CN110690793A

CN110690793A - Evaporative cooling motor

Info

Publication number: CN110690793A
Application number: CN201910899890.7A
Authority: CN
Inventors: 熊斌; 阮琳; 李国辉; 温志伟
Original assignee: Institute of Electrical Engineering of CAS
Current assignee: Institute of Electrical Engineering of CAS
Priority date: 2019-09-23
Filing date: 2019-09-23
Publication date: 2020-01-14
Anticipated expiration: 2039-09-23
Also published as: CN110690793B

Abstract

The invention relates to the technical field of motors, and particularly provides an evaporative cooling motor, aiming at solving the problems of uneven heat dissipation, longer axial dimension, larger material consumption and lower motor performance of the existing evaporative cooling motor. The motor comprises a shell, a first cavity for accommodating the stator and a second cavity positioned above the first cavity are arranged in the shell, a liquid cooling working medium is arranged in the first cavity, and the motor also comprises a condensing device arranged above the second cavity; the second cavity is respectively communicated with the first cavity and the condensing device, so that the cooling working medium is changed into a gas state, then sequentially enters the second cavity and the condensing device, is condensed into a liquid state in the condensing device, and then flows back to the first cavity under the action of gravity; the outer circumferential surface of the stator is provided with a concave structure, and at least one part of the concave structure is not communicated with the inner circumferential surface of the stator. Therefore, the cooling working medium flows more smoothly, the cooling effect is good, the axial length and the material consumption of the motor are reduced, the electromagnetic performance is optimized, and the performance of the motor is improved.

Description

Evaporative cooling motor

Technical Field

The invention relates to the technical field of motors, and particularly provides an evaporative cooling motor.

Background

The cooling mode of the existing motor mainly has two types: one is air cooling, namely a coaxial rotating fan is arranged on a rotating shaft of a motor or a cooling fan is additionally arranged outside the motor, the fan or the fan rotates to drive air to flow, and the flowing air exchanges heat with the motor and takes away heat to realize cooling; the other is water cooling, and cooling water circularly flows between a channel in the shell of the motor and the outside under the driving of a circulating water pump so as to take away the heat of the motor to realize cooling. However, air-cooled cooling is inefficient due to the small specific heat capacity of air. The water cooling is to exchange heat between cooling water and the shell of the motor, and cannot directly exchange heat with a heating component of the motor, so that the cooling efficiency is not very high.

In view of this, evaporative cooling motors have appeared on the market, in which a cooling medium is accommodated in the motor housing, and the motor stator is immersed in the cooling medium. The motor stator comprises a plurality of stator core sections, and a plurality of fan-shaped convex blocks are clamped between the stator core sections so as to form a radial liquid guide groove between the stator core sections. The cooling working medium can flow in the liquid guide groove and absorb the heat of the motor stator to be evaporated into a gaseous state, and the gaseous cooling working medium enters the condenser to be cooled into a liquid state and then flows back to the shell of the motor, so that the cooling efficiency is improved. However, as part of the stator winding penetrates through the liquid guide groove, the stator winding can interfere the flow of the cooling working medium in the liquid guide groove, the flow direction of the medium is disordered, the local heat dissipation performance is reduced, and the heat dissipation of the motor is uneven. The stator core is segmented, so that the axial length of the motor can be increased, the material consumption of the motor is increased, the electromagnetic performance of the motor is not optimized, and the performance of the motor is reduced.

Accordingly, there is a need in the art for a new solution to the above problems.

Disclosure of Invention

In order to solve the above problems in the prior art, that is, to solve the problems of uneven heat dissipation, long axial dimension, large material consumption and low motor performance of the conventional evaporative cooling motor, the invention provides an evaporative cooling motor, which comprises a housing, wherein a first cavity for accommodating a stator and a second cavity positioned above the first cavity are arranged in the housing, a liquid cooling working medium is arranged in the first cavity, and the motor further comprises a condensing device arranged above the second cavity; the second cavity is respectively communicated with the first cavity and the condensing device, so that the cooling working medium is changed into a gas state, then sequentially enters the second cavity and the condensing device, is condensed into a liquid state in the condensing device, and then flows back to the first cavity under the action of gravity; the stator is provided with a concave structure on the outer peripheral surface, and at least one part of the concave structure is not communicated with the inner peripheral surface of the stator.

In a preferred embodiment of the above evaporative cooling electric machine, the recessed structure includes a plurality of grooves arranged in a radial direction of the stator.

