Power electronics section of a starter generator without commutator

Abstract

A rotary machine assembly includes a rotary machine having a cover defining an outer surface of the rotary machine and a stator disposed within the cover. The stator is fixed relative to the cover. The rotary machine further includes a shaft rotatably disposed at least partially within the cover to define a rotational axis. The shaft includes a first end connectable to an aircraft engine and a second end opposite the first end. The rotary machine further includes a rotor attached to the shaft, the rotor being movable relative to the stator, and a power module including at least one MOSFET that periodically reverses a current direction of the rotor. The power module includes the at least one MOSFET disposed within the cover.

Description

Background Technology

[0001] Starting generators typically have a commutator on the rotor, which interacts with brushes attached to a fixed frame of the machine. The commutator and brushes have an electrical switching function because different parts of the commutator make or break electrical contact with the brushes as the commutator rotates. This switching function, which occurs in relation to rotor rotation, is essential for the normal operation of a rotating starting generator.

[0002] However, as the commutator rotates beneath the brushes, the brushes experience wear and eventually must be replaced. Brushes are typically the most restrictive wear parts in a machine, determining the amount of time the starter generator can remain on the aircraft before it must be removed for a major overhaul. Creating starter generators that allow for longer periods between overhauls is desirable, but this requires finding alternatives to the switching functions of the commutator and brushes.

[0003] One way to achieve this is to use electronic components such as MOSFETs to perform the switching function. Sensors can measure the rotor's rotational speed and position, and the electronics can use these measurements to determine when to send a signal to the MOSFET to turn it on or off. Using electronics to drive the MOSFET can replace the rotation-based switching function of brushes and commutators.

[0004] However, using this type of MOSFET in this way brings its own set of problems. One problem is where to place them, as these electronic components take up more space than traditional commutators and brushes. Another problem is how to cool the MOSFETs, because these electronic components generate more heat than traditional commutators and brushes.

[0005] To address these issues, a brushless starter generator with a separate housing to house the electronics could be used. However, this solution has potential drawbacks. For example, additional space must be provided on the aircraft for the separate housing.

[0006] Furthermore, high-current-capacity wiring must be laid between the separate enclosure and the starter generator. This high-current-capacity wiring is thick and heavy, resulting in additional weight and complex assembly techniques. These are not desirable features for aircraft applications.

[0007] Therefore, a more advanced starter generator is needed. Summary of the Invention

[0008] In view of the foregoing, the rotating machine assembly includes a rotating machine having a cover defining an outer surface of the rotating machine and a stator disposed within the cover. The stator is fixed relative to the cover. The rotating machine also includes a shaft at least partially rotatably disposed within the cover to define an axis of rotation.

[0009] The shaft includes a first end connectable to an aircraft engine and a second end opposite the first end. The rotating machine also includes a rotor attached to the shaft, the rotor being movable relative to a stator; and a power module including at least one MOSFET that periodically reverses the direction of current in the rotor. The power module, including at least one MOSFET, is housed within a cover. Attached Figure Description

[0010] Figure 1 It is a perspective view of a rotating machine component.

[0011] Figure 2 It is a partial cross-sectional perspective view of a rotating machine component.

[0012] Figure 3 This is a perspective view of the rotating machine assembly with the cover removed.

[0013] Figure 4 It is a perspective view of a rotating machine assembly with some components removed.

[0014] Figure 5 yes Figure 4 A partial cross-sectional perspective view.

[0015] Figure 6 It is along line 6-6 Figure 4 Elevation section view. Detailed Implementation

[0016] refer to Figure 1 The diagram illustrates a rotating machine assembly 10. Without departing from the scope of this disclosure, the rotating machine assembly 10 may be an electric motor (e.g., a starter used on an aircraft to start an engine) or a generator that converts rotational motion into electrical energy. Alternatively, the rotating machine assembly 10 may be a combined starter-generator used to start an aircraft engine (i.e., in start-up mode) and also generating electricity for the aircraft's use (i.e., in power generation mode).

[0017] like Figures 1-3 As shown, the rotating machine assembly 10 includes a rotating machine 12, a chassis 14 defining an air passage 16, a fan 18, and a control housing 20 having a control module 22. The rotating machine 12 includes a cover 24, a stator 26, and a shaft 28. The shaft 28 includes a first end 28a and a second end 28b and defines a rotation axis 30.

