Systems and methods for electrical short and fire hazard mitigation in electric propulsion systems

Abstract

A method of mitigating electrical faults includes detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generating a torque that counters windmilling of the electrical propulsion system by performing at least one of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

Description

Agent Ref 16497.0027-00304SYSTEMS AND METHODS FOR ELECTRICAL SHORT AND FIRE HAZARD MITIGATION IN ELECTRIC PROPULSION SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 632,502, filed on April 10, 2024, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of aerial vehicles and, more particularly, tilt-rotor aircraft that use electrical propulsion systems. Certain aspects of the present disclosure generally relate to addressing issues related to electrical faults in an aircraft. Other aspects of the present disclosure generally relate to improvements in safety mechanisms for propulsion systems that may be used in other types of aerial vehicles but provide particular advantages in vertical takeoff and landing aircraft.BACKGROUND

[0003] Vertical takeoff and landing aircraft typically include one or more propellers, or other means of propulsion. The propellers provide vertical lift by propelling air downward (e.g., for takeoff, landing, and hovering). The aircraft may also generate forward propulsion using the same propellers (e.g., by using tiltable propellers, or tilt rotors). Electrically powered propellers may implement electrical components (e.g., windings, batteries, or the like) that use a high electrical current to spin the propellers. The reverse process is also a valid electrical scenario (e.g., airflow through propellers of an electrical generator may spin a magnet to generate current in windings, thereby generating electrical current / power).

[0004] For safety reasons, electrically powered aircrafts implement a variety of safety mechanisms that allow the aircrafts to continue to perform in a number of malfunction scenarios or otherwise allow the aircraft enough maneuverability and range to make an emergency landing. An electrical fault or short is a malfunction scenario that may cause a propeller to become unresponsive, as well as create a path of very low electrical resistance at the short location. Hence, a failure in an electrical propulsion system may result in the rotor spinning uncontrollably as the aircraft moves against air during flight (e.g., uncontrolled windmilling or simply “windmilling”). Windmilling may cause a high amount of current to pass through the electrical short. Electrical overcurrent may lead to overheating and fire. It is desirable to provide devices and methods to mitigate overcurrent and heating issues when a malfunction occurs during flight.Agent Ref: 16497.0027-00304SUMMARY

[0005] Embodiments of the present disclosure provide protection against fire hazards caused by electrical failure, such as due to an electrical short, in an electrical propulsion system of an aircraft. Vertical take-off and landing (VTOL) aircraft may use electrical propulsion systems. Electrical propulsion systems may include inverters to provide the multiphase electrical current signals to windings (e.g., three-phase power). The current flowing through the windings may electromechanically interact with a magnet attached to a thrustproducing element (e.g., a propeller). During flight, an electrical fault in an inverter may reduce thrust and create a fire hazard due to windmill-based overcurrent.

[0006] Some embodiments described herein implement devices and operations to mitigate unsafe conditions resulting from an electrical fault in an electrical propulsion system. For example, the windings in an electrical propulsion system may be structured with electrical disconnect mechanisms. The disconnect mechanism may be disposed at a wye junction of the windings. The disconnect mechanism may be a fuse-type device that is set to break the electrical connection upon activation. A less destructive mitigation mechanism may include adjusting the malfunctioning inverter in the electrical propulsion system, as well as any remaining working inverters, to generate a torque that counters the windmilling motion, thereby reducing the amount of overcurrent.

[0007] In some embodiments, a computer-implemented method of mitigating electrical faults is provided. The method may comprise detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter. The method may also comprise activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter. The method may also comprise thereafter generating a torque that counters windmilling of the electrical propulsion system by performing at least one of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

[0008] In some embodiments, a system for mitigating electrical faults is provided. The system may comprise at least one processor and memory. The memory may store a set of instructions which, when executed by the at least one processor, cause the system to: detect an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafterAgent Ref: 16497.0027-00304 generate a torque that counters windmilling of the electrical propulsion system by performing at least one of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

[0009] In some embodiments, a non-transitory computer-readable medium that stores a set of instructions for mitigating electrical faults is provided. The set of instructions may be executable by at least one processor to cause the at least one processor to perform operations. The operations may comprise detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter. The operations may also comprise activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter. The operations may also comprise thereafter generating a torque that counters windmilling of the electrical propulsion system by performing at least one of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

[0010] In some embodiments, a computer-implemented method of mitigating electrical faults is provided. The method may comprise detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter. The method may also comprise activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter. The method may also comprise thereafter reversing a three-phase timing of at least three AC signals applied to the second inverter having a second three-phase electrical circuitry to generate a torque that counters windmilling of the electrical propulsion system.

[0011] In some embodiments, a non-transitory computer-readable medium that store a set of instructions for protecting against electrical faults is provided. The set of instructions may be executable by at least one processor to cause the at least one processor to perform operations. The operations may comprise detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter. The operations may also comprise activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter. The operations may also comprise thereafter reversing a three-phase timing of at least three AC signals applied to the second inverter having a second three-phase electrical circuitry to generate a torque that counters windmilling of the electrical propulsion system.Agent Ref: 16497.0027-00304

[0012] In some embodiments, an electrical aerial vehicle is provided. The electrical aerial vehicle may comprise an electrical propulsion system comprising a first inverter, a second inverter, a sensor, and one or more processors. The first inverter may comprise a first three- phase electrical circuitry coupled to first set of windings. The electrical propulsion system may be configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter. The sensor may sense an electrical fault in the electrical propulsion system. The one or more processors may be configured to detect an electrical fault at the first inverter; activate a three-phase short at the first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generate a torque that counters windmilling of the electrical propulsion system by: activating a three-phase short at the second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

[0013] In some embodiments, a propulsion system for an electric vehicle is provided. The propulsion system may comprise an electrical motor, an actuator, a sensor, and a processor. The electrical motor may drive the electric vehicle. The electric motor may comprise a set of stator windings. The set of stator windings may comprise a common node. The actuator may be connected to the common node of the set of stator windings. The sensor may be coupled to the set of stator windings. The processor may receive, from the sensor, one or more signals indicating a fault has occurred. The processor may, after receiving the one or more signals indicating a fault has occurred, also cause the actuator to disconnect the set of stator windings at the common node.

[0014] In some embodiments, an electrical propulsion system is provided. The electrical propulsion system may comprise a first inverter, a second inverter, a sensor, and one or more processors. The electrical propulsion system may be configured to generate torque using by applying at least three AC signals with a three-phase timing from to the second inverter. The first inverter may include a first three-phase electrical circuitry. The second inverter may include a second three-phase electrical circuitry. The sensor may be configured to sense an electrical fault. The one or more processors may be configured to detect an electrical fault at the first inverter; activate a three-phase short at the first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generate a torque that counters windmilling of the electrical propulsion system by: activating a three- phase short at the second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.Agent Ref: 16497.0027-00304BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is an illustration of a perspective view of an exemplary VTOL aircraft, consistent with some embodiments of the present disclosure.

[0016] Figure 2 is another illustration of a perspective view of an exemplary VTOL aircraft in an alternative configuration, consistent with some embodiments of the present disclosure.

[0017] Figure 3 is an illustration of a top plan view of an exemplary VTOL aircraft, consistent with some embodiments of the present disclosure.

[0018] Figure 4 is a schematic diagram illustrating exemplary propeller rotation of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0019] Figure 5 is a schematic diagram illustrating exemplary power connections in a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0020] Figure 6 is a block diagram illustrating an exemplary architecture and design of an electric propulsion unit of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0021] Figure 7 is a schematic diagram illustrating an exemplary tilt electric propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0022] Figures 8A-8C are illustrations of an exemplary tilt electric propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0023] Figure 9 is a schematic diagram illustrating an exemplary lift electric propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0024] Figures 10A-10B are illustrations of an exemplary lift electric propulsion systems of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0025] Figure 11 is a diagram illustrating a portion of an exemplary electrical propulsion system for a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0026] Figure 12 is a diagram illustrating a portion of an exemplary electrical propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0027] Figures 13A-13B are illustrations of an exemplary actuator in an electrical propulsion system, consistent with some embodiments of the present disclosure.

[0028] Figure 14 is a diagram illustrating a portion of an exemplary electrical propulsion system for a VTOL aircraft, consistent with some embodiments of the present disclosure.Agent Ref: 16497.0027-00304

[0029] Figure 15 is a graph chart of generated torque and electrical current in an inverter of an exemplary electrical propulsion system for a VTOL aircraft, consistent with some embodiments of the present disclosure.

[0030] Figure 16 is a torque graph chart and a current graph chart for an exemplary electrical propulsion system, consistent with some embodiments of the present disclosure.

[0031] Figure 17 is a flowchart of an example method for controlling a functional inverter in a malfunctioning electrical propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0032] The present disclosure addresses systems, components, and techniques primarily for use in an aircraft. The aircraft may be an aircraft with a pilot, an aircraft without a pilot (e.g., an unmanned aerial vehicle (UAV)), a drone, a helicopter, and / or an airplane. An aircraft includes a physical body and one or more components (e.g., a wing, a tail, a propeller) configured to allow the aircraft to fly. The aircraft may include any configuration that includes at least one propeller. In some embodiments, the aircraft is propelled by one or more electric propulsion systems (hereinafter referred to as electric propulsion units or “EPUs”), which may include at least one engine, at least one rotor, at least one propeller, or any combination thereof. The aircraft may be fully electric, hybrid, or hydrocarbon fuel powered. For example, in some embodiments, the aircraft is a tilt-rotor aircraft configured for frequent (e.g., over 50 flights per work day), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated regions. The aircraft may be configured to carry 4-6 passengers or commuters who have an expectation of a comfortable experience with low noise and low vibration.

[0033] Disclosed embodiments provide new and improved configurations of aircraft components, some of which are not observed in conventional aircraft, and / or identified design criteria for components that differ from those of conventional aircraft. Such alternate configurations and design criteria, in combination with addressing drawbacks and challenges with conventional components, yielded the embodiments disclosed herein for various configurations and designs of components for an aircraft (e.g., electric aircraft or hybridelectric aircraft) driven by a propulsion system.

[0034] In some embodiments, the aircraft driven by a propulsion system of the present disclosure may be designed to be capable of both vertical and conventional takeoff and landing, with a distributed propulsion system enabling vertical flight, horizontal and lateralAgent Ref 16497.0027-00304 flight, and transition (e.g., transitioning between vertical flight and horizontal / forward flight). The aircraft may generate thrust by supplying high voltage electrical power to a plurality of engines of the distributed propulsion system, which may include components to convert the high voltage electrical power into mechanical shaft power to rotate a propeller.

[0035] Embodiments may include an electric engine connected to an onboard electrical power source, which may include a device capable of storing energy such as a battery or capacitor, and may optionally include one or more systems for harnessing or generating electricity such as a fuel powered generator or solar panel array. In some embodiments, the aircraft may comprise a hybrid aircraft configured to use at least one electric-based energy source and at least one fuel-based energy source to power the distributed propulsion system, which may be configured to provide power simultaneously or in or alternating fashion. In some embodiments, the aircraft may be powered by one or more batteries, internal combustion engines (ICE), generators, turbine engines, or ducted fans.

[0036] The engines may be mounted directly to the wing, or mounted to one or more booms attached to the wing. The amount of thrust each engine generates may be governed by a torque command from a Flight Control System (FCS) over a digital communication interface to each engine. Embodiments may include forward engines (and associated propellers) that are capable of altering their orientation, or tilt.

[0037] The engines may rotate the propellers in a clockwise (CW) or counterclockwise (CCW) direction. In some embodiments, the difference in propeller rotation direction may be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and gearing may be used to achieve different propeller rotation directions.

[0038] In some embodiments, an aircraft may possess quantities of engines in various combinations of forward and aft engine configurations. A forward engine may be considered an engine that is positioned predominantly towards the leading edge of a wing. An aft engine may be considered an engine that is positioned predominantly towards the trailing edge of a wing. For example, an aircraft may possess six forward and six aft engines, five forward and five aft engines, four forward and four aft engines, three forward and three aft engines, two forward and two aft engines, or any other combination of forward and aft engines, including embodiments where the number of forward engines and aft engines are not equivalent.

[0039] In some embodiments, for a vertical takeoff and landing (VTOL) task, the forward and aft engines may provide vertical thrust during takeoff and landing. During flight phasesAgent Ref: 16497.0027-00304 where the aircraft is moving forward, the forward engines may provide horizontal thrust, while the propellers of the aft engines may be stowed at a fixed position in order to minimize drag. The aft engines may be actively stowed with position monitoring.

[0040] Transition from vertical flight to horizontal flight and vice-versa may be accomplished via the tilt propeller subsystem. The tilt propeller subsystem may redirect thrust between a primarily vertical direction during vertical flight phase (e.g., hover-phase) to a horizontal or near-horizontal direction during a forward-flight cruising phase, based on a tilt of one or more propellers (e.g., determining directionality of one or more propellers). A variable pitch mechanism may change the forward engine’s propeller-hub assembly blade collective angles for operation during phases of flight, such as a hover-phase, transition phase, and cruise-phase. Vertical lift may be thrust in a primarily vertical direction (e.g., during a hover-phase). Horizontal thrust may be thrust in a primarily horizontal direction (e.g., during a cruise-phase).

