Filling motor slots with thermoplastic compounds

Abstract

Slot closures for motor winding slots are to be produced efficiently. To this end, a viscous groove sealing material is provided (S5, S6), in which magnetisable particles are mixed in a thermoplastic polymer matrix. Applying (S7) a viscous slot sealing material into the slot of the electric machine. Finally, the viscous groove sealing material in the groove is cooled (S8), so that the groove sealing material in the groove hardens.

Description

Technical Field

[0001] This invention relates to a method for filling slots in an electric motor. The invention also relates to a corresponding apparatus for filling such slots. Background Technology

[0002] Low-voltage motors are typically manufactured using round wire windings, which are pre-wound into coils by a flying wire / template winding machine and then automatically fed into laminations with corresponding slots. Throughout this process, the critical element is always the slot gap defined by two adjacent slot teeth. This slot gap is significantly smaller than the width of the slot body. This facilitates more efficient magnetic circuit closure, but requires the entire bundle of copper wire windings to pass through this narrow, cross-sectionally contracted area. To achieve ideal magnetic field characteristics in the lamination, the slot gap should be as narrow as possible, to the point that its net width is less than the diameter of a single conductor in the winding. However, this presents significant manufacturing challenges because conventional winding and embedding processes are no longer feasible. Current lamination geometries represent a compromise that balances these two requirements. The net width of the slot gap is approximately equal to the diameter of two to four single conductors. With a suitable lamination guide mechanism, the copper wire bundle can be locally compressed within this width during embedding, thus balancing the adverse effects on magnetic circuit dimensions to an acceptable degree.

[0003] Especially for larger motors with higher requirements (medium- or high-voltage motors), the existing slot gaps are subsequently sealed with magnetic slot closures. Various forms of magnetic iron particles are used for this purpose, typically forming a composite with plastic. This composite (filler particles = iron, matrix = plastic) is usually prefabricated as a cover plate and mechanically embedded. The disadvantage is that during motor operation, vibration and forces can cause the slot closures to loosen and detach, thus hindering the rotor and ultimately leading to motor failure and shutdown.

[0004] Furthermore, prefabricated trough enclosures are not an economical solution for a diverse portfolio of low-voltage motors.

[0005] Another application in medium- and high-voltage motors is the use of a highly filled, uncrosslinked paste composed of iron-filled particles and a chemically reactive resin (approximately 90% by weight of iron filler and 10% by weight of polymer matrix). To ensure uniform dispersion of the particles in the matrix, and because the material is a single-component reactive material, it needs to be kneaded for several hours under active cooling conditions, followed by storage and transportation at low temperatures. The matrix is, for example, an anhydride-cured epoxy resin, which hardens at higher temperatures (150 °C for several hours) to form a molding material with sufficient mechanical strength and a glass transition temperature exceeding 140 °C, thus meeting the requirements of medium- and high-voltage motors for insulation systems and peripheral components. Given the choice of matrix and iron-filled components, and the high mechanical requirements for the final molded material during application and in the finished product, additional additives, such as talc (as a lubricant) and polymer fibers (for reinforcement and imparting thixotropy during processing), are typically added in single-weight percentages. The material is typically applied at room temperature by hand (scraping) or by (semi-)automatic cord application and then pressed in with a special scraper. Subsequent thermosetting can be achieved via a hot air furnace or by energizing the windings. Summary of the Invention

[0006] The purpose of this invention is to provide an economical and energy-efficient slot filling solution, particularly for low-voltage motors.

[0007] The above-mentioned objects of the present invention are achieved by the method and apparatus defined in the independent claims. Advantageous improvements of the present invention are given in the dependent claims.

[0008] This invention is based on the understanding that high-efficiency low-voltage motors have minimal power losses, manifested primarily as heat generation in the rotor and stator. This virtually eliminates temperatures exceeding 100°C, particularly in areas with potential slot enclosures. This allows for a fresh perspective on the thermal stability of the insulation system and its peripheral components. Specifically, the heat resistance rating of peripheral components (e.g., covers) can be significantly lower than the F / H rating (155°C / 180°C, 20,000 hours) typically required for the main insulation system, without negatively impacting the motor's lifespan or performance.

[0009] In view of the above developments, the present invention proposes an alternative polymer solution for slot filling that is both economical and CO2-friendly in terms of application and process, and is particularly suitable for low-pressure motors.

[0010] This invention proposes a method for filling slots in an electric motor. These slots are particularly winding slots into which windings or coils can be embedded. The slots are typically constructed within the laminations of the motor's magnetic active components. The motor can be an electric motor, generator, transformer, etc.

