AN ELECTRIC TURBOMACHINE

Abstract

An electric turbomachine for use with an internal combustion engine, turbocharger or a fuel cell e-compressor, said electric turbomachine comprising: a compressor (20) that is arranged to compress fluid within a turbo compressor when it is rotationally driven about a rotational axis (R) by a shaft, said shaft being rotational supported by a drive-end bearing (65) and a non-drive-end bearing (85), and a high-speed electrical machine located within a housing (50) that is arranged to rotationally drive the shaft about the rotational axis (R); said housing comprising a drive-end wall (60) that the shafts extends through to rotationally drive the compressor, a non-drive- end wall (80) at the opposing end of the electric turbomachine to the compressor, and a side wall (55) that extends between the drive-end wall and the non-drive-end wall, and wherein the electric turbomachine comprises a cooling system (330), for receiving a flow of a coolant fluid to cool the electric turbomachine, that is integrated within the housing of the electric turbomachine.

Claims

1. An electric turbomachine for use with an internal combustion engine, a turbocharger or a fuel cell e-compressor, said electric turbomachine comprising: a compressor that is arranged to compress fluid within a turbo compressor when it is rotationally driven about a rotational axis (R) by a shaft, said shaft being rotational supported by a drive-end bearing and a non-drive-end bearing, and a high-speed electrical machine located within a housing that is arranged to rotationally drive the shaft about the rotational axis (R); said housing comprising a drive-end wall that the shafts extends through to rotationally drive the compressor, a non-drive-end wall at the opposing end of the electric turbomachine to the compressor, and a side wall that extends between the drive-end wall and the non-drive-end wall, and wherein the electric turbomachine comprises a cooling system, for receiving a flow of a coolant fluid to cool the electric turbomachine, that is integrated within the housing of the electric turbomachine.

2. The electric turbomachine of claim 1, wherein the cooling system comprises a drive-end coolant cavity located within the drive-end wall for receiving a flow of coolant fluid to cool the electric turbomachine.

3. The electric turbomachine of claim 2, wherein the drive-end coolant cavity encircles the shaft as it extends through the drive-end wall.

4. The electric turbomachine of claim 2, wherein the drive-end coolant cavity is arranged to cool the drive-end bearing.

5. The electric turbomachine of claim 4, wherein the drive-end coolant cavity encircles the drive-end bearing.

6. The electric turbomachine of claim 1, wherein the cooling system comprises a non-drive-end coolant cavity located within the non-drive-end wall for receiving a flow of fluid coolant to cool the electric turbomachine.

7. The electric turbomachine of claim 6, wherein the non-drive-end coolant cavity encircles the non-drive end of the shaft.

8. The electric turbomachine of claim 6, wherein non-drive-end coolant cavity encircles the non-drive end bearing.

9. The electric turbomachine of claim 6, wherein the non-drive-end coolant cavity is arranged to cool power electronics that are mounted on an exterior surface of the non-drive-end wall.

10. The electrical turbomachine of claim 9, wherein non-drive-end coolant cavity comprises one or more plate-like or disc-like portions that are arranged to cool the power electronics mounted on the exterior surface of the non-drive- end wall.

11. The electric turbomachine of claim 9, wherein the non-drive-end coolant cavity is arranged to cool a control printed circuit board that is mounted on the exterior surface of the non-drive-end wall.

12. The electric turbomachine of claim 9, wherein the non- drive-end coolant cavity is arranged to cool capacitors.

13. The electric turbomachine of claim 1, wherein the cooling system comprises a side wall coolant cavity located within the side wall for receiving a flow of coolant fluid to cool the electric turbomachine.

14. The electric turbomachine of claim 13, wherein the side wall coolant cavity is arranged to cool the electrical machine.

15. The electric turbomachine of claim 14, wherein the side wall coolant cavity is arranged to cool power electronics that are mounted on an exterior surface of the side wall.

16. The electric turbomachine of claim 15, wherein the side wall coolant cavity is arranged to cool a power printed circuit board that is mounted on the exterior surface of the side wall.

17. The electric turbomachine of claim 16, wherein the side wall coolant cavity is arranged to cool a plurality of power PCBs that are mounted on one or more exterior surfaces of the side wall.

18. The electric turbomachine of claim 14, wherein the majority of the side wall coolant cavity is formed between an interior surface of the side wall and one or more channels in the surface of a jacket that supports the electrical machine.

