Wave spring and diagnostic system for this

Abstract

Wave spring (400; 500; 600; 700; 800), comprising the following: one or more conductive layers (424; 520; 640, 650; 710, 730; 820); one or more non-conductive layers (422; 510, 530; 610, 620, 630; 720, 740, 750; 810, 830, 840, 850), wherein the conductive layer(s) (424; 520; 640, 650; 710, 730; 820) and the non-conductive layer(s) (422; 510, 530; 610, 620, 630; 720, 740, 750; 810, 830, 840, 850) are laminated together to form a symmetrical stack of layers; characterized in that the non-conductive layer(s) (422; 510, 530; 610, 620, 630; 720, 740, 750; 810, 830, 840, 850) include: at least a first layer (510; 610, 630; 740, 750; 810, 830) consisting essentially of unidirectional fibers aligned along a first axis (402); at least a second layer (520; 620; 720; 840, 850) consisting essentially of unidirectional fibers aligned along a second axis (413), where the first axis (402) is essentially orthogonal to the second axis (413).

Description

BACKGROUND OF THE INVENTION

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

[0002] Armature windings, also known as stator bar windings, are routinely inspected in electric generators to verify their proper functioning. In some generators, a stator yoke surrounds an armature core and partially encloses the armature windings. The stator windings consist of numerous 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-current characteristics during operation.

[0003] A generator typically incorporates a wedge system with wave springs to generate a holding force acting radially or circumferentially on the stator, thereby reducing the movement of the bar windings in the stator slot. However, if the wedge system itself loosens or a defect occurs in the wave springs (e.g., cracks form in them), 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 damage the insulation surrounding the stator bars, and short circuits to ground can cause a failure of the bar winding. Such wedge and wave spring systems for electrodynamic machines are known, for example, from US 7,418,858 B2 and US 2004 O 119 364 A1.

[0004] US 2005 / 0284241A1 and US 7112909B2 each disclose a wave spring for a stator wedge system of an electric generator, which has the features of the preamble of independent claim 1. BRIEF DESCRIPTION OF THE INVENTION

[0005] According to the present invention, a wave spring is provided with one or more conductive layers and one or more non-conductive layers. The conductive layer(s) and the non-conductive layer(s) are laminated together to form a symmetrical layer stack. The non-conductive layer(s) further comprises: at least a first layer consisting essentially of unidirectional fibers aligned along a first axis; at least a second layer consisting essentially of unidirectional fibers aligned along a second axis, the first axis being essentially orthogonal to the second axis.

[0006] Particularly preferred embodiments of the invention are the subject of the dependent patent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects and advantages of the present invention are better understood when the following detailed description is read with reference to the accompanying drawings, in which the same reference numerals consistently denote the same parts. Fig. 1 is a perspective end view of an electrical machine according to one aspect of the present invention; Fig. Figure 2 is a partial exploded view of a section of the stator located in Fig. 1 electrical machine shown according to one aspect of the present invention; Fig. 3 is a partial cross-section of a slot in a stator of an electric machine according to one aspect of the present invention; Fig. Figure 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-section of a multilayer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 6 is a cross-section of a multilayer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 7 is a cross-section of a multilayer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. 8 is a cross-section of a multilayer wave spring used in the stator slot of an electric machine according to one aspect of the present invention; Fig. Figure 9 is a simplified schematic representation of a measuring system according to one aspect of the present invention, which is used to measure the strength of the stator windings or the condition of the wave springs in an electric machine; Fig. Figure 10 is a simplified flowchart of a diagnostic procedure, not claimed as such, for determining the condition of the wave springs in an electric machine. DETAILED DESCRIPTION OF THE INVENTION