[0011] In this method, a groove sealing material (in a hardened or molten state) is first provided, in which magnetizable particles are mixed into a thermoplastic polymer matrix. Therefore, the groove sealing material can be provided as a standalone product before processing, for example, as a granular material or in other forms. Regardless, the groove sealing material exists in a hardened, i.e., solid form. This groove sealing material has a thermoplastic polymer matrix and contains magnetizable particles. Preferably, the magnetizable particles are dispersed as uniformly as possible within the polymer matrix. Specifically, the magnetizable particles can be ferromagnetic particles, especially iron powder. This yields a so-called composite material, which consists of a polymer matrix and filler particles (e.g., iron). Alternatively, other ferromagnetic metals or alloys can be used as the magnetizable particles instead of iron.

[0012] When a hardened (i.e., solid) groove sealing material is provided, the groove sealing material is melted. The groove sealing material (composite) is heated to a temperature suitable for processing. For efficiency reasons, the heating temperature should not be significantly higher than the temperature required for processing. After melting, the previously solid groove sealing material transforms into a viscous state, i.e., a high-viscosity fluid.

[0013] In the subsequent steps, molten or viscous slot sealant is applied to the slots of the motor. Typically, the corresponding windings or coils are already in the slots at this point, so the molten slot sealant is applied to the corresponding wire harness or cover plate. Sufficient slot sealant should be introduced into the slots so that it can form a suitable slot closure structure after hardening.

[0014] In another process, the molten or viscous tank sealant is cooled in a tank, thereby hardening in the tank. Because a thermoplastic polymer matrix is ​​used, the tank sealant can cool and harden in the tank after a single heating, without the need for reheating.

[0015] Therefore, a simple and particularly energy-efficient method for filling the slots of an electric motor can be advantageously provided.

[0016] In one embodiment, the polymer matrix is ​​a polyolefin hot melt adhesive. Polyolefins are polymers obtained by chain polymerization of olefins (such as ethylene, propylene, 1-butene, or isobutene). They are particularly common as partially crystalline thermoplastics, easy to process, and possess good electrical insulation properties. Hot melt adhesives (also known as hot melt binders) are solvent-free, essentially solid at room temperature, and become viscous liquid upon heating; they reversibly harden upon cooling and can form a strong bond between adjacent components. Therefore, polyolefin hot melt adhesives combine the advantageous properties suitable for motors with ease of processing.

[0017] Alternatively, the polymer matrix can also be a polyamide hot melt adhesive, especially polyamide-6 hot melt adhesive. Polyamides are linear polymers with regularly repeating amide bonds in the main chain, possessing excellent strength and toughness, and good resistance to organic solvents; they are also thermoplastic polymers. Polyamide-6 (also known as polycaprolactam) is known for its toughness and abrasion resistance and can be used as a hot melt adhesive possessing the above properties.

[0018] In another embodiment, the groove sealing material (composite) is mixed with 75 to 90% by weight of magnetizable particles, particularly ferromagnetic particles (such as iron powder). A higher weight proportion of magnetizable particles can achieve a highly efficient groove sealing effect.

[0019] Furthermore, the molten groove sealing material can be applied to the motor groove via extrusion or injection molding. This allows for the use of a mature and standardized application process.

[0020] Specifically, the groove sealing material can be applied using a single-screw extruder or a coating gun. Since the composite used is a premixed system of polymer matrix and filler, no component mixing is required during application. Therefore, a simple single-screw extruder can be used to apply the groove sealing material, and the same applies to a coating gun. In principle, a hot melt glue gun that can melt the thermoplastic polymer matrix can be used for application.

[0021] In another embodiment, the groove sealing material is obtained by melting particulate material. That is, the composite is provided in particulate form, and each particle contains a mixture of polymer matrix and (iron) filler, thus eliminating the need for further mixing.

[0022] According to another advantageous embodiment, the groove sealing material is melted immediately before application. For example, melting can be completed in an extruder or coating gun, and the molten material is immediately applied to the groove. This has the advantage of eliminating the need to maintain the material in a viscous state for an extended period, thus saving energy.

[0023] In another embodiment, when a viscous or molten slot sealing material is applied to the motor slot, a viscous cord ("cord-like" compound) made of the slot sealing material is applied to the wire bundle in the slot. This viscous cord is essentially a "strip" formed from the compound paste. Typically, it is not applied directly to the wire bundle, but rather to a cover plate that covers the wire bundle. This advantageously achieves a seal at the slot opening.

