternatively be incorporated into any other suitable vehicle. For example, in other exemplary embodiments, the propulsion system may be incorporated into a nautical vehicle utilizing one or more turbine engines (such as a ship or submarine), a locomotive vehicle utilizing one or more turbine engines, etc..

Referring now briefly to <FIG>, a schematic view is provided for a hybrid electric propulsion system in accordance with the present disclosure. The exemplary hybrid electric propulsion system may incorporate aspects of the systems described above with reference to <FIG>. For example, the exemplary hybrid electric propulsion system <NUM> can include a gas turbine engine <NUM> having an HP electric machine <NUM> rotatable with an HP shaft <NUM> of the gas turbine engine <NUM> and an LP electric machine <NUM> rotatable with an LP shaft <NUM> of the gas turbine engine <NUM>. The HP electric machine <NUM> and LP electric machine <NUM> can be part of an electric power system <NUM> that also includes a power distribution unit (PDU) <NUM>. PDU <NUM> can provide multiple DC voltages that are generated by the electric power system <NUM>. Such multiple DC voltages can be provided at the same and/or different values, provided at fixed and/or varied levels, and configured as either regulated and/or unregulated voltages. In some implementations, such as when the LP electric machine <NUM> is a generator and the HP electric machine is a starter-generator, power generated by the electric power system <NUM> can include electric power that flows between LP and HP spools (e.g., from the LP generator to the HP starter-generator) for the purpose of improving specific fuel consumption.

The exemplary hybrid electric propulsion system <NUM> further includes an electric propulsion assembly <NUM> having a fan/propulsor <NUM> and an electric motor <NUM>. The exemplary hybrid electric propulsion system <NUM> also includes an electrical power connection assembly <NUM> electrically coupling the gas turbine engine (or rather the HP and LP electric machines <NUM>, <NUM>) with the electric propulsion assembly <NUM> (or rather the electric motor <NUM>).

The system depicted in <FIG> can additionally include an aircraft load <NUM> that is coupled to the PDU <NUM> and that is powered by the multiple DC channels. In some implementations, aircraft load <NUM> can correspond to one or more engine electrical loads such as but not limited to fuel pump(s), cooling pump(s) and engine icing protection. In some implementations, aircraft load <NUM> can correspond to one or more environmental control systems such as but not limited to systems for cabin pressurization, cabin air-conditioning, and the like, flight control electrified actuators, avionics, wing icing protection, and other systems requiring DC power within an aircraft.

Notably, the electrical power connection assembly <NUM> is configured as a dual bus system whereby PDU <NUM> includes first and second independent electrical power buses. The first electrical power bus can electrically connect and provide a first source of DC power from the electric power system <NUM> to the electric propulsion assembly <NUM> and/or to aircraft load <NUM>. For instance, a first set of one or more cables or connectors <NUM> can be provided to transfer power from the first electrical power bus of PDU <NUM> to the electric propulsion assembly <NUM> (or rather the electric motor <NUM>), and/or to aircraft load <NUM>. The second electrical power bus can electrically connect and provide a second source of DC power from the electric power system <NUM> to the electric propulsion assembly <NUM> and/or to aircraft load <NUM>. For instance, a second set of one or more cables or connectors <NUM> can be provided to transfer power from the second electrical power bus of PDU <NUM> to the electric propulsion assembly <NUM> (or rather the electric motor <NUM>) and/or to aircraft load <NUM>. The second electrical power bus of PDU <NUM> is configured to be electrically independent from the first electrical power bus. Although only first and second sets of cables/connectors <NUM>, <NUM> are illustrated in <FIG> and discussed with reference to first and second electrical power buses of PDU <NUM>, it should be appreciated that additional layers of redundancy (e.g., a plurality of electrical power buses including first, second, third, or more power buses) are possible.

Referring still to <FIG>, electric power system <NUM> can be configured as a high-voltage electric power system, and propulsion system <NUM> can be configured as a high-voltage propulsion system. As such, the power generated by HP electric machine <NUM> and LP electric machine <NUM> and ultimately transferred by PDU <NUM> to the electric propulsion assembly <NUM> and/or to aircraft load <NUM> can be configured to provide electrical power at a voltage exceeding <NUM> volts ("V"). For example, in certain exemplary embodiments, the electric power buses within PDU <NUM> can be configured to transfer electrical power received from HP electric machine <NUM> and LP electric machine <NUM> to the electric propulsion assembly <NUM> and/or to aircraft load <NUM> at a bipolar voltage level between about +/- <NUM> V and about +/- <NUM> V, or more particularly between about +/- <NUM> V and about +/- <NUM>,<NUM> V. In other embodiments, the electric power buses within PDU <NUM> can be configured to transfer electrical power received from HP electric machine <NUM> and LP electric machine <NUM> to the electric propulsion assembly <NUM> and/or to aircraft load <NUM> at a bipolar or unipolar voltage level between <NUM> and <NUM>, below <NUM>, between <NUM> and <NUM>, about <NUM>, about <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM>, about <NUM>, about <NUM>, about <NUM>, between <NUM> and <NUM>, about <NUM>, between <NUM> and <NUM>, and/or above <NUM>. By transferring electrical power from the electric power system <NUM> to the electric propulsion assembly <NUM> and/or the aircraft load <NUM> (via the first and second independent power buses) at relatively high voltages, electrical power can be transferred at a lower electrical current while still delivering a desired amount of power. Such a configuration may allow for cables (e.g., cables <NUM>, <NUM>) having a reduced thickness, or diameter, which may save weight in an aircraft including the exemplary propulsion system <NUM>. Because transfer cables can often be required to extend relatively long distances, a reduced thickness, or diameter, within such cables can advantageously save an appreciable amount of size and weight within the aircraft.

For example, in certain exemplary embodiments, PDU <NUM> may be configured to transfer electrical power to the electric propulsion assembly <NUM> and/or aircraft load at an electrical current between about <NUM> amps ("A") and about <NUM>,<NUM> A, such as between about <NUM> A and about <NUM>,<NUM> A. With such an exemplary embodiment, the PDU <NUM> may be configured to transfer at least about <NUM> kilowatts of electrical power to the electric propulsion assembly <NUM> and up to about twelve (<NUM>) megawatts of electrical power. For example, in certain exemplary embodiments the PDU <NUM> may be configured to transfer at least about one (<NUM>) megawatt of electrical power to the electric propulsion assembly <NUM> and/or aircraft load <NUM>, such as between about one (<NUM>) megawatt of electrical power and about two (<NUM>) megawatts of electrical power.