[0041] In some embodiments, a “phase of flight” or “flight phase,” (e.g., hover, cruise, forward flight / wing-borne flight, takeoff, landing, transition) may be defined by a combination flight conditions (e.g., a combination of flight conditions within particular ranges), which may include one or more of an airspeed, ground speed altitude, pitch angle (e.g., of the aircraft), tilt angle (e.g., of one or more propellers), roll angle, rotation speed (e.g., of one or more propellers), torque value, pilot command, or any other value indicating a current or requested (e.g., commanded) state of at least part of the aircraft. A “flight state” may include a flight phase and / or forces or environmental factors experienced by the aircraft, such as at least one of weather conditions, air density, natural wind movements, humidity, a proximity of at least one component to a vortex ring state, etc.

[0042] “Vertical flight” or a “hover” phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by engines (e.g., EPUs), rather than one or more wings. “Horizontal flight, a “cruise” phase of flight, or a wing-borne phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by one or more wings, rather than by any engine (e.g., EPU). “Transition” may be considered any phase of flight where an aircraft is shifting from vertical flight to horizonal flight, or vice versa.

[0043] In some embodiments, in a conventional takeoff and landing (CTOL) task, the forward engines may provide horizontal thrust for wing-borne take-off, cruise, and landing, and the wings may provide vertical lift. In some embodiments, the aft engines may not beAgent Ref: 16497.0027-00304 used for generating thrust during a CTOL task and the aft propellers may be stowed in place. In other embodiments, the aft engines may be used at reduced power to shorten the length of the CTOL takeoff or landing.

[0044] The following disclosure provides different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and / or configurations discussed.

[0045] The terms used in this specification generally have their ordinary meanings in the art and in the specific context where each term is used. The use of examples in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given in this specification.

[0046] Although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0048] In the present disclosure, the term “coupled” may also be termed as “electrically coupled”, and the term “connected” may be termed as “electrically connected.” “Coupled” and “connected” may also be used to indicate that two or more elements cooperate or interact with each other.Agent Ref: 16497.0027-00304

[0049] The present disclosure addresses components of electric vertical takeoff and landing (eVTOL) aircraft primarily for use in a non-conventional aircraft. For example, the eVTOL aircraft of the present disclosure may be intended for frequent (e.g., over 50 flights per workday), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated regions. The aircraft may be intended to carry 4-6 passengers or commuters who have an expectation of a low-noise and low-vibration experience. Accordingly, it may be desired that their components are configured and designed to withstand frequent use without wearing, that they generate less heat and vibration, and that the aircraft include mechanisms to effectively control and manage heat or vibration generated by the components. Further, it may be intended that several of these aircraft operate near each other over a crowded metropolitan area.

[0050] Accordingly, it may be desired for aircraft components to generate low levels of noise interior and exterior to the aircraft, and to have a variety of safety and backup mechanisms. For example, it may be desired for safety reasons that the aircraft are propelled by a distributed propulsion system, avoiding the risk of a single point of failure, and that the aircraft are capable of conventional takeoff and landing on a runway. Moreover, it may be desired that the aircraft can safely vertically takeoff and land from and into relatively restricted spaces (e.g., vertiports, parking lots, or driveways) compared to traditional airport runways while transporting around 4-6 passengers or commuters with accompanying baggage. Such factors may place design constraints on aircraft size, weight, operating efficiency (e.g., drag, energy use).

[0051] Disclosed embodiments provide new and improved configurations of aircraft components, some of which are not observed in conventional aircraft, and / or identified design criteria for components that differ from those of conventional aircraft. Such alternate configurations and design criteria, in combination with addressing drawbacks and challenges with conventional components, yielded the embodiments disclosed herein for various configurations and designs of components for an aircraft (e.g., electric aircraft or hybridelectric aircraft) driven by a propulsion system.

[0052] Some embodiments of electrical engines may include protection features in the forward and aft electrical engines (e.g., monitoring internal temperatures, detecting anomalous behavior, or the like). In some embodiments, electrical overcurrent may lead to overheating and fire. A failure in an electrical propulsions system (e.g., also referred to as an engine) may result in the rotor spinning uncontrollably as a result of moving against airAgent Ref 16497.0027-00304 during flight. Some embodiments of the present disclosure provide safety mechanisms for protecting against such engine failures.

[0053] It is appreciated that while some embodiments may refer to influencing or controlling operations (e.g., rotation) of a “propeller,” such techniques may be equally applied to other similar or related components of an electric propulsion system, such as a rotor, ducted fan, or the like.

[0054] Fig. 1 is an illustration of a perspective view of an exemplary VTOL aircraft, consistent with disclosed embodiments. Fig- 2 is another illustration of a perspective view of an exemplary VTOL aircraft in an alternative configuration, consistent with embodiments of the present disclosure. Figs. 1 and 2 illustrate a VTOL aircraft 100, 200 in a cruise configuration and a vertical take-off, landing and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. Elements corresponding to Figs. 1 and 2 may possess like numerals and refer to similar elements of the aircrafts 100, 200. Aircraft 100, 200 may include fuselage 102, 202, wings 104, 204 mounted to fuselage 102, 202 and one or more rear stabilizers 106, 206 mounted to the rear of fuselage 102, 202. Aircraft 100, 200 may include one or more effectors, which are considered to be any structure capable of influencing flight, such as by manipulating one or more forces to move the aircraft. For example, an effector may include a control surface, an EPU, and / or an actuator (e.g., configured to tilt an EPU or other propulsion device). A plurality of lift propellers 112, 212 may be mounted to wings 104, 204 and may be configured to provide lift for vertical take-off, landing and hover. A plurality of tilt propellers 114, 214 may be mounted to wings 104, 204 and may be tiltable (e.g., configured to tilt or alter orientation) between the lift configuration in which they provide a portion of the lift required for vertical take-off, landing and hovering, as shown in Fig. 2, and the cruise configuration in which they provide forward thrust to aircraft 100 for horizontal flight, as shown in Fig. 1. As used herein, a tilt propeller lift configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily lift to the aircraft and tilt propeller cruise configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily forward thrust to the aircraft.

[0055] While the term “tilt propeller” is used herein, it is appreciated that this term does not necessarily apply to just propellers themselves, but may also include other components of an electric propulsion unit (EPU) of which the propellers are a part, and accordingly may refer to an EPU that can tilt about an axis (e.g., using an actuator). While the term “liftAgent Ref: 16497.0027-00304 propeller” is used herein, it is appreciated that this term does not necessarily apply to just propellers themselves, but may also include other components of an EPU of which the propellers are a part, and accordingly may refer to an EPU that cannot tilt.

[0056] In some embodiments, lift propellers 112, 212 may be configured for providing lift only, with all horizontal propulsion being provided by the tilt propellers. For example, lift propellers 112, 212 may be configured with fixed positions and may only generate thrust during take-off, landing and hover phases of flight. Meanwhile, tilt propellers 114, 214 may be tilted upward into a lift configuration in which thrust from propellers 114, 214 is directed downward to provide additional lift.

[0057] For forward flight, tilt propellers 114, 214 may tilt from their lift configurations to their cruise configurations. In other words, the orientation of tilt propellers 114, 214 may be varied from an orientation in which the tilt propeller thrust is directed downward (to provide lift during vertical take-off, landing and hover) to an orientation in which the tilt propeller thrust is directed rearward (to provide forward thrust to aircraft 100, 200). The tilt propellers assembly for a particular electric engine may tilt about an axis of rotation defined by a mounting point connecting the boom and the electric engine. When aircraft 100, 200 is in full forward flight, lift may be provided entirely by wings 104, 204. Meanwhile, in the cruise configuration, lift propellers 112, 212 may be shut off. Blades 120, 220 of lift propellers 112, 212 may be held in low-drag positions for aircraft cruising. In some embodiments, lift propellers 112, 212 may each have two blades 120, 220 that may be locked, for example while the aircraft is cruising, in minimum drag positions in which one blade is directly in front of the other blade as illustrated in Fig. 1. In some embodiments, lift propellers 112, 212 have more than two blades. In some embodiments, tilt propellers 114, 214 may include more blades 116, 216 than lift propellers 112, 212. For example, as illustrated in Figs. 1 and 2, lift propellers 112, 212 may each include, e.g., two blades, whereas and tilt propellers 114, 214 may each include more blades, such as the five blades shown. In some embodiments, each of tilt propellers 114, 214 may have 2 to 5 blades, and possibly more depending on the design considerations and requirements of the aircraft.

[0058] In some embodiments, the aircraft may include a single wing 104, 204 on each side of fuselage 102, 202 (or a single wing that extends across the entire aircraft). At least a portion of lift propellers 112, 212 may be located rearward of wings 104, 204 (e.g., rotation point of propeller is behind a wing from a bird’s eye view) and at least a portion of tilt propellers 114, 214 may be located forward of wings 104, 204 (e.g., rotation point ofAgent Ref: 16497.0027-00304 propeller is in front of a wing from a bird’s eye view). In some embodiments, all of lift propellers 112, 212 may be located rearward of wings 104, 204 and all of tilt propellers 114, 214 may be located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to the wings — e.g., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 112, 212 may be all located rearwardly of wings 104, 204 and tilt propellers 114, 214 may be all located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inwardly of the ends of wing 104, 204.

[0059] In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to wings 104, 204 by booms 122, 222. Booms 122, 222 may be mounted beneath wings 104, 204, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted directly to wings 104, 204. In some embodiments, one lift propeller 112, 212 and one tilt propeller 114, 214 may be mounted to each boom 122, 222. Lift propeller 112, 212 may be mounted at a rear end of boom 122, 222 and tilt propeller 114, 214 may be mounted at a front end of boom 122, 222. In some embodiments, lift propeller 112, 212 may be mounted in a fixed position on boom 122, 222. In some embodiments, tilt propeller 114, 214 may mounted to a front end of boom 122, 222 via a hinge. Tilt propeller 114, 214 may be mounted to boom 122, 222 such that tilt propeller 114, 214 is aligned with the body of boom 122, 222 when in its cruise configuration, forming a continuous extension of the front end of boom 122, 222 that minimizes drag for forward flight.

[0060] In some embodiments, aircraft 100, 200 may include, e.g., one wing on each side of fuselage 102, 202 or a single wing that extends across the aircraft. According to some embodiments, the at least one wing 104, 204 is a high wing mounted to an upper side of fuselage 102, 202. According to some embodiments, the wings include control surfaces, such as flaps, ailerons, spoilers, and / or flaperons (e.g., configured to perform functions of both flaps and ailerons). According to some embodiments, wings 104, 204 may have a profile that reduces drag during forward flight. In some embodiments, the wing tip profile may be curved and / or tapered to minimize drag.

[0061] In some embodiments, rear stabilizers 106, 206 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design for providing lift, directionality, stability, and / orAgent Ref 16497.0027-00304 any other characteristic beneficial for aircraft. In some embodiments, the wings have a tapering leading edge.

[0062] In some embodiments, lift propellers 112, 212 or tilt propellers 114, 214 may be canted relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214, where canting refers to a relative orientation of the rotational axis of the lift propeller / tilt propeller about a line that is parallel to the forward-rearward direction, analogous to the roll degree of freedom of the aircraft.

[0063] In some embodiments, one or more lift propellers 112, 212 and / or tilt propellers 114, 214 may canted relative to a cabin of the aircraft, such that the rotational axis of the propeller in a lift configuration is angled away from an axis perpendicular to the top surface of the aircraft. For example, in some embodiments, the aircraft is a flying wing aircraft and some or all of the propellers are canted away from the cabin.

[0064] Fig. 3 is an illustration of a top plan view of an exemplary VTOL aircraft, consistent with embodiments of the present disclosure. Aircraft 300 shown in the figure may be a top plan view of aircraft 100, 200 shown in Figs. 1 and 2, respectively. As discussed herein, an aircraft 300 may include twelve electric propulsion units (EPUs) distributed across aircraft 300, though it is appreciated that an aircraft may include any number of electric propulsion systems, connected at different locations on the aircraft. In some embodiments, a distribution of EPUs may include six forward EPUs 314 and six aft EPUs 312 mounted on booms forward and aft of main wings 304 of aircraft 300. In some embodiments, forward EPUs may be mounted to wings 304 by booms 322. In some embodiments, aft EPUs may be mounted to wings 304 by booms 324. In some embodiments, a length of the rear end of boom 324 from wing 304 to a lift propeller (part of EPU 312) may comprise a similar rear end of boom 324 length across the numerous rear ends of the booms. In some embodiments, the length of the rear ends of the booms may vary, for example, across the six rear ends of the booms. Further, Fig. 3 depicts an exemplary embodiment of a VTOL aircraft 300 with forward propellers (part of EPU 314) in a horizontal orientation for horizontal flight and aft propeller blades 320 in a stowed position for a forward phase of flight.

[0065] Fig. 4 is a schematic diagram illustrating exemplary propeller rotation of a VTOL aircraft, consistent with disclosed embodiments. Aircraft 400 shown in the figure may be a top plan view of aircraft 100, 200, and 300 shown in Figs. 1, 2, and 3, respectively. An aircraft 400 may include six forward electric propulsion units (EPUs) with three of the forward EPUs being of CW type 424 and the remaining three forward EPUs being of CCWAgent Ref: 16497.0027-00304 type 426. In some embodiments, three aft EPUs may be of CCW type 428 with the remaining three aft EPUs being of CW type 430. Some embodiments may include an aircraft 400 possessing four forward EPUs and four aft EPUs, each with two CW types and two CCW types. In some embodiments, aircraft 400 may include a fuselage 402, wing(s) 404 mounted to fuselage 402, and one or more rear stabilizers 406 mounted to the rear of fuselage 402. In some embodiments, each forward EPU may include propeller blades 416. In some embodiments, each aft EPU may include propeller blades 420. In some embodiments, EPUs may be mounted to wing(s) 404 by booms 422. In some embodiments, propellers may counter-rotate with respect to adjacent propellers to cancel torque steer, generated by the rotation of the propellers, experienced by the fuselage or wings of the aircraft. In some embodiments, the difference in rotation direction may be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and gearing may be used to achieve different propeller rotation directions.