[0008] Fig.Figure 1 is a perspective end view of an electric machine 10. The electric machine 10 comprises a laminated core 16 with a plurality of stator slots 12 for receiving a winding to generate a magnetic flux. The stator slots 12 are designed to receive stator windings arranged in the stator slots defined around an inner circumference of the laminated core 16 (also referred to as the stator core). The bar windings can be formed from a plurality of flat bar conductors or stator bars connected to each other to form a predetermined winding path. In one aspect of the invention, the stator bars are made of copper. A rotor (not shown) can be arranged in the stator core 18, with an air or coolant gap defined between the rotor and the stator core 16. A partial exploded view of the stator is shown with reference numeral 20 and is described with reference to Fig.2 described in detail. The electric machine can be any electric rotary machine or dynamo-electric machine, for example, among others, a motor or a generator.

[0009] Fig. Figure 2 shows a partial exploded view of a section of the electric machine 10. Fig.1. In one aspect of the invention, the stator 20 comprises a lower bar winding 22, an upper bar winding 24, and one or more slot filler elements 26, 28 are arranged at least partially within each stator slot 21. The wedge or retaining system comprises a retaining device or wave spring 32. In one aspect of the invention, the retaining device comprises a wave spring 32 which is arranged 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 by means of a plurality of stator wedge slides 34 and stator wedges 36. The wave spring 32 can also be replaced by 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 slides 34 in a first direction (shown by arrow 38 and relative to the stator wedges 36) or by moving the stator wedges 36 in a second direction (shown by arrow 40 and relative to the stator wedge slides 34) a holding pressure is triggered on the outer stator rod 22 and the inner stator rod 24, so that the fastening of the outer stator rod 22 and the inner stator rod 24 in the stator groove 21 is promoted.

[0010] Fig.Figure 3 shows a cross-section of a stator slot according to another aspect of the invention. The stator 300 comprises a stator lamination stack 301 and is part of a dynamo-electric or electric machine, such as a motor or a generator. The stator lamination stack 301 comprises a plurality of radially extending stator slots 302 for receiving the windings or stator bars 322 and 324. It is evident that the stator lamination stack 301 extends around 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 radially inwards. In the illustrated configuration, the lateral shaft springs 342 and 344 hold the stator bars 322, 324 firmly pressed against the opposite sides of the stator slot 302.The lateral wave springs 342 and 344 can also be replaced by one of the wave springs 400, 500, 600, 700, and 800, which are described in more detail below. Radially oriented space in the stator slots 302 can be occupied by radial filler elements 350. An upper retaining device 330 comprises the stator wedges 336, which extend longitudinally along a radially inner section of the stator slots 302, their lateral edges resting in formed grooves or dovetails 337 formed in the stator slots 302, and an upper wave spring 332, which is arranged 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 fastened in the stator groove 302 by means of a plurality of stator wedge slides 334 and stator wedges 336.The upper wave spring 332 can also be replaced by one of the wave springs 400, 500, 600, 700 and 800, which are described in more detail below.

[0011] 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 an axis substantially perpendicular to the longitudinal axis. 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 may be substantially parallel to the longitudinal axis 402. The valleys 411 run along a valley axis 413, which may be substantially parallel to the transverse axis. However, it should be noted that the wavelength axis and / or the valley axis could also be oriented in any suitable direction, including parallel to the longitudinal axis, parallel to the transverse axis, or at any suitable angle in between.

[0012] The wave spring 400 consists of a layering or stack of one or more non-conductive layers 422 and one or more conductive or semi-conductive layers 424, all of which form a symmetrical stacking or layering. The non-conductive layers 422 can consist of multiple layers, wherein at least one first layer consists essentially of unidirectional fibers aligned along a first axis, and at least one second layer consists essentially of unidirectional fibers aligned along a second axis, the first axis being essentially orthogonal to the second axis. For example, the first layer can have fibers aligned along the longitudinal axis 402, and the second layer can have fibers aligned along the valley axis 413.The conductive layers 424 can contain carbon fibers, graphite, copper, silver, gold, and aluminum. The conductive layers 424 can be electrically and / or thermally conductive, depending on the specific application.