<FIG> generally provide additional details of the dual bus system within PDU <NUM> and other aspects of an electric power system <NUM> that includes a plurality of electric machines (e.g., HP electric machine <NUM> and LP electric machine <NUM>). The dual bus system is designed to add a level of redundancy to the electric power system <NUM>. To that effect, if a fault occurs within various locations (e.g., in an electric machine connection, internal to an electric machine, in electrical cables, in a power converter, etc.), one of the electrical power buses can be taken offline while the other electrical power bus(es) continue to operate.

Referring now to <FIG>, additional aspects of electric machine connections within an electric power system <NUM> are schematically illustrated. <FIG> depict example connection configurations for windings and terminals within an electric machine, while <FIG> provide corresponding schematic illustrations of how the connection configurations of <FIG> can be coupled to subsequent components within an electric power system. It should be appreciated that the connection configurations and corresponding schematics of <FIG> illustrate only a single electric machine. However, the configurations can be equally applied across multiple electric machines (e.g., a first electric machine such as LP electric machine (LP generator) <NUM> and a second electric machine such as HP electric machine (HP generator <NUM>). When multiple electric machines are included within an electric power system embodiment, the machines can include the same or different configurations, and can be designed to deliver the same or different voltage/power levels across multiple DC channels. In some instances, a given electric machine can include windings designed for carrying different currents within the same electric machine. In addition, the winding configurations of <FIG> depict a particular number of winding sections. It should be appreciated that each configuration with a plurality of windings can be modified to include a different number of windings. For example, a configuration with four (<NUM>) windings can be modified to include a greater number of windings and still be within the spirit and scope of the disclosed technology.

<FIG> is a schematic representation of a first example electric machine connection configuration <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric machine connection configuration <NUM> can be implemented as part of an electric machine. In some examples, electric machine connection configuration <NUM> can be implemented as part of a first electric machine (e.g., LP electric machine <NUM>) and/or as part of a second electric machine (e.g., HP electric machine <NUM>).

In accordance with electric machine connection configuration <NUM>, an electric machine can include first, second, third, and fourth winding sections <NUM>-<NUM>. Such plurality of winding sections <NUM>-<NUM> can be multi-phase and/or substantially magnetically decoupled. The winding sections <NUM>-<NUM> can be provided in a configuration such that an electric machine including electric machine connection configuration <NUM> is mechanically balanced even if one of the plurality of windings is de-energized. In some implementations, the plurality of windings can be tooth-wound and/or spatially distributed. However, it should be appreciated that other coil winding configurations can be employed. For instance, distributed winding configurations and/or concentrated winding configurations can be additionally or alternatively utilized. In addition, the winding configurations can be designed such that magnetic flux travels in different manners throughout the electric machine(s), for instance yielding a radial-flux machine and/or an axial-flux machine.

Accordingly, it will be appreciated that as used herein, the term "substantially magnetically decoupled" with respect to a plurality of winding sections refers to a nominal level of magnetic coupling between and among various winding sections. More particularly, although it may be difficult to ensure complete magnetic decoupling among winding sections, winding sections that are "substantially magnetically decoupled" can correspond to winding sections in which an amount of magnetic coupling is minimized, below a nominal threshold value, and/or as close to zero as possible. Magnetic decoupling can be generally achieved at least in part by the way in which winding sections are wound within an electric machine and/or by properly adjusting phase angle between sets of winding sections. Magnetic decoupling among a group of windings enables remaining windings in the group to continue to operate while at least one winding in the group is not functioning normally. One example would be when a winding has insulation failure, in which case the winding is desired to either be de-energized or operated in an insulation failure mitigation scheme.

In addition, it will be appreciated that the term "mechanically balanced" as used herein refers to the active balancing of a plurality of windings in an electric machine. The plurality of windings can be individually excited (e.g., magnetized and loaded) in a way that the combined mechanical forces normal to the airgap of the electric machine produced by the plurality of windings are well balanced. Even if at least one of the plurality of windings is de-energized or is in limited operation, the excitation of the remaining plurality of windings can be adjusted to maintain the mechanical balance or to reduce the unbalance to a manageable level. For example, a group of windings (e.g., the pair of windings <NUM> and <NUM> in the embodiment depicted in <FIG>) can be configured for operation in a manner that balances each other while another group of windings (e.g., the pair of windings <NUM> and <NUM>) can also be configured for operation in a manner that balances each other. Still further, it will be appreciated that the term "multi-phase" as used herein shall cover various configurations in which more than one phase of electrical power is supplied.

Referring still to <FIG>, the first winding section <NUM>, second winding section <NUM>, third winding section <NUM>, and fourth winding section <NUM> can each spatially span about one-quarter of the length of its associated electric machine. Each winding section <NUM>-<NUM> includes three terminals for three-phase (3ph) electric power. Three-phase power terminals associated with the first winding section <NUM> can collectively form a first wye-configuration, or star-configuration, connection <NUM>. Three-phase power terminals associated with the second winding section <NUM> can collectively form a second wye-configuration, or star-configuration, connection <NUM>. Three-phase power terminals associated with the third winding section <NUM> can collectively form a third wye-configuration, or star-configuration, connection <NUM>. Three-phase power terminals associated with the fourth winding section <NUM> can collectively form a fourth wye-configuration, or star-configuration, connection <NUM>. In some embodiments, AC power generated at the first and third connections <NUM>, <NUM> can be diametrically shifted by <NUM> degrees from the AC power generated at the second and fourth connections <NUM>, <NUM>.

Although <FIG> and others depict or describe wye-configuration, or star-configuration, connections, it will be appreciated that other suitable connection configurations can be employed. By way of example, power terminals associated with the various winding sections can be configured using one or more of a delta connection, a parallel connection, a series connection, an open-ended connection, etc. In some instances, different connection configurations can be used. For example, at least one winding section in an electric machine can have a first connection configuration (e.g., wye-connected) and at least another winding section can have a second connection configuration (e.g., delta-connected) that is different than the first connection configuration.

<FIG> is a schematic representation of a first generator and converter assembly <NUM> using the first example electric machine connection configuration <NUM> of <FIG>. More particularly, electric machine <NUM> can include the first star-configuration connection <NUM>, second star-configuration connection <NUM>, third star-configuration connection <NUM>, and fourth star-configuration connection <NUM> depicted in <FIG>. A first set of AC cables <NUM> electrically couples the first connection <NUM> of electric machine (generator) <NUM> to a converter <NUM>. A second set of AC cables <NUM> electrically couples the second connection <NUM> of electric machine (generator) <NUM> to converter <NUM>. A third set of AC cables <NUM> electrically couples the third connection <NUM> of electric machine (generator) <NUM> to converter <NUM>. A fourth set of AC cables <NUM> electrically couples the fourth connection <NUM> of electric machine (generator) <NUM> to converter <NUM>. In some examples, converter <NUM> can be an active power rectifier assembly including, for example, one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>. In other examples, converter <NUM> can be a passive power rectifier assembly including, for example, a plurality of diode rectifiers and AC capacitors provided at terminals of the electric machine <NUM>. In some embodiments, a first set of terminals within the electric machine <NUM> can be coupled to an active power rectifier, while a second set of terminals within the electric machine <NUM> can be coupled to a passive power rectifier.