[0018] like Figure 2As shown, the rotating machine assembly may also include a shaft sensor 32, which can sense or measure the rotational speed and position of the shaft 28 and therefore the rotor 34. The shaft sensor 32 may be of known technology. Furthermore, without departing from the scope of this disclosure, the shaft sensor 32 may be positioned in multiple locations. Additionally, the shaft sensor 32 may be connected to the control module 22 via wired or wireless means to allow communication between the shaft sensor 32 and the control module 22.

[0019] The rotating machine 12 also includes a rotor 34 connected to the shaft 28. The rotating machine 12 may also include a power module 36 having at least one MOSFET 38. Figure 3 As shown, at least one MOSFET 38 is mounted on circuit board 42. Circuit board 42 may be a printed circuit board.

[0020] For convenience, this disclosure refers to (one or more) printed circuit boards simply as circuit boards, but it will be understood to include multiple printed circuit boards. For clarity, wires that transmit power between power module 36, MOSFET 38 and various other components, whether for electrical or signal communication purposes, are omitted from the figures.

[0021] Pay attention again Figures 1-2 Cover 24 defines the outer surface 24a of the rotating machine 12 and serves to contain the components together in an easily maneuverable package to aid in installation into the aircraft. Cover 24 can be made of any amount of material, including, for example, sheet metal. As illustrated, cover 24 can be attached to chassis 14 using fasteners, but other attachment methods are also contemplated. Cover 24 can be non-structural in nature. Additionally, the cross-section of cover 24 in a plane orthogonal to the axis of rotation 30 defines a cylindrical shape.

[0022] For reference, the outer diameter of this cylindrical shape of the rotary machine 12 is equal to that of a conventional rotary machine that uses brushes and a commutator for rotation-based switching. By having the same outer diameter as a conventional rotary machine, space can be saved and the retrofitting of the machine components can be simplified. Furthermore, keeping the outer diameter of this rotary machine 12 the same as that of a conventional starter generator, and eliminating the need to connect it to a separate housing with thick wires, will make it easier to install this rotary machine assembly 10 into an aircraft.

[0023] The stator 26 has a known construction. The stator 26 is a fixed part of the rotating machine 12 and is therefore fixed relative to the cover 24. When the rotating machine assembly 10 is a generator, energy flows into or out of the rotor 34 through the stator 26, as is known. When the rotating machine assembly 10 is a starter, the stator 26 provides a rotating magnetic field to drive the rotating armature, also known in the art. When the rotating machine assembly 10 is a generator, the stator 26 converts the rotating magnetic field into electric current. The stator 26 is housed within the cover 24.

[0024] The rotating machine 12 also includes a shaft 28 rotatably, at least partially, housed within a cover 24. As illustrated, a first end 28a of the shaft extends out of the cover 24. The cross-section of the shaft 28 in a plane orthogonal to the axis of rotation 30 may be circular. The shaft 28 may be housed within one or more bearings.

[0025] like Figure 2 As shown, the first end 28a of shaft 28 may include multiple splines for rotatably connecting the rotating machine assembly 10 to an aircraft engine. It should be understood that, without departing from the scope of this disclosure, other methods besides splines may be used to connect the rotating machine assembly 10 to the aircraft engine. The second end 28b of shaft 28 is opposite the first end 28a of shaft 28 along the axis of rotation 30.

[0026] The rotating machine 12 also includes a rotor 34 attached or coupled to the shaft 28 such that the shaft 28 and the rotor 34 rotate together. The rotor 34 has a known construction. The rotation of the rotor 34 is caused by the interaction between the windings and the magnetic field, which generates torque about the axis of rotation 30. The rotor 34 is movable relative to the stator 26.

[0027] like Figure 3 As shown, power module 36 includes at least one MOSFET 38. However, as illustrated, multiple MOSFETs 38 may be used without departing from the scope of this disclosure. MOSFET 38 is a metal-oxide-semiconductor field-effect transistor. In particular, MOSFET 38 is a type of field-effect transistor (FET) fabricated by controlled oxidation of silicon. MOSFET 38 has an insulated gate (not shown) whose voltage determines the conductivity of the device.

[0028] This ability to change conductivity with the amount of applied voltage can be used to amplify or switch electronic signals. According to this disclosure, the MOSFET 38 periodically reverses the current direction of the rotor 34, thereby replacing appropriate power switching electronics. For example, the MOSFET 38 replaces the electrical switching function of the commutator and brushes present in conventional rotating machine 12 assemblies. As illustrated, a power module 36 including at least one MOSFET 38 is housed within a cover 24.

