RU2706016C1 - Electric machine stator with liquid cooling - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: stator of an electric machine with liquid cooling comprises a core of ferromagnetic material with a winding installed on it, an outer shell, ring-shaped pressure elements located on both end sides of the core and attached to the shell by welding, expansion or gluing, sealed channels for cooling liquid, located axially between shell and outer surface of core in grooves made on outer surface of core opposite to its teeth, and interconnected in series and / or in parallel by means of collectors, adapted for supply and discharge of cooling liquid cooled in external heat exchanger. Headers are made in ring-shaped pressure elements. Places of their connections with core are sealed by filling of gaps with sealing material and / or application of additional parts from resilient material. Core of the stator can be assembled from sheets of ferromagnetic material with a self-adhesive coating. Sheets can have low accuracy of making their outer contour. Sealing of channels is performed without use of tubes due to application of gluing of core sheets and / or installation of sealing heat-conducting film or foil on its external surface. On inner surface of shell there can be made grooves located opposite to core grooves and providing increased cross section of channels. Shell is made by bending and welding from metal sheet. It can have artificial created irregularities on its inner surface.

EFFECT: invention improves cooling and manufacturability of the stator structure.

8 cl, 4 dwg

Description

The invention relates to electrical engineering and can be used in electric motors and generators, including for traction drives.

Known stator of an electric liquid-cooled machine, containing a cooling jacket with channels evenly covering the outer surface of the stator core through which coolant is pumped (RU 2223584 C2, Н02К 1/20, Н02К 9 / 02,20.01.2003; US 8686606 B2, Н02К 9/00, 01/01/2014).

The disadvantage of this technical solution is the low heat engineering efficiency of cooling the windings of an electric machine, which is due to the remoteness of the channels with the coolant from the most heated inner part of the stator - from the tooth zone of the location of the windings.

A stator of an electric machine is known in which the elements of its liquid cooling (coolers), made in the form of flat silumin segments with coils filled from them from a stainless steel tube with cooling liquid, are placed between sections of the stator core divided along the length (SU 1667201 A1, Н02К 9 / 19, Н02К 15/00, 07/30/1991).

Its disadvantages include increased overall dimensions, since the installation of coolers between sections of the stator core leads to an increase in its axial length. In addition, the reduced thermal conductivity of stainless steel compared with the thermal conductivity of copper or aluminum, as well as the presence of technological gaps between the individual segments of the coolers, lead to a decrease in the thermal technical efficiency of cooling.

In addition, the stator of an electric liquid-cooled machine is known, in which coolers with a cooling liquid are placed without a gap between the sections of a stator core divided along the length, drawn from insulated sheets of electrical steel. Coolers consist of copper tubes, inside which coolant flows, and copper housings in which these tubes are embedded. Technological gaps between the tubes and the cooler case are filled with heat-conducting paste (RU 2439768 C2, Н02К 9/19, Н02К 1/12, 10.01.2012).

This stator and the electric machine based on it also have increased overall dimensions due to the increase in the length of the stator core by the total thickness of the coolers and the relatively low thermal performance of cooling due to the presence of technological gaps in the path of the heat flux between the copper tube and the housing filled with heat-conducting paste, which has, in comparison with metals, higher thermal resistance.

Also known is the stator of an electric liquid-cooled machine, which implements forced pumping of coolant through axial channels inside its magnetic circuit. It contains a system of tubes (coolers) made of metal and embedded in the body of the stator core, through which a coolant (water, oil, etc.) circulates, cooled in an external heat exchanger. Tubes (coolers) are placed in the channels of the stator core according to the axial or radial scheme and are close to its windings (US 20130076167 Al, Н02К 9/19, 03/28/2013; Filippov IF Issues of cooling electrical machines. - M.-L .: Energy, 1964, pp. 197-199).

Placing coolers (tubes) inside the magnetic circuit near the windings allows to increase the cooling efficiency of the windings and the magnetic circuit by reducing the length of the heat flux propagation path from the active heat-generating parts of the stator to the boundary with the coolant.

However, the presence of many holes in the stator core with tubes installed in them leads to a complication of the stator design and a decrease in the manufacturability of its manufacture. In addition, during the operation of the electric machine, part of the time-varying magnetic flux in the core back propagates between the channels with coolant and the outer surface of the stator, which leads to the emergence of an emf on them, the passage of stray electric current through them and, consequently, to an increase in losses in the stator and to its additional heating.