In a preferred embodiment of the above evaporative cooling electric machine, the recess is an annular groove provided on an outer circumferential surface of the stator.

In the above-mentioned evaporation cooling motor's preferred technical scheme, the stator includes stator core, stator core includes a plurality of first silicon steel sheets and a plurality of second silicon steel sheets, wherein, the external diameter of first silicon steel sheet is greater than the external diameter of second silicon steel sheet so that adjacent first silicon steel sheet and second silicon steel sheet form on stator core's outer peripheral face after along the axial stack together in turn the annular groove.

In the above-mentioned evaporation cooling motor's preferred technical scheme, the stator includes stator core, stator core includes a plurality of first silicon steel sheets and a plurality of second silicon steel sheets, and at least one first silicon steel sheet is folded and is pressed and form first silicon steel sheet unit, and at least one second silicon steel sheet is folded and is pressed and form second silicon steel sheet unit, wherein, the maximum external diameter of first silicon steel sheet unit is greater than the maximum external diameter of second silicon steel sheet unit so that adjacent first silicon steel sheet unit and second silicon steel sheet unit form along the axial after alternately folding together the annular groove.

In the above-mentioned preferred technical scheme of the evaporative cooling motor, the stator includes a stator core, the stator core includes a plurality of silicon steel sheets that are laminated together, and the annular groove is formed on the peripheral surface of at least a part of the silicon steel sheets.

In the above preferred technical solution of the evaporative cooling electric machine, a communication structure is provided between adjacent annular grooves.

In the above-mentioned preferred technical scheme of the evaporative cooling motor, the stator includes stator core, stator core includes a plurality of silicon steel sheets, the outer lane of silicon steel sheet distributes along circumference has a plurality of breachs, under the overlapping condition of a plurality of silicon steel sheets every breach on the silicon steel sheet corresponds the connection so that form on stator core's the outer peripheral surface the recess.

In a preferred embodiment of the above evaporative cooling electric machine, the second cavity has an open structure with an opening at a lower portion thereof, and at least a part of an upper portion of the annular groove is covered with the opening.

In the above-mentioned preferred technical solution of the evaporation cooling electric machine, the opening covers a part of the plurality of annular grooves in the axial direction of the stator core, and the opening covers a part of the annular grooves in the circumferential direction of the stator core.

As can be understood by those skilled in the art, in the technical solution of the present invention, the stator is accommodated in the first cavity with the liquid cooling medium and the outer circumferential surface of the stator is provided with a recessed structure, at least a portion of the recessed structure is not open to the inner circumferential surface of the stator. Through the arrangement, the contact area of the stator and the cooling working medium is increased, so that the heat dissipation efficiency is improved. At least one part of the concave structure is not communicated with the inner peripheral surface of the stator, the condition that the stator winding penetrates through the concave structure is reduced, so that the interference of the stator winding on the flowing of cooling working media in the concave structure is reduced, the cooling working media flow more smoothly, the activity of bubbles is uniformly distributed, the cooling working media are favorable for taking away heat, the cooling effect is good, the problems that the local heat radiation performance is reduced, and the heat radiation of the motor is not uniform are solved. The stator core avoids the sectional arrangement, relatively reduces the axial length of the motor, reduces the material consumption of the motor, optimizes the electromagnetic performance of the motor and improves the performance of the motor.

Preferably, the recess structure comprises a plurality of grooves arranged in a radial direction of the stator. The concave structure is arranged into a plurality of grooves which are arranged along the radial direction of the stator, so that the contact area of the stator and a cooling working medium is further increased, and the heat exchange efficiency is improved. Preferably, the recess is an annular groove provided on the outer circumferential surface of the stator. Through the arrangement, the cooling working medium in the first cavity can be better convected along the annular groove in the up-down direction, so that the temperatures of the cooling liquid at different positions are kept consistent as much as possible, and the problem of local heat accumulation is avoided. In addition, the plurality of grooves are arranged on the peripheral surface of the stator, so that a flow channel of a cooling working medium is formed, the distribution of magnetic lines of force of the stator core part is improved, the axial length of the stator is effectively shortened under the condition of ensuring the same output performance, the size of the motor is reduced, the power density of the motor is improved, the using amount of permanent magnets is reduced, and the cost is reduced. Along with the shortening of the axial length of the motor, the axial length of the stator winding is shortened, the resistance value is reduced, the loss is reduced, and the output efficiency of the motor is improved.