[0013] Each layer of the Wave Spring 400 can contain glass or carbon fibers. The glass fibers can be essentially unidirectional glass fibers, E-glass fiber (e.g., aluminum borosilicate glass), S-glass fiber (e.g., aluminum silicate glass), fiberglass, or any suitable fiber-reinforced polymer made from a plastic matrix reinforced with fine glass fibers. The carbon fiber can be a woven fabric made from many individual carbon fibers or any other suitable carbon fiber material or composite material.

[0014] In some known prior art wave springs with an asymmetric layer stack, cracks have developed along the valleys. The asymmetric arrangement led to unequal internal spring forces, resulting in higher stress in the outer layers. These unequal internal spring forces were particularly problematic in layers adjacent to those aligned with the wavelength or axis. These cracks can ultimately lead to failure of the wave spring and subsequently, potentially, to failure of the windings.

[0015] Accordingly, the wave spring 400 is formed from one or more layers (or plies) that are laminated together and then formed to create a wave spring with a symmetrical layer stack and improved crack resistance and flexural strength. The following table compares the approximate flexural strength and breaking strength of a wave spring with an asymmetrical layer stack to that of the wave spring according to the invention with a symmetrical layer stack. TABLE 1 Breaking force in kN (lbf) SWF OWF Asymmetric wave spring 0,12-0,17(27-38) 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)

[0016] The breaking force of the asymmetric upper wave spring was approximately 0.49 kN (approx. 110 lbf (pound force)), and of the symmetric upper wave spring according to the invention, the breaking force was approximately 0.62 kN (approx. 140 lbf), while the breaking force of the carbon fiber upper wave spring according to the invention was approximately 0.69 kN (approx. 154 lbf). A wave spring with lower flexural strength is more prone to cracking or malfunction during operation of the electric machine. Practical experience showed that the asymmetric wave spring developed cracks prematurely during operation, leading to undesirable machine shutdowns and costly repairs. The symmetric wave spring has increased strength, which offers a significant practical advantage, as the tendency to crack is eliminated or at least considerably reduced compared to the asymmetric wave springs.In fact, by changing the arrangement and orientation of each layer in the symmetrical wave spring, a higher result (i.e., improved bending strength) than expected was achieved. The bending strength can be further increased by adding carbon fiber layers.

[0017] Fig.Figure 5 shows a cross-section of a wave spring 500 with a symmetrical layer stack and improved bending force or flexural strength. The wave spring 500 can 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, 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 substantially aligned along the longitudinal axis or wavelength axis 402, which is shown as running horizontally across the side.The middle layers 520 are also formed from unidirectional glass fibers, and these fibers are essentially aligned along the valley axis 413, which is shown as extending into or out of the side. The upper layers 530 are formed from unidirectional glass fibers, and the fibers in the upper layers are essentially aligned along the wavelength axis 402.

[0018] Each layer can be formed by impregnating a unidirectional glass fabric with a binder. Several layers can be formed into a laminate after drying or partial curing, and each formed laminate could have a thickness in the range of approximately 0.10 mm to approximately 0.20 mm (approximately 4 to approximately 8 mils). Due to their symmetrical design, these laminates can therefore be assembled to form a uniform and symmetrical wave spring with the desired wave cycles. The impregnating binder may include, 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 whose thermal resistance exceeds the operating temperature of an electrical machine.These impregnating resin binders can be filled with electrically and / or thermally conductive materials to improve the dispersion of accumulated charges and heat on or in surfaces of insulated stator bars towards the walls of steel-made grooves.

[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 further away from the surface of the wave spring. The surface could be either the upper or the lower surface, since both surfaces are in contact with sections of the electrical machine or the support arrangement. The wave spring 500 is formed from a multitude of layers with alternating fiber orientations, and this alternating arrangement is important for maintaining the strength of the wave spring. For example, if all the layers were oriented in the same direction and a crack were to form, it would propagate rapidly 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 strength of the symmetrical upper wave spring 500 is approximately 0.62 kN (140 lbf).

