GB2594934A

GB2594934A - Apparatus for cooling an electrical machine

Info

Publication number: GB2594934A
Application number: GB2006720.3A
Authority: GB
Inventors: Shi Juntao
Original assignee: IMRA Europe SAS
Current assignee: IMRA Europe SAS
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2021-11-17
Anticipated expiration: 2040-05-06
Also published as: GB202006720D0; GB2594934B

Abstract

A rotor 100 for an electrical machine comprising, a body 120 and a mount for the body, coils affixed to the surface of the rotor located proximate to an air gap between the rotor and a stator of the machine. One or more channels 110 are formed in the body allowing coolant to flow to and from the channels adjacent to the surface. The channels comprise an inlet 116a, an outlet 116b, two extending radial portions112a, 112b, and one or more extending axial portions 114 to connect the radial portions, where the axial portions are located at a periphery of the rotor. The axial portions may comprise a cover material 140 located at the surface made from a higher thermal conductivity than a remainder of the body. One or more extending circumferential portions may be provided to connect the axial portions. The inlet and outlet may be located at a same axial position of the rotor or offset from each other in an axial direction. The axial portions may be angled in the axial direction. The rotor may be located closer or further to the axis of rotation of the machine than the stator. The rotor may comprise a shaft 130 comprising holes connected to the inlet and outlets. The rotor body may be formed of a nonmagnetic material. A similar coolant channel arrangement may be provided for the stator.

Description

Apparatus for Cooling an Electrical Machine

Field of the Invention

The invention relates generally to electrical machines and in particular to thermal control of such electrical machines.

Background

Electrical machines are used to generate mechanical or electrical power, dependent on the particular type of electrical machine. For example, electrical motors generate mechanical power in response to electrical input, while generators produce electrical power in response to mechanical input. However, both types of power generation result in the production of heat as a result of losses in the system (for example mechanical, resistive and/or magnetic losses).

The generation of heat in this manner limits the capacity of the electrical machine. In general, an electrical machine with a high power production will also generate a greater quantity of heat. In order to avoid the excessive build-up of heat and possible malfunction or failure of the electrical machine, this heat must be effectively dissipated from the electrical machine. Accordingly, cooling systems are sometimes incorporated into electrical machine in order to aid the dissipation of heat from the electrical machine.

The present inventors have identified an approach for improving cooling to rotors and stators of electrical machines. Accordingly, the overall risk of component failure or malfunction can be reduced and the overall power output of the electrical machine can be increased. It additionally means that the electrical machine can operate in closer proximity to other components thus allowing for smaller devices or systems to be made incorporating electrical motors as described herein.

Summary of the Invention

Aspects of the invention are set out in the accompanying claims.

In a first aspect of the invention there is provided a rotor for an electrical machine. The rotor comprises a rotor body; a rotor mount on which the rotor body is mounted; one or more coils affixed to an active surface of the rotor, wherein the active surface of the rotor is located proximate to an air gap of the electrical machine between the rotor and a stator of the electrical machine; and one or more channels formed in the rotor body, the one or more channels configured to allow a coolant to flow to and from a portion of the channel arranged adjacent to the active surface.

The one or more channels comprise: an inlet for a coolant to enter the one or more channels, an outlet for the coolant to exit the one or more channels, two radial portions extending from the rotor mount in a radial direction of the rotor body, and one or more axial portions extending in an axial direction of the rotor body and connecting the two radial portions, wherein the one or more axial portions are located at a periphery of the rotor body. The axial portion provides a portion of the channel which is adjacent to the active surface.

According to this first aspect, coolant can be supplied directly to the periphery of the rotor body where the active surface of the rotor is located, and subsequently evacuated shortly thereafter. The active surface may be otherwise referred to as a peripheral surface of the electrical machine and is the surface of the rotor arranged to magnetically interact with the corresponding surface of the stator. As such, the channels allows the coolant to flow very close to the active surface where there is high heat generation. Generally, the active surface of the rotor is the surface of the rotor extending in an axial direction of the rotor i.e. in a direction parallel to the axis of rotation of the electrical machine. The rotor mount may for example be a rotor shaft, however other types of rotor mount may be used, for example depending on the type of electrical machine and whether the rotor is an internal or external rotor.

