A slot wedge of an electric machine and a method and an apparatus for manufacturing the same

Abstract

A method for manufacturing a slot wedge (101) for an electric machine comprises feeding one or more electric conductor wires (102) through an aperture of an extruder die (103), and simultaneously extruding body material (104) of the slot wedge at least partially around the one or more electric conductor wires so that the aperture of the extruder die defines a cross-sectional shape of the slot wedge such that the width of the slot wedge is greater than the thickness of the slot wedge Furthermore, the method comprises cutting the slot wedge coming out from the aperture of the extruder die to have a predetermined length.

Description

[0001] A slot wedge of an electric machine and a method and an apparatus for manufacturing the same

[0002] Field of the technology

[0003] The disclosure relates generally to rotating electric machines. More particularly, the disclosure relates to a slot wedge of an electric machine and to a method and an apparatus for manufacturing a slot wedge of an electric machine. Furthermore, the disclosure relates to an electric machine and to a method for manufacturing an electric machine.

[0004] Background

[0005] In many cases, an electric drive comprises a frequency converter arranged to supply alternating voltages to an electric machine. The frequency converter produces high voltage gradients, i.e. high du / dt values, on windings of the electric machine as a corollary of fast switching operations of power electronic components such as e.g. Insulated Gate Bipolar Transistors “IGBT”. The high voltage gradients cause in turn capacitively coupled stray currents through electric insulators between the windings and a core structure of the electric machine as well as through an airgap of the electric machine. The above-mentioned stray currents may flow through bearings of the electric machine and / or through mechanical devices such as gears which are connected to a shaft of the electric machine. The stray currents are harmful as they may damage the bearings and / or the mechanical devices connected to the shaft of the electric machine.

[0006] A known solution to reduce bearing currents is to use bearings which are electrically insulated from the frame of an electric machine. This approach is however not free from challenges. On one hand, an insulator layer between a bearing and the frame may need to be relatively thick to achieve sufficient impedance against high frequency stray currents. On the other hand, it may be challenging to achieve sufficient mechanical strength when the insulator layer is thick. Another known solution against bearing currents is to use insulated bearings where balls or other roller elements are made of electrically non-conductive material such as e.g. ceramics. A drawback of insulated bearings of the kind mentioned above is that they are relatively expensive. A third known solution against bearing currents and against other stray currents is to provide a frequency converter with output inductors or filters which reduce the voltage gradients. In many cases there can be, however, a need to design case-specific inductors or filters for different lengths of a cable of an electric machine. Therefore, standardization can be difficult with this approach. A fourth known approach is to provide slot wedges of an electric machine with electric conductors which are grounded to form an electrostatic shield for reducing capacitive stray currents through bearings and / or other sensitive parts. A slot wedge comprising an electric conductor is presented in US patent publication US5821652. Electrostatic shielding of the kind mentioned above has its advantages and thus there is a need for further development of structures for implementing electrostatic shielding. A fifth known approach is to use shaft grounding brushes via which currents can bypass bearings. More information about known countermeasures against bearing currents is presented e.g. in the publication: Konstantin Vostrov, Reduction of non-circulating bearing currents by electrical machine design, Lappeenranta-Lahti University of Technology LUT, Acta Universitatis Lappeenrantaensis, 2023.

[0007] Summary

[0008] The following presents a simplified summary to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments.

[0009] In this document, the word “geometric” when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional. In accordance with the invention, there is provided a new method for manufacturing a slot wedge for an electric machine. The method according to the invention comprises:

[0010] - feeding one or more electric conductor wires through an aperture of an extruder die,

[0011] - extruding body material of the slot wedge at least partially around the one or more electric conductor wires so that the aperture of the extruder die defines the cross-sectional shape of the slot wedge such that the width of the slot wedge is greater than the thickness of the slot wedge, and

[0012] - cutting the slot wedge coming out from the aperture of the extruder die to have a predetermined length.

[0013] The above-mentioned body material of the slot wedge may comprise for example resin and / or plastic. In cases where a magnetic slot wedge is needed, the resin and / or plastic can be mixed with particles of ferromagnetic material whose relative permeability is greater than one, i.e. pr> 1. The ferromagnetic material can be for example iron powder. Material of the one or more electric conductor wires can be for example copper or aluminum.

