GB2560757A

GB2560757A - Stator tooth assembly and associated method and apparatus

Info

Publication number: GB2560757A
Application number: GB1704706.9A
Authority: GB
Inventors: Sovrea Claudia
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2018-09-26
Anticipated expiration: 2037-03-24
Also published as: GB2560757B; DE102018204309A1; GB201704706D0; GB2560757A8

Abstract

A method of assembling a stator tooth for an electric machine comprises disposing a sheet of insulating material such as paper 32 over an end of a tooth portion; winding a wire 26 over the insulation material and then dividing the insulating material into first and second portions. After the winding is formed the insulation material can be divided in the region over the end of the tooth by cutting or tearing to form two insulating loops 33,34 that can be folded over the winding and joined to edge portions 30,31 using adhesive. The insulating sheet can be pre-formed to match the tooth profile and attached to side walls of the tooth before winding using laser, thermal or adhesive bonding. Edges 31,32 of the insulation may be gripped with the base of the tooth during winding. The stator tooth assembly may comprise plural laminations in a stack and a bobbin (fig 4) to guide the wire while winding.

Description

(54) Title of the Invention: Stator tooth assembly and associated method and apparatus

Abstract Title: A method of assembling a stator tooth includes dividing an insulating sheet after winding wire around the stator tooth (57) A method of assembling a stator tooth for an electric machine comprises disposing a sheet of insulating material such as paper 32 over an end of a tooth portion; winding a wire 26 over the insulation material and then dividing the insulating material into first and second portions. After the winding is formed the insulation material can be divided in the region over the end of the tooth by cutting or tearing to form two insulating loops 33,34 that can be folded over the winding and joined to edge portions 30,31 using adhesive. The insulating sheet can be pre-formed to match the tooth profile and attached to side walls of the tooth before winding using laser, thermal or adhesive bonding. Edges 31,32 of the insulation may be gripped with the base of the tooth during winding. The stator tooth assembly may comprise plural laminations in a stack and a bobbin (fig 4) to guide the wire while winding.

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STATOR TOOTH ASSEMBLY AND ASSOCIATED METHOD AND APPARATUS

TECHNICAL FIELD

The present disclosure relates to a stator tooth assembly and associated method and apparatus. In particular, but not exclusively, the present disclosure relates to a method of assembling a stator tooth assembly for an electric machine. The present disclosure also relates to a stator tooth assembly, and to an electric machine incorporating one or more of the stator tooth assembly. The present disclosure also relates to a vehicle incorporating an electric machine. A further aspect of the present invention relates to an apparatus for assembling the stator tooth assembly.

BACKGROUND

A stator of an electric machine may comprise a plurality of stator teeth each having a winding of an electrically conductive wire. The stator teeth are formed from an electrically conductive material, such as electrical steel. In order to insulate the winding from the stator tooth, an electrically insulating material, such as insulation paper, may be provided between the stator teeth and the winding. Currently, a piece of paper is fitted on each side of the stator tooth before the winding operation begins. The pieces of paper each have two free (loose) ends and, when winding begins, due to winding speed, design tolerances (of winding machine and stator tooth) and accuracy of fitting the paper there is a risk that the wire might slide underneath one of the free ends of the paper and contact the stator tooth. This defeats the purpose of fitting the insulation paper. A current solution to avoid interpolation of the wire between the stator tooth and the paper is to slow the winding process (at least initially) to ensure correct winding direction and/or position. However, this still requires final inspection and the reduced speed of the winding process may not be suitable for high volume production. Alternatively, or in addition, a robust and thorough part inspection must be undertaken after each winding. However, this is costly and is not ideal for high volume production.

At least in certain embodiments, the present invention seeks to overcome or obviate at least some of the shortcomings associated with prior art assembly techniques.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a method of assembling a stator tooth assembly; a stator tooth assembly; a stator; an electric machine; a vehicle and an apparatus as claimed in the appended claims.