[0024] In a particularly advantageous embodiment, the wire harness is pressed towards the bottom of the groove before the viscous cord is applied. Specifically, a cover plate disposed on the wire harness can be pressed downwards towards the bottom of the groove, thereby indirectly pressing the wire harness towards the bottom of the groove. This pressing action creates additional space between the wire harness / cover plate and the groove opening for at least partial filling of the groove sealing material.

[0025] In another improved design, after the application of viscous cord, the conductor bundle relaxes within the groove, compressing a portion of the cord in the process to create a form-fit connection behind the groove protrusion. For example, during the application of the viscous cord, a portion is inserted into the undercut of the groove; subsequently, as the conductor bundle relaxes after being pressed in, the cord portion in the undercut is further pressed into the undercut. Thus, after the groove sealing material hardens, a form-fit connection can be achieved within the groove.

[0026] In another embodiment, the viscous cord is stretched to be flush with the surface and / or smoothed by means of a heating device after being placed in the groove. Stretching can be accomplished by applying the tool itself or by a separate stretching tool. To achieve surface smoothing, a heating device (e.g., an infrared lamp) can be used, which can at least surface-melt the surface layer of the groove sealing material and utilize surface tension to achieve smoothing.

[0027] The above-mentioned objective of the present invention is also achieved by a device for filling motor slots (winding slots), wherein: - A melting device is provided, which is designed to melt a tank sealing material in which magnetizable particles have been mixed into a thermoplastic polymer matrix; - An application device is provided, which is designed to apply molten or viscous groove sealing material into the groove of the motor and allow the molten groove sealing material to cool in the groove, thereby hardening in the groove.

[0028] The melting device can also be integrated into the application device. The application device is capable of, for example, applying the above-mentioned cord-like paste to the cover plate in the tank.

[0029] The advantages and variations described above related to the method of the present invention also apply to the device of the present invention, wherein each method feature can be regarded as a corresponding functional feature of the device.

[0030] For application scenarios or working conditions that may occur during the implementation of the method but are not explicitly described in this document, it may be stipulated that error messages and / or prompts for user feedback be output according to the method, and / or a certain default setting and / or a predetermined initial state be set.

[0031] Regardless of the grammatical part of speech of a term, it includes terms that are masculine, feminine, or other parts of speech. Attached Figure Description

[0032] For ease of explanation, the invention will be further described in conjunction with the accompanying drawings. The drawings show: Figure 1 The image shows the slots of the motor filled with wire harnesses; Figure 2 Show Figure 1 The groove shown contains an embedded wire bundle; Figure 3The groove is shown to have been coated with groove sealing material; Figure 4 A slot with a closed opening is shown; Figure 5 The method of applying the groove sealing material along the longitudinal direction of the groove is shown; and Figure 6 The schematic process flow is shown. Detailed Implementation

[0033] The following embodiments are preferred embodiments of the present invention.

[0034] Given that low-pressure motors, in particular, can operate at high efficiency, the temperature of the groove closure will hardly exceed 100°C. This invention utilizes this fact by employing a thermoplastic composite to form the groove closure, the composite having a thermoplastic polymer matrix with a filler composed of magnetizable particles.

[0035] In one specific embodiment, the polymer matrix (regardless of the composition of the iron-based filler and its optional particle size distribution optimization) employs an alternative to existing technologies. Due to the significantly narrower slot gap (approximately 2 mm to 5 mm, compared to approximately 2 cm in large machines), reinforcement by adding polymer fibers is unnecessary. Therefore, at least one embodiment should be based on the premise that the thermoplastic matrix is ​​free of polymer fibers. Consequently, conventional subsystems can be used when applying the thermoplastic melt, as there is no need to add "high-shear / high-viscosity" components to the thermoplastic polymer, thus avoiding significant difficulties for fully automated conveying and placement.

[0036] Accordingly, the composite for filling the (winding) slots of an electric motor according to the present invention comprises a thermoplastic polymer matrix and magnetizable particles (e.g., iron powder). In practice, for example, fillers (e.g., iron powder) can be incorporated into a polyolefin hot melt adhesive matrix or a polyamide-6 hot melt adhesive matrix in a ratio of 75 to 90% by weight. If the mechanical performance requirements of the motor / electrical equipment during operation permit (softening temperature below 100 °C is still acceptable), then polyolefins are more suitable due to their lower melting and processing temperatures (melting point approximately 140 °C, processing temperature approximately 200 °C).

[0037] The lamination of filler (iron powder) with the thermoplastic polymer matrix can be performed independently of the tank sealing process or immediately before tank sealing. If lamination is performed directly before tank sealing, the composite does not need to be melted twice. Conversely, if lamination and tank sealing are independent of each other, the tank sealing material can be pre-processed into an intermediate form, such as granular material (for easy extrusion) or strips (for application guns), and then melted before application.