[0014] In accordance with the invention, there is also provided a new apparatus for manufacturing a slot wedge for an electric machine. The apparatus comprises a crosshead extruder that comprises:

[0015] - a first member comprising a supply channel for conducting body material of the slot wedge and a chamber connected to the supply channel,

[0016] - a second member in the chamber, the second member having a tubular part and an end-wall provided with one or more apertures for receiving one or more electric conductor wires, and

[0017] - an extruder die in the chamber successively with the second member so that an aperture of the extruder die is in line with each of the one or more apertures of the end-wall of the second member. A wall of the tubular part of the second member has apertures on opposite sides of the tubular part for conducting the body material from a room between a wall of the chamber of the first member and an outer surface of the tubular part to an interior of the tubular part and to the extruder die. The apertures of the wall of the tubular part are symmetrically with respect to an end of the supply channel of the first member connecting to the chamber of the first member so that distances from the end of the supply channel to all the apertures of the wall of the tubular part are same.

[0018] In an apparatus according to an exemplifying and non-limiting embodiment, the second member comprises adjusting screws for changing sizes of the apertures of the wall of the tubular part and thus for adjusting flow rates of the body material through these apertures.

[0019] In accordance with the invention, there is also provided a new method for manufacturing an electric machine. The method comprises:

[0020] - manufacturing slot wedges by carrying out a method according to the invention to manufacture each slot wedge,

[0021] - installing the slot wedges on openings of slots of a core structure of the electric machine to close the slots, and

[0022] - grounding a first end of each electric conductor wire of the slot wedges and leaving a second end of the electric conductor wire as an open conductor end.

[0023] In accordance with the invention, there is also provided a new slot wedge for an electric machine. The slot wedge according to the invention comprises body material at least partially around one or more electric conductor wires whose longitudinal direction is parallel with the longitudinal direction of the slot wedge, wherein the width of the slot wedge is greater than the thickness of the slot wedge, and the body material has been extruded at least partially around the one or more electric conductor wires and thereby an outer surface of the body material is free from mold seam traces. In accordance with the invention, there is also provided a new electric machine. The electric machine comprises:

[0024] - a stator,

[0025] - a rotor rotatably supported with respect to the stator, at least one of the rotor and the stator comprising a core structure and windings whose coil sides are located in slots of the core structure,

[0026] - slot wedges according to the invention and arranged to close the slots of the core structure, and

[0027] - electric conductors having galvanic connections with the stator and coupled to first ends of the electric conductor wires of the slot wedges, the second ends of the electric conductor wires of the slot wedges being open conductor ends.

[0028] The electric conductor wires of the slot wedges can be arranged to constitute an electrostatic shield which reduces capacitively coupled stray currents between the coil sides and other parts of the electric machine.

[0029] Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

[0030] Various non-limiting exemplifying embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and nonlimiting embodiments when read in connection with the accompanying drawings.

[0031] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

[0032] Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality. Brief description of figures

[0033] Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: figures 1 a, 1 b, and 1 c illustrate an apparatus for manufacturing a slot wedge according to an exemplifying and non-limiting embodiment, figure 1 d shows a section view of a slot wedge according to an exemplifying and non-limiting embodiment, figure 1e shows a flowchart of a method according to an exemplifying and nonlimiting embodiment for manufacturing a slot wedge for an electric machine, figure 2a illustrates an apparatus for manufacturing a slot wedge according to an exemplifying and non-limiting embodiment, figure 2b shows a section view of a slot wedge according to an exemplifying and non-limiting embodiment, figures 3a, 3b, and 3c show section views of a slot wedges according to exemplifying and non-limiting embodiments, and figure 4 shows a section view of a detail of an electric machine that comprises a slot wedge according to an exemplifying and non-limiting embodiment.

[0034] Description of exemplifying and non-limiting embodiments

[0035] The specific examples provided in the description given below should not be construed as limiting the scope and / or the applicability of the appended claims. Furthermore, it is to be understood that lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

[0036] Figures 1 a, 1 b, and 1 c illustrate an apparatus 130 for manufacturing a slot wedge 101 according to an exemplifying and non-limiting embodiment. Figure 1 b shows a section taken along a geometric line A-A shown in figure 1a so that the geometric section plane is parallel with the xz-plane of a coordinate system 199. Figure 1 c shows a section taken along a geometric line B-B shown in figure 1 b so that the geometric section plane is parallel with the yz-plane of the coordinate system 199. Figure 1 d shows a section view of the slot wedge 101 . The section shown in figure 1 d is taken along a geometric line C-C shown in figure 1 b so that the geometric section plane is parallel with the xy-plane of the coordinate system 199.