<FIG> is a schematic representation of a second example electric machine connection configuration <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric machine connection configuration <NUM> can be implemented as part of an electric machine. In some examples, electric machine connection configuration <NUM> can be implemented as part of a first electric machine (e.g., LP electric machine <NUM>) and/or as part of a second electric machine (e.g., HP electric machine <NUM>).

In accordance with electric machine connection configuration <NUM>, an electric machine can include a plurality of self-balancing windings, such as first and second winding sections <NUM>, <NUM>. Such plurality of winding sections <NUM>-<NUM> can be multi-phase and/or substantially magnetically decoupled. The winding sections <NUM>-<NUM> can be provided in a configuration such that an electric machine including electric machine connection configuration <NUM> is mechanically balanced even if one of the plurality of windings is de-energized. In some implementations, the plurality of windings can be tooth-wound and/or spatially distributed.

Each winding of the plurality of windings in <FIG> is arranged to mechanically balance on its own. For example, with a four (<NUM>) winding section arrangement, a diametrical pair of windings can be combined (e.g., in series or in parallel) to form a single multi-phase winding. As such, each of the first and second winding sections <NUM>, <NUM> each correspond to a multi-phase winding formed by combining a diametrical pair of windings that is respectively combined. It should be appreciated that additional or alternative configurations can be achieved with a different number of winding sections than illustrated. For instance, if there are six (<NUM>) winding sections spaced by <NUM> degrees, a first group of three windings spaced <NUM> degrees apart can be combined into a first multi-phase winding, while a second group of three windings spaced <NUM> degrees apart can be combined into a second multi-phase winding. Additionally or alternatively, such a six-winding embodiment can be configured to include three (<NUM>) self-balancing windings, by connecting (e.g., in series or in parallel) each diametric pair spaced by <NUM> degrees into a single winding. In this arrangement, mechanical balance can be maintained, even though one winding is excited (magnetized and loaded) differently from another winding.

Referring still to <FIG>, each winding section <NUM>, <NUM> includes three terminals for three-phase (3ph) electric power. Three-phase power terminals associated with the first winding section <NUM> can collectively form a first wye-configuration, or star-configuration, connection <NUM>. Three-phase power terminals associated with the second winding section <NUM> can collectively form a second wye-configuration, or star-configuration, connection <NUM>.

<FIG> is a schematic representation of a second generator and converter assembly <NUM> using the second example electric machine connection configuration <NUM> of <FIG>. More particularly, electric machine <NUM> can include two instances 334a, 334b of the first star-configuration connection <NUM> and two instances 335a, 335b of the second star-configuration connection <NUM> depicted in <FIG>. A first set of AC cables <NUM> electrically couples the two instances 334a, 334b of the first connection <NUM> of electric machine (generator) <NUM> to a converter <NUM>. A second set of AC cables <NUM> electrically couples the two instances 335a, 335b of the second connection <NUM> of electric machine (generator) <NUM> to converter <NUM>. In some examples, converter <NUM> can be an active power rectifier assembly including, for example, one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>. In some examples, converter <NUM> can be a passive power rectifier assembly including, for example, a plurality of diode rectifiers and AC capacitors provided at terminals of the electric machine <NUM>. In some embodiments, a first set of terminals within the electric machine <NUM> can be coupled to an active power rectifier, while a second set of terminals within the electric machine <NUM> can be coupled to a passive power rectifier. Compared with the assembly <NUM> of <FIG>, assembly <NUM> of <FIG> only requires half the number of AC cables, thus providing an increase in volumetric efficiency, and reduction in cost, size, and weight of the cables.

<FIG> is a schematic representation of a third example electric machine connection configuration <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric machine connection configuration <NUM> can be implemented as part of an electric machine. In some examples, electric machine connection configuration <NUM> can be implemented as part of a first electric machine (e.g., LP electric machine <NUM>) and/or as part of a second electric machine (e.g., HP electric machine <NUM>).

In accordance with electric machine connection configuration <NUM>, an electric machine can include a winding section <NUM>. Winding section <NUM> can include a plurality of coupled winding pairs (e.g., four coupled winding pairs). Such plurality of windings (e.g., the plurality of coupled winding pairs in winding section <NUM>) can be multi-phase and/or substantially magnetically decoupled. The windings can be provided in a configuration such that an electric machine including electric machine connection configuration <NUM> is mechanically balanced even if one of the plurality of windings is de-energized. In some implementations, the plurality of windings can be tooth-wound and/or spatially distributed.

Referring still to <FIG>, winding section <NUM> can spatially span the full length of its associated electric machine, and can include six terminals for six-phase (6ph) electric power. Six-phase power terminals associated with the winding section <NUM> can collectively form a double-wye-configuration, or double-star-configuration, connection <NUM>. In some examples, the six-phase power terminals associated with the winding section <NUM> are configured such that each of first and second phase power terminals, third and fourth phase power terminals, and fifth and sixth phase power terminals are shifted from one another by thirty (<NUM>) degrees, while first, third and fifth power terminals are shifted from one another by <NUM> degrees, and second, fourth, and sixth power terminals are shifted from one another by <NUM> degrees. The six-phase power configuration of <FIG> can help lower harmonics to advantageously reduce the possibility of torque ripple within an electric machine while also achieving a better power quality.

<FIG> is a schematic representation of a third generator and converter assembly <NUM> using the third example electric machine connection configuration <NUM> of <FIG>. More particularly, electric machine <NUM> can include four instances 352a, 352b, 352c, 352d of the double-star-configuration connection <NUM> depicted in <FIG>. A first set of AC cables <NUM> electrically couples the four instances 352a, 352b, 352c, 352d of connection <NUM> of electric machine (generator) <NUM> to a converter <NUM>. A second set of AC cables <NUM> electrically couples the four instances 352a, 352b, 352c, 352d of the connection <NUM> of electric machine (generator) <NUM> to converter <NUM>. In some examples, converter <NUM> can be an active power rectifier assembly including, for example, one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>. In some examples, converter <NUM> can be a passive power rectifier assembly including, for example, a plurality of diode rectifiers and AC capacitors provided at terminals of the electric machine <NUM>. In some embodiments, a first set of terminals within the electric machine <NUM> can be coupled to an active power rectifier, while a second set of terminals within the electric machine <NUM> can be coupled to a passive power rectifier.

