Closed slot stator with fluid injection cooling system for an electric machine and electric machine comprising such stator

Abstract

A stator (15) with closed slots is described comprising a first internal stator part (25) with teeth (26) and a second external stator part (35), a winding comprising at least one conductor (22) wound in the closed slots (14) inside which the conductors (22) are inserted overlapping to form a lower channel (3) between the lower conductor (5) and the bottom wall (38) of the slot (14) and an upper channel (4) between the teeth (26) and the second external stator part (35), a circular channel (20) which supplies the lower (3) and upper (4) channels with a cooling fluid, the channels (3, 4, 20) being used for the passage of a cooling fluid for the stator (15); an electric machine is also described comprising such stator (15) and a cooling system for the stator (15).

Description

[0001] CLOSED SLOT STATOR WITH FLUID INJECTION COOLING

[0002] SYSTEM FOR AN ELECTRIC MACHINE AND ELECTRIC MACHINE

[0003] COMPRISING SUCH STATOR

[0004] The present invention relates to a stator for an electric machine with a fluid inj ection cooling system and to an electric machine comprising such a stator .

[0005] In particular, the invention refers to a stator for a rotating electric machine with closed slots , preferably with continuous winding made using a metal lamella, comprising a cooling system by inj ecting oil directly into the closed slots , in particular in channels created near said slots .

[0006] Known electric machines comprise a fixed part , the stator, and a moving part , the rotor, arranged coaxially one inside the other . Typically, the rotor comprises a pack of laminations fixed on a rotation shaft , and is inserted inside the stator which comprises an electric winding capable of generating a magnetic field that causes the rotor to rotate . The stator is generally annular in shape and comprises a plurality of radial slots , inside which the electrical winding is made .

[0007] To create the electrical windings of stators with closed slots , it is known to use electrical conductors made using continuous strips or wires , or copper strips that are bent in the central part to form hairpin-shaped strips , known as "hairpins" , to be inserted into the stator slots .

[0008] These strips are inserted into the stator slots according to a speci fic pattern, to obtain the exact number of turns needed to make up the stator winding .

[0009] A known problem of stators is caused by the heat flow generated by the Joule ef fect when the winding is crossed by the electric current : this heat flow must be removed with a cooling system to improve ef ficiency and prevent damage to the electric machine .

[0010] There are known systems for cooling electric motor stators , using oil that flows through channels present in the external part of the stator .

[0011] A problem with known stator cool ing systems is that the oil flows in the outermost part of the stator, away from the windings which are the main source of heat in the machine , decreasing the efficiency of the heat exchange .

[0012] Another problem with known stator cooling systems is that they require stator modi fications to obtain oil flow channels close to the slots , increasing design and manufacturing complexity .

[0013] Obj ect of the present invention is solving these problems by means of a closed-slot stator for an electric machine and an electric machine comprising such a stator, which allow ensuring a very high heat exchange between the cooling fluid and the motor windings ; other obj ects of the invention are the following : to improve the performance of an electric machine during continuous operations , increasing the duration of the performance before derating; to improve the performance of the electric machine during peak operations , allowing to reach higher peak current values ; overall improvement of the ef ficiency of the electric machine ; possibility of obtaining more powerful motors , with the same dimensions , compared to the equivalent versions without the cooling system of the invention; to obtain a cooling system that allows a lower complexity of assembly and production .

[0014] The above and other obj ects and advantages of the invention, as will result from the following description, are achieved by a closed-slot stator for an electric machine and by an electric machine comprising such a stator as those described in the independent claims .

[0015] Preferred embodiments and non-trivial variations of the present invention form the subj ect matter of the dependent claims .

[0016] It is understood that all attached claims form an integral part of this description .

[0017] It will be immediately obvious that countless variations and modi fications can be made to what i s described ( for example relating to shape , dimensions , arrangements and parts with equivalent functionality) without departing from the scope of the invention as appears from the attached claims .

[0018] The present invention will be better described by some preferred embodiments , provided by way of example and not of limitation, with reference to the attached drawings , in which :

[0019] FIG . 1 shows a schematic side view of a crosssection of an electric machine according to the invention; FIG . 2 shows a schematic front section view of a stator of an electric machine according to the invention;

[0020] FIG . 3A, 3B show schematic front views in partial section of an electric machine according to the invention;

[0021] FIG . 4A shows an exploded view o f components of a stator of an electric machine according to the invention;

[0022] FIG . 4B shows schematic front views of components of a stator of an electric machine according to the invention;

[0023] FIG . 5 shows a partial lateral sectional schematic view of an electric machine according to the invention .

