GB2599942A

GB2599942A - Winding for electrical machine

Info

Publication number: GB2599942A
Application number: GB2016399.4A
Authority: GB
Inventors: Komi Yoshiyuki
Original assignee: IMRA Europe SAS
Current assignee: IMRA Europe SAS
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2022-04-20
Anticipated expiration: 2040-10-16
Also published as: GB2599942B; GB202016399D0

Abstract

An electrical machine 300 comprising a stator 200 and rotor 100, the stator comprising a housing 210, and one or more windings 220 attached to the housing. Each of the stator windings comprise a first 221 and second layer 222, where the first layer is located further from an axis of rotation than the second layer. The rotor comprises a rotor body 110, and one or more rotor windings 120 attached to the body, each of the rotor windings comprises a first 121 and second layer 122, where the first layer is located closer to the axis of rotation than the second layer. The second layer of the stator windings is located closer to the axis of rotation than the second layer of the rotor windings. The first layer of the stator windings may be fixed to the housing and the second layer of the stator windings may not be fixed to the housing such that the first and second layers overlap one another. The first layer of the rotor windings may be fixed to the rotor body and the second layer may not be fixed to the body such that the first and second layers overlap one another. The layers of windings are connected by joining portions 123, 223. Third interposing layers of stator and rotor windings may be provided. The machine may be used in a vehicle.

Description

Winding for Electrical Machine

Field of the Invention

The invention relates generally to electrical machines and in particular windings for rotors and stators of electrical machines.

Background

As the need to move away from the use of fossil fuels increases, the use of electric motors has substantially increased. For example, many motor vehicles are now hybrid vehicles or are fully electric. Similarly, prototype fully electric aeroplanes are in development. Accordingly, there is a need for electric motors to provide significant power while being light and compact.

One approach to reduce the weight of an electric machine is to replace the magnetic core of the rotor (made of a material such as iron) with a lighter, non-magnetic material. While this may significantly reduce the weight of the motor, the iron core contributes significantly to magnetic coupling between the rotor and the stator of the electric motor. As such, its removal significantly reduces the power output of the electric motor.

In order to increase the magnetic coupling between the rotor and the stator of the electric motor, often the electric motor is made larger in size. However, as there is a desire for electric motors to be more compact, such a solution is unsuitable.

The present inventors have identified an improved approach for significantly increasing the magnetic coupling between the rotor and stator of an electrical machine. Accordingly, the electric machine can be made smaller in size while achieving the same level of power output.

Summary of the Invention

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

In a first aspect there is provided an electrical machine comprising: a stator, the stator comprising: a stator housing, and one or more stator windings attached to the stator housing, each of the one or more stator windings comprising a first layer and a second layer, wherein the first layer of the one or more stator windings is located further from an axis of rotation of the electrical machine than the second layer of the one or more stator windings. The electrical machine further comprises a rotor, the rotor comprising: a rotor body, and one or more rotor windings attached to the rotor body, each of the one or more rotor windings comprising a first layer and a second layer, wherein the first layer of the one or more rotor windings is located closer to the axis of rotation of the electrical machine than the second layer of the one or more rotor windings; and wherein the second layer of the stator windings is located closer to the axis of rotation of the electrical machine than the second layer of the one or more rotor windings In effect portions of the stator windings and portions of the rotor windings are arranged to overlap or interpose one another. The stator and rotor windings may be arranged in alternating and reciprocating directions parallel to the axis of rotation of the electrical machine.

Accordingly, an electrical machine is provided where the stator and rotor windings overlap one another in order to increase the magnetic interaction between the rotor and stator windings. As such, the magnetic coupling between the rotor and stator can be increased relative to traditional electrical machines of comparable size. In other words, the power output density per unit volume of the electrical machine is increased. Consequently, for a given power output, the electrical machine can be made smaller in size and weight.

In some aspects, the first layer of the one or more stator windings is fixed to the stator housing and wherein the second layer of the one or more stator windings is not affixed to the stator housing such that the first and second layers of the one or more stator windings overlap one another. As such, the magnetic interaction between the rotor and stator windings may be increased using a stator windings including two integrally formed layers, such that the stator housing, and the manner in which the stator windings are mounted, does not need to be altered.