Referring now to <FIG>, additional system-level aspects of electric power systems in accordance with the disclosed technology are depicted. <FIG> depict respective electric power systems such as might be implemented as part of the electric power system <NUM> depicted in <FIG>. It should be appreciated that aspects from one power system in <FIG> can be combined with aspects from other power systems in such figures to create additional embodiments than those specifically depicted.

<FIG> depicts a first electric power system <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric power system <NUM> can include at least one electric machine. As depicted, electric power system <NUM> includes a plurality of electric machines, which can include at least a first electric machine <NUM> and a second electric machine <NUM>. In some embodiments, the first electric machine <NUM> is an LP electric machine or LP generator, such as LP electric machine <NUM>, while the second electric machine <NUM> is an HP electric machine or HP generator, such as HP electric machine <NUM>. First electric power system <NUM> also includes first and second electrical channels <NUM> and <NUM> that are electrically independent from one another.

First electrical channel <NUM> electrically couples the first electric machine <NUM> to a first electrical power bus <NUM> and to a second electrical power bus <NUM>. First electrical channel <NUM> can also include a first converter <NUM> (e.g., an LP converter) positioned between the first electric machine <NUM> (e.g., an LP generator) and the first and second electrical power buses <NUM>, <NUM>. First electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of first electric machine <NUM> to a first converter <NUM> (e.g., an LP converter). First electrical channel <NUM> can also include a second plurality of AC cables <NUM> coupling respective second wye-connection instances of first electric machine <NUM> to the first converter <NUM> (e.g., LP converter). The multiple instances of wye-connections within the first electric machine <NUM> as coupled to the first plurality of AC cables <NUM> and to the second plurality of AC cables <NUM> provide first and second independent inverter channels that are magnetically balanced within first electrical channel <NUM>. In some examples, first converter <NUM> can include one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>.

Second electrical channel <NUM> electrically couples the second electric machine <NUM> to the first electrical power bus <NUM> and to the second electrical power bus <NUM>. Second electrical channel <NUM> can also include a second converter <NUM> (e.g., an HP converter) positioned between the second electric machine <NUM> (e.g., an HP generator) and the first and second electrical power buses <NUM>, <NUM>. Second electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of second electric machine <NUM> to a second converter <NUM> (e.g., an HP converter). Second electrical channel <NUM> can also include a second plurality of AC cables <NUM> coupling respective second wye-connection instances of electric machine <NUM> to the second converter <NUM> (e.g., HP converter). The multiple instances of wye-connections within the second electric machine <NUM> as coupled to the first plurality of AC cables <NUM> and to the second plurality of AC cables <NUM> provide first and second independent inverter channels that are magnetically balanced within second electrical channel <NUM>. In some examples, second converter <NUM> can include one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>.

It will be appreciated from the description herein that although the various AC cables within the first and second electric machines are described as using a "wye-connection", in other exemplary embodiments one or more of such AC cables may alternatively use any other suitable connection configuration. By way of example, in certain exemplary embodiments, one or more of such AC cables may use one of a delta connection, a parallel connection, a series connection, an open ended connection, etc..

Electric power system <NUM> can also include a power distribution unit (PDU) <NUM>. PDU <NUM> can include the first electrical power bus <NUM>, the second electrical power bus <NUM>, and various switches <NUM>-<NUM>. A first switch <NUM> is positioned between DC cables from the first converter <NUM> and the first electrical power bus <NUM>. A second switch <NUM> is positioned between DC cables from the second converter <NUM> and the first electrical power bus <NUM>. A third switch <NUM> is positioned between DC cables from the first converter <NUM> and the second electrical power bus <NUM>. A fourth switch positioned between DC cables from the second converter <NUM> and the second electrical power bus <NUM>. Switch <NUM> (e.g., a disconnect switch) is positioned between and electrically couples the first electrical power bus <NUM> and the second electrical power bus <NUM>. Switches <NUM>-<NUM> can be variously toggled between first and second positions depending on whether faults are detected within electric power system <NUM>. For example, switch <NUM> can be configured for operation in a first position (e.g., an open position) during normal steady-state operation of the electric power system <NUM>. Switch <NUM> can be configured for operation in a second position (e.g., a closed position) during fault operation of the electric power system <NUM>. In this way, power can be provided to both electrical power busses <NUM> and <NUM> even in the case of failure of one of the electric machines <NUM>, <NUM>. Fault operation can correspond to operation of the electric power system during a timeframe in which a fault is detected. Faults that would affect operation of one of the electrical power buses <NUM>, <NUM> could include but are not limited to faults in the connections to electric machines <NUM>, <NUM>, faults internal to an electric machine <NUM>, <NUM>, faults in electrical cables that are part of the first and second electric electrical channels <NUM>, <NUM>, faults in a power converter <NUM>, <NUM>, or the like.

<FIG> depicts a second electric power system <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric power system <NUM> includes a plurality of electric machines. The plurality of electric machines can include at least a first electric machine <NUM> and a second electric machine <NUM>. In some embodiments, the first electric machine <NUM> is an LP electric machine or LP generator, such as LP electric machine <NUM>, while the second electric machine <NUM> is an HP electric machine or HP generator, such as HP electric machine <NUM>. Second electric power system <NUM> also includes first and second electrical channels <NUM> and <NUM> that are electrically independent from one another.

First electrical channel <NUM> electrically couples the first electric machine <NUM> to a first electrical power bus <NUM> and to a second electrical power bus <NUM>. First electrical channel <NUM> can also include a first converter <NUM> (e.g., an LP converter) positioned between the first electric machine <NUM> (e.g., an LP generator) and the first and second electrical power buses <NUM>, <NUM>. First electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of first electric machine <NUM> to a first converter <NUM> (e.g., an LP converter). First electrical channel <NUM> can also include a second plurality of AC cables <NUM> coupling respective second wye-connection instances of first electric machine <NUM> to the first converter <NUM> (e.g., LP converter). The multiple instances of wye-connections within the first electric machine <NUM> as coupled to the first plurality of AC cables <NUM> and to the second plurality of AC cables <NUM> provide first and second independent inverter channels that are magnetically balanced within first electrical channel <NUM>. In some examples, first converter <NUM> can include one or more common mode filters <NUM> and one or more AC/DC converter circuit elements <NUM>.

Second electrical channel <NUM> electrically couples the second electric machine <NUM> to the first electrical power bus <NUM> and to the second electrical power bus <NUM>. Second electrical channel <NUM> can also include a second converter <NUM> (e.g., an HP converter) positioned between the second electric machine <NUM> (e.g., an HP generator) and the first and second electrical power buses <NUM>, <NUM>. Second electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of second electric machine <NUM> to a second converter <NUM> (e.g., an HP converter). Second electrical channel <NUM> can also include a second plurality of AC cables <NUM> coupling respective second wye-connection instances of electric machine <NUM> to the second converter <NUM> (e.g., HP converter). The multiple instances of wye-connections within the second electric machine <NUM> as coupled to the first plurality of AC cables <NUM> and to the second plurality of AC cables <NUM> provide first and second independent inverter channels that are magnetically balanced within second electrical channel <NUM>. In some examples, second converter <NUM> can include one or more common mode filters <NUM> and one or more AC/DC converter circuit elements <NUM>.