[0037] The apparatus 130 comprises a crosshead extruder that is configured to receive body material 104 of the slot wedge 101 in molten form from a material supply system 131 and an electric conductor wire 102 from a wire supply system 132. The crosshead extruder comprises a first member 133, a second member 134, and an extruder die 103. The first member comprises a supply channel 135 for conducting the body material 104 and a chamber 136 connected to the supply channel 135. The second member 134 and the extruder die 103 are successively in the chamber of the first member 133. The second member 134 has a tubular part 137 and an end-wall 138 that is provided with an aperture for receiving the electric conductor wire 102. The second member 134 and the extruder die 103 are successively so that an aperture of the extruder die 103 is in line with the aperture of the end-wall 138 of the second member 134. A wall of the tubular part 137 of the second member 134 has apertures 138 and 139 on opposite sides of the tubular part for conducting the body material 104 from a room 140 between a wall of the chamber of the first member 133 and an outer surface of the tubular part 137 to an interior of the tubular part 137 and subsequently to the extruder die 103. The apertures 138 and 139 of the wall of the tubular part 137 are symmetrically with respect to an end of the supply channel 135 connecting to the chamber 136 so that distances from the end of the supply channel 135 to both the apertures 138 and 139 of the wall of the tubular part are same. The symmetric arrangement of the apertures 138 and 139 with respect to the supply channel 135 makes it possible that the body material is supplied equally on both sides of the electric conductor wire 102. This, in turn, makes it easier to keep the electric conductor wire 102 in a desired position inside the slot wedge 101 , e.g. in the middle of the slot wedge 101 .

[0038] In an apparatus according to an exemplifying and non-limiting embodiment, the second member 134 comprises adjusting screws 141 and 142 for changing sizes of the apertures 138 and 139 of the wall of the tubular part 136 and thus for adjusting flow rates of the body material 104 through these apertures138 and 139.

[0039] Figure 1 e shows a flowchart of a method according to an exemplifying and nonlimiting embodiment for manufacturing a slot wedge. The method for manufacturing the slot wedge comprises feeding 121 an electric conductor wire 102 through a aperture of an extruder die, and simultaneously extruding 122 the body material of the slot wedge around the electric conductor wire so that the aperture of the extruder die defines the cross-sectional shape of the slot wedge. The cross-sectional shape of the slot wedge is such that the width of the slot wedge is greater than the thickness of the slot wedge. The width of the slot wedge can be for example at least two, three, or four times the thickness of the slot wedge. In figure 1 d, the width of the slot wedge 101 is denoted with W and the thickness of the slot wedge 101 is denoted with T. As the slot wedge is manufactured with an extrusion process, the longitudinal direction of the electric conductor wire is parallel with a longitudinal direction of the slot wedge. The extrusion process is advantageously carried out with an apparatus of the kind illustrated in figures 1 a-1 c. The electric conductor wire crosses with a flow of the molten body material at the crosshead of the apparatus 130, hence the name crosshead. Furthermore, the method for manufacturing the slot wedge comprises cutting 123 the slot wedge coming out from the aperture of the extruder die to have a desired length in the longitudinal direction of the slot wedge. Means for cutting the slot wedge are not shown in figures 1a-1 c.

[0040] Figure 2a illustrates an apparatus 230 for manufacturing a slot wedge 201 according to an exemplifying and non-limiting embodiment. Figure 2b shows a section view of the slot wedge 201 . The section is taken along a line A-A shown in figure 2a, and the geometric section plane is parallel with the xy-plane of a coordinate system 299. The method for manufacturing the slot wedge 201 comprises feeding electric conductor wires 202a and 202b through an aperture of an extruder die 203, and simultaneously extruding body material 204 of the slot wedge 201 around the electric conductor wires 202a and 202b so that the aperture of the extruder die 203 defines the cross-sectional shape of the slot wedge 201 . As the slot wedge 201 is manufactured with the above-described extrusion process, the longitudinal direction of the electric conductor wires 202a and 202b is parallel with a longitudinal direction of the slot wedge 201 . The cross-sectional shape of the slot wedge 201 is such that the width W of the slot wedge is greater than the thickness T of the slot wedge 201 . In this exemplifying case, the slot wedge 201 comprises the electric conductor wires 202a and 202b parallel with each other and a distance away from each other in the width direction of the slot wedge, i.e. in the x-direction of the coordinate system 299. In some cases, the two electric conductor wires 202a and 202b of the slot wedge 201 may constitute a better electrostatic shield than the single electric conductor wire 102 of the slot wedge 101 illustrated in figures 1 b, 1 c, and 1 d.

