阅读说明：本技术 具有电压调节器的飞行器推进系统 (Aircraft propulsion system with voltage regulator ) 是由 托马斯·威廉·布朗 保罗·罗伯特·杰明 潘迪 多米尼克·巴龙 于 2020-11-18 设计创作，主要内容包括：本公开的各方面总体上涉及一种用于飞行器的飞行器推进系统。飞行器推进系统可以包括至少一个电源、电机、电压调节器和至少一个螺旋桨。电压调节器调节从电源提供给电机的电力。该电源能够提供交流或直流电输出,并且可以包括带有发电机或蓄电装置的内燃机。(Aspects of the present disclosure generally relate to an aircraft propulsion system for an aircraft. An aircraft propulsion system may include at least one power source, a motor, a voltage regulator, and at least one propeller. The voltage regulator regulates power supplied from the power source to the motor. The power source is capable of providing an ac or dc output and may include an internal combustion engine with a generator or an electrical storage device.)

1. An aircraft propulsion system for an aircraft, comprising:

a propeller;

a motor operable to rotate the propeller;

a power supply that provides power to the motor; and

a voltage regulator that regulates the power provided to the motor from the power source, and that is configured to control a voltage of the power provided as a function of ambient air pressure in at least a portion of the aircraft.

2. The aircraft propulsion system of claim 1, further comprising an electrical conductor connecting the voltage regulator to the electric machine, and the at least a portion of the aircraft comprises at least a portion of the electrical conductor.

3. The aircraft propulsion system of claim 2, wherein the electrical conductor comprises an electrical insulator.

4. The aircraft propulsion system according to claim 3, characterized in that the electrical insulator is dimensioned to prevent partial discharges at the maximum voltage of the power supply at the ambient air pressure.

5. The aircraft propulsion system according to claim 4, wherein the electrical insulator is not sized to prevent partial discharge throughout a flight envelope of the aircraft propulsion system.

6. The aircraft propulsion system of claim 5, wherein the voltage regulator is configured to control the voltage of the provided power to prevent partial discharge throughout the flight envelope.

7. The aircraft propulsion system according to any one of claims 1 to 6, further comprising an ambient air pressure sensor operably coupled to the voltage regulator.

8. The aircraft propulsion system according to claim 7, characterized in that the ambient air pressure sensor is an altimeter.

9. The aircraft propulsion system according to any one of claims 1 to 6, characterised in that the electrical conductor is exposed to atmospheric pressure and the ambient air pressure is the prevailing atmospheric pressure.

10. The aircraft propulsion system according to any one of claims 1 to 6, wherein the power source is one of an alternating current or a direct current power source.

Technical Field

The present invention relates generally to electric aircraft propulsion systems, and more particularly to control of voltage for such systems.

Background

Although more interest in this is being shown, aircraft with electric propulsion systems are not currently widespread. Electric propulsion systems face unique challenges compared to combustion propulsion systems, particularly if the aircraft with the electric power system is to operate safely in the same or similar flight envelope as the aircraft with the combustion power system.

One particular technical problem that must be overcome is that the electric propulsion system comprises electric conductors that must be insulated so that they do not experience partial discharges throughout the flight envelope. This is particularly true for aircraft having flight envelopes that include higher altitudes, where reduced air density provides less electrical insulation, which increases the likelihood of partial discharge, all other conditions being equal.

Disclosure of Invention

In one aspect, the present disclosure is directed to an aircraft propulsion system for an aircraft including a propeller, a motor operable to rotate the propeller, a power source to provide power to the motor, and a voltage regulator. The voltage regulator to regulate the power provided to the motor from the power source and is configured to control a voltage of the provided power as a function of ambient air pressure in at least a portion of the aircraft.

In another aspect, the present disclosure is directed to a method of operating a power distribution system having an electrical conductor that supplies power to a motor that rotationally drives a propeller in an aircraft, the method comprising sensing an ambient air pressure of the electrical conductor, and controlling a voltage at the electrical conductor based on the sensed ambient air pressure.

Drawings

FIG. 1 is a schematic illustration of an aircraft having an aircraft propulsion system.

FIG. 2 is a schematic illustration of a variation of the aircraft having the aircraft propulsion system of FIG. 1.

FIG. 3 is a schematic illustration of another variation of an aircraft having the aircraft propulsion system of FIG. 1.

FIG. 4 is a schematic illustration of a variation of the aircraft having the aircraft propulsion system of FIG. 3.