Electric power system <NUM> can also include a power distribution unit (PDU) <NUM>. PDU <NUM> can include the first converter <NUM>, second converter <NUM>, first electrical power bus <NUM>, second electrical power bus <NUM>, and various switches <NUM>-<NUM>. Notably, the first converter <NUM> (e.g., an LP converter), the second converter <NUM> (e.g., an HP converter), the first electrical power bus <NUM>, and the second electrical power bus <NUM> are all co-located within PDU <NUM>. For example, the first converter <NUM> (e.g., an LP converter), the second converter <NUM> (e.g., an HP converter), the first electrical power bus <NUM>, and second electrical power bus <NUM> can all be mechanically positioned within a same structural housing defining PDU <NUM>.

Comparing second electric power system <NUM> of <FIG> to the first electric power system <NUM> of <FIG>, co-location of some components within PDU <NUM> enables elimination or reduction of other components. Component reduction can advantageously reduce size and weight of the power system, which can be especially desirable for aircraft applications. For instance, DC cables in first electric power system <NUM> of <FIG> connecting the first converter <NUM> to the first and second electrical power buses <NUM>, <NUM> and connecting the second converter <NUM> to the first and second electrical power buses <NUM>, <NUM> can be removed in the second electric power system <NUM> of <FIG>. Instead, busbars can be used to connect first converter <NUM> to first and second electrical power buses <NUM>, <NUM> and to connect second converter <NUM> to first and second electrical power buses <NUM>, <NUM>. DCCM filters <NUM>, <NUM> in the first and second converters <NUM>, <NUM> of first electric power system <NUM> can also be removed in the second electric power system <NUM> of <FIG>. Elimination and/or reduction of the DC cables and DCCM filters can also advantageously reduce DC capacitance within the second electric power system <NUM>, provide a common thermal interface within PDU <NUM>, and increase overall volumetric power density within second electric power system <NUM>.

Referring still to <FIG>, a first switch <NUM> can be positioned at a location on the busbars associated with the first electrical power bus <NUM> that is coupled to the first converter <NUM>, a second switch <NUM> can be positioned at a location on the busbars associated with the first electrical power bus <NUM> that is coupled to the second converter <NUM>, a third switch <NUM> can be positioned at a location on the busbars associated with the second electrical power bus <NUM> that is coupled to the first converter <NUM>, and a fourth switch <NUM> can be positioned at a location on the busbars associated with the second electrical power bus <NUM> that is coupled to the second converter <NUM>. Switch <NUM> (e.g., a disconnect switch) can be positioned between and electrically couple the first electrical power bus <NUM> and the second electrical power bus <NUM>. Switches <NUM>-<NUM> can be variously toggled between first and second positions depending on whether faults are detected within electric power system <NUM>. For example, switch <NUM> can be configured for operation in a first position (e.g., an open position) during normal steady-state operation of the electric power system <NUM>. Switch <NUM> can be configured for operation in a second position (e.g., a closed position) during fault operation of the electric power system <NUM>. In this way, power can be provided to both electrical power busses <NUM> and <NUM> even in the case of failure of one of the electric machines <NUM>, <NUM>. Fault operation can correspond to operation of the electric power system during a timeframe in which a fault is detected. Faults that would affect operation of one of the electrical power buses <NUM>, <NUM> could include but are not limited to faults in the connections to electric machines <NUM>, <NUM>, faults internal to an electric machine <NUM>, <NUM>, faults in electrical cables that are part of the first and second electric electrical channels <NUM>, <NUM>, faults in a power converter <NUM>, <NUM>, or the like.

<FIG> depict aspects of the second example electric machine connection configuration <NUM> of <FIG> and the second generator and converter assembly <NUM> of <FIG>. However, it should be appreciated that other example electric machine connection configurations (such as but not limited to the first example electric machine connection configuration <NUM> of <FIG> and the third example electric machine connection configuration <NUM> of <FIG>) and other example generator and converter assemblies (such as but not limited to the first generator and converter assembly <NUM> of <FIG> and the third generator and converter assembly <NUM> of <FIG>) can be employed instead of those depicted in <FIG>.

<FIG> depicts a third electric power system <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric power system <NUM> includes a plurality of electric machines. The plurality of electric machines can include at least a first electric machine <NUM> and a second electric machine <NUM>. In some embodiments, the first electric machine <NUM> is an LP electric machine or LP generator, such as LP electric machine <NUM>, while the second electric machine <NUM> is an HP electric machine or HP generator, such as HP electric machine <NUM>. In some examples, first electric machine <NUM> includes a plurality of diode-rectifiers <NUM> (e.g., four diode-rectifiers <NUM>), one diode-rectifier <NUM> being positioned at a terminal connection configuration associated with each winding section of the first electric machine <NUM>. The plurality of diode-rectifiers are configured to rectify the power provided from the first electric machine <NUM> to the first and second electrical power buses <NUM>, <NUM>. In some examples, first electric machine <NUM> includes a plurality of AC capacitors <NUM> (e.g., four AC capacitors <NUM>), one AC capacitor <NUM> positioned at a terminal connection configuration associated with each winding section of the first electric machine <NUM>. The plurality of AC capacitors <NUM> are configured to provide reactive power to the first electric machine <NUM>. In some examples, the diode-rectifiers <NUM> and capacitors <NUM> are integrated directly within the first electric machine <NUM>, thus providing a passive rectifier assembly for the first electric machine <NUM>.

It will be appreciated that as used herein, the term "integrated" with respect to a converter/ rectifier and electric machine may mean that the two components are co-located within a common housing, hermetically sealed together (or at least components thereof hermetically sealed together), utilizing a shared thermal management system or features, or the like.

Third electric power system <NUM> also includes first and second electrical channels <NUM> and <NUM> that are electrically independent from one another. First electrical channel <NUM> electrically couples the first electric machine <NUM> to a first electrical power bus <NUM> and to a second electrical power bus <NUM>. First electrical channel <NUM> can include a variable DC bus <NUM> coupling the various wye-connection configurations of first electric machine <NUM> to a first DC/DC converter <NUM>. The multiple instances of wye-connections within the first electric machine <NUM> as coupled to the variable DC bus <NUM> provide first and second independent inverter channels that are magnetically balanced within first electrical channel <NUM>.