19. The electric turbomachine of claim 14, wherein the majority of the side wall coolant cavity is formed within the side wall of the housing.

20. The electric turbomachine of claim 1, wherein the cooling system comprises a drive-end coolant cavity located within the drive-end wall for receiving a flow of coolant fluid to cool the electric turbomachine, a non-drive-end cavity located within the non-drive-end wall for receiving a flow of fluid coolant to cool the electric turbomachine, and a side wall coolant cavity located within the side wall for receiving a flow of coolant fluid to cool the electric turbomachine.

21. The electric turbomachine of claim 20, wherein the drive-end coolant cavity, the non-drive-end coolant cavity and the side wall coolant cavity are fluidly connected to one another to form a continuous pathway inside the housing for receiving a flow of coolant fluid to cool the electric turbomachine.

22. The electric turbomachine of claim 21, wherein the fluid connections between the drive-end coolant cavity, non-drive-end coolant cavity and the side wall coolant cavity are integrated within the drive-end wall, non-drive-end wall and the side wall.

23. The electric turbomachine of claim 22, wherein the drive-end coolant cavity is fluidly connected to the side wall coolant cavity, and the side wall coolant cavity is fluidly connected to the non-drive-end coolant cavity.

24. The electric turbomachine of claim 23, wherein the cooling system is arranged such that, in use, coolant fluid flows into the cooling system via an inlet into the non-drive-end wall cavity and coolant fluid flows out of the cooling system via an outlet from the drive-end wall cavity.

25. The electric turbomachine of claim 1, wherein the cooling system is the only system used to actively cool the electric turbomachine.

Description

DETAILED DESCRIPTION

[0059] Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0060] FIG. 1 is a cross-section of an electric compressor in accordance with the present claimed invention;

[0061] FIG. 2 is a perspective view of a section of the electric compressor of FIG. 1;

[0062] FIG. 3 is a second perspective view of a second section of the electric compressor of FIG. 1, where electric compressor includes the compressor;

[0063] FIG. 4 is a perspective view of the exterior of the electric compressor of FIG. 1, and in particular the power PCBs, where the power cover has been omitted;

[0064] FIG. 5 is an exploded perspective view of the features shown in FIG. 4;

[0065] FIG. 6 is the perspective view of the electric compressor of FIG. 4, where the power cover is included;

[0066] FIG. 7 is a cross-section of the electric compressor of FIG. 1, where the pathway of the cooling system remains in the half of the machine removed in the cross-section; and

[0067] FIG. 8 is a schematic layout of an electric compressor connected to an internal combustion engine in accordance with the present claimed invention.

[0068] Referring to FIGS. 1 to 3 of the drawings, there is depicted a cross-section, a first perspective sectioned view and a second perspective sectioned view of an electric compressor 10, in accordance with the present claimed invention. The electric compressor 10 comprises a compressor 20 situated within a turbo compressor 25. The compressor 20 is connected to a shaft 30 by a threaded fixing 40. The compressor 20, turbo compressor 25 and threaded fixing 40 are known in the state of the art and are not within the scope of the invention.

[0069] The shaft 30 protrudes from its fixing with the compressor 20 through the rear-side of the compressor 20 into the housing 50 of the electric compressor 10. The end of the housing 50 adjacent to the compressor 20 is the drive-end (DE) of the housing 50 and electric compressor 10, and the opposing end of the housing 50 and electric compressor 10 removed from the compressor 20 is known as the non-drive-end (NDE).

[0070] The wall of the housing at the DE of the housing 50 is known as the drive-end wall 60 and the wall of the housing at the NDE of the housing 50 is known as the non-drive-end wall 80. The NDE wall 80 and DE wall 60 are connected by a side wall 55 of the housing 50 that extends between them.

[0071] The shaft 30 extends through the DE wall 60 of the housing 50 through the generally cylindrical central cavity 70 inside the housing 50 towards the NDE wall 80. The DE wall 60 and the NDE wall 80 are separated by the side wall 55 of the housing 50. The interior side of the side wall 55 is generally cylindrical helping to give the central cavity 70 its generally cylindrical shape. The DE wall 60 and the side wall 55 of the housing 50 are integrally formed from a single piece of aluminium. The NDE wall 80 of the housing 50 is a separate piece that is fixed in position onto the housing 50 by fixings between flanges 56 at the end of the side walls 55 and the NDE wall 80. In this embodiment, the NDE wall 80 is made aluminium because of its excellent thermal conductance; however, other embodiments are envisaged in which the metals or materials are envisaged. The NDE wall 80 can be removed from the housing 50 to provide access to the central cavity 70.