FIG. 5 is a flow chart illustrating a method of operating a power distribution system that may be at least partially performed by an aircraft having the aircraft propulsion system of FIGS. 1-4.

Detailed Description

Aspects of the present disclosure describe an aircraft propulsion system having an electric motor that rotates at least one propeller, fan, turbine, or similar device. As a non-limiting example, the at least one propeller may be any propeller or propulsion device. Power is supplied to the motor from a power source via electrical conductors. The voltage regulator may regulate a voltage provided to the motor from the power source and, thus, to at least a portion of the electrical conductor. Alternatively, the voltage regulator may regulate the voltage provided to one or more inverters, wherein the one or more inverters provide the voltage to the electric machine. The voltage of the power provided may be a function of the ambient air pressure of the electrical conductor. With the electrical conductor exposed to atmospheric pressure, the ambient air pressure is a function of the aircraft altitude, making the voltage a function of altitude.

Connection references (e.g., attached, coupled, connected, secured, fastened, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for illustrative purposes only, and the dimensions, positions, order and relative dimensions reflected in the accompanying drawings may vary.

FIG. 1 is a schematic illustration of an aircraft 10 having an aircraft propulsion system 12. The aircraft propulsion system 12 includes at least one power source 14, at least one electric motor 16, at least one voltage regulator 18, and at least one propeller 20. The propeller 20 is operatively rotated by the motor 16. The motor 16 is powered by the power source 14 via a voltage regulator 18. The voltage regulator 18 regulates the power provided to the motor 16 from the power source 14.

The power source 14 may be any configuration of elements that provide an electrical output, such as Alternating Current (AC) or Direct Current (DC). The power source 14 may be an electrical storage device. Non-limiting examples of electrical storage machines may include one or more of a battery, a capacitor, or a thermal system. Additionally or alternatively, the power source 14 may be an internal combustion engine with a generator or rectifier. By way of non-limiting example, the internal combustion engine may be a turbine engine or a piston engine.

The electric machine 16 may be any electromagnetic machine that can convert electrical energy to mechanical energy or mechanical energy to electrical energy. That is, the electric machine 16 includes one or more stator/rotor combinations. Non-limiting examples include generators, motors, or generator/motor combinations. The generator or motor may be an AC or DC generator or motor.

The voltage regulator 18 may include any number of electrical or mechanical components resulting in the output from the voltage regulator 18 being a stable, predetermined, and controlled value. The output value from the voltage regulator 18 may be greater than the input voltage to the voltage regulator 18, although it is contemplated that the output value may be equal to or less than the input value. By way of non-limiting example, the voltage regulator 18 may be located within the power supply 14 or directly coupled to the power supply 14. Alternatively, the voltage regulator 18 may include any combination of one or more of an inverter, converter, rectifier, capacitor, resistor, diode, inductor, transistor, regulator, switch, transformer, or amplifier. The voltage regulator 18 may function as a power sink or source, wherein the voltage regulator 18 may be used to control power, voltage, or current.

A first electrical conductor 22 may connect the power source 14 to the voltage regulator 18. A second electrical conductor 24 may connect the voltage regulator 18 to the electric machine 16. At least a portion of the first electrical conductor 22 or the second electrical conductor 24 is located in at least a portion of the aircraft 10.

The first and second electrical conductors 22, 24 may include electrical insulation. The electrical insulation may be any known electrically insulating material for reducing the likelihood of partial discharges, aging of the electrical conductor, or other types of insulation failures. By way of non-limiting example, the first electrical insulator 32 may surround, wrap, coat, or otherwise insulate the first electrical conductor 22. Similarly, second electrical insulator 34 may surround, wrap, coat, or otherwise insulate second electrical conductor 24. The first electrical insulator 32 may have a different composition or different dimensions than the second electrical insulator 34. Dimensions or sizes may include, but are not limited to, dimensions, diameters, cross-sectional areas, or other measurable aspects of the insulator.

At least a portion of the first electrical conductor 22 having the first electrical insulator 32 or the second electrical conductor 24 having the second electrical insulator 34 may be exposed to pressure of the surrounding environment and will be referred to as ambient pressure. It is conceivable that in most cases the ambient pressure will be the ambient pressure outside the aircraft at the current altitude, i.e. atmospheric pressure. In this case, the ambient pressure is the same as atmospheric pressure. However, some aircraft include a pressurized region that is actively or passively pressurized relative to atmospheric pressure, and if the electrical conductor is located in the pressurized region, the ambient pressure will be different than atmospheric pressure.