Second electrical channel <NUM> electrically couples the second electric machine <NUM> to the first electrical power bus <NUM> and to the second electrical power bus <NUM>. Second electrical channel <NUM> can also include a converter <NUM> (e.g., an HP converter) positioned between the second electric machine <NUM> (e.g., an HP generator) and the first and second electrical power buses <NUM>, <NUM>, thus providing an active rectifier assembly for second electric machine <NUM>. In some examples, converter <NUM> can be integrated with the second electric machine <NUM>. Second electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of second electric machine <NUM> to converter <NUM>, a second plurality of AC cables <NUM> coupling respective second wye-connection instances of second electric machine <NUM> to converter <NUM>, a third plurality of AC cables <NUM> coupling respective third wye-connection instances of second electric machine <NUM> to converter <NUM>, and a fourth plurality of AC cables <NUM> coupling respective fourth wye-connection instances of second electric machine <NUM> to converter <NUM>. The multiple instances of wye-connections within the second electric machine <NUM> as coupled to the first plurality of AC cables <NUM>, second plurality of AC cables <NUM>, third plurality of AC cables <NUM>, and fourth plurality of AC cables <NUM> help provide first and second independent inverter channels that are magnetically balanced within second electrical channel <NUM>. In some examples, converter <NUM> can include one or more common mode filters <NUM>, one or more AC/DC converter circuit elements <NUM>, and one or more DC common mode (DCCM) filters <NUM>. Second electrical channel <NUM> can include a variable DC bus <NUM> coupling converter <NUM> to a second DC/DC converter <NUM>.

Electric power system <NUM> can also include a power distribution unit (PDU) <NUM>. PDU <NUM> can include the first electrical power bus <NUM>, the second electrical power bus <NUM>, the first DC/DC converter <NUM>, the second DC/DC converter <NUM>, and various switches <NUM>-<NUM>. First DC/DC converter <NUM> and second DC/DC converter <NUM> can generally be characterized as high-density low-loss devices that provide high frequency isolation and allow optimum aircraft DC voltage levels to be respectively provided to the first and second electrical power buses <NUM>, <NUM>. In some implementations, the first DC/DC converter <NUM> and/or the second DC/DC converter <NUM> can be isolated DC/DC converters having two or more respective DC terminals. In some implementations, one or more of the DC/DC converter(s) <NUM>, <NUM> can be configured to additionally or alternatively operate as a fast-acting DC breaker.

A first switch <NUM> is positioned between an output of first DC/DC converter <NUM> and the first electrical power bus <NUM>. A second switch <NUM> is positioned between an output of second DC/DC converter <NUM> and the second electrical power bus <NUM>. Switch <NUM> (e.g., a disconnect switch) is positioned between and electrically couples the first electrical power bus <NUM> and the second electrical power bus <NUM>. Switches <NUM>-<NUM> can be variously toggled between first and second positions depending on whether faults are detected within electric power system <NUM>. For example, switch <NUM> can be configured for operation in a first position (e.g., an open position) during normal steady-state operation of the electric power system <NUM>. Switch <NUM> can be configured for operation in a second position (e.g., a closed position) during fault operation of the electric power system <NUM>. Fault operation can correspond to operation of the electric power system during a timeframe in which a fault is detected. In this way, power can be provided to both electrical power busses <NUM> and <NUM> even in the case of failure of one of the electric machines <NUM>, <NUM>. Faults that would affect operation of one of the electrical power buses <NUM>, <NUM> could include but are not limited to faults in the connections to electric machines <NUM>, <NUM>, faults internal to an electric machine <NUM>, <NUM>, faults in electrical cables that are part of the first and second electric electrical channels <NUM>, <NUM>, faults in a power converter <NUM>, or the like.

<FIG> depicts a fourth electric power system <NUM> in accordance with an exemplary embodiment of the present disclosure. Electric power system <NUM> includes a plurality of electric machines. The plurality of electric machines can include at least a first electric machine <NUM> and a second electric machine <NUM>. In some embodiments, the first electric machine <NUM> is an LP electric machine or LP generator, such as LP electric machine <NUM>, while the second electric machine <NUM> is an HP electric machine or HP generator, such as HP electric machine <NUM>. In some examples, first electric machine <NUM> includes a plurality of diode-rectifiers <NUM> (e.g., four diode-rectifiers <NUM>), one diode-rectifier <NUM> being positioned at a terminal connection configuration associated with each winding section of the first electric machine <NUM>. The plurality of diode-rectifiers are configured to rectify the power provided from the first electric machine <NUM> to the first and second electrical power buses <NUM>, <NUM>. In some examples, first electric machine <NUM> includes a plurality of AC capacitors <NUM> (e.g., four AC capacitors <NUM>), one AC capacitor <NUM> positioned at a terminal connection configuration associated with each winding section of the first electric machine <NUM>. The plurality of AC capacitors <NUM> are configured to provide reactive power to the first electric machine <NUM>. In some examples, the diode-rectifiers <NUM> and capacitors <NUM> are integrated directly within the first electric machine <NUM>, thus providing a passive rectifier assembly for the first electric machine <NUM>.

Fourth electric power system <NUM> also includes first and second electrical channels <NUM> and <NUM> that are electrically independent from one another. First electrical channel <NUM> electrically couples the first electric machine <NUM> to a first electrical power bus <NUM> and to a second electrical power bus <NUM>. First electrical channel <NUM> can include a variable DC bus <NUM> coupling the various wye-connection configurations of first electric machine <NUM> to a first DC/DC converter <NUM> and second DC/DC converter <NUM>. The multiple instances of wye-connections within the first electric machine <NUM> as coupled to the variable DC bus <NUM> provide first and second independent inverter channels that are magnetically balanced within first electrical channel <NUM>.

Second electrical channel <NUM> electrically couples the second electric machine <NUM> to the first electrical power bus <NUM> and to the second electrical power bus <NUM>. Second electrical channel <NUM> can also include a converter <NUM> (e.g., an HP converter) positioned between the second electric machine <NUM> (e.g., an HP generator) and the first and second electrical power buses <NUM>, <NUM>. Converter <NUM> can effectively provide an active power rectifier assembly for second electric machine <NUM>. Second electrical channel <NUM> can include a first plurality of AC cables <NUM> coupling respective first wye-connection instances of second electric machine <NUM> to converter <NUM>, a second plurality of AC cables <NUM> coupling respective second wye-connection instances of second electric machine <NUM> to converter <NUM>, a third plurality of AC cables <NUM> coupling respective third wye-connection instances of second electric machine <NUM> to second converter <NUM>, and a fourth plurality of AC cables <NUM> coupling respective fourth wye-connection instances of second electric machine <NUM> to converter <NUM>. The multiple instances of wye-connections within the second electric machine <NUM> as coupled to the first plurality of AC cables <NUM>, second plurality of AC cables <NUM>, third plurality of AC cables <NUM>, and fourth plurality of AC cables <NUM> help provide first and second independent inverter channels that are magnetically balanced within second electrical channel <NUM>. In some examples, converter <NUM> can include one or more common mode filters <NUM> and one or more AC/DC converter circuit elements <NUM>. Second electrical channel <NUM> can also include a DC bus <NUM> coupling the converter <NUM> to first DC/DC converter <NUM> and second DC/DC converter <NUM>.