[0020] Fig.Figure 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, and the conductive or semiconducting layers 640, 650. However, it should be noted that one, two, 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 602. The lower layer 610, the middle layers 620, and the upper layer 630 are nonconducting layers formed from unidirectional glass fibers. The fibers in layers 610 and 630 are substantially aligned along the wavelength axis 402.The middle layers 620 are also formed from unidirectional glass fibers, but the fibers in these layers are essentially aligned along the valley axis 413. The first electrically and / or thermally conductive layer is located between the lower layer 610 and the middle layer 620. The second electrically and / or thermally conductive layer 650 is located between the middle layer 620 and the upper layer 630. The conductive layers 640 and 650 may be formed from carbon fiber material. The carbon fiber material provides additional strength to the wave spring 600. The carbon fiber material can also be used to detect the condition or compression of each wave spring or the condition and strength of the winding system in general.Using a time-temperature profile of the curing process and employing a binder, each laminate layer can be shaped to form a wave spring. The degree of curing can be controlled and monitored after shaping and post-curing using the glass transition temperature of the binder. For example, the breaking strength of this symmetrical upper wave spring 600 is approximately 0.69 kN (154 lbf).

[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 conductive or semiconducting carbon fiber layers 710, 730, a non-conductive first layer 740, one or more non-conductive middle layers 720, and a non-conductive second layer 750. It should be noted, however, that one, two, 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 conductive lower layer 710 and the conductive upper layer 730 can be made of carbon fiber material. The carbon fiber material gives the wave spring 700 additional strength.The first layer 740 is located between the lower conductive layer 710 and the middle layer 720, and the first layer 740 is formed from unidirectional glass fibers that are substantially aligned along the wavelength axis 402. The middle layers 720 are also formed from 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 upper conductive layer 730, and the second layer 750 is formed from unidirectional glass fibers that are substantially aligned along the wavelength axis 402. Each layer can be bonded to adjacent layers using any suitable epoxy material or binder.Furthermore, the laminate layers can be formed together to create wave spring plates from which a single wave spring of any desired dimension can be cut.

[0022] Fig.Figure 8 shows a cross-section of a wave spring 800 with a symmetrical layer stack. The wave spring 800 can be formed from one or more non-conductive lower layers 810, a non-conductive first layer 840, one or more conductive or semi-conductive middle carbon fiber layers 820, a non-conductive second layer 850, and one or more non-conductive upper layers 830. It should be noted, however, that one, two, 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 802. The non-conductive lower layer 810, the non-conductive first layer 840, the non-conductive second layer 850, and the non-conductive upper layer 830 can be formed from unidirectional glass fibers.The fibers in the lower layer 810 and the upper layer 830 are substantially aligned along the wavelength axis 402. The fibers in the first layer 840 and the second layer 850 are substantially aligned along the valley axis 413. The conductive middle layers 820 may be formed of carbon fiber material, and the carbon fiber material imparts additional strength to the wave spring 800. Each layer may be bonded to adjacent layers using any suitable epoxy material or binder.

[0023] During its use, the wave spring 400 is at least partially arranged in the stator groove 21, and the stator wedges 36 are then inserted into the stator groove 21 to form a bearing on the wave spring 32 (in Fig.(2 shown) to generate a compressive force. More precisely, the stator wedges 36 are rearranged to facilitate the compression of the wave spring 400 so that it is essentially flat, achieving a full radial holding force at that point. For example, when the wave spring 400 is not compressed, i.e., the wave spring 400 is relaxed, its unaltered height 405 can be between approximately 2.54 mm (100 mil (2.540 micrometers or 0.1 in)) and approximately 6.1 mm (240 mil). However, when the wave spring 400 is compressed by the stator wedges 36, it is compressed to a thickness between approximately 1 mm and 1.8 mm (40 mil and approximately 70 mil).