[0066] Some embodiments may include an aircraft 400 possessing forward and aft electric propulsion units (EPUs) where the amount of CW types 424 and CCW types 426 is not equal among the forward EPUs, among the aft EPUs, or among the forward and aft EPUs.

[0067] Fig. 5 is a schematic diagram illustrating exemplary power connections in a VTOL aircraft, consistent with disclosed embodiments. A VTOL aircraft may have multiple power systems connected to diagonally opposing electric propulsion units (EPUs). In some embodiments, the power systems may include high voltage power systems. Some embodiments may include high voltage power systems connected to electric engines via high voltage channels. In some embodiments, an aircraft 500 may include six power systems (e.g., battery packs), including power systems 526, 528, 530, 532, 534, and 536 stored within wing 570 of aircraft 500. The power systems may power EPUs and / or other electric components of aircraft 500. In some embodiments, aircraft 500 may include six forward EPUs having six electric engines 502, 504, 506, 508, 510, and 512 and six aft EPUs having six electric engines 514, 516, 518, 520, 522, and 524. In some embodiments, one or more power systems (e.g., battery packs) may include a battery management system (“BMS”) (e.g., one BMS for each battery pack). While six power systems are shown in Fig. 5, aircraft 500 may include any number and / or configuration of power systems.

[0068] In some embodiments, the one or more battery management systems may communicate with a Flight Control System (“FCS”) of the aircraft (e.g., FCS 612 shown in Fig 6). For example, the FCS may monitor the status of one or more battery packs and / orAgent Ref: 16497.0027-00304 provide commands to the one or more battery management systems which make corresponding adjustments to the high voltage power supply.

[0069] Fig. 6 illustrates block diagram of an exemplary architecture and design of an electric propulsion unit 600 consistent with disclosed embodiments. Exemplary electric propulsion unit 600 includes an electric propulsion unit (EPU) 602, which may be configured to control aircraft propellers. EPU 602 may include an electric engine subsystem 604 that may supply torque, via a shaft, to a propeller subsystem 606 to produce the thrust of EPU 602. Some embodiments may include electric engine subsystem 604 receiving low voltage direct current (LV DC) power from a Low Voltage System (LVS) 608. In some embodiments, electric engine subsystem 604 may be configured to receive high voltage (HV) power from a High Voltage Power System (HVPS) 610 comprising at least one battery or other device capable of storing energy. In some embodiments, electric propulsion system 602 may include one or more energy generation devices, such as a hydrocarb on -fueled turbine or generator, which may provide power to HVPS 610 and / or directly to electric propulsion system 602. HV power may refer to power that is higher in voltage than voltage provided by Low Voltage System (LVS) 608.

[0070] Some embodiments may include an electric propulsion unit (EPU) 602, a system that includes an electric engine subsystem 604 receiving signals from and sending signals to a flight control system 612. In some embodiments, a flight control system (FCS) 612 may comprise at least one flight control computer (FCC), comprising at least one processor and at least one memory, capable of using Controller Area Network (“CAN”) data bus signals to send commands to electric engine subsystem 604 and receive status and data from electric engine subsystem 604. Electric engine subsystem 604 may include at least one processor and at least one memory to store instructions to be executed by the at least one processor, such as instructions executable to perform operations corresponding to a method disclosed herein, including method 1700 and the operations described as carried out using the systems and configurations described in, for example, Figs. 11-14 (e.g., electrical propulsion systems 1100, 1200, or 1400, configurations 1300A or 1300B). An FCC may include a device configured to perform one or more operations (e.g., computational operations) for an aircraft, such as at least one processor and a memory component, which may store instructions executable by the at least one processor to perform the operations, consistent with disclosed embodiments, such as operations corresponding to a method disclosed herein, including method 1700 and the operations described as carried out using the systems and configurationsAgent Ref: 16497.0027-00304 described in, for example, Figs. 11-14 (e.g., electrical propulsion systems 1100, 1200, or 1400, configurations 1300A or 1300B). It should be understood that while CAN data bus signals may be used between the flight control computer and the electric engine(s), some embodiments may include alternate forms of communication means enabling transmitting and receiving data from an FCC to an electric engine. Some embodiments may include electric engine subsystems 604 capable of receiving operating parameters from and communicating operating parameters to an FCC in FCS 612, including speed, voltage, current, torque, temperature, vibration, propeller position, and / or any other value of operating parameters.

[0071] In some embodiments, a flight control system 612 may also include Tilt Propeller System (“TPS”) 614 capable of sending and receiving analog, discrete data to and from electric engine subsystem 604 of tilt propellers (e.g., EPUs capable of tilting). Tilt propeller system (TPS) 614 may include an apparatus capable of communicating operating parameters to an electric engine subsystem 604 and articulating an orientation of propeller subsystem 606 to redirect the thrust of the tilt propellers during various phases of flight using mechanical means such as a gearbox assembly, linear actuators, and any other configuration of components to alter an orientation of propeller subsystem 606. In some embodiments, electric engine subsystem may communicate an orientation of the propeller system (e.g., an angle corresponding to, or between, a lift configuration and forward thrust configuration) to TPS 614 and / or FCS 612 (e.g., during flight).

[0072] Fig. 7 is a schematic diagram illustrating an exemplary tiltable electric propulsion system 700 of a VTOL aircraft, consistent with some embodiments of the present disclosure. In some embodiments, tiltable electric propulsion system 700 may include an electric engine assembly 702 aligned along a shaft 724 that is connected to an output shaft 738 that is mechanically coupled to a propeller assembly 720 comprising a hub, a spinner, and tilt propeller blades. In some embodiments, electric engine assembly 702 may include a motor and gearbox assembly 704 aligned along and mechanically coupled to shaft 724. In some embodiments, motor and gearbox assembly 704 may include an electric motor assembly comprising a stator 706 and a rotor 708. Stator 706 may include multiple stator windings connected to inverter 716. Stator 706 may incorporate one or more redundances so that, in the event one set of windings were to fail, power would still be transmitted to stator 706 via one or more remaining windings, so that electric engine assembly 702 retains power and continues to generate thrust at propeller assembly 720.Agent Ref: 16497.0027-00304

[0073] In some embodiments, motor and gearbox assembly 704 may contain a gearbox 710 aligned along shaft 724 to provide a gear reduction between the torque of shaft 724 from the electric engine assembly and output shaft 738. Torque applied to output shaft 738 may be transferred to propeller assembly 720. Some embodiments may include gearbox 710 containing an oil pump. In such an embodiment, the oil pump may drive a circulation of oil throughout motor and gearbox assembly 704 at a speed equivalent to the rotation of output shaft 738 to cool and lubricate the gearbox and electric motor components. In some embodiments, the oil pump may drive a circulation of oil at a speed greater than or less than the rotation of output shaft 738. In some embodiments, motor and gearbox assembly 704 may include propeller position sensors 712 that may detect a magnetic field produced by the electric engine assembly to determine a propeller position. Further embodiments may include propeller position sensors 712 that are powered by inverter 716 and send collected data to inverter 716.

[0074] In some embodiments, electric engine assembly 702 may also include an inverter assembly 714 substantially aligned along shaft 724. Inverter assembly 714 may include inverter 716 and an inverter power supply 740. Inverter power supply 740 may accept low voltage DC power from a low voltage system 734 located outside electric engine assembly 702. Inverter power supply 740 may accept low voltage DC power originating from a high voltage power system 732, located outside the electric engine assembly 702, that has been converted to low voltage DC power via a DC-DC converter 742. Inverter 716 may supply high voltage alternating current (AC) to stator 706 via at least one three-phase winding. Inverter 716 that may receive flight control data from a flight control computing subsystem 736.

[0075] In some embodiments, motor and gearbox assembly 704 may be located between inverter assembly 714 and propeller assembly 720. Heat exchanger 718 may include, for example, a folded fin or other type of heat exchanger. In some embodiments, tiltable electric propulsion system 700 may circulate oil or other coolant throughout electric engine assembly 702, motor and gearbox assembly 704, or inverter assembly 714 to transfer heat generated from the components to the oil or other coolant liquid. The heated oil or other coolant liquid may circulate through heat exchanger 718 to transfer the heat to an air flow 722 passing through the fins of the heat exchanger.

[0076] In some embodiments, electric engine assembly 702 may be mounted or coupled to a boom structure 726 of the aircraft. A variable pitch mechanism 730 may be mechanicallyAgent Ref: 16497.0027-00304 coupled to propeller assembly 720. Variable pitch mechanism 730 may abut electric engine assembly 702. In some embodiments, variable pitch mechanism 730 may be remotely mounted within the boom, wing, or fuselage of the aircraft. In some embodiments, variable pitch mechanism 730 may include a shaft or component traveling within or adjacent to shaft 724. Variable pitch mechanism 730 may serve to change the collective angle of the forward electric engine’s propeller assembly blades during the hover-phase, transition phase, and cruise-phase. In some embodiments, electric engine assembly 702 may be mechanically coupled to a tilt propeller subsystem 728 that may redirect thrust between a primarily vertical direction during vertical flight mode to a mostly horizontal direction during forward-flight mode. In some embodiments, tilt propeller subsystem 728 may abut the variable pitch mechanism 730. Some embodiments may include a tilt propeller subsystem 728 comprising various components located in various locations. For example, a component of the tilt propeller subsystem may be coupled to the electric engine assembly 702 and other components may be coupled to the variable pitch mechanism 730. These various components of the tilt propeller subsystem 728 may work together to redirect the thrust of the tiltable electric propulsion system 700.

[0077] Figs. 8A-8C are illustrations of an exemplary tiltable electric propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure. Figs. 8A- 8C possess like numerals and refer to similar elements of tiltable electric propulsion system 800A, 800B, 800C, albeit in different views to illustrate element positioning. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0078] Figs. 8A and 8B illustrate a side profile and perspective view, respectively, of an exemplary tiltable electric propulsion system 800A, 800B in a cruise configuration integrated into a boom 812A, 812B, consistent with some embodiments of the present disclosure. Tiltable propeller electric propulsion system 800A, 800B may comprise an electric engine assembly 802A, 802B housed within a boom 812A, 812B of a VTOL aircraft. In some embodiments, a cruise configuration may include the electric engine assembly 802A, 802B being posited within the boom 812A, 812B. An electric engine assembly 802A, 802B may comprise an electric motor assembly, a gearbox assembly, an inverter assembly with power connection channels 810A, 810B, and a heat exchanger 804A, 804B, as described herein. Electric engine assembly 802A, 802B may be mechanically coupled to a propulsion assembly 808A, 808B comprising a shaft flange assembly 806A, 806B, a spinner, and propeller blades.Agent Ref: 16497.0027-00304

[0079] Fig. 8C illustrates a top-down view, along a spinner 808C, of an exemplary tiltable electric propulsion system 800C in a lift configuration integrated into a boom 812C, consistent with some embodiments of the present disclosure. As shown in Fig. 8C, tiltable electric propulsion system 800C in a lift configuration may comprise the electric engine assembly 802 A, 802B being posited outside of boom 812C and changing its orientation with respect to boom 812C. Heat exchanger 804C may correspond to heat exchanger 804A, 804B of Figs. 8A and 8B. Shaft flange assembly 806C may correspond to shaft flange assembly 806A, 806B of Figs. 8A and 8B. Power connection channels 810C may correspond to power connection channels 810A, 81 OB of Figs. 8A and 8B.

[0080] As discussed herein, a lift electric propulsion system may be configured to provide thrust in one direction and may not provide thrust during all phases of flight. For example, a lift system may provide thrust during take-off, landing, and hover, but may not provide thrust during cruise.

[0081] Fig. 9 is a schematic diagram illustrating an exemplary lift electric propulsion system 900 of a VTOL aircraft, consistent with some embodiments of the present disclosure. In some embodiments, lift electric propulsion system 900 may be mounted or coupled to a boom structure 924 of the aircraft. Lift electric propulsion system 900 may include electric engine assembly 902 aligned along a shaft 940 that is connected to an output shaft 932 that is mechanically coupled to a propeller assembly 920 comprising a hub and tilt propeller blades. In some embodiments, electric engine assembly 902 may include a motor and gearbox assembly 904 aligned along and mechanically coupled to shaft 940. In some embodiments, motor and gearbox assembly 904 may include a stator 906 and a rotor 908. Stator 906 may include multiple stator windings connected to an inverter 916. In such a configuration, stator 906 may incorporate one or more redundancies and backup measures to avoid a single point of failure in the case. For example, stator 906 may include multiple windings such that, if a winding fails, power may continue to be transmitted to stator 906 via remaining windings, allowing electric engine assembly 902 to retain power and continue to generate thrust at propeller assembly 920.

