Side wave spring

Abstract

Wave spring (500), wherein the wave spring (500) has a length extending along a longitudinal axis (402) and a width extending along a transverse axis (404), wherein the longitudinal axis (402) is substantially orthogonal to the transverse axis (404), wherein the wave spring (500) comprises a sinusoidal surface with a wavelength extending along a wavelength axis (412), wherein the wavelength axis (412) is offset from the longitudinal axis (402) by approximately forty-five degrees, wherein the sinusoidal surface has one or more valleys (411) extending along a valley axis (413), wherein the valley axis (413) is substantially orthogonal to the wavelength axis (412), wherein the wave spring (500) has: several laminated layers (510-530), wherein the several laminated layers (510-530) form a symmetrical stack, wherein the several laminated layers (510-530) comprise one or more lower layers (510), one or more middle layers (520) and one or more upper layers (530); wherein the lower layer(s) (510), the middle layer(s) (520) and the upper layer(s) (530) are essentially composed of unidirectional fibers; wherein the unidirectional fibers of the lower layer(s) (510) and the upper layer(s) (530) are substantially aligned along the wavelength axis (412) and wherein the unidirectional fibers of the middle layer(s) (520) are essentially aligned along the valley axis (413).

Description

BACKGROUND OF THE INVENTION

[0001] The invention relates generally to electrical machines and, more particularly, to a wave spring used in an electrical machine.

[0002] Armature windings, also known as stator bar windings, are routinely inspected on electric generators to verify their operation. In some generators, a stator yoke within the generator surrounds a lamination stack and partially encloses the armature windings. The stator windings are formed from a multitude of copper conductors wound into loops within the armature. The armature windings can be arranged in a stator slot to ensure the generator maintains the desired voltage and current characteristics during operation.

[0003] A generator typically includes a wedge system with wave springs to create a radial or circumferential holding force on the stator through wedges or wave springs, thus reducing the movement of the bar windings in the stator slot. However, if the wedge system itself becomes loose or a defect occurs in the wave springs (e.g., breakage), the holding force is reduced to such an extent that the bar windings could vibrate during operation. Over time, the relative movement of the bar windings can cause damage to the insulation surrounding the stator bars, and ground faults can cause bar winding failure.

[0004] US 2009 / 0 294 235 A1 discloses a laptop or notebook case with a spring protection system comprising a wave spring surrounded by two foam layers that, together with the wave spring, form a symmetrical stack. The wave spring is thermoformed from ABS (acrylonitrile butadiene styrene) plastic, and the foam layers are made of EVA (ethylene vinyl acetate) plastic.

[0005] US 2005 / 0 284 241 A1 discloses a wedge system for an electric generator with a wave spring comprising a plurality of laminated layers, the layers forming a symmetrical stack. The layers comprise one or more lower and one or more upper layers, each formed from a non-conductive material, e.g., a plastic laminate, and a middle layer made of a conductive material, e.g., a metal foil.

[0006] DE 30 16 990 A1 discloses a device for securing winding bars in slots of electrical machines, comprising a slot closure wedge, at least one corrugated slot closure tongue extending in the longitudinal direction of the slot, and at least one corrugated slot side tongue extending between a flank of the winding bar and the adjacent slot side wall. The slot side tongue is made of a glass fabric embedded in a curable resin.

[0007] Based on this, it is an object of the invention to provide a wave spring which enables secure holding of stator bars of a generator and has improved crack resistance and bending strength. BRIEF DESCRIPTION OF THE INVENTION