In some aspects, the first layer of the one or more rotor windings is fixed to the rotor body and wherein the second layer of the one or more rotor windings is not affixed to the rotor body such that the first and second layers of the rotor windings overlap one another. As such, the magnetic interaction between the rotor and stator windings may be increased using rotor winding including two integrally formed layers, such that the rotor body, and the manner in which the rotor windings are mounted, does not need to be adapted.

Advantageously, the second layer of the one or more rotor windings overlaps with the second layer of the one or more stator windings. In some aspects, the arrangement of the one or more stator windings and the one or more rotor windings creates a plurality of electromagnetic interaction layers in the presence of a driving signal. As such, the magnetic interaction between the rotor and stator windings can be significantly increased, thereby increasing the power output density per unit volume of the electrical machine.

Advantageously, the rotor body is formed of a non-conductive and non-magnetic material. As such, the weight of the electrical machine can be significantly reduced. While electrical machines including a non-magnetic rotor body have a reduced the magnetic coupling as compared to electrical machines with a magnetic rotor body, the first aspect allows the magnetic coupling to be increased to at least partially compensate for the loss of magnetic coupling associated with removing the magnetic rotor body. In some aspects, the stator body is formed of a non-conductive and nonmagnetic material. As such, the weight of the electrical machine can be reduced.

In some aspects, the one or more stator windings and the one or more rotor windings are formed of copper or aluminium. As such, the rotor windings can be easily shaped to achieve desired dual-layer winding and will also maintain their shape. Independent of the material from which the windings are formed, the windings may be conductors in the form of a conductive bar and may optionally include a conductive coil wrapped around the conductive bar.

In some aspects, the one or more stator windings further comprise a third layer, and the one or more rotor windings further comprise a third layer; wherein the third layer of the one or more stator windings is located closer to the axis of rotation of the electrical machine than the first and second layers of the one or more stator windings. The third layer of the rotor windings is located further from the axis of rotation of the electrical machine than the first and second layers of the one or more stator windings; the third layer of the one or more stator windings is located: closer to the axis of rotation of the electrical machine than the second and third layers of the one or more rotor windings, and further from the axis of rotation of the electrical machine than the first layer of the one or more rotor windings. The third layer of the one or more rotor windings is located further from the axis of rotation of the electrical machine than the second and third layers of the one or more stator windings, and closer to the axis of rotation of the electrical machine than the first layer of the one or more stator windings. As such, three layers of magnetic interaction may be created between the rotor and stator windings thus further increasing the magnetic coupling between the rotor and stator.

Advantageously, the one or more stator windings further comprise one or more joining portions joining the first and second layers of the one or more stator windings, the one or more rotor windings further comprise one or more end portions, and the one or more joining portions of the one or more stator windings are located closer to the axial centre of the electrical machine than the one or more end portions of the one or more rotor windings. The joining portions of the stator windings may extend in a substantially radial direction between the first and second layers. The end portions of the rotor windings are the portion of the rotor windings configured to electrically connect multiple rotor windings together and extend in a circumferential direction of the electrical machine.

Accordingly, the layers and joining portion of the stator windings are arranged such that the layers of the stator windings do not overlap with the end portions of the rotor windings. As the end portions of the rotor windings extend in a circumferential direction of the electrical machine, they do not contribute to the magnetic coupling between the rotor and the stator. As such, preventing overlap between the end portions of the rotor windings and the stator windings increases the magnetic interaction between the rotor windings and the stator windings.

In some aspects, the one or more rotor windings further comprise one or more joining portions joining the first and second layers of the one or more rotor windings, the one or more stator windings further comprise one or more end portions, and the one or more joining portions of the one or more rotor windings are located further from the axial centre of the electrical machine than the one or more end portions of the one or more stator windings. The joining portions of the rotor windings may extend in a substantially radial direction between the first and second layers. The end portions of the stator windings are the portion of the stator windings configured to electrically connect multiple stator windings together.

Accordingly, the layers and joining portion of the rotor windings are arranged such that the layers of the rotor windings do not overlap with the end portions of the stator windings. As the end portions of the stator windings extend in a circumferential direction of the electrical machine, they do not contribute to the magnetic coupling between the rotor and the stator. As such, preventing overlap between the end portions of the stator windings and the rotor windings increases the magnetic interaction between the rotor windings and the stator windings.

In some aspects, the electrical machine is an electrical motor for a vehicle. For example, the electrical machine may be small in size and weight and as such may be included in a car, bike or aeroplane.