[0024] Consequently, the thickness 405 of the wave spring 400 in the stator slot 21 changes in response to vibration during operation or an increase (or decrease) in the wedge pressure when the pressure on the wave spring 400 is increased (or decreased) during operation of the electric machine 10 by a rearrangement of the wedges 36 in the stator slot 21. The thickness 405 of the wave spring is both predictable and measurable in the compressed and uncompressed states by means of the conductive layer 424, which is designed to reflect and / or generate signals based on the mechanical boundary conditions present in the stator slot 21. A measuring instrument can be used to acquire a profile of the wave spring 400. The measured profile is then used to determine the strength of the stator winding in the stator slot 21 and / or the condition of the individual wave springs 400.

[0025] According to one aspect of the present invention, at least one conductive or semiconducting layer 424 is embedded in or attached to the wave spring. The conductive layer(s), which may contain carbon fiber, are designed to generate signals that can be related to at least one aspect of the winding and the spring. The thickness or height of the wave spring 400 can, for example, be used to indicate the strength of the stator winding 22, 24.

[0026] Fig. Figure 9 shows a measuring system 900 that can be used to determine the strength of the stator winding 22, 24 and / or the condition of the wave spring 400 in an electromechanical device such as, among others, the electric machine 10 (in Fig.(1 shown). The measuring system 900 comprises a measuring device 910. The measuring device 910 includes a transceiver or sensor 920 configured to detect a parameter associated with the conductive layer 424. This parameter can be, for example, the capacitance. The measuring system 900 can also include a computer 930 configured to receive data from the measuring device 910 and to analyze data received from the transceiver 920. The transceiver 920 can be any suitable device for measuring the capacitance or any desired parameter. In another aspect, the measuring device 910 includes a power source 940 for supplying power to the measuring device 910 and the transceiver 920.The term "computer" as used here does not refer exclusively to the integrated circuits that are called computers in this field, but refers more broadly to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application-specific integrated circuits, and any other programmable circuit.

[0027] The power source 940 may include an energy harvesting mechanism that potentially generates current from the magnetic flux in the environment or from vibrations in the electric machine. During operation, the measuring system 900 is powered by the power source 940, thus transferring energy to the transceiver 920. The measuring device 910 is configured such that the transceiver, in conjunction with the conductive layer 424, detects a signal. The capacitance between the transceiver 920 and the conductive layer 424 is inversely proportional to the distance between the two elements. The change in capacitance as the transceiver moves along the groove 21 can be correlated with the respective compression of each wave spring and the tightness of the seating of the corresponding wedges located nearby.A change in capacitance may indicate a change or deviation in the strength of the winding, or a malfunction or defect in a wave spring.

[0028] In one aspect of the present invention, transfer functions relating the capacitance to the measured thickness, height, or flexion of the wave spring 400 are used to determine the winding tightness and / or the condition of the wave spring in the electromechanical device 10. In the event of a deviation from a predetermined value for the winding tightness, an error signal can be generated. The error signal can also be transmitted to a desired location using any suitable communication means. The wave spring profile can also be acquired, for example, using the measuring device 910 or the computer 930 connected to the measuring device, to determine the thickness, height, or flexion of the wave spring 400. Likewise, an error signal can be generated if excessive flexion or thickness is detected.Such a fault signal can be used to mitigate faults by means of a corrective action, for example by switching off the electric machine 10. It should be noted that the fault signal contributes to the diagnosis and mitigation of faults. A method implemented in the measuring system 900, which is not claimed as such, is described in . Fig. 10 described.

[0029] Fig.Figure 10 is a flowchart of a diagnostic procedure 1000 for monitoring the tightness of the windings and / or the condition of the wave springs. The procedure described here assists an operator in easily checking the winding system of an electromechanical device (e.g., a generator, motor, etc.) to determine the tightness of the winding system in the stator slot or the condition of the wave springs. In particular, the procedures described here facilitate the accurate measurement of the key seating tightness when the wave spring system is in use during operation of the electromechanical device.