By supplying the coolant directly to the periphery of the rotor body, heat generated by the rotor coils affixed to the active surface can be effectively dissipated away from the rotor coils and active surface via conduction. Furthermore, the coolant which has already been supplied to the periphery of the rotor body is removed via a radial portion, thus preventing coolant which has been heated by the active surface from remaining close to the active surface. As such, the proximity of the channel to the periphery of the rotor body allows heat to be removed from the active surface. This in turn removes heat from the rotor coils. A series of channels arranged to communicate coolant to and from the outer surface of the rotor allows for effective heat dissipation without interference with the rotation and operation of the rotor and electrical machine.

Advantageously, the one or more axial portions of the one or more channels may be provided with a cover material located at the active surface of the rotor body. The cover material may be the same material as the rotor body. Advantageously, the cover material may have a higher thermal conductivity than the remainder of the rotor body. As such, the cover material may form a portion of the active surface of the rotor. Accordingly, by providing a cover material with a higher thermal conductivity, heat generated by the rotor coils can be more effectively transferred to the coolant via conduction, therefore improving heat conduction. Example cover materials include aluminium, an aluminium alloy (such as an aluminium magnesium alloy), and aluminium nitride, however other cover materials may be used. The cover material has a high thermal conductivity, for example approximately 100 W/m.K or more, approximately 150 W/m.K or more, approximately 200 W/m.K or more, or approximately 250 W/m.K or more.

Advantageously in this aspect, the cover material may be configured to contain the coolant within the one or more channels. As such, the coolant can be supplied to the active surface of the rotor without passing into the air gap of the electrical machine. By preventing the coolant from passing into the air gap, this aspect reduces the risks of short circuit faults, corrosion of components by the coolant and additional friction loss caused by the rotation of the rotor within the coolant present in the air gap.

Advantageously in some aspects one or more rotor coils are arranged in alignment with the cover material. As such, the rotor coils may be affixed to the rotor body in substantially the same location as the cover material. Accordingly, heat generated by the rotor coils may be conductively dissipated away via the cover material and the coolant.

In some aspects, the rotor comprises two or more axial portions connecting the two radial portions, and the rotor further comprises one or more circumferential portions extending in a generally circumferential direction of the rotor body and connecting the two or more axial portions. In this manner, a greater number of coils can be cooled per radial portion of the channel. That is, the number of radial portions can be reduced to at most one per axial portion. Accordingly, a large number of axial channels can be provided without compromising the structural integrity of the rotor body due to a large number of radial portions.

In some aspects, the inlet and outlet are located at a same axial position of the rotor. In other words, the inlet and outlet are located in the same position along an axis of rotation of the rotor, however the inlet and outlet are removed from one another in a circumferential direction of the rotor. In other aspects, the inlet and outlet are offset from each other in an axial direction of the rotor. As such, flexibility is provided in the manner in which the inlet and outlet, as well as the radial portions, are provided in the rotor body. Furthermore, the layout of the radial portions can be altered depending on the desired number of axial portions per radial portion to provide the coolant with a short exit path, as well as to avoid indirect heating of the ingress coolant by the egress coolant.

Advantageously in some aspects, the one or more axial portions are angled with respect to the axial direction of the rotor. Accordingly, the coils may be provided with additional mechanical support.

For example, if the rotor coils themselves are not angled in the same manner as the axial portion, the angling of the axial portions ensures that each coil can include a portions which overlaps with the channels. This is particularly beneficial in arrangements where the number of axial portions is less than two times the number of rotor coils affixed to the active surface of the rotor, as in these examples the width of a coil may be narrower than a width of the axial portions of the one or more channels. In some examples, a skewed rotor coil arrangement may be provided while maintaining alignment of the axial portions of the channels and the coils, therefore maintaining the level of heat dissipation in the rotor.

In some aspects, a total number of axial portions in the rotor is greater than or equal to two times a number of rotor coils affixed to the active surface of the rotor. Accordingly, all coils present on the rotor can be cooled by the axial portions of the corresponding cooling channels, regardless of whether the axial portions are skewed (as described with respect to the previous aspect). However, it will be appreciated that a greater number of axial portions of the cooling channels per rotor coil will improve the cooling performance.