Furthermore, while the electrical machine according to the above described aspects is described as an electrical machine in which the rotor is an internal rotor (i.e. closer to an axis of rotation of the electrical machine than the stator), the electrical machine may instead comprise an external rotor (i.e. the rotor is further from the axis of rotation than the stator).

Advantageously, an axial length (i.e. the length along a direction parallel to an axis of rotation of the electrical machine) of the second layer of the one or more stator windings is smaller than an axial length of the first layer of the one or more stator windings. Similarly, an axial length of the second layer of the one or more rotor windings is smaller than an axial length of the first layer of the one or more rotor windings. As such, it is possible to prevent the second layers of the rotor and stator windings are prevented from contacting the joining portions of the corresponding stator or rotor windings and causing short circuits without the need to provide electrical insulation.

Brief Description of the 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 for an electrical machine according to a first example teaching of the disclosure.

Figure 2 depicts a stator for an electrical machine according to the first example teaching of the disclosure.

Figure 3 depicts an electrical machine according to the first example teaching of the disclosure.

Figure 4 depicts an electrical machine according to a second example teaching of the disclosure.

Figure 5 depicts a stator for an electrical machine according to a third example teaching of the disclosure.

Figure 6 depicts an electrical machine according to the third example teaching of the disclosure.

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 for an electrical machine according to a first example teaching of the disclosure. The rotor 100 includes a rotor body 110 and rotor windings 120 and the axis of rotation of the rotor is shown by the horizontal dashed line. Rotor body 110 may be a solid body formed of a magnetic material (such as iron) or formed of a non-magnetic and/or non-conductive material (such as a plastic material). Alternatively, the rotor body may be a scaffolding on which the rotor windings are mounted.

Rotor windings 120 include a first layer 121 which is directly affixed to the rotor body 110. In Figure 1, the first layer 121 extends in a substantially axial direction of the rotor 100, however in some examples the first layer 121 may be angled with respect to the axial direction such that the first layer 121 has an axial length and a circumferential length. Rotor windings 120 further include a second layer 122 which is not directly affixed to the rotor body 110 but is instead attached to the rotor body 110 via the first layer 121. The second layer 122, like the first layer 121, may extend in a substantially axial direction of the rotor 100 or may be angled with respect to the axial direction. Second layer 122 and first layer 121 are arranged to overlap one another in a radial direction. The rotor windings 120 further include a joining portion 123 arranged to connect the first and second layers to one another. The joining portion 123 of the rotor windings 120 extend in a substantially radial direction of the rotor 100.

The rotor windings 120 include an end portion 124. The end portions 124 extend in a generally circumferential direction of the rotor 100 and electrically connect multiple rotor windings 120 to one another. The rotor windings may take many forms, for example the rotor windings may take the form bars of conductive material (such as copper or aluminium) or may take the form of conductive bars wrapped in a coil of conductive material. The end portions 124 of rotor windings 120 are not hardened when manufacturing the rotor windings 120, thereby making the rotor 100 easier to assemble.

Figure 2 shows a stator 200 for an electrical machine according to the first example teaching of the disclosure. The stator 200 includes a stator housing 210 and stator windings 220 and the axis of rotation of the electrical machine in which the stator 200 would be included is shown by the horizontal dashed line. The stator housing 110 may be a contiguous shell on which the stator windings 220 are attached, or may be a scaffolding on which the stator windings 220 are mounted, and may be formed, for example, of a non-magnetic and non-conductive material) Stator windings 220 include a first layer 221 which is directly affixed to the stator housing 210. In Figure 2, the first layer 221 extends in a substantially axial direction of the stator 200, however in some examples the first layer 221 may be angled with respect to the axial direction such that the first layer 221 has an axial length and a circumferential length. Stator windings 220 further include a second layer 222 which is not directly affixed to the stator housing 210 but is instead attached to the stator housing 210 via the first layer 221. The second layer 222, like the first layer 221, may extend in a substantially axial direction of the stator 200 or may be angled with respect to the axial direction. Second layer 222 and first layer 221 are arranged to overlap one another in a radial direction. The stator windings 220 further include a joining portion 223 arranged to connect the first and second layers to one another. The joining portion 223 of the stator windings 220 extend in a substantially radial direction of the stator 200.