[0072] The shaft 30 is mounted on two bearings: the DE bearing 65 and the NDE bearing 85. The DE bearing 65 is situated within the DE wall 60 and located between the compressor 20 and the rest of the electric turbomachine 10 such as the central cavity 70. The NDE bearing 85 is located adjacent to the NDE wall 80 in a bearing housing 87. The bearing housing 87 is attached via an interference fit to the interior side of NDE wall 80. The bearing housing 87 thermally connects the NDE bearing to the NDE wall.

[0073] The shaft 30 is arranged to be rotated about rotational axis R by a high-speed electrical machine 90 that is located within the central cavity 70 of the housing 50. The rotational axis R is parallel and coaxial with the longitudinal axis of the shaft 30. The DE wall 60 and the NDE wall 80 are substantially perpendicular to the rotational axis R of the shaft 30, and the side wall 55 is substantially parallel to the rotational axis R of the shaft 30.

[0074] The shaft 30 comprises a rotor portion 100 that is the rotor of the electrical machine 90. The rotor portion 100 comprises permanent magnets 105 embedded of the surface of the shaft 30. In alternative embodiments, the permanent magnets 105 are embedded within the interior of the shaft. The rotor portion 100, and shaft 30, extend through the stator 110 of the high-speed electrical machine 90. In this embodiment, the electrical machine 90 is a permanent magnet synchronous motor and the rotor portion 100 and stator 110 are configured in line with the state of the art. The rotor 100 and stator 110 are located approximately centrally along the length of the shaft 30 and approximately centrally between the DE wall 60 and the NDE wall 80 of the housing 50.

[0075] Surrounding the electrical machine 90 is a jacket 120. The jacket 120 is generally cylindrical is located around the circumferential walls of the stator 110 such that the jacket 120 is located between the stator 110 and the side wall 55 of the housing 50. In this way, the jacket 120 acts as an EMI shield for the electrical machine 90. The jacket 120 also comprises a plurality of cooling channels 130. The cooling channels 130 are grooves or recesses in the outside surface of the jacket 120. The cooling channels 130 in combination with the inside surface of the side wall 55 define a helical cooling cavity 140 which are arranged for a flow of coolant fluid around the circumference of the jacket 120 and stator 110. In this way, the jacket 120 is arranged to cool the electrical machine 90. The cooling of the electric compressor 10, and electrical machine 90, is discussed in depth later.

[0076] The stator 110 comprises windings 150 that extend from either end of the substantially cylindrical stator member 160 into the central cavity 70 of the housing 50. The windings 150 are configured such that the electrical machine 90 is a three-phase motor as is known in the state of the art. Further embodiments are envisaged where the motor is a six-phase or a nine-phase motor for larger electrical machines.

[0077] The stator member 160 is held in place inside the central cavity 70, relative to the rotor portion 100, by the jacket 120, where the substantially cylindrical stator member 160 sits within and is fixed in place by a friction fit with a shoulder 170 in the interior surface of the jacket 120.

[0078] The NDE end of windings 150 is electrically connected to a power PCB 180a of power electronics assembly 190, or power electronics by an AC busbar 200a and a first electrical connection member 210. In this embodiment, the power PCB is split up into three separate power PCBs 180a, 180b, 180c, where each power PCBs 180a, 180b, 180c is connected by one of the three separate AC busbars 200a, 200b, 200c to the winding 150 of the stator 110. The windings 150 are then connected to one another by a star connection.

[0079] Each of power PCBs 180a, 180b, 180c comprises substantially the same circuitry, including transistors 195, such that this circuitry is triplicated within the power electronics assembly 190. Other embodiments are envisaged where the power PCB is not split or alternatively split into a number of boards, e.g. two or six. It is preferred that the PCB is split into the number of phases of the electrical machine 90 or motor.

[0080] The electrical connection member 210 extends through the central cavity 70 from the windings 150 towards to NDE wall 80. From the electrical connection member 210, the respective AC busbar 200a, 200b, 200c extends up and through the side wall 55 of the housing 50 in a direction substantially perpendicular to the rotational axis R and is electrical connected to the power PCB 180a. Each of the AC busbars 200a, 200b, 200c electrically connects the windings 150 at a single point to the AC supplied by its respective power PCB 180a, 180b, 180c. The AC busbar 200a, 200b, 200c is of the braided-type such that it can withstand the heating changes and vibrational forces generated during the lifetime of the machine.