In some aspect, the rotor is located closer to an axis of rotation of the electrical machine than a stator of the electrical machine. Alternatively, the rotor is located further from an axis of rotation of the electrical machine than a stator of the electrical machine. As such, the aspects described above can be applied to electrical machines with either an internal or external rotor.

Advantageously, the rotor further comprises a rotor shaft on which the rotor body is mounted, and the rotor shaft comprises a plurality of holes each connected to the inlet and the outlet of the one or more channels of the rotor. Accordingly, the coolant may be supplied to the channels and also removed from the channels via the rotor shaft. Consequently, the number of radial portions can be increased, therefore reducing the total length of the axial portion per radial portion. As such, overall cooling performance can be increased. Furthermore, the use of the rotor shaft in this manner allows the rotor to be cooled despite its rotation as there is not relative motion between the rotor shaft and the rotor body.

In some aspects, the rotor body is formed of a non-magnetic material. For example, the rotor body may be formed of a plastic material which may additionally be reinforced to provide structural stability (e.g. with carbon fibre or glass). This prevents magnetic saturation caused by armature reaction which occurs in electrical machines with magnetic cores. However, as the thermal conductivity of non-magnetic rotor bodies is usually lower than that of magnetic core rotors (made, for example, from iron), the cooling configurations described above are particularly beneficial in such rotors.

According to a second aspect, there is provided an electrical machine comprising a rotor as described above and a stator. As discussed above, the electrical machine may comprise an internal rotor or an external rotor. Accordingly, the above described aspects are applicable to a variety of electrical machines. In addition, the electrical machine may be an electric motor or a generator. As such, the rotor coils can be replaced by permanent magnets, depending on the type of electrical machine. The electrical machine may also be a synchronous electrical machine, where the rotation of the rotor is synchronised to the frequency of the supply current.

According to a third aspect, there is provided a stator for an electrical machine. The stator comprises: a stator body; a stator mount on which the stator body is mounted; one or more coils affixed to an active surface of the stator, wherein the active surface of the stator is located proximate to an air gap of the electrical machine between the stator and a rotor of the electrical machine; one or more channels configured to allow a coolant to flow therethrough formed in the stator body.

The one or more channels comprise: an inlet for a coolant to enter the one or more channels, an outlet for the coolant to exit the one or more channels, two radial portions extending from the stator mount in a radial direction of the stator body, and one or more axial portions extending in an axial direction of the stator body and connecting the two radial portions, wherein the one or more axial portions are located at a periphery of the stator body.

As such, the numerous aspects described above in relation to a rotor can be equally applied to a stator of an electrical machine. According to this aspect, coolant can be supplied directly to the periphery of the stator body where the active surface of the stator is located, and subsequently evacuated shortly thereafter. The active surface may be otherwise referred to as a peripheral surface of the electrical machine and is the surface of the stator arranged to magnetically interact with the corresponding surface of the rotor. Generally, the active surface of the stator is the surface of the stator extending in an axial direction of the stator. The stator mount may for example be a stator shaft, however other types of stator mount may be used, for example depending on the type of electrical machine and whether the stator is an internal or external stator.

By supplying the coolant directly to the periphery of the stator body, heat generated by the stator coils affixed to the active surface can be effectively dissipated away from the stator coils and active surface via conduction. Furthermore, the coolant which has already been supplied to the periphery of the stator body is removed via a radial portion, thus preventing coolant which has been heated by the active surface from lingering close to the active surface. As such, the periphery of the stator body, and hence the stator coils, are supplied with coolant which has not already been substantially heated by other stator coils, therefore improving heat dissipation.

According to a fourth aspect, there is provided an electrical machine comprising a stator according to the third aspect and a rotor. As discussed above, the electrical machine may comprise an internal rotor or an external rotor. Accordingly, the above described aspects are applicable to a variety of electrical machines. In addition, the electrical machine may be an electric motor or a generator. As such, the particular coils can be replaced by permanent magnets, for example in a Halbach array, depending on the type of electrical machine.