The stator windings 220 include an end portion 224. The end portions 224 extend in a generally circumferential direction of the stator 200 and electrically connect multiple stator windings 220 to one another. The stator windings may take many forms, for example the stator windings may take the form bars of conductive material (such as copper or aluminium) or may take the form of conductive bars wrapped in a coil of conductive material. The end portions 224 of stator windings 220 are not hardened when manufacturing the stator windings 220, thereby making the stator 200 easier to assemble.

Figure 3 shows an electrical machine 300 including the rotor 100 of Figure 1 and the stator 200 of Figure 2, with the axis of rotation of the electrical machine 300 shown by the dashed horizontal line.

As can be seen, the rotor windings and stator windings overlap one another in a radial direction of the electrical machine. That is, the second layer 222 of the stator winding is located closer to the axis of rotation than the second layer 122 of the rotor windings. As such, the rotor and stator windings create multiple magnetic interaction layers. Therefore, the magnetic coupling (and hence output torque) of the electrical machine 300 is increased relative to other electrical machines of comparable axial length (i.e. the length of the electrical machine along the axis of rotation of the electrical machine). As such, the electrical machine 300 will have increased output torque relative to comparable electrical machines.

The second layers 122, 222 of the rotor and stator windings are shorter in axial length than the first layers 121, 221 of the respective windings to prevent the second layers 122, 222 of the rotor and stator windings contacting the joining portions 223, 123 of the corresponding stator or rotor windings. As such, short circuits between the rotor and stator windings are prevented.

As can be seen in Figure 3, the joining portions 123 of the one or more rotor windings are located further from the axial centre (measured along an axis of rotation of the electrical machine) of the electrical machine 300 than the end portions 224 of the stator windings. Similarly, the joining portions 223 of the stator windings are located closer to the axial centre of the electrical machine 300 than the end portions 124 of the rotor windings.

As the end portions 124, 224 extend in a circumferential direction of the electrical machine, they do not contribute to the magnetic coupling between the rotor 100 and stator 200. As such, arranging the end portions 124, 224 and the joining portions 123, 223 in this manner ensures that the sections of the windings which contribute to the magnetic coupling between the rotor 100 and the stator 200 overlap each other to the largest extent possible, without overlapping with regions of the windings which do not contribute to the magnetic coupling, such as the end portions 124, 224.

Figure 4 shows an electrical machine 400 according to a second example teaching of the disclosure. The electrical machine 400 includes a rotor 410 and a stator 420. The rotor 410 includes a rotor winding including a first layer 411, a second layer 412, a third layer 413, a first joining portion 414 connecting the first and second layer 411, 412, and a second joining portion 415 connecting the second and third layer 412, 413. The third layer 413 is located furthest from the axis of rotation of the three layers, while the first layer 411 is located closest to the axis of rotation of the three layers. Of these layers and portions, only the first layer 411 is directly affixed to the body of rotor 410. The second layer 412, third layer 413, first joining portion 414, and second joining portion 415 are all attached to the rotor body via the first layer 411. The first, second and third layers 411, 412, 413 overlap one another when viewed in a radial direction.

The second joining portion 415 and the third layer 413 may be joined to the remainder of the rotor windings using a variety of techniques. For example, a conductor bar forming the second joining portion 415 and the third layer 413 may be welded to the remainder of the rotor winding, however other suitable means may be used.

The stator 420 includes a first layer 421, a second layer 422, a third layer 423, a first joining portion 424 connecting the first and second layer 421, 422, and a second joining portion 425 connecting the second and third layer 422, 423. The first layer 421 is located furthest from the axis of rotation of the three layers, while the third layer 423 is located closest to the axis of rotation of the three layers. Of these layers and portions, only the first layer 421 is directly affixed to the housing of the stator 420.

The second layer 422, third layer 423, first joining portion 424, and second joining portion 425 are all attached to the stator housing via the first layer 421. The first, second and third layers 421, 422, 423 overlap one another when viewed in a radial direction.

The second joining portion 425 and the third layer 423 may be joined to the remainder of the stator windings using a variety of techniques. For example, a conductor bar forming the second joining portion 425 and the third layer 423 may be welded to the remainder of the stator winding, however other suitable means may be used.