[0008] To achieve this object, the present invention provides a wave spring having the features of independent claims 1, 4, 7, and 10. Particularly preferred developments of the invention are the subject of the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference characters designate like parts throughout. Fig. 1 is an end perspective view of an electric machine according to one aspect of the present invention; Fig. 2 is an exploded partial view of a portion of the stator of the Fig. 1 according to an aspect of the present invention; Fig.3 is a partial cross-sectional view of a slot in a stator of an electric machine according to one aspect of the present invention; Fig. 4 is a perspective view of a wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 5 is a cross-sectional view of a multi-layer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 6 is a cross-sectional view of a multi-layer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 7 is a cross-sectional view of a multilayer wave spring used in the stator slot of an electric machine according to one aspect of the present invention, and Fig.8 is a cross-sectional view of a multi-layer wave spring used in the stator slot of an electric machine according to one aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Fig.1 is a perspective end view of an electric machine 10. The electric machine 10 includes a lamination stack 16 having a plurality of stator slots 12 for receiving a winding to generate magnetic flux. The stator slots 12 are configured to receive stator windings disposed in the slots defined around an inner periphery of the lamination stack 16 (also referred to as a stator lamination stack). The bar windings may be formed from a plurality of flat bar conductors or stator bars connected together to form a predetermined tortuous path. In one aspect of the invention, the stator bars are made of copper. A rotor (not shown) may be disposed within the stator lamination stack 18, with an air or coolant gap defined between the rotor and the stator lamination stack 16. A partial exploded view of the stator is illustrated by reference numeral 20 and will be described with reference to Fig.2. The electrical machine can be a rotary electric machine or a dynamoelectric machine, including a motor or generator.

[0011] Fig. 2 shows an exploded partial view of a portion of the electrical machine 10 of Fig.1. In one aspect of the invention, the stator 20 includes a lower bar winding 22, an upper bar winding 24, and one or more slot filler elements 26, 28 are disposed at least partially within each stator slot 21. The key or retention system includes a retention device or wave spring 32. In one aspect of the invention, the retention device includes a wave spring 32 disposed at least partially within the stator slot 21 such that the wave spring 32 is adjacent to the slot filler element 26 and / or the slot filler element 28. The wave spring 32 is then secured in the stator slot 21 using a plurality of stator key slides 34 and stator keys 36. The wave spring 32 may also be replaced with one of the wave springs 400, 500, 600, 700, and 800, which are described in more detail below.For example, by moving the stator wedge sliders 34 in a first direction (shown by arrow 38 and related to the stator wedges 36) or by moving the stator wedges 36 in a second direction (shown by arrow 40 and related to the stator wedge sliders 34), a holding pressure is applied to the outer stator bar 22 and the inner stator bar 24, so that the fastening of the outer stator bar 22 and the inner stator bar 24 in the stator slot 21 is facilitated.

[0012] Fig.3 shows a cross-section of a stator slot according to another aspect of the invention. The stator 300 includes a stator core 301 and is part of a dynamoelectric machine or electric machine, for example, a motor or a generator. The stator core 301 includes a plurality of radially extending stator slots 302 for receiving the windings or stator bars 322 and 324. It will be appreciated that the stator core 301 extends about a central axis and that the stator slots 302, as well as the stator bars 322 and 324, extend longitudinally parallel to this axis and substantially inwardly. In the illustrated form, the lateral wave springs 342 and 344 firmly press the stator bars 322, 324 against opposite sides of the stator slots 302. The lateral wave springs 342 and 344 may also be replaced by one of the wave springs 400, 500, 600, 700 and 800, which are described in more detail below.Radial space within the stator slots 302 may be occupied by radial filler elements 350. An upper retainer 330 includes stator keys 336 extending longitudinally along a radially inner portion of the stator slots 302 with their lateral edges resting in shaped grooves or dovetails 337 formed in the stator slots 302, and an upper wave spring 332 disposed at least partially within the stator slot 302 such that the wave spring 332 is adjacent to at least one slot filler element 328. The upper wave spring 332 is then secured in the stator slot 302 by a plurality of stator key slides 334 and stator keys 336. The upper wave spring 332 may also be replaced by one of the wave springs 400, 500, 600, 700 and 800, which are described in more detail below.