Brief Description of Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the following figures.

In accordance with one (or more) embodiments of the present invention the Figures show the following: Figure 1 depicts a rotor according to a first example teaching.

Figure 2 depicts a cross-sectional view of the rotor shown in Figure 1 taken along line A-A.

Figure 3a depicts an external sectional view of the rotor shown in Figure 1 viewed from line B-B.

Figure 3b depicts a rotor of a second example teaching, viewed from the same viewpoint as Figure 3a.

Figure 3c depicts a rotor of a third example teaching, viewed from the same viewpoint as Figures 3a and 3b.

Figure 4 depicts a rotor of a fourth example teaching, viewed from the same viewpoint as Figures 3a-3c.

Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to". The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognised that the invention covers not only individual embodiments but also combination of the embodiments described herein.

The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Detailed Description

Figure 1 shows a rotor 100 according to a first example. The rotor 100 includes a rotor body 120 mounted on a rotor mount. In this example, the rotor body 120 is formed of a non-magnetic material, such as a plastic material, however a magnetic material could be used instead.

Furthermore, in this example the rotor mount is a rotor shaft 130, however the rotor body 120 could be mounted on a different form of rotor mount in other examples. The rotor may include rotor coils (not shown) mounted on an outer peripheral surface of the rotor.

In this example, the rotor 100 includes rotor channels 110 formed in the rotor body 120. The rotor channels 100 include a radial portion 112 extending radially from the rotor shaft 130 and a port 116 allowing communication of a coolant between the inside of the rotor shaft and the channel 110. The port 116 may be either an inlet or an outlet and as such the radial portion 112 allows coolant to flow from the port 116 to the periphery of the rotor body 120 or from the periphery of the rotor body 120 to the port 116.

The rotor further includes an axial portion 114. The radial portion 114 extends in an axial direction parallel to the axis of rotation of the rotor (into the page from the perspective of Figure 1). The axial portion 114 is arranged to receive coolant from the radial portion 112 or to provide coolant to the radial portion 112, based on whether the radial portion 112 includes an inlet or an outlet. The axial portion 114 is shown as having a circumferential width (the distance measured circumferentially at a given radius from the axis of rotation of the rotor) greater than that of the radial portion 112. In such an example, the axial portion 114 of the channel 110 may have a total cross-sectional area equal to the radial portion 112 of the channel 110, however the greater circumferential width of the axial portion 114 results in a greater surface area at the outer peripheral surface of the rotor. As such, heat exchange between the outer peripheral surface of the rotor and the coolant in the channel 110 can be improved.

Figure 2 shows a cross-sectional view of the rotor 100 shown in Figure 1 taken along line A-A, where the axis of rotation of the rotor 100 is shown by the dashed horizontal line. As shown, the channel 110 includes two radial portions 112 in order to communicate coolant from the rotor shaft 130 to the axial portion 114 and then return the coolant to the rotor shaft via a separate inlet and outlet. The radial portions 112 are formed inside the rotor body 120 such that a portion of the rotor body 120 is present between the radial portions 112 and the ambient. The provision of two separate radial portions 112a, 112b removed from one another along the axis of rotation prevents the outgoing coolant from heating the incoming coolant.

In use, the coolant flows within the rotor shaft 130 through inlet 116a to the channel 110. The coolant is prevented from continuing to flow along the rotor shaft 130 by the rotor shaft 130 itself and as such is forced into the channel 110. Inside the channel 110, the coolant flows along a first radial portion 112a in a radially outward direction towards the outer peripheral surface of the rotor 100. At the periphery of the rotor 100, the coolant flows along axial portion 114 in an axial direction parallel to the axis of rotation of the rotor 100. The coolant then flows along a second radial portion 112b in a radially inwards direction towards the rotor shaft 130. The coolant then passes through outlet 116b to return to rotor shaft and begins to flow along the rotor shaft 130 once again.

The axial portion 114 of channel 110 includes a cover material 140 located at the outer peripheral surface of the rotor 100. The cover material 140 is a high thermal conductivity material arranged to conduct heat from the outer peripheral surface of the rotor 100 to the coolant. Rotor coils (not shown) are affixed to the outer peripheral surface of the rotor 100 and as such heat produced by the rotor coils themselves can be conductively transferred to the coolant via the cover material 140.