First electrical insulator 32 or second electrical insulator 34 may be sized to prevent partial discharge or insulation failure of first electrical conductor 22 and second electrical conductor 24 at ambient pressure when power source 14 is at a maximum voltage.

By way of non-limiting example, the first electrical insulator 32 may be sized to prevent partial discharge or insulation failure of the first electrical conductor 22 at a maximum voltage within the flight envelope of the overall aircraft propulsion system 12. Alternatively, electrical insulator 34 may not be sized to prevent partial discharge or insulation failure of second electrical conductor 24 at a maximum voltage throughout the flight envelope of aircraft propulsion system 12.

At least one sensor 40 may be used to obtain ambient air pressure or information related to ambient air pressure. The ambient air pressure may be the pressure at any point in or around the aircraft 10. As shown, at least one sensor 40 may be located inside the aircraft 10. It is contemplated that the at least one sensor 40 may be coupled to any portion of the aircraft 10 including an exterior 42 of the aircraft 10. It is further contemplated that the at least one sensor 40 may be a plurality of sensors mounted to any portion of the aircraft 10. As non-limiting examples, the at least one sensor 40 may be one or more of a pressure sensor, an altimeter, a humidity sensor, a Global Positioning Sensor (GPS), or a temperature sensor.

At least one sensor 40 may be operatively coupled to the voltage regulator 18. Optionally, the controller 44 may provide communication from the at least one sensor 40 to the voltage regulator 18. Many known types of controllers may be used for controller 44. The particular type of controller is not relevant to the present disclosure. The controller 44 may be included in or in communication with known flight management systems.

By way of non-limiting example, an aircraft propulsion system 12 is shown, the aircraft propulsion system 12 being coupled to or housed within a fuselage 46 of the aircraft 10. It is contemplated that any portion of the aircraft propulsion system 12 may be coupled to or housed within other components of the aircraft 10, which may include, but is not limited to, the wings 48.

Although the voltage regulator is shown by way of example as a single voltage regulator 18. Any number of voltage regulators may be used in the aircraft 10 to regulate the power of the electric motor 16. It is contemplated that voltage regulator 18 may regulate the voltage at first conductor 22, second conductor 24, or both first conductor 22 and second conductor 24. It is also contemplated that the voltage regulator 18 may regulate the voltage of any electrical conductor within the aircraft 10.

FIG. 2 schematically illustrates an aircraft 110 having an aircraft propulsion system 112, the aircraft 110 being substantially similar to the aircraft 10 having the aircraft propulsion system 12. Accordingly, like parts will be identified with like numerals, increased by 100. Similar components of aircraft propulsion system 12 apply to aircraft propulsion system 112 unless otherwise noted.

The aircraft propulsion system 112 includes a power source 114, a motor 116, a voltage regulator 118, a first propeller 120a, and a second propeller 120 b. The power source 114 includes an internal combustion engine 126 with a generator 128, wherein the internal combustion engine 126 and the generator 128 may be formed together or separately. Optionally, an electrical communication 130 having an insulator 131 may provide an electrical connection between the internal combustion engine 126 and the generator 128. Insulator 131 may be similar to first electrical insulator 132. The first propeller 120a is rotatably coupled to an internal combustion engine 126.

A first electrical conductor 122 having a first electrical insulator 132 may electrically connect the generator 128 of the power source 114 with the voltage regulator 118. A second electrical conductor 124 having a second electrical insulator 134 may electrically connect the voltage regulator 118 with the electric machine 116. Optionally, a second electrical conductor 124 may couple the voltage regulator 118 to the inverter 136. An electrical communication 138 having an insulator 139 can connect the inverter 136 to the motor 116. The insulator 139 is similar in size or insulating properties to the second electrical insulator 134. The second propeller 120b is operatively rotated by the motor 116.

The motor 116 is powered by the power supply 114 via a voltage regulator 118. The voltage regulator 118 regulates the electrical power or voltage provided to the motor 116 from the power source 114.

It is contemplated that inverter 136 may be any combination of known electronic devices for varying electrical signals, and may further include additional voltage control mechanisms.