[0013] Fig.Figure 4 shows a perspective view of a wave spring 400 according to one aspect of the present invention. The wave spring 400 has a length 401 extending along a longitudinal axis 402 and a width 403 extending along a transverse axis 404. The longitudinal axis 402 is substantially orthogonal to the transverse axis 404. The wave spring 400 also has a substantially sinusoidal surface or shape, and the sinusoidal surface has a wave cycle or wavelength W LThe surface consists of a series of alternating peaks 410 and valleys 411, and the wavelength direction or axis 412 may be oriented in a direction that deviates by approximately 45 degrees from the longitudinal axis 402. The valleys 411 extend along a valley axis 413 that is substantially orthogonal to the wavelength axis 412. However, it should be noted that the wavelength axis 412 could also be oriented in any suitable direction, including parallel to the longitudinal axis, parallel to the transverse axis, or at any suitable angle therebetween.

[0014] Each layer of wave spring 400 may contain glass or carbon fibers. The glass fibers may be substantially unidirectional glass fibers, E-glass, S-glass, fiberglass, or any suitable fiber-reinforced polymer composed of a plastic matrix reinforced with fine glass fibers, although unidirectional electrical-grade E-glass is one of the preferred materials. The carbon fiber may be a woven fabric formed from many individual carbon fibers or any other suitable carbon fiber material or composite.

[0015] In some known prior art wave springs featuring an asymmetric layer stack, cracks have developed along the valleys. The asymmetric arrangement resulted in unequal internal spring forces, causing higher stress in the outer layers. The unequal internal spring forces were particularly problematic in the layers or plies adjacent to layers aligned along the wave length or axis. These cracks can ultimately lead to wave spring failure and subsequently, potentially, to the windings.

[0016] Accordingly, wave spring 400 is formed from one or more layers (or plies) that are laminated together and then molded together to form a wave spring with a symmetrical layer stack and improved crack resistance and flexural strength. The following table compares the approximate flexural strength of wave springs with an asymmetrical layer stack to the wave spring with a symmetrical layer stack of the present invention. "SWF" denotes a side wave spring, and "OWF" denotes an upper wave spring. TABLE 1 Breaking force in kN (lbf) SWF OWF Asymmetric wave spring approx. 0.12-0.17 (27-38) approx. 0.49 (110) Symmetrical wave spring approx. 0.24 (54) approx. 0.60-0.64 (135-145) Symmetrical wave spring with carbon fiber approx. 0.66 (149) approx. 0.69 (154)

[0017] The maximum breaking force for the asymmetric wave spring was approximately 0.17 kN (38 lbf (poundforce)), and for the symmetric lateral wave spring (SWF) according to the invention, the breaking force was approximately 0.24 kN (54 lbf). For the symmetric wave spring with carbon fiber, the breaking force was approximately 0.66 kN (149 lbf). A wave spring with a lower bending strength is more likely to break or fail during operation of the electrical machine. Practical experience showed that the asymmetric wave spring broke prematurely during operation, leading to unwanted machine shutdowns and expensive repairs. The symmetric wave spring has increased strength, which offers significant practical benefits because the tendency to break is eliminated or at least significantly reduced compared to asymmetric wave springs.In fact, by changing the arrangement and orientation of each layer in the symmetrical wave spring, a higher than expected result (i.e., improved bending force or bending strength) was achieved. The bending force or bending strength can be further increased by adding carbon fiber layers.

[0018] Fig.Figure 5 shows a cross-section of a wave spring 500 with a symmetrical layer stack, resulting in improved bending strength. The wave spring 500 may be formed from one or more lower layers 510, one or more middle layers 520, and one or more upper layers 530. In this arrangement, the wave spring is symmetrical about the dashed line 502. Two examples of each layer are shown, but it should be noted that one, two, or three or even more layers could be used for some or all of the various sections. The lower layers 510 are formed from unidirectional glass fibers, and the fibers are aligned substantially along the wavelength axis 412, which is shown running horizontally across the page.The middle layers 520 are also formed from unidirectional glass fibers, and these fibers are substantially aligned along the valley axis 413, which is shown extending into and out of the page. The upper layers 530 are formed from unidirectional glass fibers, and the fibers in the upper layers are substantially aligned along the wavelength axis 412. Each layer can be formed by impregnating a unidirectional glass fabric with a binder. Multiple layers can be formed into a laminate after drying or partially curing, and each formed laminate could have a thickness ranging from approximately 0.10 mm to approximately 0.20 mm (4 to 8 mils). Therefore, because of the symmetrical design, these laminates can be molded together to form a uniform and symmetrical wave spring with the desired wave cycles.The impregnating binder may contain, but is not limited to, epoxy, polyester, polyesterimide, polyamide-imide, epoxy-phenol, epoxy-novolac resin, epoxy-polyimide, or combinations thereof, or any other suitable binder with a temperature rating above the operating temperature of an electrical machine. These impregnating resin binders may be filled with electrically and / or thermally conductive materials to dissipate the accumulated charges and heat on or in the surfaces of insulated stator bars toward the walls of steel slots.