[0029] Conventional components include brushes that make or break contact with the commutator's rods. These rods are parallel to the axis of rotation, and as the shaft rotates, the brushes make or break contact with these rods of the commutator.

[0030] Therefore, the electrical contact from the brushes to the commutator bar is a function of the shaft rotational position. This rotational switching function, which is a function of the shaft rotational position, is replaced in this disclosure by MOSFET 38. Thus, when the shaft 28 rotates, the control module 22, taking into account the signal from the shaft sensor 32, tells MOSFET 38 to turn on or off depending on the rotational position of the shaft 28.

[0031] Multiple MOSFETs 38 can be mounted on multiple printed circuit boards 42 circumferentially mounted on the chassis 14 so as to be located between the air passage 16 and the cover 24, thereby radially surrounding the air passage 16. As illustrated, there are six circuit boards 42, each including multiple MOSFETs 38.

[0032] Mounting the MOSFET 38 in this manner minimizes wasted space while providing an efficient way to dissipate the generated heat into the phase change material or airflow. Furthermore, multiple pads 40 can be individually positioned between multiple printed circuit boards 42 and the chassis 14. The pads 40 can have a generally rectangular shape and a nominal thickness to allow for a sheet-like construction.

[0033] Furthermore, multiple pads 40 are thermally conductive and electrically insulating to electrically isolate the printed circuit board 42 from the chassis 14. The pads 40 can be very thin, similar in thickness to a sheet of paper. Therefore, as shown, the pads 40 may appear to be merely the outer surface of the chassis 14, but are actually separate from the chassis 14.

[0034] The control module 22 is housed within the control housing 20. It should be noted that the control module 22 is separate from and distinct from the power module 36. Furthermore, the control housing 20 is mounted on the cover 24 of the rotating machine 12 so as to be external to and attached to the rotating machine 12. As illustrated, the control housing 20 has a rectangular box-like structure that is mounted to the outer diameter of the rotating machine 12.

[0035] As will be understood, power module 36 uses MOSFET 38 to turn the power supply on and off. However, power module 36 itself does not know when to turn the power supply on and off. Instead, control module 22 receives input from axis sensor 32, and therefore control module 22 knows when the power supply should be turned on or off.

[0036] The control module 22 then sends a low-power electrical signal to the power module 36, which informs the power module 36 when to turn on or off. In other words, the power module 36 functions like a relay, and the control module 22 tells the relay when to activate.

[0037] refer to Figures 1-3 The chassis 14 is housed within the cover 24 and is at least partially positioned near the second end 28b of the shaft 28. The chassis 14 can be made of any number of materials, including, for example, aluminum. Aluminum has good strength, light weight, and high thermal conductivity. The chassis 14 combines and performs several functions. For example, the chassis 14 serves as a heat sink.

[0038] Furthermore, chassis 14 can be a structural component to which all other components of power module 36 can be attached, and it can also provide essential components for docking the rotating machine assembly 10 with the aircraft. Notably, chassis 14 can provide all attachment points for each component in power module 36, as well as connections to the rest of the rotating machine 12 and air inlet hoses (not shown). Because chassis 14 is a single component performing multiple functions, the size of the rotating machine assembly 10 is kept to a minimum.

[0039] like Figure 2 and Figure 4 As shown, the chassis 14 may include a main body portion 14a and an inlet portion 14b disposed at opposite ends thereto. The inlet portion 14b and the first end 28a of the shaft 28 are disposed at opposite ends of the rotating machine assembly 10 such that the main body portion 14a is disposed between them. The main body portion 14a includes a shroud 14a' and defines an inner circumference and an outer circumference of the main body. The shroud 14a' may serve as the housing of the fan 18 and further guide the air that has traveled through the air passage 16.

[0040] Furthermore, the entrance portion 14b defines the inner perimeter and outer perimeter of the entrance. The outer perimeter of the main body is greater than the outer perimeter of the entrance and the inner perimeter of the main body. Due to the illustrated shapes of the main body portion 14a, the protective cover 14a', and the entrance portion 14b, it should be understood that the term perimeter can be replaced by the term diameter without departing from the scope of this disclosure.

[0041] This shape allows air to pass efficiently through the air passage 16 and properly cool the MOSFET 38, as will be described in more detail below. For example, the air passage 16 is in fluid communication with the rotor 34 to dissipate heat from the power module 36, which includes at least one MOSFET 38 attached to the chassis 14.