Electric power system <NUM> can also include a power distribution unit (PDU) <NUM>. PDU <NUM> can include the converter <NUM>, first electrical power bus <NUM>, second electrical power bus <NUM>, first DC/DC converter <NUM>, second DC/DC converter <NUM>, and various switches <NUM>-<NUM>. Notably, the converter <NUM>, first electrical power bus <NUM>, second electrical power bus <NUM>, first DC/DC converter <NUM>, second DC/DC converter <NUM>, and various switches <NUM>-<NUM> are all co-located within PDU <NUM>. For example, the converter <NUM>, first electrical power bus <NUM>, second electrical power bus <NUM>, first DC/DC converter <NUM>, second DC/DC converter <NUM>, and various switches <NUM>-<NUM> can all be mechanically positioned within a same structural housing defining PDU <NUM>.

First DC/DC converter <NUM> and second DC/DC converter <NUM> can generally be characterized as high-density low-loss devices that provide high frequency isolation and allow optimum aircraft DC voltage levels to be respectively provided to the first and second electrical power buses <NUM>, <NUM>. In some implementations, the first DC/DC converter <NUM> and/or the second DC/DC converter <NUM> can be isolated DC/DC converters having two or more respective DC terminals. In some implementations, one or more of the DC/DC converter(s) <NUM>, <NUM> can be configured to additionally or alternatively operate as a fast-acting DC breaker.

Comparing fourth electric power system <NUM> of <FIG> to the third electric power system <NUM> of <FIG>, co-location of components within PDU <NUM> enables elimination or reduction of some components (e.g., connector cables). Component reduction can advantageously reduce size and weight of the power system, which can be especially desirable for aircraft applications. For instance, variable DC bus cables in third electric power system <NUM> of <FIG> connecting the first electric machine <NUM> to the first and second electrical power buses <NUM>, <NUM> can be reduced in the second electric power system <NUM> of <FIG>. DCCM filters <NUM> in converter <NUM> of third electric power system <NUM> can also be removed in the fourth electric power system <NUM> of <FIG>. Elimination and/or reduction of the DC cables and DCCM filters can also advantageously reduce DC capacitance within the second electric power system <NUM>, provide a common thermal interface within PDU <NUM>, and increase overall volumetric power density within second electric power system <NUM>.

Referring still to <FIG>, first switch <NUM> is positioned between an output of first DC/DC converter <NUM> and the first electrical power bus <NUM>. Second switch <NUM> is positioned between an output of second DC/DC converter <NUM> and the second electrical power bus <NUM>. Switch <NUM> (e.g., a disconnect switch) is positioned between and electrically couples the first electrical power bus <NUM> and the second electrical power bus <NUM>. Switches <NUM>-<NUM> can be variously toggled between first and second positions depending on whether faults are detected within electric power system <NUM>. For example, switch <NUM> can be configured for operation in a first position (e.g., an open position) during normal steady-state operation of the electric power system <NUM>. Switch <NUM> can be configured for operation in a second position (e.g., a closed position) during fault operation of the electric power system <NUM>. Fault operation can correspond to operation of the electric power system during a timeframe in which a fault is detected. Faults that would affect operation of one of the electrical power buses <NUM>, <NUM> could include but are not limited to faults in the connections to electric machines <NUM>, <NUM>, faults internal to an electric machine <NUM>, <NUM>, faults in electrical cables that are part of the first and second electric electrical channels <NUM>, <NUM>, faults in a power converter <NUM>, or the like.

Comparing the electric power systems <NUM>, <NUM> of <FIG> to the electric power systems <NUM>, <NUM> of <FIG> reveal the elimination of a converter within one of the electrical channels. For example, first electrical channel <NUM> of electric power system <NUM> and first electrical channel <NUM> of electric power system <NUM> can respectively eliminate a converter (such as first converter <NUM> of the first electric power system <NUM> of <FIG> or first converter <NUM> of the second electric power system <NUM> of <FIG>). Elimination of this LP converter capitalizes on a dynamic of some engine configurations whereby LP generator pushes power but does not absorb power. In keeping with such an operational configuration, power is always transferred from the LP generator to the HP generator. So at any point in time, the LP is never absorbing power but always pushing power out. This is in contrast with the HP generator which is typically configured to run in both motor/generator modes. Under starting conditions, the HP electric machine will run as a motor and then it will start generating power. By assuming that power transfer always happens from LP to HP, the LP active converter can be eliminated, and instead power can be rectified at the LP generator directly, providing a configuration that is even more power dense, reliable, and affordable. This can be accomplished at least in part by positioning capacitor-diode rectifiers at the terminals of the LP electric machine.

<FIG> depict aspects of the first example electric machine connection configuration <NUM> of <FIG> and the first generator and converter assembly <NUM> of <FIG>. However, it should be appreciated that other example electric machine connection configurations (such as but not limited to the second example electric machine connection configuration <NUM> of <FIG> and the third example electric machine connection configuration <NUM> of <FIG>) and other example generator and converter assemblies (such as but not limited to the second generator and converter assembly <NUM> of <FIG> and the third generator and converter assembly <NUM> of <FIG>) can be employed instead of those depicted in <FIG>.

Referring now to <FIG>, an example method <NUM> for generating electric power for an aircraft in accordance with an exemplary embodiment of the present disclosure is depicted. At (<NUM>), method <NUM> can include generating power at a first electric machine. In some examples, generating power at (<NUM>) can include generating a first power flow at an LP generator. In some examples, the LP generator configured to generate the first power flow at (<NUM>) can include a plurality of multi-phase windings that are substantially magnetically decoupled and that is mechanically balanced even if one of the plurality of windings is de-energized. In some examples, the LP generator configured to generate first power flow at (<NUM>) includes multi-phase windings that are tooth-wound and/or that are spatially distributed in a magnetic core (e.g., in stators of the magnetic core) of the LP generator. In some examples, the LP generator can include first and second multi-phase winding sections, each multi-phase winding section including three terminals for three-phase electric power. In some examples, the LP generator can include a plurality of coupled multi-phase winding pairs and six terminals for delivering six-phase electric power from the plurality of coupled multi-phase winding pairs. In some examples, the LP generator can include first, second, third, and fourth multi-phase winding sections, each multi-phase winding section including three terminals for three-phase electric power.

