Minimal length generator with nested components and multiple function carrier

Abstract

Electric generators for vehicles such as aircraft include a shaft, a main stage, a permanent magnet generator stage, and an exciter stage. The main stage includes a main stator and main rotor. The permanent magnet generator stage comprising a permanent magnet generator stator and a permanent magnet generator rotor. The exciter stage includes an exciter stator and an exciter rotor. In certain aspects, the permanent magnet generator stage and the exciter stage are arranged such that the permanent magnet generator stage is nested within the exciter stage in a radial direction from the shaft.

Description

Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application MINIMAL LENGTH GENERATOR WITH NESTED COMPONENTS AND MULTIPLE FUNCTION CARRIER FIELD OF THE INVENTION

[0001] The field of the invention relates to passenger vehicles, and, more particularly, to generators with nested components for passenger vehicles. BACKGROUND

[0002] Passenger vehicles, such as aircraft, include an electric generator or other means to generate electricity for use onboard the passenger vehicle, for example, illuminating lights or providing avionic power while the passenger vehicle is in operation. The electric generator may include various stages or components that contribute to a weight and volume / size of the electric generator dependent on the aircraft loading requirements. For example, the stages or components of the electric generator may be positioned inline or in series with each other to achieve power (e.g., via electric) generation. This may cause the weight and / or the volume / size of the electric generator to be excessive and may cause inefficiencies on the passenger vehicle. For example, an excessively heavy electric generator may cause a higher overhung moment on the engine gearbox causing damage on the passenger vehicle. An excessively long electric generator may occupy excessive space in the passenger vehicle, thereby reducing usable space for wiring, pumps, or other necessary items within the passenger vehicle. SUMMARY

[0003] The terms “invention,” “the invention,” “this invention” and “the present invention” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference toAttorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application appropriate portions of the entire specification of this patent, any or all drawings and each claim.

[0004] According to certain embodiments, an electric generator for a passenger vehicle includes a shaft and a main stage. The main stage includes a main stator and main rotor. The electric generator also includes a permanent magnet generator (PMG) stage with a PMG stator and a PMG rotor and an exciter stage with an exciter stator and an exciter rotor. In certain embodiments, the PMG stage and the exciter stage are arranged such that the PMG stage is nested within the exciter stage in a radial direction from the shaft.

[0005] According to various embodiments, an electric generator for a passenger vehicle includes a shaft, a first stage with a first stator and a first rotor, a second stage with a second stator and a second rotor, and a carrier. The carrier is rotatable with the shaft and supports the first rotor and the second rotor in a nested arrangement in a radial direction.

[0006] According to various embodiments, an electric generator for a passenger vehicle includes a shaft, a main stage including a main stator and main rotor, a PMG stage with a PMG stator and a PMG rotor, and an exciter stage with an exciter stator and an exciter rotor. In certain embodiments, in a radial direction, the arrangement of the PMG stator relative to the PMG rotor is opposite from the arrangement of the exciter stator relative to the exciter rotor. In one non-limiting example, the arrangement of the PMG stator relative to the PMG rotor is opposite the arrangement of the exciter stator relative to the exciter rotor and the PMG stator is inside the PMG rotor.

[0007] Various implementations described herein may include additional systems, methods, features, and advantages, which cannot necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a perspective view of a generator rotor having nested components according to certain embodiments of the present invention.

[0009] FIG. 2 is a set of perspective views of a carrier assembly of the generator of FIG.1.

[0010] FIG.3 is a set of views of a carrier of the carrier assembly of FIG.2.Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application

[0011] FIG.4 is a set of perspective views of a bearing liner of the carrier assembly of FIG.2.

[0012] FIG.5 is a sectional view of the generator of FIG.1.

[0013] FIG.6 is a set of views of an oil-cooled version of a nested generator according to embodiments of the present invention. DETAILED DESCRIPTION

[0014] The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described.