[0038] For example, a composite of 90% by weight iron powder filler with polyamide-6 hot melt adhesive can be used and processed by extrusion or injection molding. This composite softens at 120°C to 150°C and can be processed at 230°C to 250°C.

[0039] As another specific thermoplastic base sealant, a polyolefin matrix can also be used. In this case, the processing (mixing) temperature is, for example, about 200 °C, and a 90:10 (filler to matrix weight ratio) can be achieved.

[0040] After compounding, materials (such as particulate materials) can be added to the application equipment and heated to the processing temperature. Using a single-screw extruder or a suitable thermoplastic coating gun (hot melt glue gun), the cord-like compound can be filled into the stator slot at or slightly above the processing temperature. Specifically, the cord can be applied through the slot opening to a "cover plate" (used to seal the wire bundle above) located in the slot. After cooling to below the softening temperature, the slot-sealing portion preferably engages and bonds with the undercut of the slot geometry.

[0041] Application can be achieved by laying "beads" (i.e., composite paste strips) to form a shape-fit connection with the slot / cover plate. For the outer stator, it is preferable that the beads are flush with the inner diameter of the lamination assembly. Alternatively, the copper conductor / wire bundle can be briefly compressed before application, so that the beads are mechanically pressed into the undercut while still at high temperature. The following description, in conjunction with embodiments, further illustrates this.

[0042] Figures 1 to 4 A slot 1 is shown disposed in the lamination assembly 2. The slot 1 has a slot bottom 3 (formed, for example, radially outward in the outer stator). Opposite to the slot bottom 3 (radially inward in the outer stator) is a slot opening 4. The slot opening 4 is located between one or two slot protrusions 5 in the circumferential direction.

[0043] A wire harness 6 for the motor windings is installed in slot 1. The wire harness 6 is placed in slot 1 through slot opening 4. A cover plate 7, extending longitudinally along the slot and forming a shape-fitting connection with the slot protrusion 5, prevents the wire harness 6 from detaching from slot 1. Figure 1 In the state shown, the cover plate 7 is adjacent to the groove protrusion 5 via the wire harness 6.

[0044] Figure 5 The figure shows a longitudinal sectional view of groove 1. It is labeled with "I" in the figure. Figure 1 The cross-sectional position before applying the beaded / thermoplastic groove sealant.

[0045] Figure 2 It shows Figure 5 The cross-section of groove 1 at position II shown. Specifically, at this position, the cover plate 7 and the wire harness 6 below it are pressed and compacted towards the bottom of the groove using the pressure roller 8 or other suitable tool. Similarly, from... Figure 5 As can be seen, at cross-sectional position II, the cover plate 7 is pressed into a deeper groove.

[0046] Immediately downstream of the pressure roller 8, using an application device 9 (e.g., a heated extruder or coating gun), molten groove sealing material (comprising a thermoplastic polymer matrix and magnetizable particles) is applied in the form of a cord or bead string 10 onto the wire harness 6 or cover plate 7. Figure 3 This is shown at cross-sectional position III. At this point, at cross-sectional position III, the wire harness 6 / cover plate 7 is still pressed by the pressure roller 8. Figure 5 It also shows that cover plate 7 is located in a deeper position.

[0047] The bead string 10 may have an arc-shaped cross-section. Its width is preferably slightly larger than the slot 4. This has the following advantages: when the wire bundle 6 is as... Figure 4 When the relaxation occurs again and the cover plate 7 is pushed towards the groove 4, a portion of the bead string 10 (i.e., the groove sealing material) extends beyond the groove protrusion 5 and forms the undercut 11. At this time, the still-hot, plastic bead string 10 fills the groove 4, thus forming... Figure 4 The groove seal 12 shown has a T-shaped cross-section with an undercut 11.

[0048] Figure 4 Also shown is an enlarged partial view of the groove closure 12. It can be seen that, in particular, the undercut portion 11 of the groove closure 12 extends below the groove protrusion 5, thereby forming a shape-fit connection after the groove sealing material hardens into a solid state.

[0049] Optionally, the bead string 10 is removed at the upper surface 13 of the groove 1 so that the groove closure 12 is flush with the upper surface 12. The application device 9 or a separate tool can be used for removal.

[0050] Because hot melt adhesive pastes have a high filler content (e.g., 75 to 90% by weight of iron powder filler), they maintain shape stability in the bath and cool and harden rapidly. This eliminates the need for a high-CO2-emission and time-consuming material hardening process. Compared to thermosetting solutions, thermoplastic materials can be recycled through remelting and can utilize recycled ingredients.