[0024] With reference to the figures , a stator 15 with closed slots with a fluid inj ection cooling system, preferably with continuous winding, for an electric machine according to the invention will be described below, which comprises a first internal stator part 25 comprising a plurality of longitudinal teeth 26 , spaced by a space configured to form the lower part of the closed slots 14 of the stator, and a second external annular stator part 35 , preferably comprising a plurality of seats 36 complementary to the upper ends 16 of the teeth 26 of the first stator part 25 and configured to fit together with the first stator part 25 so as to form the closed slots 14 , the lower 3 and upper 4 cooling channels and the stator 15 .

[0025] The closed slots 14 are arranged, preferably equidistant from each other, along a cylindrical internal wall 32 of the stator 15 configured to house a rotor 30 and each slot 14 comprises a bottom wall 38 arranged in the direction of the longitudinal Y-axis of the stator 15 , in proximity to the internal wall 32 at a distance from said internal wall 32 and an upper wall 40 .

[0026] The stator 15 with closed slots according to the invention also comprises a cooling system comprising a circular channel 20 , preferably made hal fway along its axial length, which supplies a plurality of lower axial channels 3 and upper axial channels 4 arranged respectively in proximity to lower conductors 5 and upper 6 ; in correspondence with the circular channel 20 , a plurality of radial channels 50 are made to connect the lower axial channels 3 and upper axial channels 4 , allowing them to be suppl ied simultaneously with a flow of cooling fluid, for example oil , coming from the circular channel 20 .

[0027] Figure 1 shows the path of the cooling fluid in the cooling system of an electric machine 100 comprising a stator 15 with closed slots according to the invention, where I indicates the path o f entry of the fluid ( oil ) into the machine 100 , U indicates the outlet of the fluid, 1 the path of entry of the fluid into the rotor 30 and 2 the path of the fluid entering the circular channel 20 , the radial channels 50 , the lower axial channels 3 and the upper axial channels 4 of the stator 15 .

[0028] The fluid inj ection cooling system of the closed-slot stator 15 according to the invention comprises inj ection means , for example a pump, which inj ect a cooling fluid, preferably oil , into the electric machine 100 , which i s divided into two flows : one directed to the stator 15 and the other to the rotor 30 .

[0029] Preferably, the cooling system of an electric machine 100 and the stator 15 with closed slots according to the invention comprise sealing means 55, 56 which are interposed between the motor housing 19 and the stator 15 and are configured to contain the cool ing fluid ( oil ) exiting from the lower axial channels 3 and upper axial channels 4 of the stator 15 , indicated with US in figure 5 , inside the heads 18 , preventing it from coming into contact with the rotor 30 .

[0030] Preferably, the sealing means comprise a first element 55 and a second element 56 for front sealing, for example consisting of two rubber lips , which deform when abutting respectively with the motor housing 19 and with the stator 15 ; in one embodiment , the sealing means consist of a central body 57 made of non-conductive material connected to two rubber lips 55 , 56 which deform to ensure the seal and are shown in the non-deformed configuration in figure 5 .

[0031] Each closed slot 14 of the stator 15 is formed by two side walls 42 of two adj acent teeth 26 made in the first internal stator part 25 , by the bottom wall 38 connecting the two adj acent teeth 26 and by the upper wall 40 , preferably formed by a connecting wall of two adj acent seats 36 , made in the second external stator part 35 .

[0032] Preferably, said slots 14 are arranged in the direction of the longitudinal Y-axis of the stator 15 and have an asymmetrical shape .

[0033] In a preferred embodiment of the invention, the side walls 42 of a slot 14 are asymmetrical , preferably curved or concave , and more preferably have the concavity designed to optimi ze the efficiency or operation of the electrical machine 100 in a desired operating direction; for example , the concavity faces in a given direction relative to a preferred direction of rotation of the rotor 30 .