[0015] The described embodiments of the invention provide generators with nested components for passenger vehicles. While the generators with nested components are discussed for use with aircraft, they are by no means so limited. Rather, embodiments of the generators with nested components may be used in passenger vehicles of any type or otherwise as desired.

[0016] According to certain embodiments of the present invention, and as illustrated in FIGS.1-6, a generator 100 (see FIG.5) includes a rotor assembly 101 with a main stage 102, a permanent magnet generator (PMG) stage 104 with a set of magnets, and an exciter stage 106. The generator 100 also includes a shaft 108 that generally extends from a first end 110 to a second end 112 of the generator 100, and the stages 102, 104, 106 may generally be arranged about and / or relative to the shaft 108. As discussed in detail below, portions of each stage 102, 104, 106 may rotate with the shaft 108 while other portions of each stage 102, 104, 106 generally remain stationary relative to the shaft 108. In certain embodiments, and as discussed in detail below, the rotor assembly 101 of the generator 100 includes a carrier 114, which may allow for one stage (e.g., the PMG stage 104) to be nested within another stage (e.g., the exciter stage 106) in a radial direction relative to the shaft 108.

[0017] Each of the stages 102, 104, 106 includes a stationary (stator) part and a rotating (rotor) part. In particular, the main stage 102 includes a main stator 116 and a main rotor 118, the PMG stage 104 includes a PMG stator 120 and a PMG rotor 122 with one or more magnets, and the exciter stage 106 includes an exciter stator 124 and an exciter rotor 126. The interactionAttorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application between each rotor and its associated stator generates electric current in each stage. The cascading of the stages (e.g., the PMG stage 104 energizes the exciter stage 106, and the exciter stage 106 energizes the main stage 102) in conjunction with an electronic controller allows for the system to provide regulated voltage output without any other power source.

[0018] Traditionally, the stators 116, 120, 124 have been fitted into a main housing 130 of the generator 100, and the rotors 118, 122, 126 have been mounted on the common shaft 108 and supported by bearings, typically one at each end of the shaft 108. Thus, the typical orientation of a particular stage in the radial direction as measured by an axis defined by the shaft 108 includes the rotor being the inner component and the stator being the outer component, and the rotor rotates within an inner periphery of the stator.

[0019] Compared to traditional approaches, the rotor assembly 101 of the generator 100 includes two stages that are nested in the radial direction relative to the shaft 108. In FIGS. 1-6, the PMG stage 104 is illustrated as being nested within the exciter stage 106, although the particular arrangement illustrated should not be considered limiting. In various embodiments, the nested stages 104, 106 are arranged such that the orientation of the stator and rotor of one stage is the opposite or inside-out of the orientation of the stator and rotor of the other stage (e.g., in one orientation, the rotor is outside the stator, and in the opposite orientation, the stator is outside the rotor). In one specific example, the arrangement of the PMG stator relative to the PMG rotor is opposite (e.g., the PMG stator is inside the rotor) the arrangement of the exciter stator relative to the exciter rotor. Compared to the typical orientation, the inside-out orientation refers to an arrangement where the rotor rotates about an outer periphery of the stator.

[0020] For example, in the embodiment illustrated, the inner stage in the radial direction – the PMG stage 104 – has an orientation where the PMG stator 120 is radially inwards relative to the PMG rotor 122, and the outer stage – the exciter stage 106 – has an orientation where the exciter rotor 126 is radially inwards relative to the exciter stator 124. Thus, in a radial direction, the order of nested components (listed from closest to the shaft 108 to furthest from the shaft 108) includes the PMG stator 120, the PMG rotor 122, the exciter rotor 126, and then the exciter stator 124. As illustrated, the nested components generally overlap each other in the radial direction to the shaft 108 and may generally be considered aligned in a radial direction at a given point along the shaft 108. The nested stages may provide space savings for the overall generator 100 and maximize an amount of usable space within the generator 100. In certain embodiments, the inside-out arrangement may improve the use of available space.Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application