The three-layer structure of the rotor windings and stator winding creates three layers of magnetic interaction between the rotor and stator windings. That is, the third layer 413 of the rotor winding is located between the first and second layers 421, 422 of the stator winding, and the second layer 412 of the rotor winding is located between the second and third layers 422, 423 of the stator winding.

Similarly, the third layer 423 of the stator winding is located between the first and second layers 411, 412 of the rotor winding, and the second layer 422 of the stator winding is located between the second and third layers 412, 413 of the rotor winding.

As such, the magnetic coupling between the rotor and stator is significantly increased without increasing the axial length of the rotor. Instead, only a small increase in the radial length of the electrical machine is necessary. The rotor and stator windings may be provided with substantially any number of layers according to particular power output and size requirements.

Figure 5 shows a simplified, front-on view of a stator 500. The view of stator 500 shown corresponds to a cross-section of through a stator along line A-A of stator 200 shown in Figure 2. The stator 200 in Figure 2 may share the structure of the stator in Figure 5, or the stator 200 in Figure 2 may have a different structure.

The stator 500 of Figure 5 includes stator windings 510. Each of stator windings 510 include a first layer 511 and a second layer 512. In the example of Figure 5, the stator 500 includes thirty-six stator windings, each having a first layer and second layer, however a different number of stator windings may be used. The first and second layers of particular stator windings are offset from each other in a circumferential direction of the stator 500. For example, first layer 511(A1) and second layer 512(A1) are both part of the same stator winding and are offset from one another circumferentially. Alternatively, windings 511(A1) and 512(A1) may be thought of as different windings connected to one another.

The stator windings of first layer 511 include three groups of stator windings each with a different electrical phase. In Figure 5, these groups are labelled A, B, and C. In other words, stator windings 511(A1)-511(Al2) shown in Figure 5 belong to group A, stator windings 511(B1)-511(B12) shown in Figure 5 belong to group B, and stator windings 511(C1)-511(C12) shown in Figure 5 belong to group C. The stator windings shown in Figure 5 includes a six-pole stator winding arrangement. As such, the stator windings of each group of the first layer 511 are divided into six equally numbered and equally spaced sub-groups. In the example of Figure 5, there are twelve stator windings in group A of the first layer 511, and so the stator windings of group A of the first layer 511 are divided into six sub-groups, each sub-group including two stator windings. For example, windings 511(A1) and 511(A2) are included in a sub-group, while windings 511(A3) and 511(A4) are included in a different subgroup. Alternative arrangements are possible, including different numbers of overall stator windings, different number of poles (and hence different numbers of sub-groups), and different numbers of windings per sub-group).

The windings in group B and group C follow the same pattern as the windings of group A. Furthermore, the sub-groups for a particular group are separated from one another in a circumferential direction of the stator and are separated by sub-groups of the different groups. For example, the sub-group of group A including windings 511(A1) and 511(A2) is separated from the sub-group of group A including windings 511(A3) and 511(A4), and these sub-groups are separated by a sub-group of group B (including windings 511(B1) and 511(B2)), and by a sub-group of group C (including windings 511(C1) and 511(C2)).

As the arrangement of Figure 5 includes a six-pole stator winding arrangement, there are six repetitions (or sequences) of this pattern of the sub-groups of the windings of the first layer 511. That is, each repetition includes six stator windings out of the total thirty-six stator windings. Each sequence of six stator windings mechanically covers a 60 degrees arc of the first layer of the stator 500. For example, windings 511(A1), 511(A2), 511(B1), 511(B2), 511(C1), and 511(C2) are mechanically spread over 60 degrees of the total 360 degrees of the first layer of the stator 500.

The windings of the second layer 512 of the stator 500 have substantially the same arrangement as the first layer. That is the stator windings of second layer 512 include three groups of stator windings each with a different electrical phase, in the same manner as the correspondingly labelled stator windings of the first layer 511.

The stator windings of the second layer 512 also include a six-pole stator winding arrangement, similar to the first layer 511. As such, the stator windings of each group of the second layer 512 are divided into six equally numbered and equally spaced sub-groups in the same manner as the stator windings of the first layer 511, with corresponding reference numerals used in Figure 5.

Joining portion 515 connects first layer 511(A1) and second layer 512(A1), as shown in Figure 5. For simplicity, only one joining portion 515 is shown, however in practice multiple joining portions may exist, joining different layers of respective stator windings. For example, there may be thirty-six joining portions each connecting respective layers of a particular stator winding. In this regard, the stator 500 and joining portion 515 shown in Figure 5 is not a schematic drawing and as such the shape of the joining portion 515 may be different to that shown in Figure 5.