Preferably, the stator includes stator core, and stator core includes a plurality of first silicon steel sheets and a plurality of second silicon steel sheets, and wherein, the external diameter of first silicon steel sheet is greater than the external diameter of second silicon steel sheet so that first silicon steel sheet and second silicon steel sheet form the annular groove on stator core's outer peripheral surface after the stack together along the axial. Through the arrangement, the annular groove can be formed on the peripheral surface of the stator core only by adopting two silicon steel sheets with different outer diameters after laminating, and the manufacturing is more convenient.

Drawings

Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an evaporative cooling electric machine according to one embodiment of the present invention;

FIG. 2 is a top view of an evaporative cooling electric machine according to one embodiment of the present invention;

FIG. 3 is a cross-sectional view taken along A-A of FIG. 2;

FIG. 4 is an enlarged view of detail B of FIG. 3;

fig. 5 is a schematic structural view of a stator core of an evaporative cooling electric machine according to an embodiment of the present invention.

List of reference numerals:

1. a housing; 11. an outer sleeve; 12. an inner sleeve; 13. an end cap; 14. a first cavity; 15. a housing; 16. a second cavity; 21. a stator core; 211. a first silicon steel sheet; 212. a second silicon steel sheet; 213. an annular groove; 22. a stator winding; 3. a rotor; 31. a substrate; 32. a permanent magnet; 4. a condensing unit; 41. a housing; 42. a condensation chamber; 51. an air inlet pipe; 52. a liquid return pipe; 53. an inlet; 54, a first electrode; and (7) an outlet.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.

It should be noted that in the description of the present invention, the terms of direction or positional relationship indicated by the terms "left", "right", "inside", "outside", etc. are based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Furthermore, it should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; either directly or indirectly through intervening media, or through the communication between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Referring to fig. 1 to 5, fig. 1 is a schematic structural view of an evaporative cooling motor according to an embodiment of the present invention; FIG. 2 is a top view of an evaporative cooling electric machine according to one embodiment of the present invention; FIG. 3 is a cross-sectional view taken along A-A of FIG. 2; FIG. 4 is an enlarged view of detail B of FIG. 3; fig. 5 is a schematic structural view of a stator core of an evaporative cooling electric machine according to an embodiment of the present invention.

Based on the problems of uneven heat dissipation, long axial dimension, large material consumption and low motor performance of the existing evaporative cooling motor pointed out in the background art, the invention provides an evaporative cooling motor, which comprises a shell 1, wherein the shell 1 comprises an outer sleeve 11, an inner sleeve 12 and an end cover 13 which is used for hermetically connecting the ends of the outer sleeve 11 and the inner sleeve 12, and a first cavity 14 is defined by the outer sleeve 11, the inner sleeve 12 and the end cover 13. The first cavity 14 accommodates a cooling working medium and a stator soaked in the cooling working medium, the stator comprises a stator core 21 and a stator winding 22, a plurality of tooth parts are formed on the inner ring of the stator core 21, a stator slot is formed between the two teeth, the stator winding 22 is positioned in the stator slot, a recessed structure is formed on the outer peripheral surface of the stator core 21, and at least one part of the recessed structure is not communicated with the inner surface of the stator. In a particular embodiment, the recess structure is a groove arranged in a radial direction of the stator. It is understood that the cooling medium may be ammonia, freon, ethane, methanol, ethanol, etc.; the recessed structure may be a blind hole or other suitable recessed structure disposed on the outer peripheral surface of the stator. The rotor 3 is provided in the middle of the inner sleeve 12, and the rotor 3 includes a base 31 and permanent magnets 32 provided on the outer peripheral surface of the base.

The housing 1 further comprises a cover 15 disposed above the outer sleeve 11, a second cavity 16 is formed in the cover 15, and the lower portion of the cover 15 has an opening through which the second cavity 16 communicates with the first cavity 14. The size of the opening of the lower portion of the housing 15 in the stator axial direction is smaller than that of the stator core 21, and the upper area of the groove of the middle portion on the outer peripheral surface of the stator core 21 is covered by the opening of the bottom portion of the housing 15. A gap is formed between the outer peripheral surface of the stator core 21 and the inner surface of the outer sleeve 11, and the stator core 21 is intermittently welded and fixed to the inner surface of the outer sleeve 11 at positions near the left and right ends. By such an arrangement, it is avoided that the opening is too large to affect the rigidity and strength of the housing 1. The condensing device 4 is arranged above the housing 15, the condensing device 4 comprises a shell 41, a condensing cavity 42 is formed in the shell 41, a heat exchange pipe is further arranged in the condensing cavity 42, an inlet 53 and an outlet 54 of the heat exchange pipe are respectively communicated with an external water circulation loop (not shown in the figure), a circulating water pump (not shown in the figure) is arranged in the water circulation loop and is communicated with the external water circulation loop, and an air inlet pipe 51 and a liquid return pipe 52 are connected between the shell 41 and the housing 15. It should be noted that the condensing device 4 condenses the gaseous steam in the condensing chamber 42 by circulating water is only a specific embodiment, and those skilled in the art can adjust the condensing device as needed, for example, cooling oil or cooling air can be circulated in the circulating pipeline to condense the gaseous steam in the condensing chamber 42 or condense by other suitable means.