[0082] In some embodiments, motor and gearbox assembly 904 may contain a gearbox 910 aligned along shaft 940 to provide a gear reduction between the torque of shaft 940 from the electric engine assembly and output shaft 932. Torque applied to output shaft 932 may be transferred to propeller assembly 920. In some embodiments, gearbox 910 may include a fluid pump for circulating cooling and / or lubrication fluid. The fluid pump may be an oilAgent Ref: 16497.0027-00304 pump. The oil pump may drive a circulation of oil throughout the motor and gearbox assembly 904 at a speed equivalent to the rotation of output shaft 932 to cool and lubricate the gearbox and electric motor components. Some embodiments of a motor and gearbox assembly 904 may include propeller position sensors 912 that may detect a magnetic field produced by the electric engine assembly to determine a propeller position. Further embodiments may include propeller position sensors 912 that are powered by inverter 916 and send collected data to inverter 916 that may be transferred to a flight control computing system 930 among other flight control data.

[0083] In some embodiments, electric engine assembly 902 may also include an inverter assembly 914 aligned along an axis sharing the axis of shaft 940. Inverter assembly 914 may include inverter 916 and an inverter power supply 934. Inverter power supply 934 may accept low voltage DC power from a low voltage system 928. Inverter power supply 934 may accept low voltage DC power originating from a high voltage power system 926, located outside the electric engine assembly 902, that has been converted to low voltage DC power via a DC-DC converter 936. Inverter 916 may supply high voltage alternating current to stator 906 of the electric engine assembly located within the motor and gearbox assembly 904 via at least one three-phase winding. Inverter assembly 914 may send data to and receive data from flight control computing subsystem 930.

[0084] In some embodiments, motor and gearbox assembly 904 may be located between inverter assembly 914 and propeller assembly 920. Some embodiments may also include a divider plate 938 coupled to motor and gearbox assembly housing 904 and inverter assembly housing 914. Divider plate 938 may create an enclosed environment for an upper portion of motor and gearbox assembly 904 via an end bell assembly, and may create an enclosed environment for a lower portion of inverter assembly 914 via a thermal plate. In some embodiments, divider plate 938 may serve as an integral mounting bracket for supporting a heat exchanger 918. Heat exchanger 918 may include, e.g., a folded fin or other type of heat exchanger. In some embodiments, lift electric propulsion system 900 may circulate oil or other coolant fluid throughout electric engine assembly 902, motor and gearbox assembly 904, or inverter assembly 914 to transfer heat generated from the components to the oil or other coolant liquid. The heated oil or other coolant liquid may be circulated through heat exchanger 918 to transfer the heat to an air flow 922 passing through the fins of the heat exchanger.Agent Ref: 16497.0027-00304

[0085] In some embodiments, a tiltable electric propulsion system and a lift electric propulsion system may have similar components. This may be advantageous with respect to many design considerations present within VTOL aircrafts. For example, from a manufacturability standpoint, different types of electric propulsion systems having similar components may be beneficial in terms of manufacturing efficiency. Further, having similar components may be beneficial in terms of risk management as similar components possess similar points of failure and these points of failure may be well explored and designed around when comparing systems having similar components to systems having different components and configurations.

[0086] While a tiltable electric propulsion system may have additional, and in some embodiments different, components compared to a lift electric propulsion system, it should be appreciated that, in some embodiments, a tiltable electric propulsion system and a lift electric propulsion system may have same configurations of components. For example, in some embodiments, a tiltable and lift electric propulsion system may contain the same components while the lift electric propulsion system may be coupled to a boom, wing, or fuselage of the aircraft such that it may not be able to provide thrust in as many directions as tiltable electric propulsion system.

[0087] Figs. 10A and 10B are illustrations of different views of an exemplary lift electric propulsion system of a VTOL aircraft, consistent with some embodiments of the present disclosure. Figs. 10A and 10B use like numerals and refer to similar elements of lift electric propulsion system 1000 A, 1000B. As such, similar design considerations and configurations may be considered throughout the embodiments.

[0088] Fig. 10A illustrates a side profile of lift electric propulsion system 1000A in a configuration for providing lift and Fig. 10B illustrates a top-down view of lift electric propulsion system 1000 in the configuration for providing lift consistent with embodiments of the present disclosure. Lift electric propulsion system 1000A, 1000B may be integrated into a boom 1010A, 1010B. Lift electric propulsion system 1000A, 1000B may comprise an electric engine assembly 1002A, 1002B housed within a boom 1010A, 1010B of a VTOL aircraft. In some embodiments, a lift configuration may include the electric engine assembly 1002 A, 1002B being posited vertically within the boom 1010A, 1010B. An electric engine assembly 1002A, 1002B may comprise an electric motor assembly, a gearbox assembly, an inverter assembly with power connection channels 1008A (hidden from view in Fig. 10B), and a heat exchanger 1004A, 1004B, as described herein. The electric engine assemblyAgent Ref: 16497.0027-003041002A, 1002B may be mechanically coupled to a propulsion assembly 1006A, 1006B comprising a shaft flange assembly and propeller blades.

[0089] Some embodiments of the disclosed electric engine may generate heat during operation and may comprise a heat management system to ensure components of the electric engine do not fail during operation. In some embodiments, coolant may be used and circulated throughout individual components of the engine, such as an inverter, gearbox, or motor, through some of the components, or through all of the components of the engine to assist with managing the heat present in the engine. Some embodiments may include using air cooling methods to cool the electric engine or using a mixture of coolant and air to manage the heat generated during operation in the electric engine. In some embodiments, the coolant being used may also be the same liquid that is being used as lubricant throughout the inverter, gearbox, or motor. For example, components of the electric engines may be cooled using a liquid or air or using a mixture of air and liquid cooling. As another example, a motor may be cooled using air cooling while the inverter and gearbox are cooled using liquid cooling. It should be understood that a mixture of cooling may be used for any combination of electric engine components or within each component.

[0090] In some embodiments, oil may be used as a lubricant throughout an electric engine and may also be used as coolant fluid to assist in managing the heat generated by the engine during operation. Further to this example, different amounts of oil may be used to act as both lubricant and coolant fluid in the electric engine, such as less than or equal to one quart, 1.5 quarts, two quarts, 2.5 quarts, three quarts, five quarts or any other amount of oil needed to lubricate and cool the electric engine, in combination with or without the assistance of air cooling. In some embodiments, the amount of the oil or liquid to be used in the system in relation to cooling may be determined based on an amount of thermal mass needed to drive heat transfer from the components of the electric propulsion system. As has been disclosed herein, an electric engine may have different primary functionalities such as being used constrained in one orientation (e.g., for lifting and landing), or being used during all stages of flight such as lifting, landing, and in-flight. An engine that is used in all stages of flight may experience various orientations throughout flight and may comprise more lubricant and coolant than the engine only used in one orientation. As such, all the engines on an aircraft may not include the same amount of lubricant and coolant. For example, a lifting and landing engine may use less than one quart of oil while an engine that operates in all stages of flight may use more than one quart of oil. In some embodiments, the amount of oil or liquid forAgent Ref: 16497.0027-00304 cooling may be of an appropriate amount to provide sufficient thermal mass to drive heat transfer from the components of the electric propulsion system no matter the orientation of the electric propulsion system. The embodiments discussed herein are exemplary, nonlimiting, and do not dictate the bounds of the amount of lubricant and coolant that may be used in an electric engine.

[0091] Some embodiments may use oil to lubricate the electric engine and to cool the electric engine. Such embodiments may use additional volumes of oil. In such embodiments, the additional oil may allow for removal of traditional components that may be used to cool such an electric engine. For example, if the electric engine were cooled by another liquid such as glycol, the engine may comprise separate heat exchangers for both the lubricant fluid and the coolant fluid. As such, in embodiments where a single fluid is being used for both lubrication and cooling, such as oil, an increase in oil would be present without a need for multiple heat exchangers, so there may be a decrease in mass, due to using less heat exchangers and potentially other components not being used, of the overall system and a more appealing drag profile may be present. Further, using one substance for the lubrication and cooling of the engine may increase efficiency of the system due to the reduction in mass and the benefits of cooling the engine with a substance rather than relying on air cooling which may have issues traveling throughout the engine.

[0092] Some embodiments of electric engines may include various components for monitoring flammable fluids, and for preventing ingress of flammable materials into certain sections of the electric engine. Some embodiments may include an electric engine possessing a wet zone enclosure that may be defined by a gearbox, motor, and / or heat exchanger. In some embodiments, an electric engine may possess up to 4 liters, or more, of air within the motor-gearbox housing which is in contact with engine oil. Embodiments of a motor-gearbox housing may equalize internal and external pressure using a breather. Embodiments of a breather may include it protruding above nearby design features to prevent inadvertent entry of external fluids. Some embodiments may include a breather that possesses a screen and a circuitous entry path to prevent entry of external debris. Embodiments may include a sight glass being present on both the tilt and lift electric engines in order to check that oil is not overfilled or underfilled during servicing.

[0093] Some embodiments of electric engines may include active protection features in the forward and aft electric engines such as monitoring vibration throughout the engine and internal temperatures such as oil temperature, stator winding set temperature, inverter bulkAgent Ref: 16497.0027-00304 capacitor temperature, power module temperature, control board power module temperature, control board control processor temperature, control board monitor processor temperature, internal hot-spot temperatures, and other various operating conditions throughout the engine as needed. Such monitoring may be accomplished using various sensors positioned throughout the electric propulsion system and aircraft. Embodiments may include vibration limits based on known failure points or resonances of components and overtemperature limits set based on known failure temperatures and operating limits in relation to auto-ignition temperatures of fluids. In some embodiments, the various sensors used to monitor the operating conditions throughout the engine may report operating conditions to the flight control system. Some embodiments may include a threshold operating value that may is to be met before an operating value is sent to, or flagged by, the flight control system. In some embodiments, a flight control system may, in response to detecting an operating condition, act to reduce the amount of power directed to an electric propulsion system. Some embodiments may include reducing the amount of power to an electric propulsion system to reduce mechanical wear or friction sparks from vibrations and / or reducing power in an effort to reduce the temperature of components present within the electric propulsion system. Further, some embodiments may include reducing power to an electric propulsion system where a detected efficiency of an inverter is less than a targeted efficiency. In some embodiments, for example where twelve electric propulsion systems are present within the aircraft, a flight control system may act to reduce power, or terminate power, to a single electric propulsion system while increasing the power directed to the remaining electric propulsion systems, or a subset thereof, to counter reduction in lift produced by the one electric propulsion system. In some embodiments, the flight control system may establish various thresholds of operating conditions to correspond with the reduction or increase of power to an electric propulsion system.

[0094] Some embodiments may include a High Voltage Power System that may have fuses at the high voltage battery terminals which may rapidly and irreversibly disconnect the engine electrical connection to mitigate and avoid overcurrent events. Such overcurrent protection may be activated when the electric engine current draw is greater than the overcurrent operating. As such, in some embodiments, failure conditions which lead to overcurrent may lead to a transient overheating, arc or spark faults. Some embodiments may include a fire threat characterization test ignition source that may be selected to be a more severe ignition source than a short occurring in the electric engine and being opened by theAgent Ref: 16497.0027-00304 engine fuse. In some embodiments, an inverter may detect AC overcurrent and isolate the erroneous phase and / or will continuously monitor input DC voltage, and will apply protective actions to keep voltages under the overvoltage operating limit.

[0095] During takeoff, landing, hover and cruise, motors and related control components of the VTOL aircraft may generate heat. The heat must be dissipated to prevent degradation or damage to the motor, control components and other elements of the VTOL aircraft. For some types of VTOL aircraft, such as electric VTOL (eVTOL) aircraft, thermal control is likewise important to maintain optimal energy efficiency of, e.g., battery-powered components.

[0096] Some elements may generate high thermal loads during certain operational periods. For example, some lift propellers for use during takeoff, landing, and hover, and may be shut off during cruise. Therefore, such lift propellers may generate a high thermal load during takeoff, landing, and hover, and generate little or no heat during cruise.

[0097] Fig. 11 illustrates a circuit schematic of a portion of an exemplary electrical propulsion system 1100 for a VTOL aircraft, consistent with some embodiments of the present disclosure. In some embodiments, electrical propulsion system 1100 may provide a dual three-phase system for motor control. As discussed further below, electrical propulsion system 1100 may be configured to generate torque by applying at least three AC signals with a three-phase timing to a first second inverter (e.g., first inverter circuit 1110) having first three-phase electrical circuitry and / or a second inverter having second three-phase electrical circuitry (e.g., second inverter circuit 1120).

[0098] Electrical propulsion system 1100 may include a first inverter circuit 1110, a second inverter circuit 1120, an electrical motor 1114 configured to drive one or more propellers of an aircraft (e.g., a VTOL aircraft), and a bus capacitor 1170 configured to stabilize a direct current (DC) bus voltage Vbus. First inverter circuit 1110 may be coupled to bus capacitor 1170 and configured to convert the DC bus voltage Vbus on the bus of first inverter circuit 1110 to alternate current (AC) voltages to drive a first set of stator windings of the electrical motor 1114, in response to a first pulse width modulation (PWM) vector. Second inverter circuit 1120 may be configured to convert the DC bus voltage Vbus on the bus of second inverter circuit 1120 to AC voltages to drive a second set of stator windings of the electrical motor 1114, in response to a second PWM vector. In some embodiments, the first PWM vector and the second PWM vector are substantially equal and opposite vectors. For example, the delay between PWM signals corresponding to the first PWM vector and theAgent Ref: 16497.0027-00304 second PWM vector may equal to or less than 0.25%, 0.5 %, 1%, or 2% of the switching cycle period. For example, the delay may be within 50 nanoseconds.