Also known is the stator of an electric liquid-cooled machine, containing a cylindrical shell, a monolithic magnetic core of ferromagnetic material with a winding mounted on it, and ring-shaped pressure elements located on the end sides of the magnetic circuit. The shell has an inner diameter greater than the outer diameter of the magnetic circuit, is hermetically connected to the pressure elements along their perimeter, and encompasses the stator magnetic circuit on its outer side, forming the outer perimeter of the toroidal cooling chamber with rectangular cooling channels filled with liquid cooled in an external heat exchanger. The channels are formed by protrusions on the outer surface of the magnetic circuit due to the assembly of the magnetic circuit package from sheets of electrical steel or amorphous ferromagnetic material having a different configuration of their external contour. Channel sealing is achieved by gluing sheets. The mechanical strength of the stator is ensured by installing axially oriented bolts, studs, rivets or planks, or a sleeve made of durable material (for example, steel) into which the magnetic circuit is pressed, or by using the specified shell of the cooling chamber having a strength sufficient for it use as a supporting structure (RU 2284627 C2, Н02К 9/19, 09/27/2006).

The disadvantage of this stator is the increased complexity of its design, due to the need to use in its magnetic circuit sheets of electrical steel or an amorphous ferromagnetic material having a different configuration of the outer contour. Its other drawback, in comparison with stators with similar overall dimensions and cooling channels located inside the magnetic circuit, is increased losses. This is due to the fact that the presence of protrusions on the outer surface of the magnetic circuit, necessary for the formation of cooling channels, leads to the need to reduce the active diameter of the stator with a corresponding decrease in the cross section of the magnetic circuit and windings, which with equal power of the electric machine leads to an increase in losses in it.

Closest to the proposed one is the stator of an induction electric machine having phase windings made in the form of concentrated coils placed on the teeth of the stator core (magnetic circuit) in its grooves and liquid cooling channels made in the form of tubes located between the body (shell) and the core stator in the recesses of the back of this core opposite its teeth. The cooling channels are interconnected sequentially and / or in parallel with the help of manifolds adapted for supplying and discharging liquid cooled in an external heat exchanger (RU 2660811 C1, H02R 19/24, Н02К 9/16, 07/10/2018).

The disadvantage of this stator is the increased complexity and reduced manufacturability of its manufacture, which is due to the presence of tubes installed in the liquid cooling channels. The disadvantages of this stator are also the reduced thermal efficiency of its cooling due to the thermal resistance of the tubes and technological gaps between the tubes and the stator core located on the heat removal paths, as well as the lack of cooling of the stator core from its end sides.

From the analysis of known analogues and the prototype, it follows that in the prior art the technical problem of creating a stator of an electric machine, which combines high thermal technical efficiency of cooling, simplicity of design and the absence of losses due to the induction of EMF on conductors formed by the cooling fluid flowing in the channels of the liquid cooling. The objective of the invention is the creation of such a stator.

The technical result to which this invention is directed is the simultaneous improvement of cooling and manufacturability of the stator structure.

In this case, the manufacturability of the stator means the totality of the properties of its design, which determine its adaptability to achieve minimum costs in the production process compared to similar designs with the same conditions for their manufacture and the same quality indicators.

In the stator of an electric liquid-cooled machine containing a core made of ferromagnetic material with a winding installed on it, housed in a shell, ring-shaped push elements located on both ends of the core and attached to the shell, sealed channels located axially between the shell and the outer surface of the core in grooves made on the outer surface of the core opposite its teeth, and connected to each other in series and / or in parallel using a collector c, adapted for supplying and discharging coolant cooled in an external heat exchanger, the specified technical result is achieved due to the fact that the collectors are made in ring-shaped pressure elements, the joints of the ring-shaped pressure elements with the core are sealed by filling gaps with sealing material and / or using additional parts of elastic material, and the sealing of the channels is made without the use of tubes.

In private embodiments of the proposed stator, the specified technical result is also achieved due to the fact that:

- the core is assembled from sheets of electrical steel or an amorphous ferromagnetic material, manufactured using a qualification of IT 13 to IT 17 for their outer contour, at least in the areas where the sealed channels are located;

- the core is made of sheets of electrical steel or an amorphous ferromagnetic material with a self-adhesive coating, which ensures the tightness of the core after gluing the sheets by compressing and heating the core, in particular, ensuring its strength sufficient to use the core as a supporting structure of an electric machine;

- a sealing heat-conducting film or foil is attached to the outer surface of the core;

- on the inner surface of the shell grooves are located located opposite the grooves of the core;

- the shell is made bent from a metal sheet or with artificially created irregularities on its inner surface, for example, corrugation, and is attached to the annular pressing elements, in particular by welding, flaring and / or glue.