According to a first aspect of the present invention there is provided a method of assembling a stator tooth assembly for an electric machine, the stator tooth assembly comprising a stator tooth having a tooth portion, a first end, and a second end, the method comprising:

disposing a sheet of an electrical insulating material on the stator tooth so as to extend around at least one of the first end and the second end and over at least a part of the tooth portion;

winding a wire onto the tooth portion over the electrical insulating material disposed on said tooth portion to form a winding; and dividing the sheet of the electrical insulating material into first and second sections after winding the wire onto the tooth portion.

By using one sheet of the electrical insulating material, a temporary loop may be formed around the at least one of the first and second ends of the stator tooth. At least in certain embodiments, the temporary loop may reduce the risk of interpolation between the wire and the electrical insulating material during winding of the stator tooth. The other sheet ends may optionally be held, for example in a coil winding machine gripper, to reduce the risk of interpolation on that side. The sheet of the electrical insulating material forms a temporary loop extending around at least one of the first and second ends of the stator tooth. By forming the temporary loop around the first end and/or the second end, the possibility of interpolation of the wire between the stator tooth and the electrical insulating material may be reduced. Thus, at least in certain embodiments, the method reduces the possibility of the wire directly contacting the stator tooth. The possibility of an electrical short circuit occurring between the stator tooth and the wire may thereby be reduced.

The sheet of the electrical insulating material may be divided by removing a section thereof. For example, the section of the sheet extending over the first end and/or the second end may be removed so as to leave the first and second sections associated with the opposing sides of the stator tooth. The first and second sections of the sheet may be attached to the stator tooth. For example, the first and second sections may be bonded to the end pole. This may be performed before, after or concurrent with dividing the sheet of the insulating material.

The method may comprise forming the first and second sections of the electrical insulating material into respective first and second insulating loops. The first and second insulating loops may extend over at least a portion of the tooth portion. The first and second sections formed by dividing the electrical insulating material may comprise respective first and second joining portions. The first and second joining portions may be joined to respective first and second edge portions of the sheet of the electrical insulating material to form said first and second insulating loops.

The sheet of the electrical insulating material is divided into said first and second sections in a region extending over the first end and/or the second end. The sheet of the electrical insulating material may be divided along or proximal to a centreline of the first end and/or the second end. At least in certain embodiments, the first and second sections of the sheet of the electrical insulating material may be substantially the same size. The first and second joining portions of the first and second sections may be substantially the same length. Dividing the sheet of the electrical insulating material may comprise cutting the sheet of the electrical insulating material. The sheet may, for example, be cut using a cutting blade; a thermal cutter, such as a cutting wire; or a laser cutter.

The method may comprise applying an adhesive to join the first and second joining portions to the first and second edge portions. The adhesive may be applied to the first and second joining portions and/or the first and second edge portions of the sheet of the electrical insulating material.

The tooth portion may comprise first and second sidewalls. The sheet of the electrical insulating material may be disposed on the stator tooth so as to extend over at least a part of the first and second sidewalls of the tooth portion. The winding may subsequently be formed over the sheet of the electrical insulating material extending over at least a part of the first and second sidewalls.

The method may comprise pre-forming the sheet of the electrical insulating material at least substantially to match the profile of the tooth portion. The pre-forming of the sheet of the electrical insulating material may comprise cutting and/or folding the sheet at least substantially to match the profile of the first end and/or the first and second sidewalls of the tooth portion.

The method may comprise attaching the sheet of the electrical insulating material to the tooth portion before winding the wire onto said tooth portion. Attaching the sheet of the electrical insulating material may comprise one or more of the following: laser welding, thermal bonding and adhesive bonding.

The method may comprise supporting the first end and/or the second end of the stator tooth. The first end and/or the second end may be supported in suitable support means, such as a gripper, jig or other support apparatus. The sheet of the electrical insulating material may be supported with the first end and/or the second end. The sheet of the electrical insulating material may have opposing first and second sheet ends. The first and second sheet ends may be gripped with the first end and/or the second end of the stator tooth.