[0099] Accordingly, first inverter circuit 1110 may be configured to output a first set of three-phase AC voltages (e.g., at phases ul, vl, wl). Second inverter circuit 1120 may be configured to output a second set of three-phase AC voltages (e.g., u2, v2, w2). A phase of the first set of three-phase AC voltages and a corresponding phase of the second set of three- phase AC voltages may be two interleaved phases with a phase-shift of substantially 180 degrees (e.g., plus or minus 5 degrees).

[0100] Voltages at phases at ul, vl, and wl may be determined by a supplied voltage (e.g., Vbus) and the opening and closing of the switch immediately above an immediately below each of the points (nodes) indicated for phases ul, vl, and w2. For example, a repeated opening and closing of the switch immediately above the node of phase ul and immediately below the node of phase ul may cause first inverter circuit 1110 to effectively convert a DC provided by Vbus to an AC (e.g., one phase of multiple phases of AC) at the node of phase ul. Similarly, a repeated opening and closing of the switch immediately above the node of phase vl and immediately below the node of phase vl may cause first inverter circuit 1110 to effectively convert a DC provided by Vbus to an AC at the node of phase vl. Likewise, a repeated opening and closing of the switch immediately above the node of phase wl and immediately below the node of phase wl may cause first inverter circuit 1110 to effectively convert a DC provided by Vbus to an AC at the node of phase wl . The same is true of phases v2, u2, and w2 and the respective switches positioned immediately above and below those voltage points (nodes), as depicted.

[0101] In particular, in electrical propulsion system 1100, first and second inverter circuits 1110 and 1120 may be electrically coupled to the internal high voltage DC supply bus and configured to provide corresponding three-phase AC voltages at phases ul, vl, and wl and three-phase AC voltages at phases u2, v2, and w2 to drive a dual three-phase motor 1114. The dual-inverter drive system shown in Fig. 11 may improve the motor performance, and improve the system reliability by increasing the number of phases.

[0102] First and second inverter circuits 1110 and 1120 may be respectively configured to convert the bus voltage Vbus on the high voltage DC supply bus to three-phase AC power to drive the motor 1114. When first and second inverter circuits 1110 and 1120 convert the DC power to the AC power, there may be a voltage difference between the power source and the neutral point of the load, which may be referred to as a common-mode voltage. Common-Agent Ref 16497.0027-00304 mode currents due to common-mode voltages in the inverters may be detrimental to the electrical systems. Specifically, the common-mode voltage may result in faults in motors, premature failure of bearings, glitches in the control equipment, etc. In an effort to reduce common mode noises, filter components may be installed in electrical propulsion system 1100.

[0103] For example, the electrical propulsion system 1100 may include a DC commonmode filter 1130 and AC common-mode chokes 1140 and 1150. DC common-mode filter 1130 may be coupled to bus capacitor 1170 and configured to reduce common mode signals at a DC-side of first inverter circuit 1110 and second inverter circuit 1120. AC commonmode chokes 1140 and 1150 may be coupled to an AC-side of first inverter circuit 1110 or second inverter circuit 1120 to reduce common mode signals.

[0104] For example, DC common-mode filter 1130 may be located between DC power source 1160 and bus capacitor 1170 and formed by a set of DC-side chokes 1132 and a set of DC common-mode filter capacitors 1134, 1136. DC-side chokes 1132 may be configured such that positive and negative lines are wound around the same magnetic core. Thus, DC- side chokes 1132 and DC common-mode filter capacitors 1134, 1136 may be configured to reduce the common mode signals at the DC-side. However, a larger filter may add volume and mass and may incur additional losses.

[0105] In some embodiments, the electrical propulsion system 1100 may achieve a common mode voltage cancelation by applying space vector modulations (SVM) to first and second inverter circuits 1110 and 1120.

[0106] The winding arrangement of motor 1114 applied in electrical propulsion system 1100 may be different in various embodiments. For example, the phase difference in electrical angle between the two sets of three-phase windings may be designed to reduce the harmonic components. In some embodiments, the first set of stator windings and the second set of stator winding of motor 1114 are shifted by 180 degrees (e.g., plus or minus 5 degrees). That is, the motor phasing between independent winding sets may be about 180 degrees out of phase.

[0107] In some embodiments, first inverter circuit 1110 is controlled using a standard center aligned space vector modulation (SVM) while second inverter circuit 1120 is controlled using an inverted center aligned space vector modulation. In such operation mode, the common mode voltage can be canceled through the equal and opposite PWM vectors.Agent Ref: 16497.0027-00304

[0108] In some embodiments, an electrical engine, as described herein, may include safety features for mitigating and protecting against a number of faults or failure modes that may be caused by shorts, such as single-phase shorts and phase-to-phase shorts. In some embodiments, the safety features may include a system including at least one sensor and at least one actuator, which together are configured to detect a short and disconnect an electrical connection once a short is detected.

[0109] In an electric aircraft, a fault in an electrical motor may cause unsafe behavior of a propeller (e.g., windmilling or uncontrollable spin as the aircraft moves through air). The uncontrolled spinning may cause a generation and build-up of current in associated stator windings, which may cause further damage to the electrical engine, create a fire hazard, and reduce flight capability of the aircraft. Accordingly, it may be desired that an electrical engine of an aircraft is configured and designed to withstand such faults.

[0110] Fig. 12 illustrates a circuit schematic of a portion of an exemplary electrical propulsion system 1200 for an aircraft (e.g., a VTOL aircraft), consistent with some embodiments of the present disclosure. In some embodiments, a set of three-phase windings are arranged in a wye configuration with a common node. The set of three-phase windings in the configuration may include at least one actuator 1210 is operatively connected to the common node, and at least one sensor 1220 is operatively connected to the set of three-phase windings (examples of sensor types are described further below, in paragraph

[0111] , for example). Common node may refer to a point at which at least two wires are connected. For example, a common node may include a point at which three wires are all connected to each other or a point at which two out of a set of three wires are connected together.

[0111] In some embodiments, a set of stator windings of an electrical motor may be arranged in a wye configuration (e.g., windings of motor 1114 (Fig. 11)). A wye configuration, also known as a “y configuration” or a “star configuration,” refers to an arrangement in which three windings are connected to each other at one common node. Further, a wye configuration may include a neutral wire (e.g., a wire connected to ground) connected at the common node.

[0112] Additionally or alternatively, in some embodiments, a set of stator windings of an electrical motor may be arranged in a delta configuration. A delta configuration refers to an arrangement in which each of three windings is connected to the other two windings to form a triangle loop with three common nodes.Agent Ref: 16497.0027-00304

[0113] The set of three-phase windings may be arranged in a wye configuration with a common node. The at least one actuator 1210 may be operatively connected to the common node. The at least one sensor 1220 may be operatively connected to the set of three-phase windings. In some embodiments, the at least one sensor 1220 may be configured to measure current, voltage, and / or heat, measurements of which may be provided to at least one processor configured to detect if a fault has occurred based on the measurements (e.g., send measurement data to an FCC or electric engine subsystem 604 (Fig. 6)). In some embodiments, the fault may be a single-phase short. Additionally or alternatively, in some embodiments, the fault may be a phase-to-phase short. In some embodiments, sensors 1220 may include sensor types such as voltage- or current-sensing circuits, components, devices, or elements that are configured to sense a short-circuit based on voltage or current signals within a circuit, such as a single-phase short circuit or a phase-to-phase short circuit (e.g., sensing that a current through a portion of the circuit has exceeded a threshold, which is indicative of abnormal behavior). Additionally or alternatively, a type of sensor may include a heat-sensing circuit, component, device, or element (e.g., sensing that a heat metric at a portion of the circuit has exceeded a threshold).

[0114] In some embodiments, the at least one actuator 1210 may comprise at least one of a pyro fuse system, a pneumatic actuator, or a solenoid. A pyro fuse system may refer to one or more pyro fuses and a pyro fuse driver configured to activate the one or more pyro fuses. A pneumatic actuator may refer to any actuator configured to convert the energy of compressed air or gas into mechanical motion. For example, a pneumatic actuator may utilize compressed air, carbon dioxide, nitrogen, or any other suitable gas. A solenoid may refer to a device configured to convert electrical energy to mechanical energy using an electromagnet formed from a coil of wire.

[0115] In some embodiments, the actuator(s) may be configured to disconnect (e.g., physically and / or electrically) at least one common node, for example to stop or prevent current flowing from or through such a common node. Disconnecting the at least one common node may include disconnecting one stator winding from two other stator windings, disconnecting three stator windings from one another, or disconnecting any number of stator windings from any other number of stator windings. For example, the at least one actuator 1210 may be configured to mechanically break a frangible busbar and open an electrical connection, as described and exemplified in further detail with respect to Figs. 13A-13B.Agent Ref 16497.0027-00304

[0116] In some embodiments, sensor(s) may be configured to transmit a signal indicating a detected short to at least one processor. For example, the at least one processor may include an FCC of an electric aircraft. In another example, the at least one processor may be part of electric engine subsystem 604 (Fig. 6). In some embodiments, after, based on, or in response to receiving a signal from the sensor(s) indicating a fault has occurred, at least one processor may cause the at least one actuator 1210 to disconnect one or more common nodes, for example, to stop or prevent current from flowing from or through the one or more common nodes. In some embodiments, the at least one actuator 1210 may be configured to disconnect the one common node of a set of stator windings in a wye configuration. Additionally or alternatively, the at least one actuator 1210 may be configured to disconnect a subset or all common nodes of a set of stator windings in a delta configuration. For example, based on received signals indicating a fault, at least one processor may determine that two of the three common nodes of a delta configuration should be opened (e.g., broken) to prevent further damage to the electrical engine and / or ensure continued safe operation of an electric vehicle.

[0117] In some embodiments, at least one actuator 1210 may comprise first and second actuators associated with respective first and second common nodes. At least one processor may cause one of the first and second actuators to disconnect one of the first and second sets of stator windings at one of the first and second common nodes, respectively. In some embodiments, an actuator may be present for each common node in a device (e.g., motor), and may be configured to be actuated to disconnect (e.g., break) its respective common node, consistent with disclosed embodiments. In an example of three common nodes, at least one actuator 1210 may be actuated to disconnect a first node, a second node, or a third node, or any combination or permutation thereof. For example, a first actuator may be configured to, upon actuation, disconnect a first node, a second actuator may be configured to, upon actuation, disconnect a second node, and a third actuator may be configured to, upon actuation, disconnect a third node.

[0118] Figs. 13A-13B illustrate exemplary configurations 1300A and 1300B of at least one actuator 1310 in an electrical propulsion system of an aircraft (e.g., a VTOL aircraft), consistent with some embodiments of the present disclosure. In some embodiments of configuration 1300 A, the at least one actuator 1310 may be operatively connected to a set of stator windings housed in a busbar 1330. In some embodiments, busbar 1330 may be designed to be a frangible busbar configured to break at predetermined locations. Frangible may refer to a characteristic of an object that is designed or configured to break intoAgent Ref: 16497.0027-00304 fragments. Example illustration 1300B shows after at least one sensor has detected a fault and a processor has sent a signal to activate the at least one actuator 1310 to break busbar 1330. After busbar 1330 is broken, the set of stator windings are disconnected at one or more common nodes. For example, when the at least one actuator 1310 breaks busbar 1330, the at least one actuator 1310 may also break wiring housed by busbar 1330, which may connect stator windings.

[0119] By way of nonlimiting example, the at least one actuator 1310 may comprise or be connected to a pyro fuse system (e.g., one or more pyro fuses and a pyro fuse driver for activating the one or more pyro fuses). The pyro fuse system may be configured blow one or more pyro fuses to cause at least one actuator to disconnect a first set of windings or a second set of windings. The at least one processor may be configured to activate (e.g., transmit a command to) the pyro fuse system (e.g., based on a detected fault), to cause the pyro fuse system to blow the one or more pyro fuses, thereby causing the at least one actuator 1310 to disconnect (e.g., break an electrical connection of) the set of stator windings. Disconnecting a set of stator windings from another set of stator windings may include disconnecting at least one common node as described throughout this disclosure, for example, in paragraph

[0115] above.

[0120] For example, prior to the one or more pyro fuses being blown, the one or more pyro fuses may maintain an electrical connection that causes the at least one actuator 1310 to remain in a particular position. Then, the at least one processor may transmit a command to a pyro fuse driver to cause the pyro fuse driver to blow the one or more pyro fuses, which may sever the electrical connection, thereby causing the at least one actuator 1310 release from its position and move to another position, where the repositioning breaks the electrical connection of the set of stator windings.

[0121] By way of non-limiting example, an electrical motor may include two sets of stator windings, each set having a corresponding set of common nodes, actuators, and sensors. In some embodiments, after one set of stator windings is disconnected, an electrical motor may continue to function via the other set of stator windings. Further, the electrical motor may function at a reduced capacity (e.g., 50%, 60%, 66%, 70%, etc.) after one set of stator windings is disconnected.

[0122] In some embodiments, the devices in Figs. 13A and 13B can be used as fusebased disconnects. Fuse-based embodiments with frangible components can be advantageous for quickly addressing electrical fire hazards in an aircraft (e.g., when high heat is generatedAgent Ref: 16497.0027-00304 due to uncontrolled spin of a propeller). However, the subsequent permanent loss of propeller function during flight may be undesirable in some situations. Therefore, some embodiments described herein provide safety features with less destructive consequences.

[0123] Fig. 14 illustrates a circuit schematic of a portion of an exemplary electrical propulsion system 1400 for an aircraft (e.g., a VTOL aircraft), consistent with some embodiments of the present disclosure. Electrical propulsion system 1400 may provide a different view of electrical propulsion system 1100 (Fig. 11) (e.g., new details shown, some details hidden) to better aid in description of different failure scenarios.