These distinctive features of the independent and dependent claims provide for the achievement of the same technical result.

In particular, the implementation of the first distinguishing feature of the independent claim, which provides for the execution of collectors in annular pressure elements with sealing of their joints with the core by filling gaps with sealing material and / or by using additional parts from elastic material, provides improved stator cooling due to more intensive cooling of the outer end surfaces of the back of the stator and the frontal parts of the winding adjacent to these pressure elements. At the same time, an improvement in the manufacturability of the structure is achieved by eliminating the need to manufacture individual collectors and pipelines connecting the channels to the collectors.

The implementation of the second distinguishing feature of the independent claim, according to which the sealing of the channels is carried out without the use of tubes, allows to improve the cooling of the stator by eliminating the thermal resistance of both the tubes themselves and the technological gap between the core and these tubes. At the same time, the technological design of the stator is improved by eliminating the need to manufacture and install these tubes.

In private alternative embodiments of the invention indicated in the dependent claims, the indicated technical result is also achieved.

In particular, the implementation of the distinguishing feature of the dependent claim, which provides for the assembly of the core from sheets of electrical steel made with low accuracy, using International Tolerance qualifications from IT 13 to IT 17 for their outer contour, at least in the areas of the sealed channels , leads to an increase in the spread in sizes (size) of sheets on the outer surface of the core. This provides, on the one hand, improved stator cooling by increasing the area of thermal contact of the coolant with the stator core and turbulization of this fluid, and, on the other hand, to improve the manufacturability of the stator by reducing the accuracy requirements for manufacturing sheets of its core.

In the case of the implementation of the distinguishing features of the 3rd and 4th dependent claims, according to which the core is made of sheets of electrical steel with a self-adhesive coating, which ensures the tightness of the core after gluing the sheets by compressing and heating it, in particular, ensuring sufficient core strength for its use as a supporting structure of an electric machine, improved stator cooling is ensured by direct contact of the coolant with the surface core. The bonding of the sheets also provides improved cooling of the stator by improving the transfer of heat along the axis of the electric machine through the back of the stator to the pressure elements in which the collectors are made. At the same time, the manufacturability of the structure is increased due to the elimination of the need to install sealing tubes and power elements that provide stator stiffness and strength.

Sealing the channels for the coolant by gluing (attaching) a sealing heat-conducting film or foil to the outer surface of the stator core, provided for by the following distinguishing feature of the dependent claim, in comparison with sealing the channels with tubes or an external cooling jacket, improves stator cooling by reducing the thickness this sealing element and, accordingly, its thermal resistance. At the same time, an improvement in the manufacturability of the stator design is achieved due to a simpler manufacture and installation of a film or foil in comparison with other sealing elements.

The device on the inner surface of the shell of the grooves located opposite the axial grooves of the core provides improved cooling by increasing the cross-section of the channels for the coolant and, accordingly, the area of contact of the coolant with the structural elements of the stator. An increase in this cross section also leads to an improvement in the manufacturability of the stator structure due to a decrease in the accuracy requirements for the manufacture of stator elements forming these channels.

The execution of the shell of a metal sheet or with artificially created irregularities on its inner surface, as well as the fastening of the shell to the annular pressure elements by welding, beading and / or glue, implemented in accordance with the latest distinguishing features of the dependent claims, in contrast to the traditionally used the bores of the outer casing or shell of the electric machine, provides improved stator cooling by increasing the area of the coolant contract with this a lacquer due to a rougher surface or artificially created protrusions and depressions on it. The use of such a shell, as well as its connection with the pressure elements without additional fasteners, also provides an increase in the manufacturability of the stator structure.

In FIG. 1 schematically shows the stator of an electric liquid-cooled machine. In FIG. 2 shows a simplified hydraulic diagram of its cooling system. In FIG. 3 shows cooling channels axially located between the shell and the outer surface of the stator core, and in FIG. 4 is an embodiment of these channels with an enlarged section.