FIG. 3 schematically illustrates an aircraft 210 having an aircraft propulsion system 212, the aircraft 210 being substantially similar to the aircraft 10 having the aircraft propulsion system 12. Accordingly, like parts will be identified with like numerals, increased by 200. Unless otherwise indicated, similar components of aircraft propulsion system 12 apply to aircraft propulsion system 212.

The aircraft propulsion system 212 includes a power source 214, a plurality of motors 216, a voltage regulator 218, and a plurality of propellers 220. The power source 214 includes an internal combustion engine 226 with a generator 228, wherein the internal combustion engine 226 and the generator 228 may be formed together or separately. An optional electrical connector 230 with an insulator 231 may provide an electrical connection between the internal combustion engine 226 and the generator 228. The insulator 231 may be similar to the first electrical insulator 232.

A first electrical conductor 222 having a first electrical insulator 232 may electrically connect the generator 228 of the power source 214 with the voltage regulator 218. A second electrical conductor 224 having a second electrical insulator 234 may electrically connect the voltage regulator 218 with the electric machine 216. Then, as shown, each of the plurality of motors 216 rotatably operates one of the plurality of propellers 220.

Optionally, the second electrical conductor 224 may couple the voltage regulator 218 to a plurality of inverters 236, wherein each of the plurality of inverters 236 is electrically connected to one of the plurality of electric machines 216. An electrical communicator 238 having an insulator 239 may connect each of the plurality of inverters 236 to one of the plurality of electric machines 216.

The motor 216 is powered by the power supply 214 via a voltage regulator 218. The voltage regulator 218 regulates the electrical power provided to the motor 216 from the power source 214.

It is contemplated that voltage regulator 218 may be a plurality of voltage regulators, wherein each of the plurality of voltage regulators is coupled to one of the plurality of inverters 236 or the plurality of electric machines 216.

It is also contemplated that the plurality of inverters 236 may be any combination of electronic devices and may further include a voltage control mechanism.

FIG. 4 schematically illustrates an aircraft 310 having an aircraft propulsion system 312, the aircraft 310 being substantially similar to the aircraft 210 having the aircraft propulsion system 212. Accordingly, like components will be identified with like numerals, increased by 100, it being understood that like components of aircraft propulsion system 212 apply to aircraft propulsion system 312 unless otherwise noted.

The aircraft propulsion system 312 includes a power source 314, a plurality of motors 316, a voltage regulator 318, and a plurality of propellers 320. The power source 314 includes an accumulator 317.

A first electrical conductor 322 having a first electrical insulator 332 may be electrically connected to the accumulator 317 of the power supply 314 and the voltage regulator 318. A second electrical conductor 324 having a second electrical insulator 334 may electrically connect the voltage regulator 318 with the electric machine 316. Then, as shown, each of the plurality of motors 316 rotatably operates one of the plurality of propellers 320.

Optionally, a second electrical conductor 324 may couple voltage regulator 318 to a plurality of inverters 336, wherein each of the plurality of inverters 336 is electrically connected to one of the plurality of electric machines 316. An electrical communicator 338 having an insulator 339 may connect each of the plurality of inverters 336 to one of the plurality of motors 316.

The motor 316 is powered by the power supply 314 via a voltage regulator 318. The voltage regulator 318 regulates the power provided to the motor 316 from the power source 314.

It is contemplated that the voltage regulator 218 may be a plurality of voltage regulators, wherein each of the plurality of voltage regulators is coupled to one of the plurality of inverters 336 or the plurality of motors 316.

It is further contemplated that plurality of inverters 336 may be any combination of electronic devices and may further include a voltage control mechanism.

Fig. 5 illustrates a method 400 for operating a power distribution system that includes a second electrical conductor or electrical conductors 24, 124, 224, 324, wherein electrical conductors 24, 124, 224, 324 supply power to motors 16, 116, 216, 316, which motors 16, 116, 216, 316 rotationally drive propellers 20, 120b, 220, 320 in an aircraft 10, 110, 210, 310. At step 202, ambient air pressure of electrical conductors 24, 124, 224, 324 is sensed. For example, at least one sensor 40 may be used to obtain ambient air pressure, such as the atmospheric pressure of electrical conductors 24, 124, 224, 324. Sensor 40 may be located in a region of aircraft 10, 110, 210 known to have the same ambient or atmospheric pressure as electrical conductor 24, 124, 224, 324.