[0042] Notice Figures 2-3Fan 18 can be mounted at a second end 28b on shaft 28. Additionally, fan 18 is fluidly positioned between inlet portion 14b of chassis 14 and rotor 34 to aid in cooling MOSFET 38, as will be described below. Since fan 18 is rotatably linked to shaft 28, rotation of shaft 28 causes rotation of fan 18. Fan 18 may include at least one blade shaped to draw air through air passage 16. The airflow direction caused by fan 18 may be from inlet portion 14b toward body portion 14a.

[0043] refer to Figures 5-6 The diagram illustrates a rotating machine 12. A chassis 14 includes an inner wall 44 defining an air passage 16. The inner wall 44 is also defined in a circular cross-section in a plane orthogonal to the axis of rotation 30. The chassis 14 also includes an outer wall 46, which is radially located outside the inner wall 44.

[0044] The outer wall 46 defines a hexagonal cross-section in a plane orthogonal to the axis of rotation 30. The chassis 14 also includes at least one side wall 48 that extends between the inner wall 44 and the outer wall 46 to define the side wall height and connect the inner wall 44 and the outer wall 46 together.

[0045] The chassis 14, and more specifically, the sidewall 48, defines at least one cavity 52. ​​Even more specifically, the inner wall 44, outer wall 46, and sidewall 48 can cooperate to define the cavity 52. ​​The cavity 52 is radially disposed between the air passage 16 and the cover 24. The inner wall 44, outer wall 46, and at least one sidewall 48 are integral to prevent fluid communication between the air passage 16 and the at least one cavity 52.

[0046] It should be noted that the chassis 14 can be manufactured using additive manufacturing (also known as 3D printing), thereby integrally forming the inner wall 44, outer wall 46, and side wall 48, as well as the ribs 58 and fins 68, which will be discussed in more detail below. This achieves better heat transfer and reduces the risks associated with the removable inner wall, outer wall, and / or side wall.

[0047] A power module 36, including at least one MOSFET 38, is radially disposed between at least one cavity 52 and a cover 24. For convenience, the cavity 52 will be described as a single object. However, six or more cavities 52 may be radially disposed around the air channel 16 to adequately manage the thermal of the six or more circuit boards 42 and the multiple MOSFETs 38 disposed on each circuit board 42. These cavities may be structurally identical to the cavity 52 described herein. As illustrated, these cavities are fluidly isolated from each other.

[0048] Phase change material 54 can be disposed within cavity 52. ​​In fact, phase change material 54 can fill all voids in cavity 52. ​​Cavity 52 may include at least one sealable port 56 through which phase change material 54 is introduced into cavity 52, and then port 56 is sealed to prevent leakage of phase change material 54 from cavity 52. ​​Phase change material 54 may be a waxy solid that melts at 108 degrees Celsius and has a heat storage capacity of 180 joules / gram, such that the heat of fusion associated with the melting of phase change material 54 absorbs heat from at least one MOSFET 38.

[0049] At 108 degrees Celsius, the phase change material 54 will melt, and the heat of melting associated with this melting transition will absorb most of the additional heat generated by the MOSFET 38, while maintaining the temperature of the phase change material 54 at 108 degrees Celsius until melting is complete.

[0050] The use of phase change material 54 allows for longer or more demanding start-up mode cycles with a smaller mass than would otherwise be required using a solid aluminum heat sink. It should be understood that different phase change materials can be used to replace the described phase change material 54 without departing from the scope of this disclosure.

[0051] Stay tuned Figures 5-6 The cavity 52 may include a plurality of ribs 58 extending between the inner wall 44 and the outer wall 46 to connect the inner wall 44 and the outer wall 46 together to define the rib height. In addition, the cavity 52 may include a plurality of fins 68 extending from the inner wall 44 toward the axis of rotation 30 to define the fin height.

[0052] This extension of the fins 68 toward the axis of rotation 30 can be radial, so that air can pass between the individual fins 68 as air travels toward the fan 18 through the air passage 16. Furthermore, the rib height can be greater than the fin height and less than the sidewall height. Further still, multiple fins 68 are in fluid communication with the air passage 16, while the ribs 58 are not in fluid communication with the air passage 16.

[0053] Ribs 58 may define a plurality of passages 62 that are in fluid communication with each other and in direct contact with the phase change material 54 disposed within the cavity 52. ​​Each of the plurality of ribs 58 may include an attachment end 64 extending from at least one sidewall 48 toward the stator 26 and a free end 66 opposite to the attachment end 64. The space between the free end 66 of each of the plurality of ribs 58 and at least one sidewall 48 allows fluid communication between the plurality of passages 62.

