# Patent

## Title
Dual redundant motor/generator for an engine

## Abstract

An exemplary electrical system may include a power plant and a dual motor/generator assembly coupled to each other. The power plant may be a gas turbine engine, and may be operable to provide motive power. The dual motor/generator assembly may include a first motor/generator and a second motor/generator operatively coupled to a common gear shaft, and a gear box configured to couple the first motor/generator and the second motor/generator to the power plant. The first motor/generator and the second motor/generator may be operable to selectively provide power to or extract power from the power plant. The dual motor/generator assembly may be configured such that the first motor/generator and the second motor/generator may operate together at part loads, or individually as a main and a redundant, backup to the other.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No. 61/920,369, filed Dec. 23, 2013, the contents of which are hereby incorporated in their entirety.


FIELD OF TECHNOLOGY
The present disclosure pertains to an electrical system with a dual redundant motor/generator for an engine of a vehicle.
BACKGROUND
It has become increasingly desirable to improve the overall system design and operation of gas turbines. In a system having a typical gas turbine engine, electrical power is extracted via an electrical generator to supply electrical power to control systems, actuators, weapons systems, climate control systems, and the like. Electrical storage, such as a battery, is typically provided to operate such systems when the gas turbine engine is not running or to provide power for starting the gas turbine engine. In some systems, the generator may have the dual capabilities of operating as a generator and as a motor to alternatively provide power for the gas turbine engine. In some known gas turbine engines, the gas turbine engine includes a high pressure shaft and a lower pressure shaft, and the electrical generator is coupled to one of the high and low pressure shafts.
However, extraction of power from the gas turbine engine via one of the shafts itself typically does not provide the redundancy required for engines utilized in applications of increasing electrical architecture. In addition, coupling multiple generators on available shaft drives at various available speeds may result in a loss in overall system life and in particular to the drive components of the engine to which the electrical generator is coupled. Coupling of multiple units at various speeds and locations may also limit system failure mode and effects power rerouting options. As such, it has become increasingly desirable to have redundant systems to ensure backup is available. For example, in military applications, the redundancy is important for return to base or mission completion. Current configurations are designed around existing hardware which limits size, power, and thermal and/or durability capabilities. A well designed redundant system will provide a matching of electrical parameters, cooling systems, and control systems so operation of the essential systems can continue uninterrupted if a problem occurs in any of the above systems.
Overcoming these concerns would be desirable and could save the industry substantial resources. Therefore, there exists a need for an electrical system that incorporates redundant capabilities, among other things.



BRIEF DESCRIPTION OF THE DRAWINGS
While the claims are not limited to a specific illustration, an appreciation of the various aspects is best gained through a discussion of various examples thereof. Referring now to the drawings, exemplary illustrations are shown in detail. Although the drawings represent the illustrations, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an example. Further, the exemplary illustrations described herein are not intended to be exhaustive or otherwise limiting or restricted to the precise form and configuration shown in the drawings and disclosed in the following detailed description. Exemplary illustrations are described in detail by referring to the drawings as follows:
FIG. 1 is a schematic block diagram of an exemplary electrical system having a dual motor/generator assembly coupled to a power plant (or engine);
FIG. 2 is a schematic block diagram of another exemplary electrical system having multiple dual motor/generator assemblies each coupled to respective power plants; and
FIG. 3 is a schematic, cross-sectional view of a motor/generator assembly coupled to an engine according to one example.