The electrical insulating material may comprise an electrical insulating paper.

The stator tooth assembly may comprise at least one bobbin for guiding the wire during winding. First and second bobbins may be provided at respective first and second longitudinal ends of the stator tooth. The first and second bobbins may each comprise an end plate for positioning against the tooth stator. The first and second bobbins may each comprise side members for positioning alongside the first end and/or the second end of the stator tooth.

The at least one bobbin may be mounted to the stator tooth before disposing the sheet of the electrical insulating material on the stator tooth. The sheet of the electrical insulating material may extend over at least a portion of the at least one bobbin.

The stator tooth may be configured such that, in use, the first end may be disposed in a radially inner position; and the second end may be disposed in a radially outer position. The first end may comprise a pole end. The second end may comprise a mounting end. The sheet of the electrical insulating material may be disposed on the stator tooth so as to extend around the pole end of the stator tooth. The stator tooth may be supported by holding said mounting end. The method may comprise gripping the opposing ends of the sheet of the electrical insulating material as the mounting end is held. In a modified arrangement, the sheet of the electrical insulating material may be formed into a continuous loop extending around both the pole end and the mounting end of the stator tooth.

The stator tooth may comprise first and second sidewalls. The sheet of the electrical insulating material may be disposed on the stator tooth so as to extend over at least a portion of the first and second sidewalls. The winding may be formed on said first and second sidewalls.

The stator tooth may be formed from electrical steel (also known as silicon steel). The stator tooth may have a unitary construction. Alternatively, the stator tooth may comprise a plurality of laminations arranged in a lamination stack.

According to a further aspect of the present invention there is provided a stator tooth assembly formed using the method described herein.

According to a still further aspect of the present invention there is provided a stator comprising at least one of the stator tooth assemblies described herein.

According to a yet further aspect of the present invention there is provided an electric machine comprising the stator described herein. The electric machine may be an electric traction machine for propelling a vehicle.

According to a further aspect of the present invention there is provided a vehicle comprising at least one electric machine as described herein. The one or more electric machine may be a traction machine.

According to a still further aspect of the present invention there is provided an apparatus for performing the method described herein. The apparatus may comprise means for disposing the sheet of the electrical insulating material over the stator tooth. The apparatus may comprise means for forming the sheet of the electrical insulating material at least substantially to match the profile of the tooth portion of the stator tooth. The apparatus may comprise cutting means for cutting the temporary loop formed by the sheet of the electrical insulating material. The apparatus may comprise means for forming one or more insulating loop around the winding on said tooth portion of the stator tooth. The apparatus may be incorporated into a coil winding apparatus, for example.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a schematic representation of a vehicle incorporating an electric traction machine in accordance with an aspect of the present invention;

Figure 2 shows a schematic representation of a transverse section of the electric traction machine shown in Figure 1;

Figure 3 shows an end view of a stator tooth of the stator of the electric traction machine;

Figure 4 shows the first and second bobbins for mounting to respective longitudinal ends of the stator tooth shown in Figure 3;

Figure 5 shows an end view of the stator tooth with the bobbin fitted to the first longitudinal end thereof;

Figure 6 shows the sheet of insulation paper for positioning on the stator tooth prior to winding;

Figure 7 shows an end view of the stator tooth with the insulation paper extending around the pole end to form a temporary loop;

Figure 8 shows a perspective view of the stator tooth with the insulation paper fitted to form the temporary loop shown in Figure 7;

Figure 9 shows an end view of the stator tooth with the winding formed on the tooth portion over the insulation paper;

Figure 10 shows a perspective view of the stator tooth with the winding formed on the tooth portion over the insulation paper;

Figure 11 shows an end view of the stator tooth with the temporary loop divided to form first and second sections; and

Figure 12 shows an end view of the stator tooth with the insulation paper configured to form first and second insulating loops around the winding.