In step 404, the voltage of electrical conductors 24, 124, 224, 324 is controlled based on the sensed ambient air pressure. For example, at least one sensor 40 may be used to obtain the ambient air pressure of electrical conductors 24, 124, 224, 324. This information may be communicated to the controller 44. The controller 44 then determines a threshold voltage corresponding to the ambient air pressure. The voltage regulators 18, 118, 218, 318 receive the threshold voltages from the controller 44. The voltage at electrical conductor 24, 124, 224, 324 is then controlled by voltage regulator 18, 118, 218, 318 to be equal to or less than the threshold voltage. Controlling the voltage based on the sensed ambient air pressure may prevent partial discharge, accelerated aging, or other insulation failures of electrical conductors 24, 124, 224, 324.

In operation, the aircraft propulsion system 12, 112, 212, 312 has a flight envelope defined by the region in which the aircraft 10, 110, 210, 310 with the aircraft propulsion system 12 may safely operate based on a variety of factors including, but not limited to, speed, altitude, air density, or angle of attack. The aircraft 10, 110, 210, 310 having the aircraft propulsion system 12 includes a first electrical conductor 22, 122, 222, 322 having a first electrical insulator 32, 132, 232, 332, the first electrical insulator 32, 132, 232, 332 being sized to prevent partial discharge or other insulation failure of the first electrical conductor 22, 122, 222, 322 at a maximum voltage across the flight envelope of the aircraft propulsion system 12, 112, 212, 312. The first electrical conductor 22, 122, 222, 322 electrically connects the power source 14, 114, 214, 314 and the voltage regulator 18, 118, 218, 318.

During flight envelope, the decrease in ambient air pressure indicates that there is less atmosphere to provide insulation for first electrical conductor 22, 122, 222, 322. The first electrical insulator 32, 132, 232, 332 on the first electrical conductor 22, 122, 222, 322 must be thick enough to reduce the likelihood of partial discharge, accelerated aging, or other insulation failure of the first electrical conductor 22, 122, 222, 322 at the highest elevation of the flight envelope when the maximum voltage is provided.

However, for example, the aircraft 10 typically does not have the same power requirements at higher altitudes as during takeoff. Reducing power requirements at higher altitudes allows the aircraft propulsion system 12, 112, 212, 312 to utilize the voltage regulator 18, 118, 218, 318 to provide a reduced voltage or power to the electric machine 16, 116, 216, 316. A second electrical conductor 24, 124, 224, 324 electrically connects the voltage regulator 18, 118, 218, 318 and the electric machine 16, 116, 216, 316. Because voltage regulator 18, 118, 218, 318 may control the voltage at second electrical conductor 24, 124, 224, 324 to be less than or equal to the maximum voltage based on ambient air pressure, second electrical insulator 34, 134, 234, 334 may be sized smaller than first electrical conductor 22, 122, 222, 322. At least one sensor 40 in communication with controller 44 may be used to determine an appropriate threshold voltage at second electrical conductor 24, 124, 224, 324, resulting in electrical power or voltage being a function of ambient air pressure. A threshold voltage of second electrical conductor 24, 124, 224, 324 is determined based on an ambient air pressure of second electrical conductor 24, 124, 224, 324 obtained by at least one sensor. The threshold voltage prevents partial discharge of second electrical conductor 24, 124, 224, 324. Since the electric machines 16, 116, 216, 316 require less power at higher altitudes, particularly during cruising, operation of the aircraft 10, 110, 210, 310 is not affected by the voltage drop at the second electrical conductor 24, 124, 224, 324.

Alternatively, the voltage regulator 18, 118, 218, 318 may provide constant power to the electric machine 16, 116, 216, 316 while regulating the voltage to a threshold voltage determined by the altitude. This is achieved by allowing the current to vary accordingly to provide constant power at varying threshold voltages.

A technical effect of the systems and methods disclosed herein is to provide a control system that may vary a supply voltage based on an ambient air pressure of an electrical conductor. The ambient air pressure may be at least partially a function of altitude, with the voltage also being a function of altitude. By controlling the voltage, at least some of the electrical conductors require less electrical insulation to reduce the likelihood of partial discharge from the electrical conductors.

In addition, aging of the conductor may be reduced based on the height control voltage. Operation of the threshold voltage to the voltage based on the altitude determination results in a lower cumulative current flowing through the conductor during flight and therefore less thermal shock to the conductor. Also, as the heat caused by the current is reduced, the wear of the insulator is reduced. The smaller the cumulative current flowing through the conductor, the lower the cumulative heat dissipation per flight.