DETAILED DESCRIPTION
An electrical system that incorporates at least one dual motor/generator assembly is described herein. Such an electrical system may provide redundant capabilities for the operation of a vehicle, such as an aircraft. An exemplary electrical system may include a power plant and a dual motor/generator assembly coupled to each other. Design of the system such that the first and second motor/generator are of common design and architecture is an important feature of the system being described. The first and second motor/generators can also be aligned very precisely which aligns phase and sensors if necessary depending on electrical machine architectures used. This provides by intent, redundant sensors, matched electrical parameters including phase, and, matched cooling systems. For example, in event of a sensor error, the electronics can simply switch to the second sensor without concern of variations. Matching the systems in both phase and voltage will allow transparent switching load units if necessary. In addition, with two motor/generators matched in phase and voltage, the output of both can be supplied to the same electrical bus, advantageous where higher power is requested per bus. Some of these advantages may depend on motor/generator architecture, and the selection of the power electronic systems described herein.
The power plant may be a gas turbine engine, and may be operable to provide motive power. The dual motor/generator assembly may include a first motor/generator and a second motor/generator operatively coupled to a common gear shaft, and a gear box configured to couple the first motor/generator and the second motor/generator to the power plant. The first motor/generator and the second motor/generator may be operable to selectively provide power to or extract power from the power plant. The electrical system may be configured such that the first motor/generator and the second motor/generator may operate together at part loads, or individually with one serving as a main and the other serving as a redundant, backup.
Another exemplary electrical system may include a first dual motor/generator assembly coupled to a first power plant, and a second motor/generator assembly coupled to a second power plant. Each motor/generator assembly may include a first motor/generator and a second motor/generator, as described above. The electrical system may be configured such that one dual motor/generator assembly may provide power to start up and run the engine coupled to the other dual motor/generator assembly.
An exemplary vehicle, such as an aircraft, may include either of the exemplary electrical systems described above.
Referring now to the Figures, FIG. 1 illustrates an exemplary electrical system 10 for a vehicle, including, but not limited to, an aircraft, in which a power plant or engine 12, such as a gas turbine engine, provides electrical power to be utilized by other components of the vehicle. It should be understood that the electrical system 10 may be an electrical-mechanical system, but for simplicity purposes, is referred to as an electrical system. The engine 12 may be coupled to an engine control unit 20 configured to control the operation of the engine 12, as well as to store and/or monitor various engine parameters including, but not limited to, temperature, vibration, torque, speed, and the like.
In addition to the engine 12, the electrical system 10 also may include a first motor/generator 14 and a second motor/generator 16 coupled to a common gear shaft 18. The first motor/generator 14 and the second motor/generator are also operatively coupled to the engine 12 via a gearbox 22. The gearbox 22 may enable at least one of the first motor/generator 14 and the second motor/generator 16 to operate with the engine 12, as depicted in FIG. 3 and described hereinafter. The first motor/generator 14 and the second motor/generator 16 may each selectively operate as either a motor, where they provide power to the engine 12, or as a generator, where they extract power from the engine 12. The first motor/generator 14 and the second motor/generator 16 may be substantially identical. For example, they may be mechanically timed such that the phase, voltage, and/or harmonics are substantially synchronized.
The use of substantially identical motor/generators 14 and 16 may provide several advantages. These advantages may include, but are not limited to, redundant capability, multiple start capability, and improved cold start capability of the electrical system 10. Further advantages may include reducing mounting loads on the gearbox 22 as there may be balanced masses, reducing internal component loads (e.g., gears, bearings) of accessory pads (not shown), and reducing system weight due to simplified system cooling and connections. In addition, matching phase and voltage allows the output to be supplied to a common electrical distribution bus within the vehicle.
To operatively couple the first motor/generator 14 and the second motor/generator 16 to the engine 12, the gearbox 22 may include a gear shaft 18 to which the first motor/generator 14 and the second motor/generator 16 are coupled, and the gearbox 22 may be configured such that either the first motor/generator 14 or the second motor/generator 16 may be operating at a given time, where the non-operating motor/generator 14 or 16 serves as a backup to provide redundancy. Alternatively, the first motor/generator 14 and the second motor/generator 16 may operate simultaneously at part loads. The gear shaft 18 may be a bevel gear shaft such that rotational energy may be translated between the first and/or the second motor/generators 14 and 16 and the engine 12.
The first motor/generator 14 and the second motor/generator 16 also may be coupled to a first Generator Control Unit (GCU) 26 and a second GCU 28, respectively. The first GCU 26 and the second GCU 28 may be configured to communicate with other system components to ultimately control the operation of the first motor/generator 14 and the second motor/generator 16, respectively.
The electrical system 10 further may include a system controller 30 to which the engine control unit 20, the first GCU 26, and the second GCU 28 are connected. The system controller 30 may be configured to regulate power flow (such as electrical currents and voltages within system 10) to provide power to various electrical busses. The power may be DC, AC, or conversion therebetween. The system controller 30 may also be configured to execute computer program instructions to control the operation of the engine 12, including, but not limited to, fuel flow, the position of any variable geometry systems (e.g., from the flight control system of an aircraft or from a steering system of a ship), and the like.