DETAILED DESCRIPTION

An electric traction machine 1 for a vehicle 2 is shown schematically in figure 1. The vehicle 2 in the present embodiment is a motor vehicle, such as an automobile. The vehicle 2 may be an electric vehicle (EV) in which the electric traction machine 1 is the only torque generating machine provided to propel the vehicle. Alternatively, the vehicle 2 may be a hybrid electric vehicle (HEV) and the electric traction machine 1 may be used in conjunction with another torque generating machine, such as an internal combustion engine (not shown).

As shown in figure 2, the electric traction machine 1 comprises a rotor 3, a stator 4 and a housing 5. The rotor 3 is configured to rotate about a longitudinal axis X1 of the electric traction machine 1. The stator 4 in the present embodiment is a segmented stator and comprises a plurality of discrete stator tooth assemblies 6-n, only one of which is illustrated in figure 2. The stator tooth assemblies 6-n are assembled separately and then installed in a stator frame 7 to form the stator 4. The stator tooth assemblies 6-n each have the same configuration and, for the sake of brevity, a first stator tooth assembly 6-1 will now be described.

The first stator tooth assembly 6-1 comprises a stator tooth 8 formed of electrical steel (also known as silicon steel). The stator tooth 8 comprises a plurality of substantially identical laminations aligned with each other to form a lamination stack. The stator tooth 8 comprises a mounting (or yoke) end 9, a tooth portion 10 and a pole end 11. The mounting end 9 is configured to be mounted in a radially outer position in the stator 4. The mounting end 9 comprises first and second lateral extensions 12, 13 having male and female features for cooperating with like features on an adjacent stator tooth assembly 6-1. In particular, the first lateral extension 12 comprises a ridge 14; and the second lateral extension 13 comprises a channel 15. The ridge 14 is arranged to locate in the channel 15 of an adjacent stator tooth assembly 6-n to inhibit relative movement in a radial direction. The pole end 11 of the first stator tooth assembly 6-1 is generally T-shaped. The pole end 11 is configured to be mounted in a radially inner position in the stator 4. The pole end 11 comprises a partcylindrical concave surface 16 (centred on the rotational axis X1 of the electric traction machine 1 when in use) configured to face radially inwardly in a spaced apart relationship with the rotor 3. The tooth portion 10 is disposed between said mounting end 9 and said pole end 11. The tooth portion 10 is arranged to extend in a radial direction within the stator 4. The tooth portion 10 has first and second sidewalls 17, 18 which are arranged to face in opposite directions. The first stator tooth assembly 6-1 comprises first and second bobbins 19, 20 which are moulded from a plastics material. As shown in Figure 4, the first bobbin 19 comprises a first end plate 21 and a pair of first side members 22; and the second bobbin 20 comprises a second end plate 23 and a pair of second side members 24. The first bobbin 19 locates at a first longitudinal end of the stator tooth 8; and the second bobbin 20 locates at a second longitudinal end of the stator tooth 8. The first and second side members 22, 24 extend along the lateral edges of the pole end 11 of the stator tooth 8.

The first stator tooth assembly 6-1 comprises a winding 25 of an electrically conductive wire 26. The winding 25 extends around the tooth portion 10 of the first stator tooth assembly 6-1 and around the first and second end plates 21, 23 of the first and second bobbins 19, 20. The winding 25 extends along the first and second sidewalls 17, 18 of the tooth portion 10. As shown in Figure 4, a series of projections 27 (and/or grooves) are formed on said first and second end plates 21, 23 to guide the wire 26 during the winding process. The wire 26 has an electrically insulating coating to isolate the winding 25 from the stator tooth 8. The first and second bobbins 19, 20 provide electrical insulation between the winding 25 and the stator tooth 8 at each end thereof. In addition, an electrical insulating material is provided between the stator tooth 8 and the winding 25. In the present embodiment the electrical insulating material comprises an insulation paper 28 which is provided in the form of a sheet 29. As described herein, the insulation paper 28 is provided on the stator tooth 8 before the windings 25 are formed. The insulation paper 28 is arranged in an overlapping arrangement with the sides of the first and second bobbins 19, 20 to electrically isolate the stator tooth 8. The assembly of the first stator tooth assembly 6-1 will now be described in more detail.