During operation of the motor, the stator core 21 and the stator winding 22 of the motor generate heat. Part of the heat generated by the stator iron core 21 is transferred to the cooling working medium contacted with the stator iron core through the peripheral surface, and the temperature of the cooling working medium is increased after the cooling working medium is heated and flows in the groove, so that the temperature of the cooling working medium is uniform and consistent, and the condition of local overheating on the surface of the stator is avoided. When the temperature of the cooling working medium reaches the boiling point, the cooling working medium continues absorbing heat and turns into a gaseous state, the gaseous cooling working medium generated in the groove covered by the opening at the lower part of the housing 15 directly rises into the second cavity 16, the cooling working medium in contact with the inner surface and two end surfaces of the stator core 21 and the cooling working medium in contact with the stator winding 22 absorb heat and turn into a gaseous state and then rise to the upper part of the first cavity 14, then enter the second cavity 16 through the gap between the outer peripheral surface of the stator core 21 and the inner surface of the outer sleeve 11, and the gaseous cooling working medium collected in the second cavity 16 enters the cooling cavity 42 through the air inlet pipe 51. The cooling water enters the heat exchange pipe from the inlet 53 and flows out from the outlet 54 by the driving action of the circulation pump. The gaseous cooling medium entering the cooling cavity 42 exchanges heat with the heat exchange tube and is condensed into a liquid cooling medium, and under the action of gravity, the liquid cooling medium flows into the second cavity 16 from the liquid return tube 52, and finally flows back into the first cavity 14 to continuously absorb heat generated by the stator core 21 and the stator winding 22.

Because the peripheral face of the stator is provided with the plurality of grooves, the contact area between the peripheral face of the stator and the cooling working medium is increased, and the heat exchange efficiency is improved. The groove is formed in the outer peripheral face of the stator, the cooling working medium can flow along the groove in the outer surface of the stator, interference of a stator winding on flowing of the cooling working medium is avoided, the cooling working medium flows more smoothly, activity of bubbles is distributed uniformly, heat is taken away by the cooling working medium, the cooling effect is good, the problem that local heat dissipation performance is reduced, and heat dissipation of the motor is not uniform is solved. In addition, the plurality of grooves are formed in the peripheral surface of the stator core 21, so that a flow channel of a cooling working medium is formed, the distribution of magnetic lines of force of the stator core part is improved, the axial length of the stator is effectively shortened under the condition that the same output performance is ensured, the size of the motor is reduced, the power density of the motor is improved, the using amount of permanent magnets is reduced, and the cost is reduced. Along with the shortening of the axial length of the motor, the axial length of the stator winding is shortened, the resistance value is reduced, the loss is reduced, and the output efficiency of the motor is improved. The cooling system is combined with the structure of the motor, so that the integration level of the system is improved, the power density of the motor is improved, the electromagnetic parameters of the motor are improved, and the output performance of the motor is improved. Especially for the motor with large capacity and high power density, the evaporative cooling motor has more outstanding advantages and more excellent overall performance.

It will be understood by those skilled in the art that the second chamber 16 is only a specific embodiment, and the second chamber 16 is connected to the condensation chamber 42 of the condensation device 4 through the air inlet pipe 51 and the liquid return pipe 52, and those skilled in the art can adjust the second chamber as required to suit specific applications, for example, the bottom of the housing 41 and the upper portion of the housing 15 can be configured to have two through holes, and the second chamber 16 is connected to the condensation chamber 42 through the two through holes, or the bottom of the housing 41 and the upper portion of the housing 15 can be configured to have openings with the same size at corresponding positions, and the second chamber 16 is connected to the condensation chamber 42 through the openings, etc. In addition, in order to facilitate the collection of the gaseous cooling working medium into the second cavity 16, the size of the opening at the bottom of the housing 15 along the axial direction of the motor can be set to be larger than that of the stator core 21, so that the cooling working medium in the first cavity 14 is changed into the gaseous state and then directly enters the second cavity 16 through the opening at the bottom of the housing 15.