The electrical system 10 may further include a power conversion/distribution system 32 and a health monitoring and prognostics system 36 each coupled to the first GCU 26, the second GCU 28, and/or the system controller 30. The health monitoring and prognostics system 36 generally may be a unit that monitors the health of system components, and may be used to estimate component life based on sensor feedback received from components within the engine 12 and/or the motor generators 14 and 16.
The power conversion/distribution system 32 may be configured to receive electrical power from the first motor/generator 14 and/or the second motor/generator 16 via the first GCU 26 and the second GCU 28, respectively. The power conversion/distribution system 28 may be configured to convert the power to a more useable form such as a DC voltage for storage in an energy storage system 34, an expansion module 38, and/or an application electrical load(s) 40. The energy storage system 34 may include, but is not limited to, a battery or other energy storage system. The energy storage system 34 may be configured to store energy for providing power when the engine 12 is not running (i.e., not generating power), but also to provide power to the first motor/generator 14 and/or the second motor/generator 16 to provide starting power to the engine 12 during startup. The expansion module 38 and the application electrical load 40 represent additional electrical components, which may be standard and/or essential loads that may receive power from the power conversion/distribution system 32.
The electrical system 10 may further include a sensor 42 in communication with the system controller 30. The sensor 42 may be configured to measure and/or monitor various parameters, including, but not limited to, ambient temperature, generator temperature, oil temperature, engine speed, torque, vibration, and the like. As such, the sensor 42 may be connected to, attached to, or disposed within any one of the system components. While FIG. 1 depicts the electrical system 10 as having only one sensor, it should be appreciated that there may be any number of sensors 42 configured to measure various parameters and being located in various locations within the electrical system 10.
Computing devices, including, but not limited to, the system controller 30, the first GCU 26, and the second GCU 28, generally include computer-executable instructions such as the instructions of the system controller 30, where the instructions may be executable by one or more computing devices such as those listed above. Computer-executable instructions may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, JavaTM, C, C++, C#, Objective C, Visual Basic, Java Script, Perl, etc. In general, a processor (e.g., a microprocessor) receives instructions, e.g., from a memory, a computer-readable medium, etc., and executes these instructions, thereby performing one or more processes, including one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of computer-readable media.
A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which typically constitutes a main memory. Such instructions may be transmitted by one or more transmission media, including coaxial cables, copper wire and fiber optics, including the wires that comprise
A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which typically constitutes a main memory. Such instructions may be transmitted by one or more transmission media, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.
Databases, data repositories or other data stores described herein may include various kinds of mechanisms for storing, accessing, and retrieving various kinds of data, including a hierarchical database, a set of files in a file system, an application database in a proprietary format, a relational database management system (RDBMS), etc. Each such data store is generally included within a computing device employing a computer operating system such as one of those mentioned above, and are accessed via a network in any one or more of a variety of manners. A file system may be accessible from a computer operating system, and may include files stored in various formats. An RDBMS generally employs the Structured Query Language (SQL) in addition to a language for creating, storing, editing, and executing stored procedures, such as the PL/SQL language mentioned above.
In some examples, system elements may be implemented as computer-readable instructions (e.g., software) on one or more computing devices (e.g., servers, personal computers, etc.), stored on computer readable media associated therewith (e.g., disks, memories, etc.). A computer program product may comprise such instructions stored on computer readable media for carrying out the functions described herein.
Referring now to FIG. 2, another exemplary electrical system 100 is shown. The electrical system 100 generally may include at least two sub-systems 110 and 120 that each connects to an energy storage system 134, an expansion module 138, and an application load 140. Each sub-system 110 and 120 generally may incorporate the same components and connections as the electrical system 10 depicted in FIG. 1 and described above. The common connection to the energy storage system 134, the expansion module 138, and/or the application electrical load 140 may allow for either sub-system 110 or 120 to power the engine 12 of the other sub-system 120 in such situations as a stalled engine due to failure of any sub-system component, as well as to any other components that require power, such as the expansion module 138 and/or the application electrical load. For example, where the second sub-system 120 may lack sufficient power to run the engine 122, the sub-system 110 may provide supplemental power to the energy storage system 134. The sub-system 120 may then draw power from the energy storage system 134 to at least one of the generator/motors 142 and 162 to provide power to start up the engine 122.
Referring now to FIG. 3, an exemplary engine 12 coupled to an exemplary dual motor/generator assembly 50 is shown. The engine 12 generally may include at least one rotor shaft 44, which may be connected to a low pressure compressor and/or a high pressure compressor. The dual motor/generator assembly 50 may include the first motor/generator 14 and the second motor/generator 16 coupled to the gear shaft 18, and the gearbox 22, as described above. The dual motor/generator assembly 50 may further include the drive shaft 24, which may be coupled to the rotor shaft 44 and to the gear shaft 18. This enables the rotational movement of the rotor shaft 44 to be translated to the gear shaft 18 such that power may be extracted from the engine 12 to at least one of the first motor/generator 14 and the second motor/generator 16. Inversely, the drive shaft 24 may enable the rotational movement of the gear shaft 18 to be translated to the rotor shaft 44 to power the engine 12.
With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claims.
All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary in made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