[0034] As illustrated in Figures 10 and 11 , the closed-slot stator 15 for an electric machine according to the invention comprises : the closed slots 14 inside which are inserted conductors 5 , 6 , 22 , preferably strips , which form the winding, superimposed starting from a lower conductor ( strip ) 5 in correspondence with the bottom wall 38 of the slot 14 , up to an upper conductor ( strip ) 6 in correspondence with the upper wall 40 of the slot 14 , the lower channels 3 formed between the lower conductor (band) 5 and the bottom wall 38 of the slot 14 , the upper channels 4 formed between the upper end 16 of the teeth 26 of the first stator part 25 and the seat 36 of the second external annular stator part 35 , the circular channel 20 , preferably formed hal fway along the axial length of the stator 15 , preferably in the second external annular stator part 35 which is thus divided into two portions , preferably hal fway along its axial length, for the supply of the cooling fluid, the radial channels 50 connecting the lower axial channels 3 and the upper axial channels 4 for their simultaneous supply, said circular channels 20 , radial channels 50 , lower channels 3 and upper channels 4 being used for the passage of the stator cooling fluid 15 , preferably oil .

[0035] Preferably, the closed slot 14 comprises a narrowing and / or a support tooth 7 , preferably two teeth 7 formed on the side walls 42 of the slot 14 , in correspondence with the bottom wall 38 , to prevent the strip 22 from coming into contact with the bottom wall 38 and to leave a free space to create the lower channel 3 .

[0036] Preferably, the upper end 16 of the toothing 26 comprises a recess 9 obtained in correspondence with the contact area with the seat 36 of the second external annular stator part 35 , to leave a free space between the first stator part 25 and the second external annular stator part 35 in which the upper channel 4 is made.

[0037] In the embodiment of the stator 15 with closed slots of the invention which comprises the curved or concave side walls 42 of the slot 14, the slot 14 further comprises microchannels formed in the space between the conductor 5, 6, 22 and the side walls 42; this additional passage of fluid (oil) increases the heat exchange between the cooling fluid and the conductor 5, 6, 22.

[0038] The cooling system by means of fluid injection of the stator 15 with closed slots 14 of the invention comprises the injection means, a thermostat, and suitable temperature and flow sensors of a known type to make the cooling fluid flow inside the channels 3, 4, 20, 50 at the desired temperature and flow rate.

[0039] Due to this, the heat removal in the stator 15 is very effective, as it occurs in the proximity of the conductors 5, 6 of the winding, the main source of heat dissipation of the electric machine.

[0040] In a preferred embodiment of the invention, the first internal stator part 25 is made with a pack of laminations 60, in particular having three types of laminations 60A, 60B and 60C shown in figures 4A and 4B, which constitute the first internal stator part 25 and which, in addition to creating the closed slots 14 housing the conductors 5 , 6 , 22 and the lower channels 3 and upper channels 4 , have speci fic geometries which allow the circular channel 20 and the radial channels 50 to be created as well as a sealing surface 59 for the second front sealing element 56 .

[0041] In particular, the sheet metal package includes : a first group of laminations 60A, preferably two groups , in which the side walls 42 of the slot 14 , the lower channel 3 with the bottom wall 38 and, preferably, the teeth 7 are obtained, in addition to the recess 9 obtained in the upper end 16 of the teeth 26 to create the upper channel 4 ; a second group of laminations 60B, preferably two laminations 60B, arranged at the two axial ends of the stator, comprising a bottom wall 58 of the slot 14 made in such a way as to cause a narrowing of the lower channel 3 formed by the first group of laminations 60A and create the sealing surface 59 against which the second front sealing element 56 abuts ; a third group of laminations 60C comprising a protrusion 27 , obtained in the upper end 16 of the toothing 26 , which is inserted between the two portions of the second part 35 of the external annular stator to keep them spaced apart , so as to create in the free space between the two portions the circular channel 20 in the shape of a circular crown; in the third group of laminations 60C, the radial channels 50 are created by widening the space between the lateral walls 42 of the slot 14 so as to allow the radial flow, putting the lower channels 3 and the upper channels 4 in communication, allowing their simultaneous feeding .

[0042] In a preferred embodiment of the stator 15 with closed slots according to the invention, the second external annular stator part 35 is composed of sectors interlocked with each other .

[0043] The stator cooling system by means of fluid inj ection with closed slots according to the invention allows limiting the temperature increase of the winding during the operation of the electric machine , containing the increase in resistivity of the conductor with the temperature , reducing the conduction and proximity losses at the same current , compared to the equivalent versions without cooling channels .

