Patent Application
20230402895
The present application claims the benefit of and priority to German Pat. Appl. Nos. 10 2022 114 904.8, filed Jun. 14, 2022, and 10 2023 110 854.9, filed Apr. 27, 2023, the entire contents of each of which are incorporated herein by reference for all purposes.
The invention relates to an electrical insulation system for a stator of an electric motor, in particular for an electric motor of an electric compressor or air-conditioning compressor of a hybrid or electric vehicle. The electric motor is used to compress a fluid in vapour form, specifically a refrigerant.
Electric motors of electrically operated compressors are usually designed with an annular stator core and a rotor, the rotor being arranged inside the stator core, oriented coaxially on a common axis of symmetry or axis of rotation of the rotor. The stator core comprises on its inner side multiple radially inwardly pointing carrier teeth, on which electrical conductors are arranged to form a coil. At their radially inwardly directed head ends, the carrier teeth, which are also known to a person skilled in the art as stator teeth, T-segments, coil carriers or stator poles, can have a so-called inner flange, which radially inwardly delimits the arrangement or the winding of the stator coil. The stator coils are formed for example by winding an electrical conductor onto the carrier teeth such that a free space remains in the axial direction between adjacent stator coils produced. This free space is also referred to by a person skilled in the art as a groove or stator groove, and the distances between adjacent inner flanges are referred to as stator groove openings. As is known, the carrier teeth and the electrical conductors are provided with a plastic coating or plastic encapsulation for electrical insulation. Electrical insulators are also provided in the interstice between the stator coils and between the connection lines of the electrical conductor wires and the electrically conductive stator core, in particular in the region of the inner flange of the carrier teeth.
The desire for ever more compact designs of electric motors is associated with many challenges, in particular in terms of the distances between the components of the electric motor. In order to avoid short circuits resulting from excessively small creepage paths and air gaps, sufficiently large insulation distances must be maintained between the adjacent stator coils. For electrically operated compressors, which are operated for example in the high-voltage range of up to 1000 V, for example, particularly high demands must be met in terms of the insulation distances. High voltages thus require greater creepage paths and air gaps. Within a modern electric motor for very high voltages of approximately 400 V, in which the shortest air gap between two stator coils may usually be approximately 4 mm and the shortest creepage path may usually be approximately 5 mm, the electrical insulation system for use at ultra-high voltages of up to 1000 V is an even greater challenge.
An insulation arrangement for an electric motor of an electrical compressor is known from DE 10 2019 112 534. The insulation arrangement is provided for an electric motor having a stator core of the type described in the introduction. According to this design of stator core, electrical conducting wires are wound to form coils on the coil carriers, which extend radially inwards from the inner circumference of the stator ring with their inner flange formed on the head end, wherein an interstice, referred to by a person skilled in the art as a stator groove, exists between adjacent coils. In each of these interstices of the coils arranged radially on the inner circumference of the stator, there is arranged a coil separator in the form of a planar element, which extends inwards from the inner circumference of the stator in the radial direction and between the axial end sides of the stator in the axial direction. A particular feature of these coil separators consists in that they have an inwardly directed Y shape in cross-section perpendicular to the longitudinal direction, wherein a fork end of the Y shape in each case delimits the interstice between adjacent coils on an axial long side of the opposing inner flanges of the coil carriers. The coil separators are held in position inside the stator grooves in a pressed-in manner by elastic deformation. The axial long sides at the foot end of the Y shape then press against the inner face of the stator ring, and the head ends each press against the axial long sides of the opposing inner flanges of the coil carriers of the stator core.
The production and installation of the known coil separators is comparatively complex owing to the cross-sectional Y shape. It has also been found that simply pressing the coil separators against the components of the stator core is not sufficient to eliminate a possible current path for the leakage current flow. The risk of a gap between the aligned and adjacent components of the stator arrangement and accordingly the risk of creepage paths and undesirable current flows thus remain.
The object of the invention is therefore that of proposing an insulation system for a stator of an electric motor, in particular an electric motor of an electrical refrigerant compressor, with which the known disadvantages can be reduced or avoided.