In order to connect first layer 511(A1) and second layer 512(A1) of stator winding 510, joining portion 515 not only extends radially between the first layer and the second layer of the stator 500, but the joining portion 515 also extends in a circumferential direction of the stator 500. Accordingly, joining portion 515 connects first layer 511(A1) and second layer 512(A1), which are offset from each other in a circumferential direction of the stator. In addition, the joining portion 515 is located at a rear-most (from the present viewpoint) portion of the stator 500, as shown with joining portion 223 of Figure 2. The stator windings 510 are coated in resin and as such the second layer 512 is able to hold its shape and may be supported in place by joining portion 515.

When in use, current flows through the stator windings of group A of both the first layer 511 and second layer 512 in the following sequence: 511(A1) -> 512(A1) -> 512(A3) -> 511(A3) -> 511(A2) -> 512(A2) -> 512(A4) -> 511(A4) -> 511(A5) -> 512(A5) -> 512(A7) -> 511(A7) -> 511(A6) -> 512(A6) -> 512(A8) -> 511(A8) -> 511(A9) -> 512(A9) -> 512(A11) -> 511(A11) -> 511(A10) -> 512(A10) -> 512(Al2) -> 511(Al2). When current flows through the stator windings in this manner, a magnetic field is created between the various sub-groups described above. For example, windings 511(A1), 511(A2), 511(A5), 511(A6), 511(A9), 511(A10), 512(A3), 512(A4), 512(A7), 512(A8), 512(A11) and 512(Al2) are magnetically north, while the remaining windings of group A are magnetically south.

The same current path is used for stator winding groups B and C for the correspondingly labelled windings as group A. However, winding group B has an electrical phase offset from the phase of the windings of group A, and winding group C has an electrical phase offset from the phase of both winding groups A and B. For example, the windings of group B may have an electrical phase that is offset from the electrical phase of the windings of group B by approximately 60 degrees, however other phase offsets, such as 30 degrees or 120 degrees, may be used. The windings of group C may then have an electrical phase that is offset from the electrical phase of the windings of group B by the same amount (for example 30, 60, or 120 degrees).

Figure 5 and the above description relate to a specific implementation of a stator, however this is only one example and other alternative layouts may be used in the electrical machines as described herein. For example, respective first and second layers of particular stator windings may be aligned with one another in a circumferential direction of the stator. In this case, the joining portions extend in a radial direction of the stator. In such an example, the first and second layers of the stator winding will have the same electrical phase.

As another example, instead of a six-pole stator winding arrangement, different stator winding arrangements may be employed instead. Accordingly, the precise number of stator windings, number of stator winding sequences, number of stator windings per sequence, mechanical and electrical offset between stator windings are all subject to variation, depending on the particular application.

Figure 6 shown an electrical machine 600 including the stator 500 shown in Figure Sand a rotor 650, viewed from the same viewpoint. The rotor is shown without a rotor body for simplicity. The rotor 650 has a rotor winding arrangement similar layout of the stator windings of stator 500, however some differences exist between the two. For example, the radius of the rotor 650 is smaller than the radius of the stator 500. That is, the innermost (first) layer of the rotor 650 has a radius smaller than the radius of the innermost (second) layer of the stator 500, and the outermost (second) layer of the rotor 650 has a radius smaller than the radius of the outermost (first) layer of the stator.

In addition, the joining portion 665 of the rotor 650 is located at a front-most portion of the rotor 650, so as to be substantially opposite the joining portion 515 of the stator 500, as shown by the joining portions 123, 223 in Figure 3. Furthermore, as shown in Figure 6, the rotor windings may be thinner than the stator windings in order to reduce mechanical resistance in the rotation of the rotor.

Rotor 650 is only one implementation of a rotor and may be subject to any number of modifications or alterations for use in electrical machine described herein. For example, the rotor 650 can be subject to the various alterations described above in relation to the stator SOO.

Accordingly, from one perspective there has been described an electrical machine comprising a stator and a rotor. The stator comprises one or more stator windings comprising two layers. The rotor comprises one or more rotor windings comprising two layers. A layer of the one or more stator windings is located closer to the axis of rotation of the electrical machine than a layer of the one or more rotor windings.