[0019] Most cracks appear to form along the valley axis 413; therefore, the wave spring 500 should become more crack-resistant if the layers oriented in the crack or valley direction are arranged away from the surface of the wave spring. The surface could be either the top or bottom surface, since both surfaces are in contact with portions of the electrical machine or the support assembly. The wave spring 500 is formed from a plurality of layers with alternating fiber directions, and this alternating arrangement is important for maintaining the strength of the wave spring. For example, if all layers were oriented in the same direction and a crack were to form, it would quickly propagate along the entire wave spring.By alternating the fiber directions in a specific way and arranging the layers symmetrically, both the strength of the wave spring and its resistance to cracking and crack propagation can be improved. For example, the breaking force of this symmetrical lateral wave spring 500 is approximately 0.24 kN (54 lbf).

[0020] Fig.6 shows a cross-section of a wave spring 600 with a symmetrical layer stack. The wave spring 600 can be formed from one (as shown) or more lower layers 610, one or more middle layers 620, one or more upper layers 630, as well as a first layer 640 and a second layer 650. It should be noted, however, that one, two, or three or more layers could be used for each of the various sections. In this arrangement, the wave spring is symmetrical about the dashed line 602. The lower layer 610, the middle layers 620, and the upper layer 630 are formed from unidirectional glass fibers, and the fibers are substantially aligned along the wavelength axis 412. The first layer 640 is located between the lower layer 610 and the middle layer 620, and the first layer 640 is also formed from unidirectional glass fibers.The fibers in the first layer 640 are substantially aligned along the valley axis 413. The second layer 650 is located between the middle layer 620 and the top layer 630, and the second layer 650 is also formed from unidirectional glass fibers. The fibers in the second layer 650 are substantially aligned along the valley axis 413. Each layer can be formed into lateral wave springs, with the time-temperature curing profile of resins being known to those skilled in the art.

[0021] Fig.Figure 7 shows a cross-section of a wave spring 700 with a symmetrical layer stack. The wave spring 700 can be formed from one or more lower carbon fiber layers 710, a first layer 740, one or more middle layers 720, a second layer 750, and one or more upper carbon fiber layers 730. It should be noted, however, that one, two, or three or even more layers could be used for each of the different sections. In this arrangement, the wave spring is symmetrical about the dashed line 702. The lower layer 710 and the upper layer 730 are formed from carbon fiber material. The carbon fiber material provides additional strength to the wave spring 700. Alternatively, the carbon fiber layers can be combined with synthetic para-aramid fiber (e.g., Kevlar®, a registered trademark of EIdu Pont de Nemours and Company), graphite, copper, silver, gold, and / or aluminum. The first layer 740 is located between the bottom layer 710 and the middle layer 720, and the first layer is formed of unidirectional glass fibers substantially aligned along the wavelength axis 412. The middle layers 720 are also formed of unidirectional glass fibers, and these fibers are substantially aligned along the valley axis 413. The second layer 750 is located between the middle layer 720 and the top layer 730, and the second layer 750 is formed of unidirectional glass fibers substantially aligned along the wavelength axis 412. Each layer can be bonded to adjacent layers using any suitable epoxy material or bonding agent.