## Claims

1. An electrical system comprising:
a power plant operable to provide motive power and having at least one rotor shaft;
a dual motor/generator assembly having:
a first motor/generator and a second motor/generator operatively coupled to a common gear shaft;
a drive shaft coupled to the at least one rotor shaft and the common gear shaft; and
a gearbox configured to couple the first motor/generator and the second motor/generator to the power plant; and

an energy storage system configured to receive power from at least one of the first motor/generator and the second motor/generator, and to provide power to at least one of the first motor/generator and the second motor/generator;
wherein at least one of the first motor/generator and the second motor/generator is operable to selectively provide power to the power plant and to extract power from the power plant.

2. The electrical system of claim 1, wherein the power plant is a gas turbine engine.

3. The electrical system of claim 1, wherein the first motor/generator and the second motor/generator are substantially identical.

4. The electrical system of claim 3, wherein the first motor/generator and the second motor/generator are mechanically timed such that the at least one of the respective phases, voltages, and harmonics are substantially synchronized.

5. The electrical system of claim 1, wherein the gear shaft is a bevel gear shaft.

6. A vehicle comprising:
a gas turbine engine having at least one rotor shaft;
a dual motor/generator assembly having:
a first motor/generator and a second motor/generator operatively coupled to a common gear shaft;
a drive shaft coupled to the at least one rotor shaft and the common gear shaft; and
a gearbox configured to couple the first motor/generator and the second motor/generator to the power plant; and

an energy storage system configured to receive power from at least one of the first motor/generator and the second motor/generator, and to provide power to at least one of the first motor/generator and the second motor/generator;
wherein at least one of the first motor/generator and the second motor/generator is operable to selectively provide power to the power plant and to extract power from the power plant.

7. The vehicle of claim 6, wherein the first motor/generator and the second motor/generator are substantially identical.

8. The vehicle of claim 7, wherein the first motor/generator and the second motor/generator are mechanically timed such that the at least one of the respective phases, voltages, and harmonics are substantially synchronized.

9. The vehicle of claim 6, wherein the gear shaft is a bevel gear shaft.

10. An electrical system comprising:
a first power plant and a second power plant, each operable to provide motive power;
a first dual motor/generator assembly coupled to the first power plant, and a second dual motor/generator assembly coupled to the second power plant, each dual motor/generator assembly having:
a first motor/generator and a second motor/generator operatively coupled to a common gear shaft; and
a gearbox configured to couple the first motor/generator and the second motor/generator to the respective power plant; and

an energy storage system configured to receive power from at least one of the first motor/generator and the second motor/generator of the first and the second dual motor/generator assemblies, and to provide power to at least one of the first motor/generator and the second motor/generator;
wherein at least one of the first motor/generator and the second motor/generator is operable to selectively provide power to and extract power from the respective power plant; and
wherein the first dual motor/generator assembly is operable to provide power to be used by the second engine, and the second dual motor/generator assembly is operable to provide power to be used by the first engine.

11. The electrical system of claim 10, wherein the first motor/generator and the second motor/generator of the first dual motor/generator assembly are substantially identical, and the first motor/generator and the second motor/generator of the second dual motor/generator assembly are substantially identical.

12. The electrical system of claim 11, wherein the first motor/generator and the second motor/generator of the first dual motor/generator assembly are mechanically timed such that the at least one of the respective phases, voltages, and harmonics are substantially synchronized.

13. The electrical system of claim 11, wherein the first motor/generator and the second motor/generator of the second dual motor/generator assembly are mechanically timed such that the at least one of the respective phases, voltages, and harmonics are substantially synchronized.