[0054] The purpose of the phase change material 54 in the chamber is for the start-up mode of the rotating machine 12 so that the MOSFET 38 does not overheat. During the power generation mode of the rotating machine 12, the motor rotates at normal RPM, so the rotating fan 18 draws air through the rotating machine 12. This airflow allows the heat generated by the MOSFET 38 during power generation mode to be dissipated into the moving air through the fins 68 in the airflow. However, this does not work in the start-up mode for two reasons.

[0055] One reason is that the rotating machine 12 rotates slowly during startup mode, and the fan 18 also rotates slowly, meaning there is almost no airflow passing over the fins 68 to dissipate the heat generated by the MOSFET 38. Another reason is that the MOSFET 38 generates more heat during startup mode than during power generation mode. During startup mode, because the MOSFET 38 continuously generates more heat, and because the rotating machine 12 cannot dissipate that heat due to the lack of airflow, the MOSFET 38 has proven to overheat for certain startup mode sequences—if the described rotating machine assembly 10 is not utilized.

[0056] Ribs 58 can have multiple functions. For example, one function of ribs 58 is for start-up mode, and another is for power generation mode. During start-up mode, ribs 58 provide a rapid path for heat to reach the center of phase change material 54 because phase change material 54 has low thermal conductivity. Due to this low thermal conductivity, if ribs 58 were not present, the exterior of phase change material 54 would melt and raise its temperature to over 108 degrees Celsius, while the center of phase change material 54 would remain solid.

[0057] This would prevent the MOSFET 38 from being effectively cooled during various startup mode sequences. As shown, rib 58 connects the inner wall 44 and the outer wall 46. Therefore, rib 58 can transfer heat from the MOSFET 38 to the center of the cavity 52, and thus, to the center of the phase change material 54 during startup mode. If rib 58 were not connected to the outer wall 46, heat might not be effectively transferred to the cavity 52, and therefore, not to the center of the phase change material 54.

[0058] During power generation mode, due to the airflow, rib 58 conducts heat from MOSFET 38 to the inner wall of chassis 14, where the heat is dissipated into the airflow. Because phase change material 54 has low thermal conductivity, heat effectively bypasses phase change material 54 as it flows almost entirely through fins 68 in air channel 16.

[0059] This is why rib 58 is connected to both the outer wall 46 and the inner wall 44 of the cavity 52. ​​It is important to note that both connections ensure that heat is transferred from the MOSFET 38 to the fins 68 in the air channel 16 via rib 58. If rib 58 were not connected to both the outer wall 46 and the inner wall 44 of the cavity, heat would not be able to be transferred from the MOSFET 38 to the fins 68 in the air channel 16.

[0060] As described above, chassis 14 offers numerous advantages. For example, chassis 14 provides mounting connections for air inlet hoses (not shown) from the aircraft, directing air from the air hose inlet to the air passage 16 of fan 18, fins 68 within the air passage 16 to further aid heat transfer, and because it is arranged close to fan 18, it can function as a shroud 14a'. Notably, the fins 68 within the air passage 16 provide a means of dissipating heat generated by MOSFET 38 not during startup but during the power generation mode of rotating machine assembly 10.

[0061] The integrated shield 14a' achieves more efficient airflow through the optimized fan 18, which in turn improves the cooling of the rotating machine 12. Integrating all these functions into a single component (i.e., chassis 14) reduces complexity and the number of parts, and eliminates interface problems that can occur with multiple components performing the same function. Having this as a single component also makes airflow optimization much easier, as there are no fasteners or component interfaces that could disrupt airflow. As will be understood, this is highly desirable in aircraft.

[0062] The rotating machine components have been described in detail above. Modifications and substitutions may arise after reading and understanding the foregoing detailed description. However, the invention is not limited to the embodiments described above. Rather, the invention is broadly defined by the appended claims and their effects.

Claims

1. A rotating machine assembly, comprising: Rotating machines, including A cover, the cover defining the outer surface of the rotating machine; A stator, which is housed within the cover and is fixed relative to the cover; A shaft, which is at least partially rotatably disposed within the cover to define an axis of rotation, the shaft including a first end connectable to an aircraft engine and a second end opposite to the first end; A rotor, which is attached to the shaft and is movable relative to the stator; A power module, the power module including at least one MOSFET, the at least one MOSFET periodically reversing the current direction of the rotor, the power module including the at least one MOSFET being disposed within the cover; as well as A chassis, at least partially disposed near the second end of the shaft, including a power module of the at least one MOSFET attached to the chassis, and the chassis defining an air passage in fluid communication with the rotor to transfer heat away from the at least one MOSFET, wherein the chassis at least defines a cavity radially disposed between the air passage and the cover, and wherein at least one cavity includes a phase change material disposed therein.