[0124] In some embodiments, electrical propulsion system 1400 may include a first inverter circuit 1410, a second inverter circuit 1420, and a motor 1414. Motor 1414 may include first windings 1402 and second windings 1404. First inverter circuit 1410 may include first transistor 1406-1, second transistor 1406-2, third transistor 1406-3, fourth transistor 1406-4, fifth transistor 1406-5, and sixth transistor 1406-6. First transistor 1406-1 through sixth transistor 1406-6 may form a first three-phase circuitry responsible for setting the timing of phases ul, vl, and wl. Second inverter circuit 1420 may include seventh transistor 1406-7, eighth transistor 1406-8, ninth transistor 1406-9, tenth transistor 1406-10, eleventh transistor 1406-11, and twelfth transistor 1406-12. Seventh transistor 1406-7 through twelfth transistor 1406-12 may form a second three-phase circuitry responsible for setting the timing of phases ul, vl, and wl. Any suitable transistor type may be used, for example, a field effect transistors (FET), a metal-oxide-semiconductor field effect transistor (MOSFET), or the like.

[0125] First through sixth transistors 1406-1 through 1406-6 may be used to provide a first set of three-phase AC power signals (e.g., phases ul, vl, and wl) to first windings 1402. Seventh through twelfth transistors 1406-7 through 1406-12 may be used to provide a second set of three-phase AC power signals (e.g., phases u2, v2, and w2) to second windings 1404. The term “phase” may refer to a timing of a periodic waveform (e.g., sinusoidal, step function, or the like). For example, the three-phase configuration used in electric propulsion system 1400 may use an identically shaped cosine signal (or nearly identically shaped) for different windings of motor 1414 (e.g., cosine signals of the same frequency and amplitude), but having staggered timings. The staggered timings are denoted as the phases ul, vl, and wl. The timings, or phases, can be controlled using switches (e.g., transistors) in first and second inverter circuits 1410 and 1420.Agent Ref: 16497.0027-00304

[0126] By providing three-phase power to the windings, motor 1414 may generate a torque to rotate a propeller. Inversely, uncontrolled spinning of electrical propulsion system 1400 in the presence of airflow may generate undesirably high amounts of current through the circuitry of electrical propulsion system 1400. High electrical current capable of damaging circuits may be referred to as “overcurrent.”

[0127] In some embodiments, a malfunction of one or more phases of the inverters may occur. In some embodiments, first inverter circuit 1410 may be referred to as malfunctioning inverter 1410 and second inverter 1420 may be referred to as functional inverter 1420. An example of a single-transistor short 1408 (e.g., a single-phase short failure) is shown (e.g., a fault at phase wl). Single-transistor short 1408 may be due to a burnout or other malfunction at sixth transistor 1406-6 (e.g., a single-phase short failure), which may create a constant path of extremely low resistance for current (e.g., an electrical short). A malfunction at a transistor may include the transistor gate being stuck in a closed position (e.g., due to a short), causing loss of control of the switching functionality of the transistor, which can cause additional problems. As a result, the malfunction may cause the propeller at motor 1414 to spin uncontrollably (e.g., begin windmilling), as the phases are not all working properly to convert direct current (DC) to alternating current (AC) for normal motor function. The windmilling may send a high amount of current through first inverter 1410 due to the path of extremely low resistance at single-transistor 1408, thereby causing electrical components to heat excessively, increasing the risk of fire. An example of a phase-to-phase short 1412 is also illustrated, which may be caused by a problem on a circuit board of first inverter 1410 (e.g., a phase-to-phase short failure). Here too, windmilling may cause high current to flow between the phases, thereby increasing the risk of engine fire or other catastrophic consequences. Some approaches to solve uncontrolled windmilling may use a mechanical brake to control the windmilling behavior (e.g., drum or caliper brakes). However, these added hardware undesirably increase weight of the aircraft, which may further limit its already limited flight range. Moreover, simply disconnecting a power source, such as a battery, from a windmilling device, will have little or no effect on slowing down its rotation, since it will not impact the windmilling source. It is desirable to have a windmilling solution that adds little to no mass to the aircraft (e.g., an electrical solution).

[0128] In some embodiments, different types of electrical faults result in different phenomena. For example, single-transistor short 1408 may pose a very high fire risk because the electrical response may include a very high current amplitude that scales withAgent Ref: 16497.0027-00304 windmilling rotations per minute (RPM) and a pulsating bi-directional torque (on average does little to limit the windmilling motion). A similar issue is observed with phase-to-phase short 1412. In some embodiments, other types of shorts may provide compensatory behavior that oppose windmilling, such as the three-phase short described with reference to Fig. 15.

[0129] Fig. 15 illustrates a graph chart 1500 of generated torque and electrical current when a three-phase short is activated in an inverter of an exemplary electrical propulsion system for an aircraft (e.g., a VTOL aircraft), consistent with some embodiments of the present disclosure, such as method 1700, described below. In some embodiments, the three phase short may be activated (e.g., at operations 1708, as discussed below) in first inverter 1410 in response to detection of phase-to-phase short 1412 (Fig. 14). The activation of the three-phase short can limit the windmilling-generated current, as well as generate a breaking torque 1504 that opposes the windmilling motion, thereby opposing further increase of windmilling-generated current. Graph chart 1500 is a 2-axis chart, where the left vertical axis represents breaking torque when the three-phase short is active (negative torque denotes opposition to windmilling motion), the right vertical axis represents electrical current flowing through first inverter 1410 (Fig. 14) when the three-phase short is active, and the horizontal axis represents the RPM of the windmilling propeller.

[0130] In some embodiments, at least one processor may determine a frequency at which to activate or apply a three-phase short that will prevent a rotor of an electric propulsion system from performing a full rotation or from rotating beyond a threshold tolerance amount (e.g., + / - 5 degrees of rotation, + / - 10 degrees of rotation, + / - 45 degrees of rotation), thereby countering (e.g., at least partially offsetting) a windmilling effect. The at least one processor may cause the three-phase short to be activated (and deactivated, where activation and deactivation constitutes “toggling”) at this frequency.

[0131] In some embodiments, the frequency at which to activate or apply a three-phase short may be determined (e.g., by at least one processor) to prevent an electrical parameter (e.g., voltage, current, heat) in the system (e.g., inverter, connected components) from exceeding a predetermined safety threshold.

[0132] In some embodiments, a motor operating region 1502 denotes the nominal safe operating range of the electrical propulsion system. Three plots are illustrated: Three-phase- short breaking torque 1504, three-phase-short current amplitude 1506, and single-transistorshort current amplitude 1508. When the three-phase short is activated in first inverter 1410 (Fig. 14), such as according to operation 1708 described further below, the resulting electricalAgent Ref: 16497.0027-00304 current from windmilling generates a breaking torque (three-phase-short breaking torque 1504) that slows the windmilling motion. Furthermore, the three-phase short is activated, the windmilling current goes from unlimited scaling (single-transistor-short current amplitude 1508) to a plateauing current (three-phase-short current amplitude 1506). The three-phase short can help to maintain the electrical current in first inverter 1410 within, or close to, operating region 1502 during windmilling in the event of an electrical fault, such as singletransistor short 1408 and phase-to-phase short 1412 (Fig. 14).

[0133] In some embodiments, an electrical fault in the electrical propulsion system of the aircraft may force the aircraft to quickly make an emergency landing, thereby severely limiting its flight range. The three-phase short mitigation method (e.g., method 1700) may extend the flight range of the affected aircraft by limiting the windmilling-generated current, thereby postponing a fire event.

[0134] The three-phase short mitigation method is a less destructive solution compared to the actuator-type frangible disconnect techniques described in reference to the actuator configurations of Figs. 13A and 13B. Both techniques may be used together. For example, after, in response to, or based on detecting a fault, at least one processor may activate a three- phase short (e.g., as a first line of defense against an electrical fault that is less destructive).

[0135] Additionally, after, in response to, or based on detecting a fault, at least one processor may activate an actuator (e.g., actuator 1310) to disconnect one or more stator windings (e.g., as a last line of defense that is more destructive). For example, as a separate operation not depicted in Fig. 17, the at least one processor may be configured to activate (e.g., transmit a command to) a pyro fuse system (e.g., based on a detected fault), to cause the pyro fuse system to blow the one or more pyro fuses, thereby causing the at least one actuator to break an electrical connection of the set of stator windings, as discussed further above with respect to actuator 1210 and actuator 1310.

[0136] When an operation is executed after detecting an electrical fault (e.g., at first inverter 1410), the operation may be executed based on or in response to the detection of the electrical fault.

[0137] In some embodiments, the at least one processor may be configured to first activate a three-phase short (e.g., operation 1708) or other electrical -based mitigation method (e.g., techniques described with respect to operations 1710-1, 1710-2, 1710-3, and / or 1710- 4), which is not configured to mechanically break any component, prior to activating a mechanical -based breaking method. For example, the at least one processor may beAgent Ref 16497.0027-00304 configured to activate an electrical-based mitigation method, determine whether a performance metric has been achieved, and if the performance metric has not been achieved, activate a mechanical-based breaking method. A performance metric may include a rotor or propeller reaching an RPM below a threshold, a measured voltage being below a threshold (e.g., indicating sufficiently low risk of overheating or fire), or a measured current (e.g., into an inverter, out of an inverter, within an inverter) being below a threshold (e.g., indicating sufficiently low risk of overheating or fire).

[0138] In addition to the three-phase short in first inverter 1410, second inverter 1420 is still a working inverter that may be used to apply additional breaking torque to reduce the windmilling motion of the malfunctioning electrical propulsion system (Fig. 14), the use of which will be described with reference to Fig. 16.

[0139] Fig. 16 illustrates a torque graph chart 1600 and a current graph chart 1602 that show breaking torque and electrical current of an exemplary electrical propulsion system at different time frames, consistent with some embodiments of the present disclosure. In some embodiments, the functions described with reference to Fig. 16 are in the context of elements of Fig. 14 (e.g., first inverter 1410 and second inverter 1420).

[0140] In some embodiments, the vertical axis of current graph chart 1602 represents an electrical current provided each of first inverter 1410 and second inverter 1420, which generates the corresponding torque shown in graph chart 1600. The vertical axis of torque graph chart 1600 represents a torque applied to the propeller (e.g., instantaneous torque) from each of first inverter 1410 and second inverter 1420. The horizontal axis of both charts represents time. Both charts are aligned in time such that event periods (To, Ti, T2, and T3) are aligned across the charts (denoted via vertical dotted lines).

[0141] Normal operation period To may be a time period in which the electrical propulsion system is operating normally. Referring to current graph chart 1602, first inverter 1410 and second inverter 1420 may apply a consistent current to first windings 1402 and second windings 1404 during normal operation period To. The corresponding torque is shown in torque graph chart 1600, which shows consistent torques generated via both inverters. A positive torque may correspond to a rotational bias to generate thrust, whereas a negative torque may correspond to a torque in the opposite direction (e.g., a breaking torque).

[0142] An electrical fault may occur in first inverter 1410 (e.g., single-transistor short 1408, phase-to-phase short 1412, or the like), which marks a transition from normal operation period To to fault period Ti. During fault period Ti, a control system of the aircraft mayAgent Ref: 16497.0027-00304 command the electric propulsion system to operate in a temporary safe state in which the electric propulsion system or at least one inverter thereof (e.g., inverters 1410 and 1420) is temporarily shut down. The successful shut down of the propulsion system marks a transition from fault period Ti to detection period T2 (e.g., when the functional second inverter 1420 generates no torque or current).

[0143] During detection period T2, sensing and detection operations may be executed to pinpoint the location of the electrical fault. For example, at least one sensor 1220 may sense whether the fault is at first inverter 1410 or second inverter 1420, whether the is a singletransistor short or a phase-to-phase short, which phases are affected, or the like and send the sensing information to an FCC or electric engine subsystem 604 (Fig. 6)). Alternatively, at least one sensor 1220 may measure circuitry information such as a voltage, current, or temperature, and may transmit the measured information to an FCC or electric engine subsystem 604, which may determine whether the fault is at first inverter 1410 or second inverter 1420, whether the is a single-transistor short or a phase-to-phase short, which phases are affected, or the like. It is noted that even though the electrical propulsion system has been shut down, the electrical fault under the effects of windmilling can still generate high amounts of current as shown in fault period Ti and detection period T2 (e.g., as depicted by the line for the 1st inverter). In some embodiments, after, in response to, or based on the determination of the location of the electrical fault, new corrective operations may be implemented, marking a transition from detection period T2 to active protection period T3.

[0144] During active protection period T3, a three-phase short (e.g., the three-phase short described with reference to Fig. 15 and / or operation 1708) may be activated at the malfunctioning first inverter 1410. As shown in torque graph chart 1600 and a current graph chart 1602, the maximum current from first inverter 1410 is reduced and a breaking torque is generated during active protection period T3, thereby reducing the electrical heat and opposing the uncontrolled windmilling. Furthermore, the functional inverter (e.g., second inverter 1420) may be activated for generating additional breaking torque during active protection period T3. As explained below, there are a number of ways to control second inverter 1420 in response to an electrical fault in first inverter 1410, or vice versa.

[0145] Fig. 17 illustrates a flowchart of an exemplary method 1700 for controlling a functional inverter in a malfunctioning electrical propulsion system of an aircraft (e.g., a VTOL aircraft), consistent with some embodiments of the present disclosure. In some embodiments, the functions described with reference to Fig. 17 are in the context of elementsAgent Ref: 16497.0027-00304 of Figs. 14 and 16 (e.g., first inverter 1410 and second inverter 1420, periods To, Ti, T2, and T3, or the like).