The object is achieved by an insulation system having the features shown and disclosed herein.
An insulation system for a stator of an electric motor, in particular for an electric motor of an electrical compressor or air-conditioning compressor of a hybrid or electric vehicle, is proposed. The insulation system is provided for a stator which has multiple coil carriers which point radially inwards from a stator inner side and have inner flanges spaced apart on the head side, said inner flanges radially delimiting coils arranged on the coil carriers with electrical conductors. The coil carriers with the coils arranged thereon are thus arranged adjacently such that an interstice is formed between the coils and the inner flanges of adjacent coil carriers. This interstice, which is also referred to by a person skilled in the art as a stator groove, points radially inwards from the stator inner side. Between opposing flanks of adjacent inner flanges of the coil carriers there is also a gap, which is referred to by a person skilled in the art as a stator groove opening. The insulation system according to the invention comprises an arrangement of insulator elements. The insulator elements are each held at their foot end by holding grooves formed on the stator inner side in the axial direction between axial end sides of the stator and are positioned pointing radially inwards between adjacent coils with their head ends between opposing flanks of adjacent inner flanges.
The insulator elements are thus situated in a radial orientation between adjacent coils, wherein the head-side ends of the insulator elements, positioned at least with their opposing face sides between opposing flanks of adjacent inner flanges or clamped by same, close the stator groove openings. Advantageously, the head ends of the insulator elements are dimensioned such that they completely close the interstice between opposing flanks of adjacent inner flanges, so that the flank faces bear fully against the insulator elements and no air-filled free space remains between the opposing flanks.
The holding grooves which are formed on the stator inner side and in which the foot ends of the insulator elements are held are oriented as axial longitudinal grooves between the axial end sides of the stator and preferably arranged between two adjacent coil carriers such that the holding grooves and the stator groove openings can lie on a common radial. The holding grooves prove useful as guides during the arrangement of the insulator elements. Preferably, the foot ends of the insulator elements and the holding grooves can have a form-fitting geometry so that the insulator elements positioned in the holding grooves form a form fit at their foot ends. There are no restrictions in terms of the shape of the form-fitting geometry here. The axial length of the insulator elements corresponds at least to the distance between the axial end sides of the stator so that adjacent coils are spatially separated from one another both axially and radially. Advantageously, the insulator elements can protrude beyond the axial end sides of the stator in order to enlarge the air gap between adjacent coils. To this end, the length of the insulator elements in an axial orientation can be greater than the distance between the axial end sides of the stator.
According to the invention, an electrically insulating substance is introduced in the contact regions between the insulator elements and the holding grooves and/or between the insulator elements and the inner flanges of the coil carriers, in particular the opposing flanks of adjacent inner flanges. The electrically insulating substance can be in the form of a curable composition. In the introduced and cured state, the electrically insulating substance forms an adhesive join or an adhesive bonding point. The electrically insulating substance should have a certain elasticity and vibration resistance.
Within the meaning of the invention, contact regions mean the regions at which the insulator elements touch the opposing flanks of adjacent inner flanges and the holding grooves, preferably areally; this includes in particular edges of these touching positions and inner free spaces between touching positions. When introduced between the insulator elements and the holding grooves and/or between the insulator elements and the inner flanges of the coil carriers, the electrically insulating substance fills interstices which cannot be prevented by simple contact or pressure in the contact regions between the insulator elements and the holding grooves and/or between the insulator elements and the inner flanges of the coil carriers alone. Because the interstices within contact regions are filled with the electrically insulating substance, propagation paths for potential air paths and creepage paths are prevented or lengthened.
The insulator elements are electrical insulators and can be made from suitable materials.
The solution according to the invention has two essential advantages over the prior art. Firstly, the distance along the contact region at the foot ends of the insulator elements is lengthened by accommodation in the holding grooves, as a result of which the risk of creepage current breakdowns is reduced. The deeper the holding grooves in the stator inner side, the greater the distance along the contact region. Secondly, the electrical insulation is increased by introducing the electrically insulating substance, because interstices remaining in the contact regions are filled by this substance. A further advantage consists in that fewer components overall are needed to form the electrical insulation, and the insulator elements are less complex to manufacture.