With continued reference to fig. 3-5, the groove is preferably an annular groove 213 disposed on the outer circumferential surface of the stator. Specifically, the stator includes a stator core 21 and a stator winding 22, the stator core 21 includes a plurality of first silicon steel sheets 211 and a plurality of second silicon steel sheets 212, and an outer diameter of the first silicon steel sheets 211 is greater than an outer diameter of the second silicon steel sheets 212. The plurality of first silicon steel sheets 211 and the plurality of second silicon steel sheets 212 are laminated together to form the stator core 21, thereby forming the annular groove 213 at the outer surface of the stator core 21. In a specific embodiment, 8 first silicon steel sheets 211 are stacked to form a first silicon steel sheet unit, 1 second silicon steel sheet 212 forms a second silicon steel sheet unit, the outer diameter of the first silicon steel sheet unit is larger than that of the second silicon steel sheet unit, after the first silicon steel sheet unit and the second silicon steel sheet unit are stacked together alternately along the axial direction, the outer circumferential surface of the second silicon steel sheet 212 serves as the groove bottom surface of the annular groove 213, and the parts of the two opposite side surfaces of the first silicon steel sheets 211, which are clamped at the two sides of the second silicon steel sheet 212, exceeding the outer circumferential surface of the second silicon steel sheet 212 form the side surfaces of the annular groove 213, so as to form the annular groove 213.

By providing the groove as the annular groove 213 on the outer circumferential surface of the stator, the cooling medium absorbs heat and evaporates to become gaseous, and then the cooling medium can flow upward along the annular groove 213, which is favorable for the gaseous cooling medium to rise to the upper portion of the first cavity 11 and enter the second cavity 16. The stator core 21 includes a plurality of first silicon steel sheets 211 and second silicon steel sheets 212, the outer diameter of the first silicon steel sheets 211 is greater than that of the second silicon steel sheets 121, and a plurality of annular grooves 213 are formed on the outer surface of the stator core 21 after the plurality of first silicon steel sheets 211 and the second silicon steel sheets 212 are laminated together to form the stator core 21. The annular groove 213 is formed after silicon steel sheets with different outer diameters are laminated, the annular groove 213 is not required to be processed in a special process, the plurality of annular grooves 213 are formed after the plurality of first silicon steel sheets 211 and the second silicon steel sheets 212 are laminated together, and the manufacturing is convenient and fast.

Those skilled in the art can understand that 8 first silicon steel sheets 211 are stacked to form a first silicon steel sheet unit, 1 second silicon steel sheet 212 is stacked to form a second silicon steel sheet unit, the outer diameter of the first silicon steel sheet unit is greater than that of the second silicon steel sheet unit, and the first silicon steel sheet unit and the second silicon steel sheet unit are stacked alternately in the axial direction only in a specific embodiment mode, and those skilled in the art can adjust the units as required to adapt to specific application occasions, for example, the number of the first silicon steel sheets 211 in the first silicon steel sheet unit can be 4, 6, 10, etc., and the number of the second silicon steel sheets 212 in the second silicon steel sheet unit can be 3, 4, 6, etc. In order to form more annular grooves 213 on the outer circumferential surface of the stator core 21 of the same length so as to increase the heat exchange area, each of the first silicon steel sheets 211 and each of the second silicon steel sheets 212 may be alternately arranged in sequence in the axial direction, thereby forming more annular grooves 213 on the outer circumferential surface of the stator core 21 of the same length.

Preferably, in order to facilitate the flow of the cooling working medium in a gaseous state, the first silicon steel sheet 211 may be formed with a communication structure so as to communicate with the plurality of annular grooves 213. For example, a plurality of through holes are formed on the portion of the first silicon steel sheet 211 exceeding the outer diameter of the second silicon steel sheet 212, and when the plurality of first silicon steel sheets 211 and the second silicon steel sheet 212 are laminated to form the stator core 21, the through holes communicate with the plurality of annular grooves 213, and the cooling working mediums in the plurality of annular grooves 213 can flow each other, so that the cooling working mediums are mixed more uniformly, and the cooling working mediums which are cooled to be liquid can be uniformly distributed into the plurality of annular grooves 213 after flowing back to the first cavity 14. It will be understood by those skilled in the art that the communicating structure may also be a groove formed on the outer surface of the first silicon steel sheet 211 in the axial direction of the stator.