[0041] In the exemplifying slot wedges 101 and 201 illustrated in figures 1 b, 1 c, 1 d, 2a, and 2b, the electric conductor wires are round electric conductor wires. This is however not the only possible choice. Figure 3a shows a section view of a slot wedge 301 according to an exemplifying and non-limiting embodiment. The geometric section plane is parallel with the xy-plane of a coordinate system 399. The exemplifying slot wedge 301 comprises a flat electric conductor wire 302 having a width greater than its thickness. It is also possible that a slot wedge according to an exemplifying and non-limiting embodiment comprises two or more flat electric conductor wires, or a combination of one or more flat electric conductor wire and one or more round electric conductor wires. Figure 3b shows a section view of a slot wedge 311 according to an exemplifying and non-limiting embodiment. The geometric section plane is parallel with the xy-plane of the coordinate system 399. The exemplifying slot wedge 311 comprises round electric conductor wires 302a and 302b and a flat electric conductor wire 302c.

[0042] In the exemplifying slot wedge 101 illustrated in figures 1 b, 1 c, and 1 d, the cross- sectional shape is substantially a trapezoid whose sides parallel with the width direction, i.e. the x-direction, of the slot wedge 101 are longer than other two sides of the trapezoid. In the exemplifying slot wedges 201 and 301 illustrated in figures 2a, 2b, and 3a, the cross-sectional shape is substantially a hexagon so that sides parallel with the width direction, i.e. the x-direction, of the slot wedge under consideration are longer than the other four sides of the hexagon. The above- mentioned cross-sectional shapes are however not the only possible choices. In the exemplifying slot wedge 311 illustrated in figure 3b, the cross-sectional shape of the slot wedge has two straight sides parallel with the width direction, i.e. the x-direction, of the slot wedge 311 and curved convex sides connecting the straight sides together.

[0043] In the exemplifying slot wedges 101 , 201 , 301 , and 311 illustrated in figures 1 b, 1 c, 1 d, 2a, 2b, 3a, and 3b, the body material is around the one or more electric conductor wires, i.e. the body material surrounds the one or more electric conductor wires. This is however not the only possible choice. In the exemplifying slot wedge 321 illustrated in figure 3c, the body material 324 is partially around the electric conductor wires 322a and 322b so that the electric conductor wires 322a and 322b constitute a part of the outer surface of the slot wedge 321 .

[0044] In a slot wedge according to an exemplifying and non-limiting embodiment, the body material comprises electrically insulating material such as e.g. resin and / or plastic. In a slot wedge according to an exemplifying and non-limiting embodiment, the body material comprises ferromagnetic particles such as e.g. iron particles.

[0045] Since a slot wedge according to an exemplifying and non-limiting embodiment is manufactured with an extrusion process of the kind described above with reference to figures 1 a, 1 b, 1c, and 2a, an outer surface of the body material is free from mold seam traces. Thus, a slot wedge manufactured with a method according to exemplifying and non-limiting embodiment can be distinguished from e.g. slot wedges manufactured so that body material is mold cast around one or more electric wires.

[0046] In the exemplifying slot wedges 101 , 201 , 301 , 311 , and 321 illustrated in figures 1 b, 1 c, 1 d, 2a, 2b, 3a, 3b, and 3c, the shortest distance from the one or more electric conductor wires to an outer surface of the slot wedge in the width direction, i.e. in the x-direction, of the slot wedge is greater than a shortest distance from the one or more electric conductor wires to an outer surface of the slot wedge in the thickness direction, i.e. in the y direction, of the slot wedge. In figurel d, the above-mentioned shortest distance in the width direction is denoted with Dw and correspondingly the above-mentioned shortest distance in the thickness direction is denoted with Dt. It is advantageous to have grounded conductors on the middle area of a slot wedge in the width direction because the middle area is farthest from teeth of a core which is typically grounded. Figure 4 shows a section view of a detail of an electric machine that comprises a slot wedge 401 according to an exemplifying and non-limiting embodiment. The section is taken along a geometric plane parallel with the xy-plane of a coordinate system 499. Figure 4 illustrates a part of a stator 441 of the electric machine and a part of a rotor 442 of the electric machine. The rotor 442 is rotatably supported with respect to the stator 441 so that there is an airgap between the stator and the rotor. The geometric rotation axis of the rotor 442 is parallel with the z-axis of the coordinate system 499. The stator comprises a core structure 443 and windings whose coil sides are located in slots of the core structure 443. Figure 4 illustrates a coil side 444 which is located in the slot between adjacent teeth 446 and 447 of the core structure 443. The slot wedge 401 is located between the adjacent teeth 446 and 447 and closes the slot opening of the above-mentioned slot of the core structure 443.