[0022] Fig.Figure 8 shows a cross-section of a wave spring 700 with a symmetrical layer stack. The wave spring 800 can be formed from one or more lower layers 810, a first layer 840, one or more middle carbon fiber layers 820, a second layer 850, and one or more upper layers 830. It should be noted, however, that one, two, or three or more layers could be used for each of the different sections. In this arrangement, the wave spring is symmetrical about the dashed line 802. The lower layer 810, the first layer 840, the second layer 850, and the upper layer 830 are formed from unidirectional glass fibers. The fibers in the lower layer 810 and the upper layer 830 are substantially aligned along the wavelength axis 412. The fibers in the first layer 840 and the second layer 850 are substantially aligned along the valley axis 413.The middle layers 820 are formed of carbon fiber material, and the carbon fiber material provides additional strength to the wave spring 800. Each layer can be bonded to adjacent layers using any suitable epoxy material or bonding agent.

[0023] The wave spring may be adapted to be electrically and thermally conductive in applications with lateral wave springs whose surface resistivity is as low as 15,000 to 750,000 ohms per square (15,000 to 750,000 ohms / in 2) and it can be electrically insulating and / or thermally conductive in applications with upper wave springs. Electrically conductive or semi-conductive lateral wave springs can be the electrically securing element when closing the lateral groove in generators. In addition, the lateral wave springs can contain or be impregnated with conductive or semi-conductive material such as, but not limited to: graphite, metal, metal alloys, conductive or semi-conductive fibers or conductive or semi-conductive powders, conductive or semi-conductive polymers, conductive or semi-conductive elastomers and conductive or semi-conductive plastics whose temperature rating or thermal class is above the operating temperature of an electrical machine. Electrically insulating upper wave springs may be preferred and electrically insulating materials may be used to form the upper wave springs.However, in some applications, electrically and / or thermally conductive or semiconductive materials may be used to manufacture upper wave springs, and in these applications, the conductive or semiconductive material may be located near the spring center to reduce direct contact with adjacent surfaces.

[0024] This written description uses examples to disclose the invention—including the preferred (best) mode—which are also intended to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any method incorporated therein. The patentable scope of the invention is defined by the claims and may include other examples that may occur to those skilled in the art. Such other examples are intended to be included within the scope of the claims if those examples include structural elements that do not depart from the literal meaning of the claims, or if they include equivalent structural elements with insubstantial differences from the literal meaning of the claims.

[0025] A wave spring 500 is provided having one or more layers 510, 520, 530 laminated together, wherein the layer(s) form a symmetrical stack. LIST OF REFERENCE SYMBOLS: 10 electric machine 12 stator slots 16 sheet package 18 Stator laminated core 20 Stator 21 Stator slot 22 lower bar winding 24 upper bar winding 26 Groove filling element 28 Groove filling element 32 Wave spring 34 stator wedge valves 36 stator wedges 38 Arrow 40 Arrow 300 Stator 301 stator lamination stack 302 stator slots 322 stator bars 324 stator bars 328 Groove filling element 330 upper holding arrangement 332 upper wave spring 334 Stator wedge valve 336 stator wedges 337 Swallowtails 342 lateral wave spring 344 lateral wave spring 350 radial filling element 400 wave spring 401 length 402 Longitudinal axis 403 width 404 transverse axis 410 peaks 411 Valley 412 Wavelength direction / axis 413 valley axis 500 wave spring 502 dashed line 510 lower layer 520 middle layer 530 upper layers 600 wave spring 602 dashed line 610 lower layer 620 middle layer 630 upper layers 640 first layer 650 second shift 700 wave spring 702 dashed line 710 lower layer 720 middle layer 730 upper layers 740 first shift 750 second shift 800 wave spring 802 dashed line 810 lower layer 820 middle layer 830 upper layers 840 first layer 850 second shift