[0021] In the embodiment with the nested stages, the stators may be coupled to the housing 130 and / or other stationary components of the generator 100. In some embodiments, the outermost stator (e.g., exciter stator 124) may be coupled to an outer wall 131 of the housing 130. In some embodiments, the innermost stator (e.g., PMG stator 120) to be supported by a non-rotating structure of the generator 100 without requiring additional components or features. As a non-limiting example, the innermost stator (e.g., PMG stator 120) may be supported on a bearing liner 128, which may be fastened to an end face 132 of a generator housing 130 of the generator 100. In some embodiments, the bearing liner 128 may fit closely around the shaft 108 to block entry of water or other debris into a bearing 134. In various embodiments, the bearing liner 128 may fit closely around the shaft 108 without being connected to the shaft 108 (i.e., the bearing liner 128 is connected to the generator housing 130 rather than the shaft 108). Optionally, the bearing liner 128 may include one or more drainage apertures 158 that may divert the water or debris away from the bearing 134. As best illustrated in FIG.4, the bearing liner 128 may include one or more mounting features 159, such as one or more apertures 161, facilitating connection of the bearing liner 128 to the end face 132 (e.g., using one or more fasteners or other attachment techniques or mechanisms).

[0022] In certain embodiments, the carrier 114 may facilitate nesting of the stages 104, 106 in the radial direction. In certain embodiments, the carrier 114 may support the outermost component of the inner stage (e.g., the PMG rotor 122 of the PMG stage 104) and the innermost component of the outer stage (e.g., the exciter rotor 126 of the exciter stage 106). In various embodiments, the carrier 114 is rotatable (e.g., with the shaft 108) such that the supported PMG rotor 122 and exciter rotor 126 are rotatable relative to the respective stators 120, 124.

[0023] As best illustrated in FIG. 3, the carrier 114 generally includes an inner body 136 and an outer body 138 connected to the inner body 136. The outer body 138 is more outwards compared to the inner body 136 and may define a radially outermost extent of the carrier 114. In some embodiments, the outer body 138 is connected to the inner body 136 by one or more ribs 140, although in other embodiments, other structures or features may connect the inner body 136 with the outer body 138. In embodiments with the radial ribs 140, leads of the exciter rotor 126 optionally may be secured to the radial ribs 140 (see, e.g., FIG. 2), although they need not in other embodiments.

[0024] In some embodiments, the outer body 138 is coupled to the inner body 136 such that they are offset along an axis 150. However, in other embodiments, the bodies 136, 138 may have other orientations relative to each other as desired. Moreover, while the bodies 136,Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application 138 of the carrier 114 are illustrated as generally cylindrical, they need not be and instead may have other shapes in other embodiments as desired.

[0025] The inner body 136 may couple the carrier 114 to the shaft 108 (e.g., by receiving the shaft 108 through a central opening 141). The outer body 138 generally includes an inner support surface 142 and an outer support surface 144. The support surfaces 142, 144 may be curved or arcuately shaped in some embodiments, although they need not be in other embodiments. As illustrated, the outermost component of the inner stage (e.g., the PMG rotor 122 of the PMG stage 104) may be supported on the inner support surface 142, and the innermost component of the outer stage (e.g., the exciter rotor 126 of the exciter stage 106) may be supported on the outer support 144. Various techniques or mechanisms may be utilized to support the components on the carrier 114, including various mechanical fasteners or systems, adhesives, form fitting, and / or other techniques as desired.