[0047] The slot wedge 401 comprises body material 404 and an electric conductor wire 402. The electric conductor wire 402 of the slot wedge 401 constitutes an electrostatic shield for reducing capacitively coupled currents between the coil side 444 and the rotor 442 when the electric conductor wire 402 is connected to a constant electric potential. Therefore, the electric conductor wires of the slot wedges reduce e.g. bearing currents of the electric machine.

[0048] The electric machine comprises electric conductors which have galvanic connections with the stator 441 and which are coupled to first ends of the electric conductor wires of the slot wedges of the electric machine. The second ends of the electric conductor wires of the slot wedges are open conductor ends. The electric conductor wires can be connected for example to the frame of the electric machine, to the core structure 443 of the stator, or to another place from which there is a galvanic connection to the core structure 443 of the stator. Figure 4 illustrates schematically an electric conductor 445 which is coupled to the electric conductor wire 402 of the slot wedge 401 .

[0049] The exemplifying electric machine which is partially illustrated in figure 4 can be an induction machine. It is also possible that slot wedges of the kind described above are used in an electric machine other than an induction machine. The electric machine can be for example a permanent magnet machine, an electrically excited synchronous machine, a reluctance machine, or a direct current machine, i.e. a “DC” machine.

[0050] The specific examples provided in the description given above should not be construed as limiting the scope and / or the applicability of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

What is claimed is:1 . A method for manufacturing a slot wedge (101 , 201 , 301 , 311 , 321 ) for an electric machine, characterized in that the method comprises:- feeding (121 ) one or more electric conductor wires (102, 202a, 202b, 302, 302a-302c, 322a, 322b) through an aperture of an extruder die (103, 203),- extruding (122) body material (104, 204, 304, 314, 324) of the slot wedge at least partially around the one or more electric conductor wires so that the aperture of the extruder die defines a cross-sectional shape of the slot wedge such that a width (W) of the slot wedge is greater than a thickness (T) of the slot wedge, and- cutting (123) the slot wedge coming out from the aperture of the extruder die to have a predetermined length.

2. A method according to claim 1 , wherein the width (W) of the slot wedge is at least two times the thickness (T) of the slot wedge.

3. A method according to claim 1 or 2, wherein a shortest distance (Dw) from the one or more electric conductor wires to an outer surface of the slot wedge in a width direction (x) of the slot wedge is greater than a shortest distance (Dt) from the one or more electric conductor wires to an outer surface of the slot wedge in a thickness direction (y) of the slot wedge.

4. A method according to any one of claims 1 -3, wherein the one or more electric conductor wires comprise one and only one electric conductor wire (101 ) located on a middle of the slot wedge in a width direction (x) of the slot wedge.

5. A method according to any one of claims 1 -4, wherein the one or more electric conductor wires (202a, 202b, 302a-302c) are two or more electric conductor wires parallel with and a distance away from each other in a width direction (x) of the slot wedge.

6. A method according to any one of claims 1 -5, wherein the one or more electric conductor wires (102, 202a, 202b, 302a, 302b) comprise one or more round electric conductor wires.

7. A method according to any one of claims 1 -6, wherein the one or more electric conductor wires (302, 302c) comprise one or more flat electric conductor wires each having a width greater than a thickness.

8. A method according to any one of claims 1-7, wherein the cross-sectional shape of the slot wedge (101 ) is substantially a trapezoid whose sides parallel with a width direction (x) of the slot wedge are longer than other two sides of the trapezoid.