According to an advantageous embodiment of the insulation system according to the invention, the insulator elements can have protrusions formed in the head region on opposing face sides. These elements protruding on both sides of the head region form supporting ridges in the axial direction, that is, in the axial direction in relation to the axis of symmetry of the stator, said supporting ridges each having at least one supporting face for opposing flanks of adjacent inner flanges of the coil carriers. These protrusions can be formed by cut-outs at the head end of the insulator elements. The head region widened by the protrusions gives the insulator elements improved stability. Advantageously, the insulator elements are dimensioned such that, in the installed state, they are each oriented with their supporting ridges radially inwards against flank undersides of adjacent inner flanges. Furthermore, it can be provided for the supporting ridges each to press radially inwards against flank undersides of adjacent inner flanges. This can be ensured by making the insulator elements larger than a distance between a groove bottom of the holding grooves and the flank undersides of adjacent inner flanges. It is self-evident that the insulator elements can have a certain elasticity.
A resin or an adhesive can be used as the electrically insulating substance. For example, a two-component adhesive can be used as the electrically insulating substance. Preferably, this electrically insulating substance is liquid to paste-like before introduction into the contact regions. The introduction of the electrically insulating substance into interstices of the contact regions between the insulator elements and the holding grooves and/or between the insulator elements and the inner flanges of the coil carriers can take place using a vacuum pressure process after the insulator elements have been brought into position. Furthermore, it can be provided for the electrically insulating substance to be applied to the contact points before positioning, so that the electrically insulating substance is already at the desired position when the insulator elements are positioned.
In order to achieve the largest possible contact region of the opposing flanks of adjacent inner flanges, the insulator elements can protrude with their head ends pointing radially inwards beyond the inner flanges of the coil carriers. The contact region between the inner flanges and the insulator elements thus advantageously increases, starting from the supporting ridges on which the flank undersides of the inner flanges lie, along the flank faces which bear against the opposite face sides of the insulator elements. A further enlargement of the contact regions can be achieved by enlarging the supporting face of the supporting ridges.
According to a further advantageous embodiment of the insulation system according to the invention, it can be provided for the insulator elements to protrude in the axial direction beyond the coils of the coil carriers. This ensures that a longer air insulation distance is formed in the axial direction between the electrical conductor of the coil and the stator end sides or end faces and between adjacent coils.
The insulator elements can preferably be substantially planar, but other shapes or surface profiles are conceivable, to allow better utilisation of the installation space. The term planar within the meaning of the invention means a substantially flat body, the length and width of which is substantially greater than its thickness.
To simplify the installation of the planar insulator elements, it is provided for the planar insulator elements to be insertable into the stator at least one axial stator end side. Accordingly, the holding grooves can have an axial groove opening at the axial end side for insertion of the planar insulator elements.
The invention also comprises a stator arrangement having the insulation system according to the invention. This stator arrangement is provided for an electric motor, in particular for an electric motor of an electrical compressor. The stator arrangement has a stator with multiple coil carriers which point radially inwards from a stator inner side and have inner flanges spaced apart on the head side, said inner flanges radially delimiting coils arranged on the coil carriers with electrical conductors. According to the invention, holding grooves for holding insulator elements are formed on the stator inner side in the axial direction between axial end sides of the stator.
These holding grooves are preferably arranged in an axial orientation between the coil carriers such that the holding grooves and the stator groove openings lie on a common line between adjacent inner flanges of the stator carriers. The stator arrangement also comprises insulator elements, which are arranged with their foot ends held in the holding grooves and point radially inwards between adjacent coils, thus closing the gap between opposing flanks of adjacent inner flanges—this means the stator groove opening. According to the invention, an electrically insulating substance is introduced in contact regions between the insulator elements and the holding grooves and/or in contact regions between the insulator elements and the inner flanges of the coil carriers. Preferably, the insulator elements are fixed to the contact regions by being glued into the stator.