The cover material 140 may have a higher thermal conductivity than the rotor body 120. Example cover materials 140 include aluminium, an aluminium alloy (such as an aluminium magnesium alloy), and aluminium nitride, however other cover materials 140 may be used. The cover material 140 has a high thermal conductivity, for example approximately 100 W/m.K or more, approximately 150 W/m.K or more, approximately 200 W/m.K or more, or approximately 250 W/m.K or more. By providing a cover material 140 with a higher thermal conductivity in this way, heat generated by the rotor coils can be more effectively transferred to the coolant via conduction, therefore improving heat conduction.

In addition to improving conduction between the rotor coils and the coolant, the cover material 140 confines the coolant to the channel 110. In other words, the cover material 140 prevents the coolant from passing into an air gap of the electrical machine. By preventing the coolant from passing into the air gap, this aspect reduces the risks of short circuit faults, corrosion of components by the coolant and additional friction loss caused by the rotation of the rotor within the coolant present in the air gap.

The coolant may be fed into the rotor shaft 130 using any suitable means. For example, one or more ingress pipes may be arranged to supply the coolant into the rotor shaft 130. The one or more ingress pipes may be arranged to introduce coolant in an axial direction from the end of the rotor 100 or radially inwards into the rotor shaft 130 as will be understood by someone skilled in the art. The rotor 100 may be supported by a pair of bearing to allow the rotor 100 to rotate. A suitable sealing arrangement, such as a pair of axially spaced 0-ring seals around the rotor shaft 130, may be provided in combination with a coolant supply and surrounding housing to allow the coolant to be communicated into rotor shaft 130. A combination of seals and bearings may conveniently allow the coolant supply to remain stationary whilst the rotor 100 can continue to rotate. While these are just some examples by which coolant may be supplied to the rotor shaft, any other suitable known means may be used.

In addition to the one or more pipes arranged to supply the coolant into the rotor shaft 130, one or more egress pipes may be arranged to remove the coolant from the rotor shaft 130. The one or more egress pipes may be configured in any of the possible arrangements described above in relation to the ingress pipes, or in any other suitable known manner.

Figure 3a shows an external sectional view of the rotor 100 shown in Figure 1 viewed from line B-B, where the axis of rotation of the rotor 100 is shown by the dashed vertical line. The rotor 100 includes axial portions 114 arranged at the outer peripheral surface of the rotor 100, where the axial portions include cover material 140 (not shown) as described above in relation to Figure 2. In use, the coolant, after flowing along a first radial passage 112a, flows along axial portion 114 at the outer peripheral surface of the rotor 100, before flowing along a second radial passage 112b, as described in relation to Figure 2 above. The same process occurs for each of the three axial portions 114 shown in Figure 3a which each belong to a separate channel. The rotor coils may be affixed to the rotor so as to be substantially aligned with the axial portions 114 and as such the coolant may conductively dissipate heat away from the rotor coils via the cover material 140.

In this example, the radial portions 112 of the channel 100, and hence the inlet 116a and outlet 116b for a given channel, are located at the same circumferential portion of the rotor, however the radial portions 112 of the channel 100, and hence the inlet 116a and outlet 116b for a given channel, are removed from one another in a direction parallel to the axis of rotation of the rotor 300.

Figure 3b shows an external view of a rotor 300 according to a second example, viewed from the same viewpoint as Figure 3a, where the axis of rotation of the rotor 300 is shown by the dashed vertical line. The rotor 300 includes a channel including a first axial portion 314a and a second axial portion 314b. The first and second axial portions 314a, 314b are connected by a circumferential portion 345 located at a periphery of the rotor at a same radial position as the axial portions 314a, 314b. The circumferential portion 345 extends in a circumferential direction of the rotor 300 between the two axial portions 314a, 31413.