[0146] In general, it may be understood that any / all operations of the exemplary method 1700 may be performed or executed by at least one hardware processor (e.g., FCC, electric engine subsystem 604, or the like), such as according to one or more instructions stored on a computer-readable medium (e.g., non-transitory computer-readable medium).

[0147] In some embodiments, there are a number of different ways to use the functioning second inverter 1420 in the event of a malfunction at first inverter 1410. Example options, 1 through 4, are illustrated in Fig. 17. Common operations include operations share across the different options are operations 1702, 1704, 1706, 1708, and 1712. Variants of operation 1710 are denoted via the option number indicator (e.g., 1710-n, where n is the option number).

[0148] In some embodiments, multiple option sequences (e.g., at least two of Options 1, 2, 3, and 4) may be performed (e.g., executed, such as by at least one processor), either in parallel or sequentially. Alternatively, the shared operations 1702, 1704, 1706, and 1708 may be performed, and then any combination of operations 1710-1, 1710-2, 1710-3, and 1710-4 may be performed, either in parallel or sequentially. For example, after operation 1708 is performed, operations 1710-1 and 1710-2 may be performed. As another example, after operation 1708 is performed, operations 1710-1 and 1710-3 may be performed. As another example, after operation 1708 is performed, operations 1710-1 and 1710-4 may be performed.

[0149] At operation 1702, an aircraft may operate under normal flight conditions, which corresponds to normal operation period To.

[0150] Marking a transition into fault period Ti, the aircraft (e.g., at least one processor of the aircraft) may execute operation 1704 to transition an electrical propulsion system into a safe state after a malfunction (e.g., electrical fault) has occurred and / or been detected (e.g., based on determining, such as by at least one processor, that one or more measurements exceed at least one threshold) in the electrical propulsion system. For example, the at least one processor may detect an electrical fault in the form of a single-phase short failure or a phase-to-phase short failure, such as those discussed above with respect to Fig. 14. Operation 1704 may include shutting down the malfunctioning electrical propulsion system.

[0151] Transitioning into detection period T2, the aircraft (e.g., at least one processor of the aircraft) may execute operation 1706, which may include running diagnostics to locate theAgent Ref: 16497.0027-00304 source of the malfunction (e.g., whether it is at first inverter 1410 or second inverter 1420, whether it is a single-transistor short or a phase-to-phase short, which phases are affected, or the like).

[0152] At active protection period T3, the aircraft may execute (e.g., at least one processor of the aircraft), after, based on, or in response to detecting the malfunction (e.g., electrical fault) operations 1708, one or more of operations 1710-1, 1710-2, 1710-3, and 1710-4, and 1712. Operation 1708 may include activating a three-phase short at the malfunctioning inverter. Activating three-phase short may include creating an electrical short across the low-side transistors (e.g., transistors 1406-4, 1406-5, and 1406-6 (Fig. 14)) or high-side transistors (e.g., transistors 1406-1, 1406-2, and 1406-3 (Fig. 14)). The term “low- side” may be used to describe a transistor or other circuit component that is connected to a low voltage reference of a power source, or ground. Creating an electrical short across components (e.g., transistors) may include causing the respective component to have little to no electrical resistance. For example, for a transistor, creating an electrical short may be considered placing the transistor in an “on” or “closed” (with respect to its gate) switch state. The term “high-side” may be used to describe a transistor or other circuit component that is connected to a high voltage line of a power source. As explained with reference to Figs. 14 and 15, the three-phase short may help in limiting the overcurrent from windmilling, as well as provide a breaking torque to oppose windmilling motion of the malfunctioning electrical propulsion system.

[0153] It is appreciated that in some embodiments, there may be different numbers of high-side and / or low-side components, aside from the three high-side transistors and three low-side transistors depicted.

[0154] In some embodiments, the at least one the three-phase short to be activated (and deactivated), or performing any of operations 1710 at a frequency that will prevent a rotor and / or propeller of an electric propulsion system from performing a full rotation or from rotating beyond a threshold tolerance amount (e.g., + / - 5 degrees of rotation, + / - 10 degrees of rotation, + / - 45 degrees of rotation), thereby countering (e.g., at least partially offsetting) a windmilling effect. The frequency may be determined by at least one processor (e.g., at least one processor carrying out method 1700), consistent with disclosed embodiments.

[0155] In some embodiments, the frequency at which to activate or apply a three-phase short may be determined (e.g., by at least one processor) to prevent an electrical parameterAgent Ref: 16497.0027-00304(e.g., voltage, current, heat) in the system (e.g., inverter, connected components) from exceeding a predetermined safety threshold.

[0156] Any or all of operations 1710-1, 1710-2, 1710-3, and 1710-4 may also be performed at the same frequency, or a different frequency determined in the same manner.

[0157] The frequency at which to activate or apply a three-phase short (e.g., operation 1708) and / or any or all of operations 1710-1, 1710-2, 1710-3, and 1710-4 may be updated (e.g., by at least one processor) repeatedly (e.g., continually), such as while an associated aircraft is in flight, based on an airspeed of the aircraft a force (e.g., torque from windmilling) experienced by an electric propulsion system, and / or a feedback loop. For example, if an airspeed of the aircraft slows, a windmilling-based torque induced on the propellers may decrease (which may be detected at least indirectly through a feedback loop), which at least one processor may use to determine that the frequency should be decreased.

[0158] Operation 1710-1 may include activating a three-phase short at the functional inverter (e.g., second inverter 1420) to provide additional breaking torque to oppose windmilling motion of the malfunctioning electrical propulsion system. Activating three- phase short may include creating an electrical short across the low-side transistors (e.g., transistors 1406-10, 1406-11, and 1406-12 (Fig. 14)) or high-side transistors (e.g., transistors 1406-7, 1406-8, and 1406-9 (Fig. 14)).

[0159] Operation 1710-2 may include applying an opposing or inverted signal to the functional inverter. For example, the polarity of the applied voltage may be reversed during an electrical fault scenario. Additionally or alternatively, the switching timing for one or more switches may be altered so as to shift a produced alternating current by a phase shift of 180 degrees.

[0160] Operation 1710-3 may include applying the normal voltage signal to second windings 1404 with the phases reversed (e.g., reversing the three-phase timing of the three AC signals by flipping the ordered timing of phases u2, v2, w2 to w2, v2, u2), thereby generating a breaking torque to oppose windmilling motion of the malfunctioning electrical propulsion system. In some embodiments, operation 1710-3 may include rearranging the timing of the phases in different orders, such as by changing u2, v2, w2 to v2, w2, u2, changing u2, v2, w2 to v2, u2, w2, changing u2, v2, w2 to w2, u2, v2, etc. For example, the three AC signals corresponding to phases u2, v2, w2 may be similar oscillating (e.g., sinusoidal) waveforms that are shifted from each other by 120 degrees, and may be shifted by 0, 120, or 240 degrees to result in a rearranging of their timings.Agent Ref: 16497.0027-00304

[0161] Operation 1710-4 may include alternating between operations 1710-2 and 1710-3 in bursts, thereby generating a breaking torque to oppose windmilling motion of the malfunctioning electrical propulsion system. Operation 1710-4 is one example of how a hybrid of two options may be used together. In another example, a hybrid of options 1 and 2 may also be used together (e.g., alternating between activating a three-phase short at second inverter 1420 and applying a stoppage voltage via (e.g., using) second inverter 1420 to generate a torque that counters (e.g., offsets at least partially, offsets fully, or offsets to at least a threshold) windmilling of the electrical propulsion system). Other permutations and combinations of the described options are within the scope of embodiments described herein. Terms such as “stoppage voltage,” “breaking voltage,” “deceleration voltage,” or the like may be used to describe a voltage applied at an inverter for generating a torque that counters a windmilling effect.

[0162] In some embodiments, one or more of operations 1710-1, 1710-2, 1710-3, and 1710-4 may be performed repeatedly, or “toggled,” such as by performing one operation and then negating that performance. For example, at least one processor may activate a three- phase short at the functional inverter (e.g., operation 1710-1) and then subsequently deactivate the three-phase short. As another example, at least one processor may apply a breaking torque from the functional inverter (e.g., operation 1710-2, 1710-03, and / or 1710-4) and then cease to apply the breaking torque. Toggling of the operations (e.g., activation followed by deactivation, applying following by ceasing to apply) may occur in any number of repetitions, and may be performed at a frequency determined (e.g., by the at least one processor, which may use a feedback loop) to bring a propeller (e.g., operably connected to the faulty inverter) to a stop.

[0163] A “stop” of a propeller may not necessarily be a full stop (e.g., absolutely zero rotational movement), but may include certain limited amount of rotational movement, where the propeller is slowed or held. For example, the propeller may be prevented from rotationally moving outside of a permissible tolerance amount (e.g., + / - five degrees of rotation, + / - 45 degrees of rotation, full rotations permitted but at no greater than 60 revolutions per minute, etc.), consistent with disclosed embodiments. This may thereby counter (e.g., at least partially offsetting) a windmilling effect.

[0164] Method 1700 also includes operation 1712, which may be performed after, based one, or in response to performing operations 1708, 1710-1, 1710-2, 1710-3, and / or 1710-4. In some embodiments, operation 1712 includes decelerating the electrical propulsion system toAgent Ref: 16497.0027-00304 a stop. Even if a full stop is not achieved, the electrical propulsion system may be decelerated such that an electrical current in the electrical propulsion system is within safety boundaries (e.g., within operating region 1502 (Fig. 15)). For example, the electrical propulsion system may be prevented from completing a full single rotation, such as by causing a rotor of the electrical propulsion system to be “held” such that it does not rotate beyond a permissible tolerance amount, consistent with disclosed embodiments. In some embodiments, operation 1712 may result as a consequence of one or more of operations 1710-1, 1710-2, 1710-3, and 1710-4.

[0165] In some embodiments, when the rotation speed of the electrical propulsion system is within safe limits, the inverters may be disabled (e.g., to minimize losses) and re-enabled to resist windmilling when rotation speed increases again. For example, at least one processor may monitor a rotation speed of the electrical propulsion system to determine if it is within a safety limit, and based on determining that it is within a safety limit, the at least one processor may disable the associated inverter. Then, based on monitoring, the at least one processor may determine if the rotation speed is within a safety limit, and based on determining that it is not within a safety limit, the at least one processor may enable the associated inverter.

[0166] As discussed above, for example in paragraphs

[0115] -

[0122] ,

[0134] , and

[0135] , after, in response to, or based on detecting a fault, at least one processor may activate an actuator (e.g., actuator 1310) to disconnect one or more stator windings (e.g., as a last line of defense that is more destructive). This may be considered a separate operation from those depicted in and described with reference to Fig. 17, and may be performed in addition to, or instead of, one or more of operations 1708, 1710-1, 1710-2, 1710-3, 1710-4, and / or 1712. It is appreciated that disconnecting one or more stator windings may sever an electrical connection that connects a power source (e.g., power generated by windmilling) to an electrical short, thereby preventing current from flowing through the shorted circuitry, reducing overheating risks.

[0167] The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein.Agent Ref: 16497.0027-00304

[0168] The features and advantages of the disclosure are apparent from the detailed specification, and thus, it is intended that the appended claims cover all systems and methods falling within the true spirit and scope of the disclosure. As used herein, the indefinite articles “a” and “an” mean “one or more.” Similarly, the use of a plural term does not necessarily denote a plurality unless it is unambiguous in the given context. Words such as “and” or “or” mean “and / or” unless specifically directed otherwise. As used herein, unless specifically stated otherwise, being “based on” may include being dependent on, being interdependent with, being associated with, being defined at least in part by, being derived from, being influenced by, or being responsive to. As used herein, “related to” may include being inclusive of, being expressed by, being indicated by, or being based on. Further, since numerous modifications and variations will readily occur from studying the present disclosure, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

[0169] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the implementations disclosed herein. It is intended that the architectures and circuit arrangements shown in figures are only for illustrative purposes and are not intended to be limited to the specific arrangements and circuit arrangements as described and shown in the figures. It is also intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein. It is also intended that the sequence of steps shown in figures is only for illustrative purposes and is not intended to be limited to any particular sequence of steps. As such, those skilled in the art can appreciate that these steps can be performed in a different order while implementing the same method.