[0081] Referring to FIGS. 4 and 5 drawings, the configuration of the three power PCBs 180a, 180b, 180c is depicted in a perspective view and an exploded perspective view. In this embodiment, as is shown in the drawings each of the power PCBs 180a, 180b, 180c is mounted on the side wall 55 of the housing 50, and lies in a plane substantially perpendicular with the rotational axis R. That is, the three power PCBs the 180a, 180b, 180c are mounted on three separate flat surfaces 185a, 185b, 185c on the exterior of the side wall 55 of the housing 50. Each of the three flat surfaces 185a, 185b, 185c lies in a plane substantially parallel with the rotational axis R of the shaft and is substantially planar and rectangular.

[0082] The three flat surfaces 185a, 185b, 185c are configured in a generally square-bottomed U-shape relative to one another, such that one flat surface 185b is substantially perpendicular to the other two substantially parallel flat surfaces 185a, 185c. Or, in other words, the three flat surfaces 185a, 185b, 185c occupy three sides of a square. The three power PCBs 180a, 180b, 180c are each mounted onto one of the flat surfaces 185a, 185b, 185c, such that they are also configured in a generally square-bottomed U-shape relative to each other. Other arrangements of the three flats surface 185a, 185b, 185c and the power PCBs 180a, 180b, 180c, mounted thereon are envisaged, such as a generally triangular arrangement, a pentagonal arrangement or a hexagonal arrangement etc., where the power PCBs are mounted on some or all of the arrangements surfaces.

[0083] All three of the power PCBs 180a, 180b, 180c are supplied with DC power by a DC link busbar 220. The DC link busbar 220 is connected by two electrical connections 235 to the power PCBs 180a, 180b, 180c. Each of the power PCBs 180a, 180b, 180c acts as an inverter using power electronics as is known in the state of the art. The DC link busbar 220 is generally U-shaped such that it can connect with each of the three power PCBs 180a, 180b, 180c simultaneously.

[0084] Splitting the power PCB into three separate power PCBS 180a, 180b, 180c enables the power PCB to be mounted on the side wall 55 of the housing 50 without extending beyond the circumferential footprint of the DE wall 60, the turbo compressor 25. Or, in other words, the power PCB 180a, 180b, 180c does not increase the maximum diameter, or distance from the rotational axis R, of the electric compressor 10. Instead, this maximum diameter or distance from the rotational axis R is defined by the compressor 25 of the art. In this way, splitting the power PCB 180a and incorporating it onto the side of the housing 50 of the electric compressor 10 compacts it. That is, splitting the power PCBs 180a, 180b, 180c substantially reduces the size of the electric compressor 10 as the power PCB 180a, 180b, 180c is not a monolithic PCB and can fit closely and around the components of the electric compressor 10 that are harder to reduce in size. Compacting the electric compressor 10 is on particular importance in vehicle applications due to the limited size in an engine bay of a vehicle. Splitting the power electronics assembly 190 further can help reduce the mass of the electric compressor 10 that is also beneficial in vehicles.

[0085] Referring back to FIGS. 1 to 3, the DC power supplied to the DC link busbar 220 is supplied by the input busbar 250. The input busbar 250 is mounted on the exterior side of the NDE wall 80. The input busbar 250 receives DC electric from a DC source such as a battery in a vehicle. In this embodiment, the electric compressor 10 and its components are configured in this embodiment to work with a 48 V DC supply that is used to power a modern hybrid power train in a vehicle. Other embodiments are envisaged using a DC power supply in the range of 12 to 800+ V.

[0086] Further, the input busbar 250 comprises capacitors 240 that are located on the input busbar 250 and receive power from the DC power supply. The capacitors 240 are located within the NDE wall 80 of the electric compressor 10. The input busbar 250 and the capacitors 240 are mounted on the NDE wall 80 thus limiting their footprint.

[0087] The control PCB 230 controls the DC power supplied by power PCBs 180a, 180b, 180c to the electrical machine 90 in relation to in relation to the desired speed of electrical machine 90 to achieve the desired boost pressure for the internal combustion engine associated with the electric compressor 10. The main parameter that the control PCB 230 will request is the speed of the compressor 20 such that the control PCB 230 can control the high-speed electrical engine 90 to provide to boost pressure required. The control PCB 230 may also preferably receive and process inputs from the internal combustion engine such as power demand, power output, efficiency, emissions of the internal combustion engine as well as the temperature and pressure inside the internal combustion engine. In embodiments, where the electric compressor 10 is used in tandem with a turbocharger the control PCB 230 may also receive information regarding the turbocharger speed and boost pressure.