As such, in use the coolant (after flowing through a first radial portion) flows along first axial portion 314a, then along circumferential portion 345, and then along second axial portion 314b in an opposite direction to axial portion 314a. Accordingly, the coolant flows through two axial portions and a circumferential portion at a periphery of the rotor 300. In such an example, the rotor coils may be affixed to the rotor so as to be substantially aligned with the axial portions 314a, 314b and as such the coolant may conductively dissipate heat away from the rotor coils via the cover material located at the outer peripheral surface of the rotor 300. The circumferential portion 345 may also include the cover material at the outer peripheral surface of the rotor in order to increase the dissipation of heat away from the rotor coils.

In this example, the radial portions of the channel, and hence the inlet and outlet of for a given channel, are located at the same axial position of the rotor 300 (measured along the axis of rotation of the rotor), however the radial portions of the channel, and hence the inlet and outlet of for a given channel, are located at different rotational positions of the rotor 300 (measured along a circumferential direction of the rotor).

Figure 3c shows an external view of a rotor 350 according to a third example, viewed from the same viewpoint as Figures 3a and 3b, where the axis of rotation of the rotor 350 is shown by the dashed vertical line. The rotor 350 includes a channel including a first axial portion 364a, a second axial portion 364b, and a third axial portion 364c. The first and second axial portions 364a, 364b are connected by a first circumferential portion 395a located at a periphery of the rotor at a same radial position as the axial portions 364a, 364b. The second and third axial portions 364b, 364c are connected by a second circumferential portion 395b located at a periphery of the rotor at a same radial position as the axial portions 364b, 364c. The circumferential portions 395 extend in a circumferential direction of the rotor 350 between two of the axial portions 364.

As such, in use the coolant (after flowing through a first radial portion) flows along first axial portion 364a, along first circumferential portion 395a, and then along second axial portion 364b in an opposite direction to axial portion 364a. The coolant then flows along second circumferential portion 395b and along the second axial portion 364c before returning to the rotor shaft via a radial portion. Accordingly, the coolant flows through three axial portions and two circumferential portion at a periphery of the rotor 350. In such an example, the rotor coils may be affixed to the rotor so as to be substantially aligned with the axial portions 364 and as such the coolant may conductively dissipate heat away from the rotor coils via the cover material located at the outer peripheral surface of the rotor 350. The circumferential portions 395 may also include the cover material at the outer peripheral surface of the rotor in order to increase the dissipation of heat away from the rotor coils.

In this example, the radial portions of the channel, and hence the inlet and outlet of for a given channel, are located at different axial positions of the rotor 350 (measured along the axis of rotation of the rotor), and the radial portions of the channel, and hence the inlet and outlet of for a given channel, are located at different rotational positions of the rotor 350 (measured along a circumferential direction of the rotor).

The total number of axial portions per channel can therefore be set to a variety values, as shown in Figures 3a-3b, based on specific requirements. For example, while only between 1 and 3 axial portions per channel are shown in Figures 3a-3c, substantially any number of axial portions per channel could be implemented. As such, a large number of coils can be cooled per radial portion of the channel. Accordingly, a large number of axial channels can be provided without compromising the structural integrity of the rotor body due to a large number of radial portions, for example for smaller electrical machines.

Figure 4 shows an external view of a rotor 400 according to a fourth example, viewed from the same viewpoint as Figures 3a-3c, where the axis of rotation of the rotor 400 is shown by the dashed vertical line. The rotor 400 includes axial portions 414, located at the outer peripheral surface of the rotor 400, which are angled with respect to the axis of rotation of the rotor 400. Accordingly, the channels of rotor 400 including axial portions 414 can effectively dissipate heat away from the rotor coils in rotors 400 for which the rotor coils are angled with respect to the axis of rotation of the rotor 400.

Furthermore, the rotor 400 including angles axial portions 414 may include multiple axial portions 414 per channel in the same manner as described above in relation to Figures 3b and 3c. That is, the channels of rotor 400 may include circumferential portions located at the periphery of the rotor 400 which extend in a circumferential direction of the rotor to connect two axial portions of the channel.