[0170] Some embodiments may further be described using the following clauses: 1. A computer-implemented method of mitigating electrical faults, comprising: detecting, using at least one hardware processor, an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter;Agent Ref: 16497.0027-00304 activating, using the at least one hardware processor, a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generating a torque that counters windmilling of the electrical propulsion system by: activating, using at least one hardware processor, a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying, using at least one hardware processor, a stoppage voltage via the second inverter.2. The computer-implemented method of clause 1, further comprising, after detecting the electrical fault at the first inverter, activating, using the at least one hardware processor, at least one actuator of the electrical propulsion system to disconnect a set of stator windings associated with the first inverter.3. The computer-implemented method of clause 2, wherein activating the at least one actuator comprises causing a pyro fuse system to blow one or more pyro fuses, thereby causing the at least one actuator to disconnect the set of stator windings.4. The computer-implemented method of any one of clauses 2 or 3, wherein activating the at least one actuator causes the at least one actuator to disconnect at least one of a first common node of the set of stator windings; a second common node of the set of stator windings; a third common node of the set of stator windings; the first common node and the second common node; the second common node and the third common node; the first common node and the third common node; or the first common node, the second common node, and the third common node.5. The computer-implemented method of clause 4, wherein the first common node, second common node, or third common node is disconnected to stop current flowing through that common node.6. The computer-implemented method of any one of clauses 1 to 5, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.7. A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor to cause the at least one processor to perform operations for mitigating electrical faults, the operations comprising:Agent Ref: 16497.0027-00304 detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generating a torque that counters windmilling of the electrical propulsion system by: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.8. The non-transitory computer-readable medium of clause 7, wherein the operations further comprise, after detecting the electrical fault at the first inverter, activating at least one actuator of the electrical propulsion system to disconnect a set of stator windings associated with the first inverter.9. The non-transitory computer-readable medium of clause 8, wherein activating the at least one actuator comprises causing a pyro fuse system to blow one or more pyro fuses, thereby causing the at least one actuator to disconnect the set of stator windings.10. The non-transitory computer-readable medium of any one of clauses 8 or 9, wherein activating the at least one actuator causes the at least one actuator to disconnect: a first common node of the set of stator windings; a second common node of the set of stator windings; a third common node of the set of stator windings; the first common node and the second common node; the second common node and the third common node; the first common node and the third common node; or the first common node, the second common node, and the third common node.11. The non-transitory computer-readable medium of any one of clauses 7 to 10, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.12. A computer-implemented method of mitigating electrical faults, comprising: detecting, using at least one hardware processor, an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter, wherein the electrical propulsion system is configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter having second three-phase electrical circuitry;Agent Ref: 16497.0027-00304 activating, using the at least one hardware processor, a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter reversing, using at least one hardware processor, the three-phase timing of the three AC signals to generate a torque that counters windmilling of the electrical propulsion system.13. The computer-implemented method of clause 12, wherein: the three-phase timing uses a first phase at a first phase circuit of the second three- phase electrical circuitry, a second phase at a second phase circuit of the second three-phase electrical circuitry, and a third phase at a third phase circuit of the second three-phase electrical circuitry; and the reversing of the three-phase timing comprises configuring the first phase circuit to use the third phase and configuring the third phase circuit to use the first phase to generate the torque that counters windmilling of the electrical propulsion system.14. The computer-implemented method of clause 13, further comprising, based on detecting the electrical fault at the first inverter: applying, using the at least one hardware processor, a stoppage voltage via the second inverter to generate torque that counters the windmilling of the electrical propulsion system; and alternating, using the at least one hardware processor, between the applying of the stoppage voltage to the second inverter and the reversing of the three-phase timing.15. The computer-implemented method of any one of clauses 12 to 14, further comprising, after detecting the electrical fault at the first inverter, blowing, using at least one hardware processor, one or more pyro fuses to cause at least one actuator to disconnect a set of stator windings associated with the first inverter.16. The computer-implemented method of any one of clauses 12 to 15, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.17. A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor to cause the at least one processor to perform operations for mitigating electrical faults, the operations comprising: detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter, wherein the electrical propulsion system is configuredAgent Ref: 16497.0027-00304 to generate torque by applying at least three alternating current (AC) signals with a three- phase timing to the second inverter having second three-phase electrical circuitry; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter reversing the three-phase timing of the three AC signals to generate a torque that counters windmilling of the electrical propulsion system.18. The non-transitory computer-readable medium of clause 17, wherein: the three-phase timing uses a first phase at a first phase circuit of the second three- phase electrical circuitry, a second phase at a second phase circuit of the second three-phase electrical circuitry, and a third phase at a third phase circuit of the second three-phase electrical circuitry; and the reversing of the three-phase timing comprises configuring the first phase circuit to use the third phase and the third phase circuit to use the first phase to generate the torque that counters windmilling of the electrical propulsion system.19. The non-transitory computer-readable medium of clause 18, wherein the operations further comprise, based on detecting the electrical fault at the first inverter: applying a stoppage voltage via the second inverter to generate torque that counters the windmilling of the electrical propulsion system; and alternating between the applying of the stoppage voltage to the second inverter and the reversing of the three-phase timing.20. The non-transitory computer-readable medium of any one of clauses 17 to 19, wherein the operations further comprise, after detecting the electrical fault at the first inverter, blowing one or more pyro fuses to cause at least one actuator to disconnect a set of stator windings associated with the first inverter.21. The non-transitory computer-readable medium of any one of clauses 17 to 20, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.22. An electric aerial vehicle comprising: an electrical propulsion system comprising: a first inverter comprising a first three-phase electrical circuitry; a second inverter comprising a second three-phase electrical circuitry, wherein the electrical propulsion system is configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter; a sensor configured to sense an electrical fault; andAgent Ref: 16497.0027-00304 one or more processors configured to perform the method of any of clauses 1- 6.23. The electric aerial vehicle of clause 22, wherein the electrical propulsion system further comprises a pyro fuse system configured blow one or more pyro fuses to cause at least one actuator to disconnect a first set of windings or a second set of windings.24. A propulsion system for an electric vehicle, comprising: an electrical motor configured to drive the electric vehicle and comprising a set of stator windings, wherein the set of stator windings comprises a common node; an actuator connected to the common node of the set of stator windings; a sensor coupled to the set of stator windings; and a processor configured to: receive, from the sensor, one or more signals indicating a fault has occurred; and after receiving the one or more signals indicating a fault has occurred, cause the actuator to disconnect the set of stator windings at the common node.25. An electrical propulsion system comprising: a first inverter comprising a first three-phase electrical circuitry; a second inverter comprising a second three-phase electrical circuitry, wherein the electrical propulsion system is configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter; a sensor configured to sense an electrical fault; and one or more processors configured to perform the method of any of clauses 1-6.26. A computer-readable medium storing a set of instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any one of clauses 1 to 6 or 12 to 16.27 A system for mitigating electrical faults, the system comprising: at least one processor; and memory storing a set of instructions which, when executed by the at least one processor, cause the system to perform the method of any one of clauses 1 to 6.28. The system of clause 27, comprising: a sensor configured to sense the electrical fault; and the electrical propulsion system comprising the first inverter and the second inverter, the first inventor comprising the first three-phase electrical circuitry and the second inverterAgent Ref: 16497.0027-00304 comprising a second three-phase electrical circuitry, the electrical propulsion system configured to generate torque that counters windmilling of the electrical propulsion system by performing one or more of activating a three-phase short at a second three-phase electrical circuitry of the second inverter or applying a stoppage voltage via the second inverter.29 A system for mitigating electrical faults, the system comprising: at least one processor; and memory storing a set of instructions which, when executed by the at least one processor, cause the system to perform the method of any one of claims 16 to 16.30. The system of clause 29, comprising: a sensor configured to sense the electrical fault; and the electrical propulsion system comprising the first inverter and the second inverter, the first inventor comprising the first three-phase electrical circuitry and the second inverter comprising a second three-phase electrical circuitry, the electrical propulsion system configured to generate torque that counters windmilling of the electrical propulsion system by reversing the three-phase timing of the at least three AC signals applied to the second inverter having a second three-phase electrical circuitry.31. The system of clause 30, wherein the electrical propulsion system comprises a pyro fuse system configured blow one or more pyro fuses to cause the at least one actuator to disconnect at least one set of windings.32. An electric aerial vehicle comprising the system of any one of clauses 27 to 31.

[0171] In the drawings and specification, there have been disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed apparatuses, systems, and related methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed apparatuses, systems, and related methods. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

Agent Ref: 16497.0027-00304CLAIMS:

1. A computer-implemented method of mitigating electrical faults, comprising: detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; and thereafter generating a torque that counters windmilling of the electrical propulsion system by performing at least one of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter; or applying a stoppage voltage via the second inverter.

2. The computer-implemented method of claim 1, further comprising, after detecting the electrical fault at the first inverter, activating at least one actuator of the electrical propulsion system to disconnect a set of stator windings associated with the first inverter.

3. The computer-implemented method of claim 2, wherein activating the at least one actuator comprises causing a pyro fuse system to blow one or more pyro fuses, thereby causing the at least one actuator to disconnect the set of stator windings.

4. The computer-implemented method of any one of claims 2 or 3, wherein activating the at least one actuator causes the at least one actuator to disconnect at least one of: a first common node of the set of stator windings; a second common node of the set of stator windings; a third common node of the set of stator windings; the first common node and the second common node; the second common node and the third common node; the first common node and the third common node; or the first common node, the second common node, and the third common node.

5. The computer-implemented method of any one of claims 1 to 4, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.Agent Ref: 16497.0027-003046. The computer-implemented method of any one of claims 1 to 5, wherein the torque that counters windmilling of the electrical propulsion system is generated by alternating: activating a three-phase short at a second three-phase electrical circuitry of the second inverter, and applying a stoppage voltage via the second inverter.

7. A computer-readable medium storing a set of instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any one of claims 1 to 6.8 A system for mitigating electrical faults, the system comprising: at least one processor; and memory storing a set of instructions which, when executed by the at least one processor, cause the system to perform the method of any one of claims 1 to 6.

9. The system of claim 8, comprising: a sensor configured to sense the electrical fault; and the electrical propulsion system comprising the first inverter and the second inverter, the first inventor comprising the first three-phase electrical circuitry and the second inverter comprising a second three-phase electrical circuitry, the electrical propulsion system configured to generate torque that counters windmilling of the electrical propulsion system by performing one or more of: activating a three-phase short at a second three-phase electrical circuitry of the second inverter or applying a stoppage voltage via the second inverter.

10. An electric aerial vehicle comprising the system of claim 8 or 9.

11. A computer-implemented method of mitigating electrical faults, comprising: detecting an electrical fault at a first inverter of an electrical propulsion system having the first inverter and a second inverter; activating a three-phase short at a first three-phase electrical circuitry of the first inverter after detection of the electrical fault at the first inverter; andAgent Ref: 16497.0027-00304 thereafter reversing a three-phase timing of at least three AC signals applied to the second inverter having a second three-phase electrical circuitry to generate a torque that counters windmilling of the electrical propulsion system.

12. The computer-implemented method of claim 11, wherein: the three-phase timing uses a first phase at a first phase circuit of the second three- phase electrical circuitry, a second phase at a second phase circuit of the second three-phase electrical circuitry, and a third phase at a third phase circuit of the second three-phase electrical circuitry; and reversing the three-phase timing comprises configuring the first phase circuit to use the third phase and configuring the third phase circuit to use the first phase to generate the torque that counters windmilling of the electrical propulsion system.

13. The computer-implemented method of claim 12, further comprising, based on detecting the electrical fault at the first inverter: applying a stoppage voltage via the second inverter to generate torque that counters the windmilling of the electrical propulsion system; and alternating between applying the stoppage voltage to the second inverter and reversing the three-phase timing.

14. The computer-implemented method of any one of claims 11 to 13, further comprising, after detecting the electrical fault at the first inverter, blowing one or more pyro fuses to cause at least one actuator to disconnect a set of stator windings associated with the first inverter.

15. The computer-implemented method of any one of claims 11 to 14, wherein the electrical fault is a single-phase short failure or a phase-to-phase short failure.

16. A computer-readable medium that stores a set of instructions that is executable by at least one processor to cause the at least one processor to perform the method of any one of claims 11 to 15.17 A system for mitigating electrical faults, the system comprising:Agent Ref: 16497.0027-00304 at least one processor; and memory storing a set of instructions which, when executed by the at least one processor, cause the system to perform the method of any one of claims 11 to 15.

18. The system of claim 17, comprising: a sensor configured to sense the electrical fault; and the electrical propulsion system comprising the first inverter and the second inverter, the first inventor comprising the first three-phase electrical circuitry and the second inverter comprising a second three-phase electrical circuitry, the electrical propulsion system configured to generate torque that counters windmilling of the electrical propulsion system by reversing the three-phase timing of the at least three AC signals applied to the second inverter having a second three-phase electrical circuitry.

19. The system of claim 18, wherein the electrical propulsion system comprises a pyro fuse system configured blow one or more pyro fuses to cause the at least one actuator to disconnect at least one set of windings.

20. An electric aerial vehicle comprising the system of any one of claims 17 to 19.

21. An electric aerial vehicle comprising: an electrical propulsion system comprising: a first inverter comprising a first three-phase electrical circuitry; a second inverter comprising a second three-phase electrical circuitry, wherein the electrical propulsion system is configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter; a sensor configured to sense an electrical fault; and one or more processors configured to perform the method of any of claims 1- 5.

22. The electric aerial vehicle of claim 21, wherein the electrical propulsion system further comprises a pyro fuse system configured blow one or more pyro fuses to cause at least one actuator to disconnect a first set of windings or a second set of windings.Agent Ref: 16497.0027-0030423. A propulsion system for an electric vehicle, comprising: an electrical motor configured to drive the electric vehicle and comprising a set of stator windings, wherein the set of stator windings comprises a common node; an actuator connected to the common node of the set of stator windings; a sensor coupled to the set of stator windings; and a processor configured to: receive, from the sensor, one or more signals indicating a fault has occurred; and after receiving the one or more signals indicating a fault has occurred, cause the actuator to disconnect the set of stator windings at the common node.

24. An electrical propulsion system comprising: a first inverter comprising a first three-phase electrical circuitry; a second inverter comprising a second three-phase electrical circuitry, wherein the electrical propulsion system is configured to generate torque by applying at least three AC signals with a three-phase timing to the second inverter; a sensor configured to sense an electrical fault; and one or more processors configured to perform the method of any of claims 1-5.

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