The stator tooth 8 is formed in a conventional manner forming a lamination stack comprising a plurality of laminations. The first and second bobbins 19, 20 are fitted to respective first and second longitudinal ends of the lamination stack. The insulation paper 28 is then applied to the stator tooth 8. As illustrated in Figure 6, the sheet 29 of the insulation paper 28 is precut to the required size. The sheet 29 comprises opposing first and second edge portions 30, 31 which are located alongside the first and second lateral extensions 12, 13 of the mounting end 9. The insulation paper 28 forms a temporary loop 32 extending over the pole end 11 of the stator tooth 8. The first and second lateral extensions 12, 13 of the mounting end 9 are located in a gripper (not shown) of a coil winding machine (not shown). The first and second edge portions 30, 31 of the sheet 29 may also be located in the gripper. The gripper is closed to fixedly hold the stator tooth 8 and the sheet 29. As shown in Figure 7, the sheet 29 is then folded to conform to the profile of the mounting end 9, the first and second sidewalls 17, 18 and the portion of the pole end 11 adjacent to the sidewalls 17, 18. The integrity of the sheet 29 is maintained during this folding operation so as to retain the temporary loop 32 of the insulation paper 28 around the pole end 11. The insulation paper 28 may be affixed to the first and second sidewalls 17, 18 of the tooth portion 10, for example using an adhesive or a bonding process. The first stator tooth assembly 6-1 is shown in Figures 7 and 8 with the insulation paper 28 in situ. The first and second edge portions 30, 31 may be held in the gripper thereby helping to ensure that the insulation paper 28 follows the profile of the mounting end 9. Furthermore, the temporary loop 32 retains the insulation paper 28 in position as it follows the profile of the pole end 11.

Once the insulation paper 29 has been affixed to the stator tooth 8, a winding operation is performed by the coil winding machine to form the winding 25 on the tooth portion 10 of the first stator tooth assembly 6-1. The winding 25 is formed in conventional manner with the first stator tooth assembly 6-1 supported in the gripper of the coil winding machine. The first stator tooth assembly 6-1 is shown in Figures 9 and 10 after forming the winding 25 over the insulation paper 28. In prior art arrangements, the wire 26 may be introduced into a region between the insulation paper 28 and the mounting end 9 or the pole end 11 during the winding operation. This is potentially problematic since a short circuit may occur between the winding 25 and the stator tooth 8 if the electrically insulating coating applied to wire 26 is damaged. During production, electrical testing may not detect the problem since the electrically insulating coating isolates the wire 26. The method of applying the insulation paper 28 in accordance with the present embodiment can help to reduce any such problems. In particular, the insulation paper 28 is initially provided over the stator tooth 8 as a single, continuous sheet 29 which extends around the pole end 11. Since the first and second edge portions 30, 31 are held in the gripper, the insulation paper 28 forms a continuous layer extending along the inside of the mounting end 9 and the first and second sidewalls 17, 18. Thus, the wire 26 cannot readily be introduced between the insulation paper 28 and the mounting end 9 of the stator tooth 8. Furthermore, by forming the temporary loop 32 around the pole end 11, the insulation paper 28 forms a continuous layer extending along the first and second sidewalls 17, 18 and around the pole end 11. It will be understood, therefore, that the wire 26 cannot readily be introduced between the insulation paper 28 and the pole end 11 of the stator tooth 8.