Furthermore, the invention comprises a method for installing the insulation system according to the invention into a stator of an electric motor, in particular of an electric motor of an electrical compressor. The procedure is such that the insulator elements are each positioned with their foot end in holding grooves formed on the stator inner side in the axial direction between axial end sides of the stator, and pointing radially inwards between adjacent coils, and in the process are clamped with their head ends between opposing flanks of adjacent inner flanges, so that the supporting ridges of the insulator elements press radially inwards against flank undersides of adjacent inner flanges. The insulator elements can be inserted into the holding grooves from an axial end side for positioning in the axial direction. Alternatively, the insulator elements can be inserted radially into the holding grooves, with the head ends of the insulator elements locking in between opposing flanks of the adjacent inner flanges.
An electrically insulating substance is introduced between the insulator elements and the holding grooves and/or between the insulator elements and the inner flanges of the coil carriers. The electrically insulating substance can be applied to the insulator elements and/or to the contact faces of the holding grooves before positioning, so that the electrically insulating substance is already in the relevant contact regions before the positioning of the insulator elements.
Alternatively, the electrically insulating substance can be introduced after the positioning of the insulator elements. It can be provided for a vacuum pressure process to be used to introduce the electrically insulating substance.
A physically or chemically curable substance can be used as the electrically insulating substance. In this case, a further step can be provided, in which the electrically insulating substance is actively cured by means of a physical or chemical influencing variable. For example, an electrically insulating substance can be used in which curing can be activated by the influence of an additional chemical component and/or the input of heat, for example by means of microwave radiation. For example, an electrically insulating substance can be used in which curing is activatable by the influence of an additional chemical component and/or the input of heat, for example by means of microwave radiation. The selected electrically insulating substance should be elastic and vibration-stable in the cured state.
Further details, features and advantages of embodiments of the invention can be found in the description of exemplary embodiments below with reference to the associated drawings. In the drawings:
Recurring features are labelled with the same reference signs in the figures.
The planar insulator elements 7 are glued into the stator, in which an electrically insulating, cured substance is introduced in the contact regions between the planar insulator elements 7 and the holding grooves 6 and in contact regions between the planar insulator elements 7 and the inner flanges 3 of the coil carriers. This substance forms an elastic adhesive connection in the relevant contact regions.
At their foot ends 7.1, the planar insulator elements 7 have a contact region with a holding groove 6 formed on the stator inner side 2.1. An electrically insulating substance is introduced in the contact regions between the planar insulator elements 7 and the holding grooves 6 and in contact regions between the planar insulator elements 7 and the inner flanges 3 of the coil carriers, said electrically insulating substance fixing the planar insulator elements 7 in the contact regions when in the cured state.
The holding groove 6 formed on the stator inner side 2.1 contains the electrically insulating substance 10, which forms an adhesive bond with the foot end 7.1 of the planar insulator element 7 inserted in the holding groove 6. The position of the electrically insulating substance is indicated with the thick black line. The glued connection means that all the contact faces between the stator 1 and the planar insulator elements 7 are adhesively bonded to one another. The most important thing about this adhesive connection is that no current can flow from one coil 4 to the other through this barrier. Accordingly, air gaps and creepage paths only remain where there are no adhesive connections. The adhesive connection, which can also be referred to as a cemented joint, is situated at the foot end 7.1 and at the head end 7.2 of each planar insulator element 7. At the head end 7.2, the positions of the electrically insulating substance 10 are likewise indicated with thick black lines. At the head end 7.1, the electrically insulating substance 10 is situated in the contact region with an adjacent inner flange 3. Because the electrically insulating substance is positioned over the entire axial length of the planar insulator elements 7 at the foot end 7.1 and at the head end 7.2, the current on the rear of the stator cannot flow directly from one phase of a coil 4 to the other, for example. Since the foot ends 7.1 of the planar insulator elements 7 are adhesively bonded to the stator encapsulation, a current can only flow via the planar insulator elements 7 to be able to reach another phase of a coil 4. However, this is prevented by the lengthened air path, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 114 904.8 | Jun 2022 | DE | national |
| 10 2023 110 854.9 | Apr 2023 | DE | national |