The electric machine may be an electric motor and / or generator. It can be a valve-inductor (valve reactive, valve inductor-reactive) without permanent magnets and windings on the rotor, referred to in the foreign technical literature as an electric motor with variable magnetic resistance: "SRM" (Switched Reluctance Motor), synchronous with permanent magnets on the rotor , referred to in foreign literature: “PMSM” (Permanent Magnet Synchronous Motor), “BLDC” (Brushless Direct Current Motor) or “PMA-SynRM” (Permanent magnet-assisted synchronous reluctance machines), with combined (hybrid) electromagnetic and magnetoelectric excitation : “HEFSM” (Hybrid exci tation flux switching motor), as well as asynchronous: “IM” (Induction motor) with squirrel-cage or phase rotor.

The stator contains a core 1 made of sheets (plates) of electrical steel or an amorphous ferromagnetic material. It can also be made of a soft magnetic composite material based on iron powder or ferrite.

A concentrated or distributed winding 2 is placed in the grooves of the core on its teeth. It can be single-layer or multi-layer, wave or loop.

The core is placed in a shell 3, which can be made using bending (rolling) and welding of a metal sheet or pipe processing. Roughnesses artificially created by milling, stamping, knurling, etc., can be performed on its entire inner surface or in the area of the coolant channels.

On both ends of the core 1 there are ring-shaped pressure elements 4, 5 made (cast) of aluminum alloy or steel and attached to the casing 3 by welding 6, flaring and / or glue.

In the grooves of the back of the core 1 opposite its teeth are made axial sealed channels 7. Their number is chosen equal to the number of teeth of the core 1.

In order to increase the cross section and the area of the inner surface of the channels for the coolant, grooves 8 located opposite the grooves of the core can be made on the inner surface of the shell. They can be formed, in particular, by stamping a sheet before bending it.

The channels 7 (8) are hydraulically interconnected using collectors 9, 10, which are the internal cavities of the pressure ring-shaped elements 4, 5.

Bearing shields 11, 12 are attached to the pressure elements. Their shoulders enter the bores of the pressure elements 4, 5, forming internal locks.

Coolant Q (water, oil, antifreeze, etc.) is supplied to the stator through nozzles (fittings) 13 to the collector 9 from the side of the bearing shields (Fig. 1) (according to the axial diagram), or directly to the ring pressure elements 4, 5 (according to the radial pattern). In these schemes, the axis of the nozzles, respectively, are parallel or perpendicular to the axis of the electric machine.

The cooling channels 7 (8) are interconnected in series, parallel or in a mixed manner. A possible embodiment of their connections using collectors 9, 10 is shown in FIG. 2. In this drawing, a stator with 12 cooling channels contains two groups of channels, each of which contains 6 channels connected in series. Further, these groups are interconnected in parallel.

If a parallel connection of all channels is used, then the nozzles (fittings) 13 are installed on both annular pressure elements 4, 5, and the collectors 9.10 are made in the form of annular grooves in these elements.

The fluid cooled in the external heat exchanger or radiator 14 is circulated using an external pump 15. If necessary, a fan 16 is used to transfer thermal energy from the radiator (heat exchanger) to the environment (air).

In addition to liquid cooling, air convective (natural) or forced (using an external fan) cooling of the outer surface of the stator shell 3 can be used.

If the core 1 is made of sheets (plates) of electrical steel or an amorphous ferromagnetic material, then these sheets can be made with low accuracy - using the quality from IT 13 to IT 17 for their outer contour, at least in the areas of the sealed channels 7.

Sealing the channels without tubes. For this purpose, the core is made of sheets of electrical steel or an amorphous ferromagnetic material with a self-adhesive coating, which ensures the tightness of the core after gluing the sheets by compressing and heating the core. Gluing can also be carried out by first carrying glue (compound) on each side of a single sheet, then assembling the sheets into a bag onto a mandrel, compressing the bag and heat treatment it to cure the glue.

It is also possible to seal the channels by installing a sealing heat-conducting film or foil on the outer surface of the core covering the outer surface of the core and eliminating the possibility of coolant flowing between the sheets. In particular, the installation of adhesive tape based on aluminum or copper foil with an adhesive having high thermal conductivity.

In order to increase the reliability of the stator, it is also possible to simultaneously glue the sheets of the core and install a sealing film or foil on its outer surface.

The gluing of the core sheets can be carried out using glue to ensure that the core is strong enough to be used as the supporting structure of the electric machine.

In the absence of gluing, or in addition to it, sheets of electrical steel or amorphous ferromagnetic material of the stator core can be bonded to each other with the help of additional strength elements (studs, bolts, strips, overlays, etc.) placed axially outside the shell or in the holes core and tightening between each other bearing shields 11, 12, or ring pressing elements 4, 5.