After forming the winding 25, the temporary loop 32 is divided into first and second sections 33, 34, for example by performing a cutting operation (represented by a dotted line in Figure 9). As shown in Figure 11, the first section 33 has a first joining portion 35; and the second section 34 has a second joining portion 36. The temporary loop 32 is preferably divided along a centreline of the pole end 11 such that the first and second sections 33, 34 are of approximately equal length. In the present embodiment, the temporary loop 32 is cut while the stator tooth 8 is held in the coil winding machine. The cutting operation may be performed by any suitable cutting device, such as a cutting blade, a heated cutting wire or a laser cutter. The cutting operation may be performed automatically, semi-automatically or manually.

The stator tooth 8 is then removed from the coil winding machine to release the first and second edge portions 30, 31, as shown in Figure 11. The first and second edge portions 30, 31; and the first and second joining portions 35, 36 are then folded over the windings 25. In the illustrated arrangement, the first and second edge portions 30, 31 are folded upwardly over the windings 25 and the first and second joining portions 35, 36 are folded downwardly over the windings 25. The first and second joining portions 35, 36 are arranged in an overlapping arrangement extending over the first and second edge portions 30, 31. The first joining portion 35 is then joined to the first edge portion 30 to form a first insulating loop 37 extending around the windings 25 formed along the first sidewall 17 of the tooth portion 10.

The second joining portion 36 is joined to the second edge portion 31 to form a second insulating loop 38 extending around the windings 25 formed along the second sidewall 18 of the tooth portion 10. The first and second insulating loops 37, 38 may be formed manually or automatically. An end view of the first stator tooth assembly 6-1 showing the first and second insulating loops 37, 38 is shown in Figure 12. An adhesive may be applied to the first and second joining portions 35, 36 and/or the first and second edge portions 30, 31, as required. In a variant, the adhesive may be pre-applied to the insulation paper 28. For example, a contact adhesive may be pre-applied to the insulation paper 28 and covered by one or more protective strip which may be removed to join the first and second edge portions 30, 31 to the first and second joining portions 35, 36. Other techniques may be used to join the first and second edge portions 30, 31 to the first and second joining portions 35, 36 respectively. For example, a thermal bonding process may be used to form the first and second insulating loops 37, 38.

An insulating resin may be applied to the windings 25 before or after forming the first and second insulating loops 37, 38.

This assembly process is repeated to assemble each of the stator tooth assemblies 6-n. The stator tooth assemblies 6-n are then installed in the stator frame 7 to assemble the stator 4. The electric traction machine 1 is assembled in conventional manner.

The stator 4 described herein has a segmented configuration. In particular, each of the stator tooth assemblies 6-n forms a segment of the stator 4. The stator tooth assemblies 6-n have been described as each comprising a single stator tooth 8. However, in a modified arrangement, each stator tooth assembly 6-n may comprise more than one stator tooth 8. For example, each stator tooth assembly 6-n may comprise two, three or more stator teeth

8. The method and apparatus described herein are applicable in the assembly of a stator tooth assembly 6-n having more than one stator tooth 8. Furthermore, the method and apparatus described herein may be used in the assembly of a stator 4 having a nonsegmented construction. The non-segmented stator may comprise an annular member having a plurality of stator teeth 6-n. The method described herein may be used in the winding of each of the stator teeth 6-n of the annular member.

It will be appreciated that various modifications may be made to the embodiment(s) described herein without departing from the scope of the appended claims. The process described herein refers to cutting the temporary loop 32 formed by the sheet 29 of the insulation paper 28. It will be understood that other techniques may be used to divide the temporary loop 32 to form the first and second joining portions 35, 36. For example, the sheet 29 may comprise a frangible portion, for example a perforated line or a tear line, to enable dividing of the temporary loop 32 without a dedicated cutting operation.