[0044] Advantageously, the stator with closed slots with fluid inj ection cooling system of the invention allows signi ficantly increasing the ef ficiency of the electric machine and, in exchange for lower losses , improving the performance during continuous operations of the electric motor and reach higher currents during peak operations . The average power is increased, as well as the mas s power, allowing to obtain lighter machines at the same power compared to equivalent machines without direct cooling on the windings .

[0045] Advantageously, the closed-slot stator with fluid inj ection cooling system according to the invention allows producing windings with lower costs , better fi lling of the slots by the winding and also simpli fying the production process .

Claims

CLAIMS1. Stator (15) with closed slots and fluid injection cooling system comprising: a first internal stator part (25) comprising a plurality of teeth (26) , spaced by a space configured to form the lower part of the closed slots (14) of the stator; a second external stator part (35) configured to form the closed slots (14) and the stator (15) with the teeth (26) ; a winding comprising at least one conductor (22) configured to be wound in the closed slots (14) of the stator, characterized in that it further comprises: the closed slots (14) inside which the conductors (22) that form the winding are inserted, superimposed starting from a lower conductor (5) in correspondence with a bottom wall (38) of the slot (14) , up to an upper conductor (6) in correspondence with an upper wall (40) of the slot (14) , a lower channel (3) formed between the lower conductor (5) and the bottom wall (38) of the slot (14) , an upper channel (4) formed between an upperend (16) of the teeth (26) of the first stator part (25) and the second external stator part (35) , and in that it further comprises: a circular channel (20) which supplies a cooling fluid to the lower (3) and upper (4) channels located respectively near the lower (5) and upper (6) conductors, sealing means (55, 56) placed between the motor box (19) and the stator (15) and configured to contain the cooling fluid exiting from the lower (3) and upper (4) channels, preventing it from coming into contact with the rotor (30) .

2. Stator (15) with closed slots according to claim 1, characterized in that it comprises a radial channel (50) , made in correspondence with the circular channel (20) , connecting the lower (3) and upper (4) channels to supply them with the cooling fluid.

3. Stator (15) with closed slots according to claim 1 or 2, characterized in that the sealing means comprise a first element (55) and a second frontal sealing element (56) which deform when coming into contact with the motor box (19) and the stator (15) respectively.

4. Stator (15) with closed slots according to anyof the preceding claims, characterized in that the sealing means consist of a central body (57) in non-conductive material connected to two rubber lips (55, 56) which deform to ensure the seal.

5. Stator (15) with closed slots according to any of the preceding claims, characterized in that the closed slot (14) comprises a narrowing and / or a support tooth (7) obtained on the side walls (42) in correspondence with the bottom wall (38) to create the lower channel (3) and in that the upper end (16) of the toothing (26) comprises a recess (9) , obtained in correspondence with the second external stator part (35) , in which the upper channel (4) is created.

6. Stator (15) with closed slots according to any of the preceding claims, characterized in that it comprises a second external annular stator part (35) composed of sectors interlocked with each other, comprising a plurality of seats (36) complementary to the upper ends (16) of the teeth (26) of the first stator part (25) and configured to fit together with the teeth (26) so as to form a plurality of closed slots (14) , the channels (3, 4, 20, 50) and the stator (15) and in that the side walls (42) of the closed slots (14) are curved orconcave .

7. Stator (15) with closed slots according to any of the preceding claims, characterized in that the first internal stator part (25) is made with a pack of laminations comprising: a first group of sheets (60A) in which the side walls (42) of the slot (14) , the lower channel (3) and the recess (9) obtained in the teeth (26) to create the upper channel (4) are obtained; a second group of laminations (60B) arranged at the two axial ends of the stator, comprising a bottom wall (58) of the slot 14 made in such a way as to cause a narrowing of the lower channel (3) formed by the first group of laminations (60A) and create a sealing surface (59) against which the second front sealing element (56) abuts ; a third group of laminations (60C) comprising a protrusion (27) obtained in the upper end (16) of the teeth (26) , which is inserted between two portions of the second part (35) of the external annular stator to keep them spaced apart, so as to create the circular channel (20) and the radial channels (50) created by widening the spacebetween the lateral walls (42) of the slot (14) so as to allow radial flow, putting the lower channels (3) and the upper channels (4) in communication.

8. Electric machine (100) comprising a closed-slot stator (15) according to any of claims 1 to 7.

9. Cooling system for a stator (15) with closed slots (14) according to any of claims 1 to 7 comprising a pump, a thermostat and temperature and flow sensors to make the cooling fluid flow inside the channels (3, 4, 20, 50) .

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