At (<NUM>), method <NUM> can include rectifying power generated by the first electric machine at (<NUM>). For instance, a first converter (e.g., an LP converter) can be used to rectify power at (<NUM>). In some examples, rectifying power at (<NUM>) can include passively rectifying the first power flow generated by the LP generator at (<NUM>). For instance, power rectified at (<NUM>) can be rectified using a plurality of diode-rectifiers configured to rectify the power provided from an LP generator. The plurality of diode-rectifiers can be physically integrated with the LP generator. In some examples, a plurality of AC capacitors are also physically integrated into the LP generator to help provide reactive power to the LP generator.

At (<NUM>), method <NUM> can include generating power at a second electric machine. In some examples, generating power at (<NUM>) can include generating a second power flow at an HP starter-generator. In some examples, the HP starter-generator configured to generate second power flow at (<NUM>) can include a plurality of multi-phase windings that are substantially magnetically decoupled and that is mechanically balanced even if one of the plurality of windings is de-energized. In some examples, the HP starter-generator configured to generate second power flow at (<NUM>) can include multi-phase windings that are tooth-wound and/or that are spatially distributed in a magnetic core (e.g., in stators of the magnetic core) of the HP starter-generator. In some examples, the HP starter-generator can include first and second multi-phase winding sections, each multi-phase winding section including three terminals for three-phase electric power. In some examples, the HP starter-generator can include a plurality of coupled multi-phase winding pairs and six terminals for delivering six-phase electric power from the plurality of coupled multi-phase winding pairs. In some examples, the HP starter-generator can include first, second, third, and fourth multi-phase winding sections, each multi-phase winding section including three terminals for three-phase electric power.

At (<NUM>), method <NUM> can include rectifying power generated by the second electric machine at (<NUM>). For instance, a second converter (e.g., an HP converter) can be used to rectify power at (<NUM>). In some examples, rectifying power at (<NUM>) can include actively rectifying the second power flow generated by the HP starter-generator.

At (<NUM>), method <NUM> can include coupling passively rectified power from the LP generator to at least first and second DC channels. In some examples, the first and second DC channels are formed at least in part by first and second electrical power buses that are respectively coupled to the LP generator. The first and second DC channels to which passively rectified power are coupled at (<NUM>) can be formed at least in part by the first electrical power bus and the second electrical power bus. In some examples, the first and second electrical channels can additionally include an isolated DC/DC converter coupling the LP generator to the first and second electrical power buses. Such a DC/DC converter can include two or more DC terminals, and can be configured to additionally or alternatively operate as a fast-acting DC breaker.

At (<NUM>), method <NUM> can include coupling actively rectified power from the HP generator to the at least first and second DC channels. In some examples, the first and second DC channels are formed at least in part by first and second electrical power buses that are respectively coupled to the HP starter-generator. The first and second DC channels to which actively rectified power are coupled at (<NUM>) can be formed at least in part by the first electrical power bus and the second electrical power bus. In some examples, the first and second electrical channels can additionally include an isolated DC/DC converter coupling the HP starter-generator to the first and second electrical power buses. Such a DC/DC converter can include two or more DC terminals, and can be configured to operate as a fast-acting DC breaker.

At (<NUM>), method <NUM> can include powering one or more loads within a vehicle (e.g., an aircraft) with DC voltages provided by the first and second DC channels. In some implementations, the one or more vehicle loads powered at (<NUM>) can correspond to aircraft loads such as one or more engine electrical loads such as but not limited to fuel pump(s), cooling pump(s) and engine icing protection, one or more environmental control systems such as but not limited to systems for cabin pressurization, cabin air-conditioning, and the like, flight control electrified actuators, avionics, wing icing protection, and other systems requiring DC power within an aircraft. The first and second DC channels used to power one or more loads at (<NUM>) can be regulated or unregulated. The voltage levels provided by the first and second DC channels can be fixed or they can be varied (e.g., varied among two or more voltage values). The multiple DC channels used to power one or more loads at (<NUM>) can be configured to carry electrical power having a bi-polar voltage of between about +/- <NUM> volts and about +/- <NUM> volts.

At (<NUM>), method <NUM> can include detecting a fault within the electric power system resulting in power (e.g., the electric power coupled at (<NUM>) and/or (<NUM>)) being unavailable at the first and second DC channels (e.g., at first and second electrical power buses forming in part the first and second DC channels). In response to a fault being detected at (<NUM>), a connector switch positioned between the first electrical power bus and the second electrical power bus can be toggled at (<NUM>) such that power remains available to the one or more loads despite the fault. In some examples, only a portion of the power coupled at (<NUM>) and (<NUM>) is available to the aircraft loads when the connector switch is toggled at (<NUM>). However, the portion should be sufficient to allow many of the various electric machine operating modes to continue functioning. As such, even while operating under fault conditions, an aircraft can have enough power to safely finish a mission, cruise to a destination, and safely land despite encountering a fault.

When the electric power system that generates electric power in method <NUM> is operating under normal steady-state conditions, the one or more aircraft loads are powered by both first and second electrical power buses. When a fault is detected, the electric propulsion assembly is powered by one of the first and second electrical power buses, while the other electrical power bus is disconnected.

Claim 1:
A vehicle electric power system (<NUM>) comprising:
at least first and second electric machines (<NUM>, <NUM>) configured to generate respective first and second power flows, each electric machine (<NUM>, <NUM>) comprising a plurality of multi-phase windings (<NUM>-<NUM>) that are substantially magnetically decoupled, and wherein each electric machine (<NUM>) is configured to be mechanically balanced even if one of the plurality of windings (<NUM>-<NUM>) is de-energized;
a first electrical channel (<NUM>) configured to couple a generated first power flow from the first electric machine (<NUM>) to a first electrical power bus (<NUM>) and to a second electrical power bus (<NUM>); and
a second electrical channel (<NUM>) configured to couple a generated second power flow from the second electric machine (<NUM>) to the first electrical power bus (<NUM>) and to the second electrical power bus (<NUM>);
wherein multiple DC channels for the vehicle electric power system (<NUM>) are formed at least in part by the first electrical power bus (<NUM>) and the second electrical power bus (<NUM>); and
wherein a load within the vehicle is configured to be powered with DC voltages
provided by the first and second electrical power buses (<NUM>, <NUM>), wherein:
the at least first and second electric machines (<NUM>, <NUM>) respectively comprise first and second multi-phase winding sections (<NUM>-<NUM>), each multi-phase winding section (<NUM>) comprising terminals for multi-phase electric power;
the first electrical channel (<NUM>) comprises first and second parallel connections to the terminals of the first multi-phase winding sections (<NUM>-<NUM>); and
the second electrical channel (<NUM>) comprises third and fourth parallel connections to the terminals of the second multi-phase winding sections (<NUM>-<NUM>).