The collectors 9, 10 were sealed by filling the gaps between the annular pressing elements 4, 5 and the core 1 with sealing material (paste, putty, mastic, self-adhesive tape, etc.), and / or using additional parts made of elastic material (sealing gaskets) , rings, etc.) 17. If the supply and / or drain of the coolant is carried out through pipes (fittings) 13, attached to the bearing shields 11, 12 or made integral with them, then the ring joints are sealed in the same way. braznyh pressers with these boards.

The rotor 18, separated from the stator by an air gap, is mounted on the shaft and installed in bearings pressed into the bearing shields 11, 12. The rotor can be explicitly pole (gear) passive if the electric machine is an inductor reactive (SRM). It may also contain permanent magnets, in particular integrated into the rotor body in a V-shape, or a short-circuited winding if the electric machine is, respectively, a permanent magnet machine (BLDC, PMSM) or asynchronous (IM).

The proposed device operates as follows.

After applying voltage to the windings 2 of the electric machine from an external converter (inverter, controller), electric current begins to flow through these windings, which leads to the appearance of magnetic flux in the core 1 and, accordingly, a torque on the motor shaft.

In this case, the core and stator windings are heated. The generated heat spreads radially along sheets of electrical steel or amorphous ferromagnetic material to channels 7 (8) and is then transferred to the coolant flowing into them.

At the same time, heat is axially transmitted through the back of the core to the ring pressure elements 4, 5 and the collectors 9, 10 located in them, which improves the cooling of the stator.

The cooling liquid Q from the channels 7 (8) through the collectors 9, 10 and nozzles (fittings) 13 through the outlet pipe enters an external heat exchanger (radiator) 14 and, after cooling, is again fed to the electric machine using an external circulation pump 15. In this way, a closed stator liquid cooling system.

In order to ensure simultaneous improvement of cooling and manufacturability of the stator design, it implements the various alternative technical solutions mentioned above, or their combinations.

In particular, the assembly of the core from sheets of electrical steel or an amorphous ferromagnetic material made with low accuracy leads to an uneven projection of these plates on the outer contour of the core. This leads to an increase in the contact area of the coolant with the core, as well as to turbulization of its flow. Due to this, an improvement in cooling of the stator is achieved while improving the manufacturability of its design.

In the case of the implementation of channels for coolant with an increased cross section due to grooves located on the shell, as well as the use of a shell made by rolling from a metal sheet or with artificially created irregularities on its inner surface, an increase in the area of the contract of the coolant with the shell is achieved, which also provides improved cooling of the stator while simplifying its design.

For specialists in this field of technology it is clear that in addition to the described design options for the stator of an electric liquid-cooled machine, other options for its implementation are also possible based on the features set forth in the claims.

Claims (8)

1. The stator of an electric liquid-cooled machine, comprising a core made of ferromagnetic material with a winding installed on it, housed in a shell, ring-shaped push elements located on both ends of the core and attached to the shell, sealed channels located axially between the shell and the outer surface of the core in grooves made on the outer surface of the core opposite its teeth, and connected to each other in series and / or in parallel using a collector adapted for supplying and discharging coolant cooled in an external heat exchanger, characterized in that the collectors are made in ring-shaped pressure elements, the joints of the ring-shaped pressure elements with the core are sealed by filling gaps with sealing material and / or the use of additional parts made of elastic material, and channel sealing is performed without the use of tubes. 2. The stator according to claim 1, characterized in that the core is assembled from sheets of electrical steel or an amorphous ferromagnetic material made using a quality from IT 13 to IT 17 for their outer contour, at least in the areas where the sealed channels are located. 3. The stator according to claim 1, characterized in that the core is made of sheets of electrical steel or an amorphous ferromagnetic material with a self-adhesive coating, which ensures the tightness of the core after gluing the sheets by compressing and heating the core. 4. The stator according to claim 3, characterized in that the core is glued to ensure its strength sufficient to use the core as a supporting structure of an electric machine. 5. The stator according to any one of paragraphs. 1-4, characterized in that to the outer surface of the core is attached a sealing heat-conducting film or foil. 6. The stator according to any one of paragraphs. 1-4, characterized in that on the inner surface of the shell made grooves located opposite the grooves of the core. 7. The stator according to claim 1, characterized in that the shell is made bent from a metal sheet or has artificially created irregularities of its inner surface. 8. The stator according to claim 1 or 7, characterized in that the shell is attached to the annular pressure elements by welding, and / or flaring, and / or glue.

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