The above examples are described in relation to a rotor of an electrical machine located closer to an axis of rotation than a stator of the electrical machine, However these techniques can be equally applied to a stator of an electrical machine. Furthermore, while the rotor described above is located closer to an axis of rotation than a stator of the electrical machine, the techniques described above may be applied to a rotor or stator located further from the axis of rotation than the corresponding stator or rotor, where the radial portions of the channels are connected to axial portions located at an innermost peripheral surface of the rotor or stator, where the innermost peripheral surface of the rotor or stator is arranged to be located in an air gap of the electrical machine. The air gap is the region of space between the outermost peripheral surface of the internal rotor (or stator) and the innermost peripheral surface of the external stator (or rotor).

As such, from one perspective there has been described a rotor or stator for an electrical machine, the rotor or stator comprising a rotor body; a rotor mount; one or more coils; and one or more channels configured to allow a coolant to flow therethrough formed in the rotor body, the one or more channels comprising: an inlet, an outlet, two radial portions, and one or more axial portions connecting the two radial portions.

Claims

Claims 1. A rotor for an electrical machine, the rotor comprising: a rotor body; a rotor mount on which the rotor body is mounted; one or more coils affixed to an active surface of the rotor, wherein the active surface of the rotor is arranged to be located proximate to an air gap of the electrical machine between the rotor and a stator of the electrical machine; and one or more channels formed in the rotor body, the one or more channels configured to allow a coolant to flow to and from a portion of the channel arranged adjacent to the active surface, the one or more channels comprising: an inlet for a coolant to enter the one or more channels, an outlet for the coolant to exit the one or more channels, two radial portions extending from the rotor mount in a radial direction of the rotor body, and one or more axial portions extending in an axial direction of the rotor body and connecting the two radial portions, wherein the one or more axial portions are located at a periphery of the rotor body.
2. The rotor according to claim 1, wherein the one or more axial portions of the one or more channels comprise a cover material located at the active surface of the rotor body, and wherein the cover material has a higher thermal conductivity than a remainder of the rotor body.
3. The rotor according to claim 2, wherein the cover material is configured to contain the coolant within the one or more channels.
4. The rotor according to claim 2 or claim 3, wherein one or more rotor coils are arranged in alignment with the cover material.
5. The rotor according to any preceding claim, wherein the rotor comprises two or more axial portions connecting the two radial portions, and wherein the rotor further comprises: one or more circumferential portions extending in a generally circumferential direction of the rotor body and connecting the two or more axial portions.
6. The rotor according to any preceding claim, wherein the inlet and outlet are located at a same axial position of the rotor.
7. The rotor according to any of claims 1-5, wherein the inlet and outlet are offset from each other in an axial direction of the rotor.
8. The rotor according to any preceding claim, wherein the one or more axial portions are angled with respect to the axial direction of the rotor.
9. The rotor according to any preceding claim, wherein a total number of axial portions in the rotor is greater than or equal to two times a number of rotor coils affixed to the active surface of the rotor.
10. The rotor according to any preceding claim, wherein the rotor is located closer to an axis of rotation of the electrical machine than a stator of the electrical machine.
11. The rotor according to any preceding claim, wherein the rotor is located further from an axis of rotation of the electrical machine than a stator of the electrical machine.
12. The rotor according to any preceding claim, wherein the rotor further comprises a rotor shaft on which the rotor body is mounted, wherein the rotor shaft comprises a plurality of holes connected each connected to the inlet and the outlet of the one or more channels of the rotor.
13. The rotor according to any preceding claim, wherein the rotor body is formed of a non-magnetic material.
14. An electrical machine comprising: the rotor according to any of claims 1-13; and a stator.
15. A stator for an electrical machine, the stator comprising: a stator body; a stator mount on which the stator body is mounted; one or more coils affixed to an active surface of the stator, wherein the active surface of the stator is located proximate to an air gap of the electrical machine between the stator and a rotor of the electrical machine; and one or more channels formed in the stator body, the one or more channels configured to allow a coolant to flow to and from a portion of the channel arranged adjacent to the active surface, the one or more channels comprising: an inlet for a coolant to enter the one or more channels an outlet for the coolant to exit the one or more channels, two radial portions extending from the stator mount in a radial direction of the stator body, and one or more axial portions extending in an axial direction of the stator body and connecting the two radial portions, wherein the one or more axial portions are located at a periphery of the stator body.
16. An electrical machine comprising: the stator according to claim 15; and a rotor.