In another alternative embodiment, the stator core 21 may be formed by laminating a plurality of identical silicon steel sheets, each of which has an annular groove formed on an outer circumferential surface thereof and having a width smaller than a thickness of the silicon steel sheet, and the plurality of silicon steel sheets are laminated to form the stator core 21 so as to form a plurality of annular grooves 213 on the outer circumferential surface of the stator core 21. Through the arrangement, silicon steel sheets with the same specification only need to be selected and laminated, and the laminating process is simpler and more convenient.

It is understood that the groove on the outer circumferential surface of the stator core 21, which is the annular groove 213, is only a preferred embodiment, and those skilled in the art can adjust it as needed to suit the specific application, for example, the groove on the outer circumferential surface of the stator core 21 may be a straight groove extending in the axial direction of the stator or a groove with other shapes. Specifically, a plurality of notches are distributed on the outer ring of the silicon steel sheets along the circumferential direction, the silicon steel sheets are overlapped together according to the same direction, and the corresponding notches are overlapped along the axial direction of the stator, so that a straight groove extending along the axial direction of the stator is formed. When a plurality of silicon steel sheets are overlapped together, two adjacent silicon steel sheets rotate relatively by a slight angle, and the notches on the two adjacent silicon steel sheets are not completely overlapped, so that a W-shaped groove or a Z-shaped groove and the like are formed on the outer peripheral surface of the stator core 21.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.

Claims

1. An evaporative cooling motor is characterized by comprising a shell, wherein a first cavity for accommodating a stator and a second cavity positioned above the first cavity are arranged in the shell, a liquid cooling working medium is arranged in the first cavity, and the motor further comprises a condensing device arranged above the second cavity;

the second cavity is respectively communicated with the first cavity and the condensing device, so that the cooling working medium is changed into a gas state, then sequentially enters the second cavity and the condensing device, is condensed into a liquid state in the condensing device, and then flows back to the first cavity under the action of gravity;

the stator is provided with a concave structure on the outer peripheral surface, and at least one part of the concave structure is not communicated with the inner peripheral surface of the stator.

2. An evaporative cooling machine as set forth in claim 1 wherein said recessed structure includes a plurality of grooves disposed radially of said stator.

3. An evaporative cooling electric machine as set forth in claim 2, wherein the grooves are annular grooves provided on the outer peripheral surface of the stator.

4. The evaporative cooling electric machine of claim 3, wherein the stator includes a stator core comprising a first plurality of silicon steel sheets and a second plurality of silicon steel sheets,

the outer diameter of the first silicon steel sheet is larger than that of the second silicon steel sheet, so that the annular groove is formed on the outer peripheral surface of the stator core after the first silicon steel sheet and the second silicon steel sheet which are adjacent to each other are alternately stacked and pressed together along the axial direction.

5. The evaporative cooling electric machine of claim 3, wherein the stator includes a stator core comprising a first plurality of silicon steel sheets and a second plurality of silicon steel sheets,

at least one first silicon steel sheet is laminated to form a first silicon steel sheet unit, at least one second silicon steel sheet is laminated to form a second silicon steel sheet unit,

the maximum outer diameter of the first silicon steel sheet unit is larger than that of the second silicon steel sheet unit so that the adjacent first silicon steel sheet unit and the second silicon steel sheet unit are alternately stacked together along the axial direction to form the annular groove.

6. The evaporative cooling motor as claimed in claim 3, wherein the stator includes a stator core including a plurality of silicon steel sheets laminated together, and the annular groove is formed on an outer circumferential surface of at least a portion of the silicon steel sheets.

7. An evaporative cooling machine as claimed in any one of claims 3 to 6, wherein a communication structure is provided between adjacent annular grooves.

8. The evaporative cooling motor as claimed in claim 2, wherein the stator includes a stator core, the stator core includes a plurality of silicon steel sheets, a plurality of notches are distributed on an outer ring of the silicon steel sheets along a circumferential direction, and the notches on each of the silicon steel sheets are correspondingly connected so as to form the groove on an outer circumferential surface of the stator core when the plurality of silicon steel sheets are overlapped.

9. An evaporative cooling machine as claimed in any one of claims 3 to 6, wherein the second cavity is of an open construction with an opening in the lower part, at least part of the upper part of the annular groove being covered by the opening.

10. The evaporative cooling motor of claim 9, wherein the opening covers a portion of the plurality of annular grooves in an axial direction of the stator core,

the opening covers a part of the annular groove along the circumferential direction of the stator core.