[0088] The control PCB 230 comprises a sensor 260 for detecting of the speed rotation of the shaft 30, i.e. speed of the electrical machine 90. The sensor 260 is mounted directly on the control PCB 230 and is located on the rotational axis R of the shaft 30. The shaft 30 itself extends into a sensor portion 75 of the central cavity 70, where the sensor portion 75 is substantially cylindrical and extends from the end of the windings 150 towards the NDE wall 80. The sheath 270 holds the permanent magnet 280 in a position within a sensor portion 75 of the central cavity 70 adjacent to, but not engaging, the rear side of the NDE wall 80. As such, the permanent magnet 280 mounted onto the shaft 30 proximate to the rear side of the control PCB 230, and more specifically, the sensor 260. The speed of the electrical machine 90 is sensed directly by the control PCB 230 by the sensor 260 sensing the rotation of the magnetic fields of the magnet 280. The sensor 260 and permanent magnet provides an acceleration advantage for the high-speed electrical machine. Embodiments of the electrical turbomachine 10 that do not comprise the sensor 260 and permanent magnet 280 are envisaged. The control PCB 230 is protected by a control cover 290 that completely encapsulates the control PCB 230 in a watertight and airtight manner.

[0089] Referring to FIGS. 5 and 6 of the drawings, there is depicted a power cover 300 for covering and protecting the power PCBs 180a, 180b, 180c. The cover 300 is arranged to be fixed by screws 305 onto a rim 310 of the housing 50. The cover 300 is generally U-shaped and is integrally formed from a single piece. When the cover 300 is attached to the rim 310 of the housing 50, a rubber seal 320 is sandwiched between the cover 300 and the rim 310. The rubber seal 320 is compressed between the cover and the rim 310 to give a watertight seal. Using a single cover, the power cover 300, reduces the number of egress points and point points of failure of fluids.

[0090] Accordingly, due to the control cover 290 and power cover 300, the electric compressor 10 can be used in vehicles as the power electronics assembly 190 is sufficiently protected from water and cleaning products used to clean the engine bay of a vehicle.

[0091] The implementation as described of the power electronics assembly 190 as described above produces a design implementation that does not need a separate installation location, separate connections and sealing requirements and thereby avoids increasing in the number of failure modes. Further, the implementation of the power electronics assembly 190 distributes the power electronics assemblies around the machine enables the power electronics assembly 190 to stay closer to the outline of the machine and, essentially, reducing its size such that it is kept within the overall confines of circumferential footprint and space allocation of the electrical turbomachine.

[0092] Referring to FIG. 7, the cooling system 330 of the electric compressor 10 in accordance with the present invention is depicted. FIG. 7 depicts a cross-section where half of the electric compressor 10 has been removed. In the half that has been “cut-away” in FIG. 7, the cooling system 330 has been left to illustrate cooling system 330.

[0093] A single cooling system 330 is used to cool all of the components of the electric compressor 10. The cooling system 330 comprises a continuous cooling circuit around the interior of housing 50 of the electric compressor 10. The cooling system 330 is design for a coolant fluid, such as water, glycol or another suitable coolant, to be pumped, by a pump (not shown), around the interior of the electric compressor 10. The cooling system 330 comprises a plurality of individual cooling cavities, as described herein, connected directly or by a number of cooling conduits to form a complete cooling system 330 for the entire electric compressor 10. Each of the cooling cavities is surrounded by a thermally conductive material to assist in the transfer of heat form the electric compressor 10 to the coolant fluid. In this embodiment, aluminium is preferred due to its excellent the thermally conductivity, immunity to rust, resistance to corrosion and strong mechanical properties.

[0094] The coolant fluid enters the cooling system 330 at the coolant inlet 340 which is located on the side wall 55 of the housing 50 and proximate the NDE wall 80 and NDE of the electric compressor 10. The positioning of the coolant inlet 340 is flexible but it is preferred from it to be closer to the NDE of the electric compressor.

[0095] From the coolant inlet 340, the coolant fluid can flow through to a capacitor coolant cavity 350. The capacitor coolant cavity 350 is formed between the flanges 56 of the housing 50 and the NDE wall 80, and extends substantially along the end of the capacitors 240 removed from the control PCB 230.