[0030] Method 1000 comprises providing an upper or lateral wave spring that holds a winding in place (1010). The wave spring is at least partially arranged in a stator slot defined in the electromechanical device (1020). A conductive layer is provided or arranged in the wave spring (1030). The conductive layer may be made of one or a combination of the following materials: carbon fiber, graphite, copper, silver, gold, aluminum, aluminum oxides, and aluminum nitrides. The conductive layer generates signals corresponding to at least one aspect of the wave spring (1040). The signals from the conductive layer are analyzed to determine the at least one aspect or condition of the wave spring (1050) that could help mitigate or detect faults or identify defective wave springs.The signals can, for example, indicate the compression of the wave spring or whether the wave spring has cracks.

[0031] Advantageously, the recorded profile of the wave springs can then be used by an operator to determine whether the keys need to be tightened, the wave springs need to be replaced, or to estimate when tightening the keys will be necessary in the future. The capacitance measurements proposed here are relatively simple to perform and require only a minimum of electrical components, resulting in a cost-effective system. The conductive layer 424 is integrated into the wave springs, which hold the stator components in place. The electronics could also be integrated into the wave spring or located outside the generator at the user interface, providing flexibility to the measurement and diagnostic system.

[0032] The wave spring can be designed to be electrically and / or thermally conductive—in applications with side wave springs, whose specific surface resistance can be approximately 15,000 to 750,000 ohms per square (15,000 to 750,000 ohms / square)—and electrically insulating in applications with top wave springs. Electrically conductive or semiconducting side wave springs can include the electrically locking element when closing the side groove in generators. Furthermore, the side wave springs can contain or be impregnated with conductive or semiconducting material, such as, but not limited to: graphite, metal, metal alloys, conductive or semiconducting fibers or powders, conductive or semiconducting polymers, conductive or semiconducting elastomers, and conductive or semiconducting plastics whose thermal resistance or heat class exceeds the operating temperature of the 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 conductive or semiconducting materials may be used to manufacture upper wave springs, and in these applications, the conductive or semiconducting material may be located near the center of the spring or sandwiched within the center of the spring to reduce direct contact with adjacent surfaces.

[0033] This written description uses examples to disclose the invention—including the preferred (best) embodiment—which are also intended to enable all persons skilled in the art to apply the invention, including the manufacture and use of any device or system. The patentable scope of the invention is defined by the claims and may include other examples that might occur to persons skilled in the art. Such other examples shall be included in the scope of the claims if they have structural elements that do not deviate from the literal meaning of the claims, or if they have equivalent structural elements with insignificant differences from the literal meaning of the claims.

[0034] A wave spring with one or more conductive layers and one or more non-conductive layers is provided. The conductive and non-conductive layers are laminated together to form a symmetrical layer stack. REFERENCE MARK LIST: 10 electric machine 12 stator slots 16 sheet metal packages 18 Stator lamination stack 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 slide 36 stator wedges 38 Arrow 40 Arrow 300 Stator 301 Stator lamination package 302 stator slots 322 stator bars 324 stator bars 328 Groove filling element 330 upper holding arrangement 332 upper wave spring 334 Stator wedge slide 336 stator wedges 337 swallowtails 342 lateral wave spring 344 lateral wave spring 350 radial filling element 400 wave springs 401 Length 402 Longitudinal axis 403 width 405 Height 410 peaks 411 Valley 413 Valley axis 422 non-conductive layer 424 conductive layer 500 wave springs 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 shift 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 shift 850 second shift 900 measuring system 910 Measuring device 920 Transceiver 930 Computer 1000 procedures 1010 Provisioning Procedure Step 1020 Positioning procedure step 1030 Order procedure step 1040 Production process step 1050 ANALYSIS

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