[0051] Combination Figure 6 The possible process steps of the embodiments will be further described below. Not all steps are necessary. Some steps may be performed optionally and may overlap with each other in time.

[0052] In the first step S1, a thermoplastic polymer (e.g., in granular form) may be provided as a substrate for the composite. In step S2, the thermoplastic polymer is melted. In step S3, the thermoplastic polymer is mixed with magnetizable particles (especially iron powder). The mixing in step S3 may be performed before, during, or after the melting in step S2.

[0053] Optionally, in step S4, the composite is then solidified into a solid groove sealing material, for example, into a bar or granular material. Thus, the thermoplastic bar or thermoplastic granules are produced as a solid intermediate product.

[0054] The solid groove sealant can then be loaded into the application device. For example, the groove sealant can be filled into an extruder or a coating gun.

[0055] Subsequently, in step S6, a sealing material is melted in the melting device or application device to seal the melting tank.

[0056] In step S7, the molten groove sealing material is applied to the groove of the motor using an application device. Before application, a pre-treatment procedure can be performed. Figure 6 The step, not shown, involves squeezing the wire bundle in the slot downwards.

[0057] Finally, in step S8, the groove sealing material is cooled. Optionally, the thermoplastic groove sealing material is bonded to the groove and cover plate and / or forms a shape fit with the groove.

[0058] High fill power, such as 75 to 90% by weight, can be achieved using pre-formed composites. Short-term heating to processing temperature, achieved through methods such as infrared lamps, facilitates smoothing of the tank closure surface. Due to the high fill power, subsequent curing at room temperature will be very rapid.

[0059] Another advantage is that the compound requires no fiber reinforcement, thus facilitating fully automated application. For high-efficiency, low-pressure motors, a lower softening temperature may be perfectly acceptable.

[0060] Compared to three-dimensional cross-linked thermosetting polymers, thermoplastic groove seals have a particularly advantageous recyclability.

Claims

1. A method for filling a slot (1) in a motor, characterized in that, - Provide (S5, S6) a viscous groove sealing material, wherein magnetizable particles have been mixed into the thermoplastic polymer matrix of the groove sealing material. - Apply (S7) the viscous groove sealing material to the groove (1) of the motor, and - Cooling (S8) the viscous groove sealing material in the groove, thereby hardening the groove sealing material in the groove (1).

2. The method according to claim 1, wherein, The polymer matrix is ​​a polyolefin.

3. The method according to claim 1, wherein, The polymer matrix is ​​a polyamide, and in particular polyamide-6.

4. The method according to any one of the preceding claims, wherein, The groove sealing material has been mixed with 75 to 90% by weight of magnetizable particles, especially iron powder (S3).

5. The method according to any one of the preceding claims, wherein, The viscous groove sealing material is applied (S7) to the groove of the motor by extrusion or injection molding.

6. The method according to any one of the preceding claims, wherein, The application of the groove sealing material is achieved by a single-screw extruder or a coating gun.

7. The method according to any one of the preceding claims, wherein, The groove sealing material used for the application (S7) is heated to a maximum of 250°C, particularly to a maximum of 200°C.

8. The method according to any one of the preceding claims, wherein, The viscous groove sealing material is formed by melting the particulate material (S6).

9. The method according to claim 8, wherein, The melting of the groove sealing material is achieved directly before the application (S7) (S6).

10. The method according to any one of the preceding claims, wherein, During the application (S7) of the viscous groove sealing material to the groove (1) of the motor, a viscous cord (10) made of the groove sealing material is applied to the wire bundle (6) in the groove (1).

11. The method according to claim 10, wherein, Before applying (S7) the viscous cord (10), the wire bundle is directly squeezed toward the bottom (3) of the groove (1).

12. The method according to claim 11, wherein, After the viscous cord (10) is applied (S7), the wire bundle (6) in the groove is relaxed, thereby squeezing a portion of the cord (10) to form a groove protrusion (5) that extends across the groove (1) for a shape-fitting connection.

13. The method according to any one of the preceding claims, wherein, The viscous cord (10) is stretched to be flush with the surface and / or flattened by means of a heating device after being placed in the groove.

14. A device for filling a slot (1) of a motor, characterized in that, - A melting device is provided, which is designed to melt (S2, S6) groove sealing material, in which (S3) magnetizable particles have been mixed in a thermoplastic polymer matrix. - An application device is provided, which is designed to apply (S7) the molten groove sealing material into the groove of the motor and cool (S8) the molten groove sealing material in the groove (1) so as to harden the groove sealing material in the groove (1).

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