[0026] In some embodiments, and as illustrated in FIGS. 2 and 3, in addition to supporting the PMG rotor 122 and the exciter rotor 126, the carrier 114 optionally may support diodes 146 (such as but not limited to rectifier diodes) and / or resistors 148 (such as but not limited to spike-suppression resistors). In such embodiments, outer body 138 (and / or another portion of the carrier 114 such as an intermediate structure between the inner body 136 and the outer body 138) may include one or more mounting features such as but not limited to apertures 152 and 154 for receiving the rectifier diodes 146 and / or suppression resistors 148. The number of mounting features 152 and 154 should not be considered limiting. In certain embodiments, the diodes 146 and / or resistors 148 on the carrier 114 may be within an overhang of the main stator 116, thereby providing additional space savings.

[0027] Additionally, or alternatively, the carrier 114 may support one or more grounding lugs in one of the mounting features.

[0028] Optionally, the carrier 114 includes one or more balancing apertures 156 arranged around a perimeter of the carrier 114. In such embodiments, a balancing weight, such as but not limited to a set screw, weight, and / or other object or device, may be selectively positioned within and / or secure to the balancing apertures 156 to provide balancing of the rotating carrier 114 as desired.

[0029] The carrier 114 may be constructed from various materials as desired, and in certain embodiments, may be constructed from a ferromagnetic material such as iron or steel or alloys thereof. In various embodiments, because the carrier 114 fulfills many functions, is exposed to severe environments, and makes physical contact with many parts (e.g., the exciterAttorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application rotor, magnets of the PMG rotor, diodes, resistors, fasteners, shaft, and main rotor), the carrier may include various materials, coatings, finishes, etc., optionally to resist corrosion and / or provide a durable carrier 114. Additionally, or alternatively, the carrier 114 may be configured to act as a field yoke of the magnetic circuit of the PMG stage 104.

[0030] FIG. 6 illustrates another example of a rotor assembly 601 for a generator according to embodiments. The rotor assembly 601 is similar to the rotor assembly 101 of generator 100 and includes a three-piece carrier 614 allowing for the mounting of the rotating rectifier diodes 146, the PMG rotor 122 and the exciter rotor 126 to the shaft 108. Compared to the carrier 114, the carrier 614 is not a monolithic or single component, and instead includes a first section 660 and a second section 661, and a third section 662. In this embodiment, the first section 660 and the second section 661 may be split from one another and may not physically contact one another. In some embodiments, the first section 660 may be electrically hot, and the second section 661 may be or include an electrical ground, although they need not in other embodiments. Also, in this embodiment, the third section 662 supports the magnets of the PMG rotor 122. In some embodiments, the rotor assembly 601 illustrated in FIG. 6 may be configured to function with oil such as via an oil inlet 664.

[0031] In some embodiments, the generators described herein, or any component thereof, may include various metals or metallic elements as desired, including but not limited to aluminum, an aluminum alloy, titanium, a titanium alloy, nickel, a nickel alloy, copper, a copper alloy, steel, a steel alloy, stainless steel or a stainless-steel alloy, any combinations thereof, or any other suitable metal or metallic alloy. In other non-limiting examples, the generators described herein, or any component thereof, may include other types of metallic elements, such as titanium, zinc, and the like, or metallic alloys such as titanium alloys, zinc alloys, and the like. In some embodiments, some components of the generator 100 and / or rotor assemblies 101, 601 may include non-metallic elements such as rubber, polymer, plastics, and the like.

[0032] In the following, further examples are described to facilitate the understanding of the invention:

[0033] Example 1. An electric generator for a passenger vehicle, the electric generator comprising: a shaft; a main stage comprising a main stator and main rotor; a permanent magnet generator (PMG) stage comprising a PMG stator and a PMG rotor; and an exciter stage comprising an exciter stator and an exciter rotor, wherein the PMG stage and the exciter stageAttorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application are arranged such that the PMG stage is nested within the exciter stage in a radial direction from the shaft.

[0034] Example 2. The electric generator of any of the preceding or subsequent examples or combination of examples, further comprising a carrier assembly supported on the shaft and rotatable with the shaft, wherein the carrier assembly supports the exciter rotor and the PMG rotor.