[0096] From the capacitor coolant cavity 350 the coolant can flow into the NDE coolant cavity 360. The NDE coolant cavity 360 is a torus-shaped, or toroid-shaped, cavity in the NDE wall 80 that encircles the sensor portion 75 of the central cavity 70. It is important to keep the permanent magnet 280 for the sensor 260 cool, such that the magnetism of the permanent magnet 280 is not degaussed. The NDE coolant cavity 360 not only cools the sensor cavity 75 but also cools the interior and exterior sides of the NDE wall 80. The NDE coolant cavity 360 aids in cooling both the central cavity 70 and the components housed therein, including the sensor portion 75 of the cavity, but also the control board 230 mounted on the exterior surface of the NDE wall 80. The NDE coolant cavity 360 therefore performs triple-sided cooling.

[0097] Furthermore, the NDE coolant cavity 360 is thermally linked with the bearing housing 87 such that it can removed heat conducted along the shaft which heats the NDE bearing 85 and self-heating of the NDE bearing 85. These heat flows act to increase the operating temperature of this bearing 85, which would lead to a markedly reduced life if it were not cooled by the NDE coolant cavity 360.

[0098] The NDE coolant cavity 360 does not extend the full height or width of the NDE wall 80 or control board 230. A control PCB coolant cavity 370 is provided to cool the part of the control PCB 230 not sufficiently cooled by the capacitor coolant cavity 350 or the NDE coolant cavity 360. The control PCB coolant cavity 370 is substantially plate-like or disc-like and is a cavity within the NDE wall 80 and is supplied with coolant fluid from the NDE coolant cavity 360.

[0099] The capacitor coolant cavity 350, the NDE coolant cavity 360 and the control PCB cooling cavity 370 are the NDE wall coolant portion 380 of the cooling system 330 and each of the cavities is fluidly connected to allow coolant fluid to circulate throughout them via a continuous pathway or circuit.

[0100] The NDE wall coolant portion 380 is fluidly connected to the central coolant portion 390 by a first cooling conduit 400. The first cooling conduit 400 supplies coolant fluid to the central coolant portion 390 and a helix coolant cavity 410. The helix coolant cavity 410 is a continuous helix that wraps around the electrical machine 90 from the NDE wall 80 towards the DE wall 60. The helix coolant cavity 410 is formed from the coolant channels 130 in the jacket 120 engaging with the side wall 55 of the housing 50. That is, the jacket 120 comprises a helical coolant channel 130 in its exterior surface that is sealed by engaging the side wall 55. The majority of the exterior surface of the jacket 120 is the coolant channel 130. The cross-section of a portion of the helix coolant cavity 410 is generally rectangular. The longer edges of the rectangular cross-section are parallel to the rotational axis R. In this embodiment, the helix of the coolant channel 130, and the helix coolant cavity 410, has seven turns. The number of turns and the helical geometry of the helix coolant cavity 410 can be modified according to the requirements of the cooling system 330. For example, the number of turns could be increased to increase heat transfer to the coolant with the drawback of the higher inlet pressure due to increased pressure drop across the fluid. In this embodiment, seven turns was found by the applicant to be a comprise which provided adequate cooling while simultaneously not increasing the pressure beyond that of the rating of the pump typically used in the desired application. This is because the coolant fluid in this embodiment will be provided by the pump of the internal combustion engine’s coolant system. Other embodiments are envisaged in that the coolant cavity 410 is not a helix but rather interconnected parallel channels.

[0101] Coolant fluid entering the helix coolant cavity 410 will circle the electrical machine 90 seven times before exiting the helix coolant cavity 410 and entering the DE cooling portion 420 by a second conduit 430. The helix coolant cavity 410 has a double-sided cooling activity as it cools both the electrical machine 90 (i.e. central cavity 70, rotor 90, stator 110 and windings 150) and the power PCBs 180a, 180b, 180c via cooling the jacket 120 and side wall 55, respectively.