Claims

Claims 1. An electrical machine comprising: a stator, the stator comprising: a stator housing, and one or more stator windings attached to the stator housing, each of the one or more stator windings comprising a first layer and a second layer, wherein the first layer of the one or more stator windings is located further from an axis of rotation of the electrical machine than the second layer of the one or more stator windings; and a rotor, the rotor comprising: a rotor body, and one or more rotor windings attached to the rotor body, each of the one or more rotor windings comprising a first layer and a second layer, wherein the first layer of the one or more rotor windings is located closer to the axis of rotation of the electrical machine than the second layer of the one or more rotor windings; wherein the second layer of the stator windings is located closer to the axis of rotation of the electrical machine than the second layer of the one or more rotor windings.
2. The electrical machine according to claim 1, wherein the first layer of the one or more stator windings is fixed to the stator housing and wherein the second layer of the one or more stator windings is not affixed to the stator housing such that the first and second layers of the one or more stator windings overlap one another.
3. The electrical machine according to claim 1 or claim 2, wherein the first layer of the one or more rotor windings is fixed to the rotor body and wherein the second layer of the one or more rotor windings is not affixed to the rotor body such that the first and second layers of the rotor windings overlap one another.
4. The electrical machine according to any preceding claim, wherein the second layer of the one or more rotor windings overlaps with the second layer of the one or more stator windings.
5. The electrical machine according to any preceding claim, the arrangement of the one or more stator windings and the one or more rotor windings creates a plurality of magnetic interaction layers in the presence of a driving signal.
6. The electrical machine according to any preceding claim, wherein the rotor body is formed of a non-conductive and non-magnetic material.
7. The electrical machine according to any preceding claim, wherein the stator body is formed of a non-conductive and non-magnetic material.
8. The electrical machine according to any preceding claim, wherein the one or more stator windings and the one or more rotor windings are formed of copper or aluminium.
9. The electrical machine according to any preceding claim, wherein the one or more stator windings further comprise a third layer, and the one or more rotor windings further comprise a third layer; wherein the third layer of the one or more stator windings is located closer to the axis of rotation of the electrical machine than the first and second layers of the one or more stator windings; wherein the third layer of the rotor windings is located further from the axis of rotation of the electrical machine than the first and second layers of the one or more stator windings; wherein the third layer of the one or more stator windings is located: closer to the axis of rotation of the electrical machine than the second and third layers of the one or more rotor windings, and further from the axis of rotation of the electrical machine than the first layer of the one or more rotor windings; and wherein the third layer of the one or more rotor windings is located: further from the axis of rotation of the electrical machine than the second and third layers of the one or more stator windings, and closer to the axis of rotation of the electrical machine than the first layer of the one or more stator windings.
10. The electrical machine according to any preceding claim, wherein: the one or more stator windings further comprise one or more joining portions joining the first and second layers of the one or more stator windings, the one or more rotor windings further comprise one or more end portions, and the one or more joining portions of the one or more stator windings are located closer to the axial centre of the electrical machine than the one or more end portions of the one or more rotor windings.
11. The electrical machine according to any preceding claim, wherein: the one or more rotor windings further comprise one or more joining portions joining the first and second layers of the one or more rotor windings, the one or more stator windings further comprise one or more end portions, and the one or more joining portions of the one or more rotor windings are located further from the axial centre of the electrical machine than the one or more end portions of the one or more stator windings.
12. The electrical machine according to any preceding claim, wherein the electrical machine is an electrical motor for a vehicle.
13. The electrical machine according to any preceding claim, wherein an axial length of the second layer of the one or more stator windings is smaller than an axial length of the first layer of the one or more stator windings.
14. The electrical machine according to any preceding claim, wherein an axial length of the second layer of the one or more rotor windings is smaller than an axial length of the first layer of the one or more rotor windings.
15. An electrical machine comprising a stator and a rotor, the stator and rotor being arranged in use to move rotationally relative to each other, wherein the stator comprises a stator housing and an elongate stator winding extending from the stator housing, the rotor comprises a rotor body and an elongate rotor winding extending from the rotor body, and wherein the elongate stator winding and elongate rotor winding are each arranged in reciprocating and alternating directions such that portions of the rotor winding and portions of the stator winding are interposed between each other.