9. A method according to any one of claims 1-7, wherein the cross-sectional shape of the slot wedge (201 , 301 ) is substantially a hexagon whose sides parallel with a width direction (x) of the slot wedge are longer than other four sides of the hexagon.

10. A method according to any one of claims 1 -9, wherein the body material (104, 204, 304, 314) is extruded with an apparatus (130, 230) comprising a crosshead extruder.11 . A method according to claim 10, wherein the crosshead extruder comprises:- a first member (133) comprising a supply channel (135) for conducting the body material (104, 204, 304, 314, 324) and a chamber (136) connected to the supply channel,- a second member (134) in the chamber of the first member, the second member having a tubular part (137) and an end-wall (138) provided with one or more apertures for receiving the one or more electric conductor wires (102, 202a, 202b, 302, 302a-302c, 322a, 322b), and- the extruder die (103, 203) in the chamber successively with the second member so that the aperture of the extruder die is in line with each of the one or more apertures of the end-wall of the second member, wherein a wall of the tubular part (137,) of the second member has apertures (138, 139) on opposite sides of the tubular part for conducting the body material from aroom (140) between a wall of the chamber of the first member and an outer surface of the tubular part to an interior of the tubular part and to the extruder die, wherein the apertures of the wall of the tubular part are symmetrically with respect to an end of the supply channel of the first member connecting to the chamber of the first member so that distances from the end of the supply channel to all the apertures of the wall of the tubular part are same.

12. A method according to claim 11 , wherein the method comprises adjusting flow rates of the body material via the apertures of the wall of the tubular part of the second member with adjusting screws (141 ,142) for changing sizes of the apertures of the wall of the tubular part.

13. An apparatus (130, 230) for manufacturing a slot wedge (101 , 201 , 301 , 311 , 321 ) for an electric machine, the apparatus comprising a crosshead extruder that comprises:- a first member (133) comprising a supply channel (135) for conducting body material (104, 204, 304, 314, 324) of the slot wedge and a chamber (136) connected to the supply channel,- a second member (134) in the chamber, the second member having a tubular part (137) and an end-wall (138) provided with one or more apertures for receiving one or more electric conductor wires (102, 202a, 202b, 302, 302a- 302c, 322a, 322b), and- an extruder die (103, 203) in the chamber successively with the second member so that an aperture of the extruder die is in line with each of the one or more apertures of the end-wall of the second member, characterized in that a wall of the tubular part (137) of the second member has apertures (138, 139) on opposite sides of the tubular part for conducting the body material from a room (140) between a wall of the chamber of the first member and an outer surface of the tubular part to an interior of the tubular part and to the extruder die, wherein the apertures of the wall of the tubular part are symmetrically with respect to an end of the supply channel of the first member connecting to thechamber of the first member so that distances from the end of the supply channel to all the apertures of the wall of the tubular part are same.

14. An apparatus according to claim 13, wherein the second member comprises adjusting screws (141 , 142) for changing sizes of the apertures of the wall of the tubular part.

15. A method for manufacturing an electric machine, the method comprising:- manufacturing slot wedges (401 ) by carrying out a method according to any one of claims 1 -12,- installing the slot wedges on openings of slots of a core structure of the electric machine to close the slots, and- grounding a first end of each electric conductor wire (402) of the slot wedges and leaving a second end of the electric conductor wire (402) as an open conductor end.

16. A slot wedge (101 , 201 , 301 , 311 , 321 ) for an electric machine, the slot wedge comprising body material (104, 204, 304, 314, 324) at least partially around one or more electric conductor wires (102, 202a, 202b, 302, 302a-302c, 322a, 322b) whose longitudinal direction is parallel with a longitudinal direction of the slot wedge, wherein a width (W) of the slot wedge is greater than a thickness (T) of the slot wedge, characterized in that the body material has been extruded at least partially around the one or more electric conductor wires and thereby an outer surface of the body material is free from mold seam traces.

17. An electric machine comprising:- a stator (441 ),- a rotor (442) rotatably supported with respect to the stator, at least one of the rotor and the stator comprising a core structure (443) and windings whose coil sides (444) are located in slots of the core structure,- slot wedges (401 ) according to claim 16 and arranged to close the slots of the core structure, and- electric conductors (445) having galvanic connections with the stator and coupled to first ends of the electric conductor wires (402) of the slot wedges, second ends of the electric conductor wires (402) of the slot wedges being open conductor ends.

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