2. The rotating machine assembly of claim 1, further comprising a control housing, wherein a control module is disposed within the control housing, wherein the control module is separate from and distinct from the power module, and the control housing is mounted on the cover of the rotating machine so as to be located outside the rotating machine and attached to the rotating machine.

3. The rotating machine assembly of claim 1, wherein the chassis comprises a body portion and an inlet portion disposed at opposite ends thereof, the inlet portion and the first end of the shaft being disposed at opposite ends of the rotating machine assembly such that the body portion is disposed therebetween, and wherein the chassis is received in the cover.

4. The rotating machine assembly of claim 3, wherein the main body portion defines an inner circumference and an outer circumference of the main body, and the inlet portion defines an inner circumference and an outer circumference of the inlet, and wherein the outer circumference of the main body is greater than the outer circumference of the inlet and the inner circumference of the main body.

5. The rotating machine assembly of claim 3, further comprising a fan disposed at a second end on the shaft, wherein the fan is fluidly disposed between the inlet portion of the chassis and the rotor.

6. The rotating machine assembly of claim 1, wherein the phase change material is a waxy solid that melts at 108 degrees Celsius and has a heat storage capacity of 180 joules / gram, such that the heat of fusion associated with the melting of the phase change material absorbs heat from the at least one MOSFET.

7. The rotating machine assembly of claim 1, wherein the power module comprising the at least one MOSFET is radially disposed between the at least one cavity and the cover.

8. The rotating machine assembly of claim 1, wherein the at least one cavity is defined by at least one sidewall, and the at least one cavity includes a plurality of ribs in direct contact with the phase change material, the plurality of ribs defining a plurality of passages in fluid communication with each other.

9. The rotating machine assembly of claim 8, wherein each of the plurality of ribs includes an attachment end extending from the at least one sidewall toward the stator and a free end opposite the attachment end, wherein the space between the free end of each of the plurality of ribs and the at least one sidewall allows fluid communication between the plurality of passages.

10. The rotating machine assembly of claim 1, wherein the chassis includes an inner wall defining the air passage, an outer wall radially located outside the inner wall, and at least one side wall extending between the inner wall and the outer wall to define a side wall height and connect the inner wall and the outer wall together, and wherein the inner wall, the outer wall and the at least one side wall cooperate to define at least one cavity, the at least one cavity including a phase change material disposed therein.

11. The rotating machine assembly of claim 10, wherein the inner wall, the outer wall, and the at least one side wall are integral to prevent fluid communication between the air passage and the at least one cavity, and wherein the at least one cavity includes at least one sealable port through which the phase change material is introduced into the at least one cavity.

12. The rotating machine assembly of claim 10, further comprising a plurality of ribs extending between the inner wall and the outer wall to connect the inner wall and the outer wall together, thereby defining a plurality of passages in fluid communication with each other and in direct contact with the phase change material, wherein one end of the plurality of ribs is spaced apart from the at least one sidewall to allow fluid communication between the plurality of passages.

13. The rotating machine assembly of claim 10, wherein the inner wall defines a circular cross-section in a plane orthogonal to the axis of rotation.

14. The rotating machine assembly of claim 10, wherein the outer wall defines a hexagonal cross-section in a plane orthogonal to the axis of rotation.

15. The rotating machine assembly of claim 10, wherein the chassis includes a plurality of fins extending from the inner wall toward the axis of rotation to define a fin height, and wherein the plurality of fins are in fluid communication with the air passage.

16. The rotating machine assembly of claim 15, wherein the at least one cavity includes a plurality of ribs extending between the inner wall and the outer wall to connect the inner wall and the outer wall together to define a rib height, and wherein the rib height is greater than the fin height and less than the sidewall height.

17. The rotating machine assembly of claim 1, wherein the at least one MOSFET comprises a plurality of MOSFETs disposed on a plurality of printed circuit boards circumferentially mounted to the chassis such that they are located between the air passage and the cover to radially surround the air passage.

18. The rotating machine assembly of claim 17, further comprising a plurality of pads disposed between the printed circuit board and the chassis, wherein the plurality of pads are thermally conductive and electrically insulating to electrically isolate the printed circuit board from the chassis.

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