Claims

[1] Wave spring (500), wherein the wave spring (500) has a length extending along a longitudinal axis (402) and a width extending along a transverse axis (404), wherein the longitudinal axis (402) is substantially orthogonal to the transverse axis (404), wherein the wave spring (500) comprises a sinusoidal surface having a wavelength extending along a wavelength axis (412), wherein the wavelength axis (412) deviates by approximately forty-five degrees from the longitudinal axis (402), wherein the sinusoidal surface has one or more valleys (411) extending along a valley axis (413), wherein the valley axis (413) is substantially orthogonal to the wavelength axis (412), wherein the wave spring (500) comprises: a plurality of layers (510-530) laminated together, wherein the plurality of layers (510-530) laminated together form a symmetrical stack, wherein the plurality of layers (510-530) laminated together comprise one or more lower layers (510), one or more middle layers (520), and one or more upper layers (530); wherein the lower layer(s) (510), the middle layer(s) (520) and the upper layer(s) (530) are formed substantially from unidirectional fibers; wherein the unidirectional fibers of the lower layer(s) (510) and the upper layer(s) (530) are aligned substantially along the wavelength axis (412) and wherein the unidirectional fibers of the middle layer(s) (520) are aligned substantially along the valley axis (413). [2] Wave spring (500) according to claim 1, wherein the lower layer(s) (510), the middle layer(s) (520) and the upper layers (530) contain a binder, wherein the binder contains one of the following substances or combinations of the following substances: Epoxy, polyester, polyesterimide, polyamide-imide, epoxyphenol, epoxy novolac resin and epoxy polyimide. [3] Wave spring (500) according to claim 2, wherein the binding material contains at least one of the following materials or combinations of the following materials: an electrically conductive material and a thermally conductive material. [4] Wave spring (600), wherein the wave spring (600) has a length extending along a longitudinal axis (402) and a width extending along a transverse axis (404), wherein the longitudinal axis (402) is substantially orthogonal to the transverse axis (404), wherein the wave spring (600) comprises a sinusoidal surface having a wavelength extending along a wavelength axis (412), wherein the wavelength axis (412) deviates by approximately forty-five degrees from the longitudinal axis (402), wherein the sinusoidal surface has one or more valleys (411) extending along a valley axis (413), wherein the valley axis (413) is substantially orthogonal to the wavelength axis (412), wherein the wave spring (600) comprises: a plurality of layers (610-650) laminated together, wherein the plurality of layers (610-650) laminated together form a symmetrical stack, wherein the plurality of layers (610-650) laminated together comprise one or more lower layers (610), one or more middle layers (620), and one or more upper layers (630); wherein the lower layer(s) (610), the middle layer(s) (620) and the upper layer(s) (630) are formed substantially from unidirectional fibers, wherein the unidirectional fibers of the lower layer(s) (610), the middle layer(s) (620) and the upper layer(s) (630) are aligned substantially along the wavelength axis (412); a first layer (640) located between the lower layer(s) (610) and the middle layer(s) (620), the first layer (640) being formed substantially from unidirectional fibers, the unidirectional fibers of the first layer (640) being aligned substantially along the valley axis (413); and a second layer (650) located between the middle layer(s) (620) and the upper layer(s) (630), the second layer (650) being formed substantially from unidirectional fibers, the unidirectional fibers of the second layer (650) being aligned substantially along the valley axis (413). [5] Wave spring according to claim 4, wherein the lower layer(s) (610), the first layer (640), the middle layer(s) (620), the second layer (650) and the upper layer(s) (630) contain a binder, wherein the binder contains one of the following substances or combinations of the following substances: Epoxy, polyester, polyesterimide, polyamide-imide, epoxyphenol, epoxy novolac resin and epoxy polyimide. [6] Wave spring according to claim 5, wherein the binder contains at least one of the following materials or combinations of the following materials: an electrically conductive material and a thermally conductive material. [7] Wave spring (700), wherein the wave spring (700) has a length extending along a longitudinal axis (402) and a width extending along a transverse axis (404), wherein the longitudinal axis (402) is substantially orthogonal to the transverse axis (404), wherein the wave spring (700) comprises a sinusoidal surface having a wavelength extending along a wavelength axis (412), wherein the wavelength axis (412) deviates by approximately forty-five degrees from the longitudinal axis (402), wherein the