SE2050369A1 - Stator for Electric Machine, Electric Machine, Electric Powertrain, and Vehicle - Google Patents

Abstract

A stator (1) for an electric machine (3) is disclosed. The stator (1) is configured to induce a torque to a rotor (5) of the electric machine (3), wherein the rotor (5) is configured to rotate around a rotation axis (ax). The stator (1) comprises a stator core (7) comprising a number of slots (9), and a number of form wound wires (11) positioned in the slots (9). The slots (9) comprise a wedge shape in a plane (P) perpendicular to the rotation axis (ax). The wedge shape of the slots (9) extends to a radially inner delimiting surface (13) of the stator core (7). The present disclosure further relates to an electric machine (3) comprising a rotor (5) and a stator (1), an electric powertrain (30) for a vehicle (2), and a vehicle (2) comprising an electric machine (3).

Description

Stator for Electric Machine, Electric Machine, Electric Powertrain, andVehicle TECHNICAL FIELDThe present disclosure relates to a stator for an electric machine. The present disclosurefurther relates to an electric machine comprising a rotor and a stator, an electric powertrain for a vehicle, and a vehicle comprising an electric machine.

BACKGROUND The use of electric drive for vehicles provides many advantages, especially regarding localemissions. Such vehicles comprise one or more electric motors configured to provide motivepower to the vehicle. These types of vehicles can be divided into the categories pure electricvehicles and hybrid electric vehicles. Pure electric vehicles, sometimes referred to as batteryelectric vehicles, only-electric vehicles, and all-electric vehicles, comprise a pure electricpowertrain and comprise no internal combustion engine and therefore produce no emissions in the place where they are used.

A hybrid electric vehicle comprises two or more distinct types of power, such as an internalcombustion engine and an electric propulsion system. The combination of an internalcombustion engine and an electric propulsion system provides advantages with regard toenergy efficiency, partly because of the poor energy efficiency of an internal combustionengine at lower power output levels. Moreover, some hybrid electric vehicles are capable of operating in pure electric drive when wanted, such as when driving in certain areas.

Electric machines can be divided into the categories electric motors and electric generators.An electric motor is an electric machine that converts electrical energy into mechanicalenergy, whereas an electric generator is an electric machine that converts mechanicalenergy into electrical energy. Some electric machines can operate in both directions, i.e.function as an electric motor as well as an electric generator. This is the case for most electric propulsion motors for vehicles.

Most electric motors comprise magnets and a wire winding, wherein the electric motoroperate through the interaction between the magnetic field of the magnets and electriccurrent in the wire winding to generate force in the form of rotation of a rotor or to generateelectricity in the windings from the rotation of the rotor. Moreover, most electric machines comprise a rotor and a stator, wherein the rotor is surrounded by the stator. 2 Furthermore, in some electric machines, the rotor comprises a set of permanent magnetsand the stator comprises wire windings. Such electric machines are sometimes referred to aspermanent magnet machines. A stator usually comprises a stator core comprising a number of slots, Wherein the windings are positioned in the slots.

Different types of Wire windings exist, such as random Wound Wires, hairpin Wires, and formwound wires, and the like. The different types of wire windings have different advantages anddisadvantages when it comes to the design of the stator core, durability, and the complexityand cost of the manufacturing and assembling of an electric machine. ln contrast to hairpinWires, form Wound Wires is a type of continuous Wire Winding Which requires no Weldingduring an assembling procedure. However, form wound wires puts requirements on the design of a stator core.

A further problem associated with electric machines is that the wire windings are subjected tohigh and varying forces during operation of an electric machine. Furthermore, Wire windingsare subjected to varying temperatures during operation of an electric machine. Therefore,When designing an electric machine, one must preferably ensure that the Wire windings aresecurely retained in the stator. ln addition, the design of the stator core may affect the operational efficiency of the electric machine.

Furthermore, generally, on today's consumer market, it is an advantage if products, such aselectric machines and associated components, systems, and arrangements, have conditionsand/or characteristics suitable for being manufactured and assembled in a cost-efficient mannel".

SUMMARYlt is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a stator for an electricmachine. The stator is configured to induce a torque to a rotor of the electric machine. Therotor is configured to rotate around a rotation axis. The stator comprises a stator corecomprising a number of slots, and a number of form wound wires positioned in the slots. Theslots comprise a wedge shape in a plane perpendicular to the rotation axis. The wedge shape of the slots extends to a radially inner delimiting surface of the stator core. 3 Since the stator comprises slots having a wedge shape extending to the radially innerdelimiting surface of the stator core, a stator is provided having conditions for retaining theform Wound Wires in a secure manner While circumventing the need for a structure orarrangement at the radially inner delimiting surface of the stator core for retaining the form Wound Wires.