Alternatively, first and second sheets of an insulation material may be joined together by a temporary or releasable adhesive to form the single sheet 29. The sheet 29 may be disposed on the stator tooth 8 to form the temporary loop 32 in accordance with the process described herein. The temporary loop 32 may then be divided by separating the first and second sheets along the join line. The first sheet may then be used to form the first insulating loop 37; and the second sheet may then be used to form the second insulating loop 38. Unless indicated to the contrary, it will be understood that references herein to a sheet of an electrical insulating material include a sheet composed of two or more sheets joined together.

Ina variant, the stator 4 may be modified such that adjacent stator tooth assemblies 6-n are mechanically connected to each other. This arrangement may be allow the stator frame 7 to be omitted.

Claims

CLAIMS:

1. A method of assembling a stator tooth assembly for an electric machine, the stator tooth assembly comprising a stator tooth having a tooth portion, a first end, and a second end, the method comprising:

2. A method as claimed in claim 1 comprising forming the first and second sections of the electrical insulating material into respective first and second insulating loops extending over at least a portion of the winding.

3. A method as claimed in claim 2, wherein the first and second sections comprise respective first and second joining portions, the first and second joining portions may be joined to respective first and second edge portions of the sheet of the electrical insulating material to form said first and second insulating loops.

4. A method as claimed in claim 3 comprising applying an adhesive to join the first and second joining portions to the first and second edge portions.

5. A method as claimed in any one of claims 1 to 4, wherein the sheet of the electrical insulating material is divided into said first and second sections in a region extending over the first end and/or the second end.

6. A method as claimed in claim 5, wherein the sheet of the electrical insulating material is divided along or proximal to a centreline of the first end and/or the second end.

7. A method as claimed in any one the preceding claims, wherein dividing the sheet of the electrical insulating material comprises cutting the sheet of the electrical insulating material.

8. A method as claimed in any one of the preceding claims comprising pre-forming the sheet of the electrical insulating material at least substantially to match the profile of the tooth portion.

9. A method as claimed in any one of the preceding claims comprising attaching the sheet of the electrical insulating material to the tooth portion before winding the wire onto said tooth portion.

10. A method as claimed in claim 9, wherein attaching the sheet of the electrical insulating material comprises one or more of the following: laser welding, thermal bonding and adhesive bonding.

11. A method as claimed in any one of the preceding claims comprising supporting the first end and/or the second end of the stator tooth.

12. A method as claimed in claim 11, wherein the sheet of the electrical insulating material comprises opposing first and second sheet ends, the first and second sheet ends being gripped with the first end and/or the second end of the stator tooth.

13. A method as claimed in any one of the preceding claims, wherein the electrical insulating material comprises an electrical insulating paper.

14. A method as claimed in any one of the preceding claims, wherein the stator tooth comprises at least one bobbin for guiding the wire during winding.

15. A method as claimed in claim 14, wherein the at least one bobbin is mounted to the stator tooth before disposing the sheet of the electrical insulating material on the stator tooth.

16. A method as claimed in claim 14 or claim 15, wherein the sheet of the electrical insulating material extends over at least a portion of the at least one bobbin.

17. A method as claimed in any one of the preceding claims, wherein the first end comprises a pole end; and/or the second end comprises a mounting end.

18. A method as claimed in any one of the preceding claims, wherein the stator tooth comprises first and second sidewalls, the sheet of the electrical insulating material being disposed on the stator tooth so as to extend over at least a portion of the first and second sidewalls.

19. A method as claimed in any one of the preceding claims, wherein the stator tooth

5 comprises a plurality of laminations arranged in a lamination stack.

20. A stator tooth assembly formed using the method of any one of the preceding claims.

10

21. A stator comprising at least one of the stator tooth assemblies claimed in claim 20.

22. An electric machine comprising the stator claimed in claim 21.

23. A vehicle comprising at least one electric machine as claimed in claim 22, wherein 15 the electric machine is a traction machine.

24. An apparatus for performing the method claimed in any one of claims 1 to 19.

Intellectual

Property

Office

Application No: GB1704706.9 Examiner: Keaton Hill