[0035] Example 3. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein an arrangement of the PMG stator relative to the PMG rotor is opposite from an arrangement of the exciter stator relative to the exciter rotor.

[0036] Example 4. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein, the PMG rotor is provided around an outer periphery of the PMG stator, and wherein the exciter rotor is provided within an inner periphery of the exciter stator.

[0037] Example 5. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the PMG stage and the exciter stage are nested such that, in the radial direction, the PMG stator is an innermost component of the nested stages and the exciter stator is an outermost component of the nested stages.

[0038] Example 6. The electric generator of any of the preceding or subsequent examples or combination of examples, further comprising a carrier supported on the shaft and rotatable with the shaft, wherein the carrier comprises an inner support surface and an outer support surface, wherein the exciter rotor is supported on the outer support surface and the PMG rotor is supported on the inner support surface.

[0039] Example 7. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the carrier comprises an inner body and an outer body connected to the inner body, wherein the inner body couples the carrier to the shaft and the outer body is a radially outermost extent of the carrier, and wherein the inner support surface and the outer support surface are on the outer body.

[0040] Example 8. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the outer body further comprises one or more mounting features configured to support at least one of a resistor, a diode, or a balancing weight.Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application

[0041] Example 9. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the inner body and the outer body are offset along an axis.

[0042] Example 10. The electric generator of any of the preceding or subsequent examples or combination of examples, further comprising a plurality of radial ribs connecting the inner body with the outer body.

[0043] Example 11. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the generator further comprises a housing with an end face and bearing liner coupled to the end face, wherein the bearing liner is configured to support the PMG stator.

[0044] Example 12. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the bearing liner fits closely around the shaft without connecting to the shaft, and wherein the bearing liner is configured to block entry of water or debris into an adjacent bearing on the shaft.

[0045] Example 13. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the bearing liner further comprises one or more drainage apertures.

[0046] Example 14. The electric generator of any of the preceding or subsequent examples or combination of examples, further comprising at least one rotating rectifier diode and at least one resistor at least partially nested within the main stator.

[0047] Example 15. An electric generator for a passenger vehicle, the generator comprising: a shaft; a first stage comprising a first stator and a first rotor; a second stage comprising a second stator and a second rotor; and a carrier rotatable with the shaft and supporting the first rotor and the second rotor in a nested arrangement in a radial direction.

[0048] Example 16. The electric generator of any of the preceding or subsequent examples or combination of examples, further comprising a housing, the housing comprising an outer wall and an end face, wherein the first stator is coupled to the end face and the second stator is coupled to the outer wall..

[0049] Example 17. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the first stage is a permanent magnet generator (PMG) stage, wherein the second stage is an exciter stage, and wherein the electric generator further comprises a main stage, wherein the main stage comprises a main stator and main rotor arranged relative to the shaft.Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application

[0050] Example 18. An electric generator for a passenger vehicle, the electric generator comprising: a shaft; a main stage comprising a main stator and main rotor; a permanent magnet generator (PMG) stage comprising a PMG stator and a PMG rotor; and an exciter stage comprising an exciter stator and an exciter rotor, wherein, in a radial direction, the arrangement of the PMG stator relative to the PMG rotor is opposite from the arrangement of the exciter stator relative to the exciter rotor.

[0051] Example 19. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the exciter rotor is closer to the shaft than the exciter stator, and wherein the PMG stator is closer to the shaft than the PMG rotor.

[0052] Example 20. The electric generator of any of the preceding or subsequent examples or combination of examples, wherein the PMG stage and the exciter stage are nested in a radial direction relative to the shaft.

[0053] Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications may be made without departing from the scope of the claims below.

Claims

Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application CLAIMS That which is claimed is:

1. An electric generator for a passenger vehicle, the electric generator comprising: a shaft; a main stage comprising a main stator and main rotor; a permanent magnet generator (PMG) stage comprising a PMG stator and a PMG rotor; and an exciter stage comprising an exciter stator and an exciter rotor, wherein the PMG stage and the exciter stage are arranged such that the PMG stage is nested within the exciter stage in a radial direction from the shaft.