Aspects of the present disclosure provide a number of benefits. For example, by reducing the size of the second electrical insulation, the weight of the aircraft will also be reduced. The reduction in weight of the aircraft contributes to improved fuel efficiency.

Another advantage of the present disclosure is cost savings due to a reduced size or amount of second electrical insulation placed on the second electrical conductor.

Many other possible configurations are contemplated by the present disclosure in addition to those shown in the above figures. For example, more than one aircraft propulsion system may be used on a single aircraft, where multiple aircraft propulsion systems may include similar or different components. To the extent not already described, the various features and structures of the various aspects may be used in combination with other aspects as desired. A feature may not be described in all respects, this does not mean that it cannot be construed, but that it is done for brevity of description. Thus, the various features of the different aspects can be mixed and matched as desired to form new aspects, whether or not such aspects are explicitly described. Combinations or permutations of features described herein are covered by this disclosure.

This written description uses examples to disclose various aspects of the invention, including the best mode, and also to enable any person skilled in the art to practice various aspects of the invention, including making and using any machines, devices, or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples include structural elements that do not differ from the literal language of the claims, or include structural elements that differ from the literal language of the claims, but do not differ from the literal language of the claims, and are intended to be within the scope of the claims.

Further aspects of the invention are provided by the subject matter of the following clauses:

1. an aircraft propulsion system for an aircraft, comprising: a propeller; a motor operable to rotate the propeller; a power supply that provides power to the motor; and a voltage regulator that regulates power provided to the motor from the power source, and that is configured to control a voltage of the power provided as a function of ambient air pressure in at least a portion of the aircraft.

2. The aircraft propulsion system according to any preceding claim, further comprising an electrical conductor connecting the voltage regulator to the electric machine, and at least a portion of the aircraft comprises at least a portion of the electrical conductor.

3. The aircraft propulsion system according to any preceding claim, wherein the electrical conductor comprises an electrical insulator.

4. The aircraft propulsion system according to any preceding item, wherein the electrical insulator is dimensioned to prevent partial discharge at a maximum voltage of the power supply at ambient air pressure.

5. The aircraft propulsion system according to any preceding item, wherein the electrical insulator is not dimensioned to prevent partial discharge throughout a flight envelope of the aircraft propulsion system.

6. The aircraft propulsion system according to any preceding claim, wherein the voltage regulator is configured to control the voltage of the provided power to prevent partial discharge throughout the flight envelope.

7. The aircraft propulsion system according to any preceding claim, further comprising an ambient air pressure sensor operably coupled to the voltage regulator.

8. The aircraft propulsion system according to any preceding claim, wherein the ambient air pressure sensor is an altimeter.

9. The aircraft propulsion system according to any preceding claim, wherein the electrical conductor is exposed to atmospheric pressure and the ambient air pressure is the current atmospheric pressure.

10. The aircraft propulsion system of any preceding claim wherein the power source is one of an ac or dc power source.

11. The aircraft propulsion system of any preceding claim wherein the electric machine is at least one of an ac or dc electric motor.

12. The aircraft propulsion system according to any preceding claim, wherein the propeller comprises a plurality of propellers.

13. The aircraft propulsion system according to any preceding claim, wherein the motor comprises a plurality of motors, wherein each of the plurality of propellers is rotationally driven by a different motor of the plurality of motors.

14. The aircraft propulsion system according to any preceding claim, wherein the voltage regulator is electrically coupled to all of the plurality of electrical machines.

15. The aircraft propulsion system according to any preceding claim, wherein the voltage regulator comprises a plurality of voltage regulators, each of the plurality of electrical machines being electrically coupled to a different one of the plurality of voltage regulators.

16. An aircraft propulsion system according to any preceding claim wherein the power source comprises at least one of an internal combustion engine with a generator or an electrical storage device.

17. The aircraft propulsion system according to any preceding claim, wherein the voltage regulator comprises an inverter or converter.

18. A method of operating a power distribution system having an electrical conductor that supplies power to a motor that rotationally drives a propeller in an aircraft, the method comprising sensing an ambient air pressure of the electrical conductor and controlling a voltage at the electrical conductor in dependence on the sensed ambient air pressure.

19. The method of any preceding claim, wherein controlling the voltage comprises controlling the voltage based on a sensed ambient air pressure to prevent partial discharge from the electrical conductor.

20. The method of any preceding claim, wherein the sensed ambient air pressure is atmospheric pressure.