sinusoidal surface has one or more valleys (411) extending along a valley axis (413), wherein the valley axis (413) is substantially orthogonal to the wavelength axis (412), wherein the wave spring (700) comprises: a plurality of layers (710-750) laminated together, wherein the plurality of layers (710-750) laminated together form a symmetrical stack, wherein the plurality of layers (710-750) laminated together comprise one or more lower layers (710), one or more middle layers (720), and one or more upper layers (730); wherein the lower layer(s) (710) and the upper layer(s) (730) are formed substantially from carbon fibers, wherein the middle layer(s) (720) are formed substantially from unidirectional fibers, the unidirectional fibers of the middle layer(s) being aligned substantially along the valley axis (413); a first layer (740) located between the lower layer(s) (710) and the middle layer(s) (720), wherein the first layer (740) is formed substantially from unidirectional fibers, wherein the unidirectional fibers of the first layer (740) are aligned substantially along the wavelength axis (412), and a second layer (750) located between the middle layer(s) (720) and the upper layer(s) (730), the second layer (750) being formed substantially from unidirectional fibers, the unidirectional fibers of the second layer (750) being aligned substantially along the wavelength axis (412). [8] Wave spring according to claim 7, wherein the first layer (740), the middle layer(s) (720) and the second layer (750) contain a binder, wherein the binder contains one of the following substances or combinations of the following substances: Epoxy, polyester, polyesterimide, polyamide-imide, epoxyphenol, epoxy novolac resin and epoxy polyimide. [9] Wave spring according to claim 8, wherein the binder contains at least one of the following materials or combinations of the following materials: an electrically conductive material and a thermally conductive material. [10] Wave spring (800), wherein the wave spring (800) has a length extending along a longitudinal axis (402) and a width extending along a transverse axis (404), wherein the longitudinal axis (402) is substantially orthogonal to the transverse axis (404), wherein the wave spring (800) comprises a sinusoidal surface having a wavelength extending along a wavelength axis (412), wherein the wavelength axis (412) deviates by approximately forty-five degrees from the longitudinal axis (402), wherein the sinusoidal surface has one or more valleys (411) extending along a valley axis (413), wherein the valley axis (413) is substantially orthogonal to the wavelength axis (412), wherein the wave spring (800) comprises: a plurality of layers (810-850) laminated together, wherein the plurality of layers (810-850) laminated together form a symmetrical stack, wherein the plurality of layers (810-850) laminated together comprise one or more lower layers (810), one or more middle layers (820), and one or more upper layers (830); wherein the lower layer(s) (810) and the upper layer(s) (830) are formed substantially from unidirectional fibers, wherein the unidirectional fibers of the lower layer(s) (810) and the upper layer(s) (830) are aligned substantially along the wavelength axis (412); wherein the middle layer(s) (820) are formed substantially from carbon fibers; a first layer (840) located between the lower layer(s) (810) and the middle layer(s) (820), the first layer (840) being formed substantially from unidirectional fibers, the unidirectional fibers of the first layer (840) being aligned substantially along the valley axis (413), and a second layer (850) located between the middle layer(s) (820) and the upper layer(s) (830), the second layer (850) being formed substantially from unidirectional fibers, the unidirectional fibers of the second layer (850) being aligned substantially along the valley axis (413). [11] Wave spring according to claim 10, wherein the lower layer(s) (810), the first layer (840), the second layer (850) and the upper layer(s) (830) contain a binder, wherein the binder contains one of the following substances or combinations of the following substances: Epoxy, polyester, polyesterimide, polyamide-imide, epoxyphenol, epoxy novolac resin and epoxy polyimide. [12] Wave spring according to claim 11, wherein the binder contains at least one of the following materials or combinations of the following materials: an electrically conductive material and a thermally conductive material. [13] Wave spring according to claim 12, further in combination with: an electrical machine (10) having a rotor and a stator (20; 300), wherein the stator (20; 300) has a stator laminated core (18; 301) with a plurality of stator slots (21; 302); a plurality of stator bars (22, 24; 322, 324) substantially contained in the plurality of stator slots (21; 302), wherein the wave spring (800) is located between at least one of the plurality of stator bars (22, 24; 322, 324) and the stator laminated core (18; 301).

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