[0102] The turn of the helix coolant cavity 410 proximate the DE wall 60 is fluidly connected by a second cooling conduit 430 to the DE coolant cavity 440. The DE coolant cavity 430 is a torus-shaped, or toroid-shaped, cavity within the DE wall 60 that encircles the DE bearing 65 and the location on the DE wall 60 which the shaft 30 protrudes through the DE wall 60 to connect to the compressor 20. The DE coolant cavity 430 is substantially larger in volume than the similarly shaped NDE coolant cavity 360, reflecting the fact that, in use, the DE of the electric compressor 10 will be substantially hotter than the NDE of the electric compressor 10 in use. This is because of the DE proximity to the hot fluids (i.e. compressed engine intake air) onto which the turbo compressor 25 and compressor 20 have performed work. The DE coolant cavity 440 performs triple sided cooling of the central cavity 70 and DE bearing 65. Integrating the DE bearing 65 within the DE wall 60 enables the DE bearing 65 to be cooled by the DE coolant cavity 440. Heat from the compressor 25 is conducted into the electric compressor 10 through the housing 55 and heats the DE bearing 65 and the DE bearing 65 self-generates heat internally. These heat flows act to increase the operating temperature of the DE bearing 65, which would lead to a markedly reduced lifespan if not cooled. This problem is addressed by the DE coolant cavity 430 that not only cools heat from the compressor 20 but also the self-generated heat from the DE bearing 65.

[0103] The coolant fluid leaves the DE coolant cavity 440 via an outlet 450. In use, the outlet 450 is connected by piping to a radiator such that the coolant fluid can be cooled before circulating back into the cooling system 330 via the inlet 340. The cooling system 330 flows from the NDE cooling portion 380 to helix coolant cavity 410 to DE coolant cavity 440 the DE end of the electric compressor 10 is hotter than the NDE. By pumping the coolant fluid in this direction, i.e. along increasing temperature gradient, the cooling system 330 ensures that each part of the electric compressor 10 is sufficiently cooled.

[0104] In the prior art, the control PCB 230 and the power PCBs 180a, 180b, 180c are typically cooled by one or more cooling systems and the electrical machine 90 by another cooling system. This significantly increases the size of the electric compressor 10. The electric compressor 10 and cooling system 330 of the present invention has the advantage of being more compact and have less components as a single cooling system 330 or cooling circuit can cool every part of the electric turbomachine 10. This is particular advantageous in vehicle applications as it reduces the size of the electric compressor 10 such that is occupies less space in the engine bay while also reducing the mass of the overall system.

[0105] Referring to FIG. 8 of the drawings, there is shown a schematic diagram showing how an electric compressor 10 could be connected in relation to an internal combustion engine 11. The electric compressor 10 is in accordance with the present invention and comprises power electronics 190 that supplies a current to a high-speed electrical machine 90. The high-speed electrical machine 90 is arranged to convert the electric current suppled to it by the power electronics 190 to rotation of the shaft 30 and the compressor 20 connected by the end of the shaft 30. Rotation of the compressor 20 by the high-speed electrical machine 90 draws in air and compresses the air, boosting the pressure of the air. Typically, the electric compressor 10 is located downstream of pressure boosting system, such as a turbocharger, and the electric compressor 10 further boosts the pressure of the air from the turbocharger. This is particularly useful for providing a rapid increase in boost pressure during the start-up or warm-up of a system or during transient or high-load events. Alternatively, the electric compressor 10 can draw and boost the pressure of air drawn directly form the environment. The pressure-boosted air leaves the compressor 20 by the inlet conduit 12 and travels towards the internal combustion engine 11. Along the pathway of the inlet conduit 12 is located a radiator 13 which is arranged to cool the pressure-boosted air in the inlet conduit 12, prior to the pressure-boosted air entering the internal combustion engine 11. The amount of boost pressure generated by the electric compressor 10 in the pressure-boosted air is controlled by the speed of rotation of the high-speed electrical machine 90, whereby the rotational speed of the high-speed electrical machine 90 is controlled from inputs from the power electronics 190. The power electronics 190 can control the boost pressure in response to a number of sensors or readings, for example, this will typically be a request from the engine control unit that will request a set speed. However, other parameters could be measured such as the power, emissions or efficiency of the internal combustion engine 11 and the power electronics assembly 190 could respond accordingly.

[0106] The above description refers exclusively to an electric compressor 10. Other embodiments, including other electric turbomachines are envisaged. For example, a turbocharger or turbogenerator where the power electronics are similarly mounted directly onto the housing of the turbocharger or turbogenerator to reduce the footprint and packaging size. Additionally, an electric turbomachine comprising a single cooling system integrated into the housing of the turbocharger or turbogenerator to provide cooling for its electrical machine and its power electronics assembly is within the scope of the present invention.