2. The electric generator of claim 1, further comprising a carrier assembly supported on the shaft and rotatable with the shaft, wherein the carrier assembly supports the exciter rotor and the PMG rotor.

3. The electric generator of claim 1, wherein an arrangement of the PMG stator relative to the PMG rotor is opposite from an arrangement of the exciter stator relative to the exciter rotor.

4. The electric generator of claim 3, wherein, the PMG rotor is provided around an outer periphery of the PMG stator, and wherein the exciter rotor is provided within an inner periphery of the exciter stator.

5. The electric generator of claim 1, wherein the PMG stage and the exciter stage are nested such that, in the radial direction, the PMG stator is an innermost component of the nested stages and the exciter stator is an outermost component of the nested stages.

6. The electric generator of claim 1, further comprising a carrier supported on the shaft and rotatable with the shaft, wherein the carrier comprises an inner support surface and an outer support surface, wherein the exciter rotor is supported on the outer support surface and the PMG rotor is supported on the inner support surface.

7. The electric generator of claim 6, wherein the carrier comprises an inner body and an outer body connected to the inner body, wherein the inner body couples the carrier to the shaftAttorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application and the outer body is a radially outermost extent of the carrier, and wherein the inner support surface and the outer support surface are on the outer body.

8. The electric generator of claim 7, wherein the outer body further comprises one or more mounting features configured to support at least one of a resistor, a diode, or a balancing weight.

9. The electric generator of claim 7, wherein the inner body and the outer body are offset along an axis.

10. The electric generator of claim 7, further comprising a plurality of radial ribs connecting the inner body with the outer body.

11. The electric generator of claim 1, wherein the generator further comprises a housing with an end face and bearing liner coupled to the end face, wherein the bearing liner is configured to support the PMG stator.

12. The electric generator of claim 11, wherein the bearing liner fits closely around the shaft without connecting to the shaft, and wherein the bearing liner is configured to block entry of water or debris into an adjacent bearing on the shaft.

13. The electric generator of claim 12, wherein the bearing liner further comprises one or more drainage apertures.

14. The electric generator of claim 1, further comprising at least one rotating rectifier diode and at least one resistor at least partially nested within the main stator.

15. An electric generator for a passenger vehicle, the generator comprising: a shaft; a first stage comprising a first stator and a first rotor; a second stage comprising a second stator and a second rotor; and a carrier rotatable with the shaft and supporting the first rotor and the second rotor in a nested arrangement in a radial direction.Attorney Docket No.061754-1417030 Client Ref. No. B-029474PCT01 Patent Application 16. The electric generator of claim 15, further comprising a housing, the housing comprising an outer wall and an end face, wherein the first stator is coupled to the end face and the second stator is coupled to the outer wall.

17. The electric generator of claim 15, wherein the first stage is a permanent magnet generator (PMG) stage, wherein the second stage is an exciter stage, and wherein the electric generator further comprises a main stage, wherein the main stage comprises a main stator and main rotor arranged relative to the shaft.

18. An electric generator for a passenger vehicle, the electric generator comprising: a shaft; a main stage comprising a main stator and main rotor; a permanent magnet generator (PMG) stage comprising a PMG stator and a PMG rotor; and an exciter stage comprising an exciter stator and an exciter rotor, wherein, in a radial direction, the arrangement of the PMG stator relative to the PMG rotor is opposite from the arrangement of the exciter stator relative to the exciter rotor.

19. The electric generator of claim 18, wherein the exciter rotor is closer to the shaft than the exciter stator, and wherein the PMG stator is closer to the shaft than the PMG rotor.

20. The electric generator of claim 18, wherein the PMG stage and the exciter stage are nested in a radial direction relative to the shaft.

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