That is, in prior art stators accommodating form wound wires, the slots are provided with astructure or arrangement at the opening of the slots at the radially inner delimiting surface ofthe stator core for retaining the form Wound Wires. Such structure or arrangement may impairthe operational efficiency of the electric machine because of an electric field build-up at sharpcorners or edges of such structure or arrangement. Moreover, such structures orarrangements add complexity and manufacturing costs and assembling costs to the electric machine.

Accordingly, due to the wedge shape of the slots according to the embodiments herein, theform wound wires can be mechanically fixated to the stator core in a manner circumventingthe need for a structure or arrangement at the openings of the slots at the radially innerdelimiting surface of the stator core. Thus, due to these features, a stator for an electricmachine is provided having conditions and characteristics suitable for being manufacturedand assembled in a cost-efficient manner. Moreover, a stator for an electric machine is provided having conditions for an improved operational efficiency.

Furthermore, since the need is circumvented for a structure or arrangement at the openingsof the slots, a stator is provided in which the stator core is more suitable for a steel punchingprocess during manufacturing thereof. Thus, also for this reason, a stator for an electricmachine is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner. ln addition, since the stator comprises number of form Wound Wires positioned in the slots, astator is provided comprising a reliable type of Wire Winding requiring no Welding during an assembling process of the wire Winding to the stator core.

Accordingly, a stator for an electric machine is provided overcoming, or at least alleviating, atleast some of the above-mentioned problems and drawbacks. As a result, the above- mentioned object is achieved. 4 Optionally, the width of each slot, measured at the radially inner delimiting surface of thestator core, is greater than the width of the form wound wires. Thereby, a stator is providedhaving conditions and Characteristics suitable for being manufactured and assembled in afurther cost-efficient manner. This because the form wound wires can be inserted into the slots via the openings of the slots at the radially inner delimiting surface of the stator core.

Optionally, the width of the slots, measured at the radially inner delimiting surface of thestator core, is smaller than a width of the slots measured at a radial distance away from theinner delimiting surface of the stator core. Thereby, the form wound wires can be mechanically fixated to the stator core in a further secure manner.

Optionally, the stator core comprises a number of teeth, and wherein sides of two adjacentteeth form the wedge shape of a slot. Thereby, the form wound wires can be mechanicallyfixated to the stator core in a secure manner circumventing the need for a structure orarrangement at the openings of the slots at the radially inner delimiting surface of the stator COFG.

Optionally, the angle between the sides of two adjacent teeth is within the range of 1.5 - 10degrees or is within the range of 3 - 5 degrees. Thereby, the form wound wires can bemechanically fixated to the stator core in a secure manner circumventing the need for astructure or arrangement at the openings of the slots at the radially inner delimiting surface of the stator core.

Optionally, the teeth are wedge shaped in the plane perpendicular to the rotation axis.Thereby, a stator is provided having conditions for retaining the form wound wires in a securemanner without a structure or arrangement at the openings of the slots at the radially inner delimiting surface of the stator core.

Optionally, the angle between sides of one tooth of the number of teeth is within the range of0.5 - 8 degrees or is within the range of 1 - 3 degrees. Thereby, a stator is provided havingconditions for retaining the form wound wires in a secure manner without a structure orarrangement at the openings of the slots at the radially inner delimiting surface of the stator COFG.

Optionally, the stator comprises impregnation between the form wound wires and delimiting surfaces of the slots. Thereby, a stator is provided having conditions for retaining the form Wound Wires in a secure manner Without a structure or arrangement at the openings of the slots at the radially inner delimiting surface of the stator core.

According to a second aspect of the invention, the object is achieved by an electric machinecomprising a rotor configured to rotate around a rotation axis, and wherein the electric machine comprises a stator according to some embodiments of the present disclosure.

Since the electric machine comprises a stator according to some embodiments of thepresent disclosure, an electric machine is provided having conditions for retaining the formWound Wires in a secure manner While circumventing the need for a structure or arrangement at the radially inner delimiting surface of the stator core for retaining the form Wound Wires.

Thus, an electric machine is provided having conditions and characteristics suitable for beingmanufactured and assembled in a cost-efficient manner. Moreover, an electric machine is provided having conditions for an improved operational efficiency.

Accordingly, an electric machine is provided overcoming, or at least alleviating, at least someof the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the electric machine is a vehicle propulsion motor. Thereby, a vehicle propulsionmotor is provided having conditions for retaining the form Wound Wires in a secure mannerwhile circumventing the need for a structure or arrangement at the radially inner delimiting surface of the stator core for retaining the form Wound Wires.

Thus, a vehicle propulsion motor is provided having conditions and characteristics suitablefor being manufactured and assembled in a cost-efficient manner. Moreover, a vehicle propulsion motor is provided having conditions for an improved operational efficiency.

According to a third aspect of the invention, the object is achieved by an electric powertrainfor a vehicle, wherein the powertrain comprises an electric machine according to some embodiments of the present disclosure.

Since the electric powertrain comprises an electric machine according to some embodimentsof the present disclosure, an electric powertrain is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner. 6 Moreover, an electric powertrain is provided having conditions for an improved operational efficiency.

Accordingly, an electric powertrain is provided overcoming, or at least alleviating, at leastsome of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

According to a fourth aspect of the invention, the object is achieved by a vehicle comprisingan electric machine according to some embodiments of the present disclosure or an electric powertrain according to some embodiments of the present disclosure.

Since the vehicle comprises an electric machine according to some embodiments of thepresent disclosure or an electric powertrain according to some embodiments of the presentdisclosure, a vehicle is provided having conditions and characteristics suitable for beingmanufactured and assembled in a cost-efficient manner. Moreover, a vehicle is provided having conditions for an improved operational efficiency.

Accordingly, a vehicle is provided overcoming, or at least alleviating, at least some of theabove-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Further features of, and advantages With, the present invention Will become apparent When studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGSVarious aspects of the invention, including its particular features and advantages, will bereadily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 illustrates a stator for an electric machine, according to some embodiments, Fig. 2 illustrates a cross section through a portion of an electric machine according to someembodiments, Fig. 3 illustrates a cross section through a portion of an electric machine according to theembodiments illustrated in Fig. 2, and Fig. 4 illustrates a vehicle according to some embodiments.

DETAILED DESCRIPTION 7 Aspects of the present invention will now be described more fully. Like numbers refer to likeelements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 illustrates a stator1 for an electric machine, according to some embodiments. Thestator 1 is configured to induce a torque to a rotor of the electric machine, as is furtherexplained herein. The rotor may comprise a number of permanent magnets. The rotor is notillustrated in Fig. 1 for the reason of brevity and clarity. The rotor is configured to rotatearound a rotation axis ax relative to the stator 1. The wording "electric machine" as usedherein is intended to encompass an electric motor and an electric generator, as well as an electric machine capable of operating as an electric motor and an electric generator.

The stator 1 comprises a stator core 7 comprising a number of slots 9 circumferentiallydistributed on the stator core 7. The stator core 7 is configured to enclose the rotor of theelectric machine. According to the illustrated embodiments, the stator core 7 comprisesseventy two slots 9. According to further embodiments, the stator core 7 may compriseanother number of slots 9, such as a number between forty and one hundred and thirty slots9. The stator core 7 may be formed by an electro plate laminate comprising a plurality of thin plates stacked and attached to each other.

The stator 1 comprises form wound wires 11 positioned in the slots 9. Form wound wires 11is a type of pre-shaped continuous wire winding which requires no welding during anassembling procedure of the stator 1, as is further explained herein. ln embodiments wherethe electric machine operates as an electric motor, an electric current fed through the formwound wires 11 generates a magnetic field inducing a torque causing rotation of the rotoraround the rotation axis ax thereof. ln embodiments where the electric machine operates asan electric generator, an electric current is generated in the form wound wires 11 from amagnetic field of the magnets of the rotor upon rotation of the rotor around the rotation axisax. Thus, in such embodiments, and in such situations, the stator1 induces a torque to therotor braking the rotation of the rotor around the rotation axis ax. The stator 1 is thusconfigured to induce, i.e. apply, a torque to a rotor of an electric machine by the interactionbetween a magnetic field of the stator 1 and a magnetic field of the rotor. The induced torquemay be a torque causing rotation of the rotor or a torque braking rotation of the rotor, as explained above.

Fig. 2 illustrates a cross section through a portion of an electric machine 3 according to some embodiments. The electric machine 3 comprises a rotor 5 and a stator 1 according to the 8 embodiments illustrated in Fig. 1. ln Fig. 2, the cross section is made in a plane Pperpendicular to the rotation axis of the rotor 5. ln the cross section of Fig. 2, two adjacentslots 9 are visible. Moreover, a cross section of the form wound wires 11 is visible. As seen inFig. 2, the form wound wires 11 are provided with a rectangular cross section. According tothe illustrated embodiments, four form wound wires 11 are positioned in each slot 9.According to further embodiments, another number of form wound wires 11 may be positioned in each slot 9, such as one, two, three, five, six, or the like.

Furthermore, as seen in Fig. 2, the slots 9 comprise a wedge shape in the plane Pperpendicular to the rotation axis of the rotor 5. Moreover, the wedge shape of the slots 9extends to a radially inner delimiting surface 13 of the stator core 7. Thereby, the form woundwires 11 can be securely retained in the slots 9 without using a structure or arrangement atthe openings 10 of the slots 9 at the radially inner delimiting surface 13 of the stator core 7,as is further explained herein. The radially inner delimiting surface 13 of the stator core 7 is the delimiting surface 13 of the stator core 7 being closest to the rotation axis of the rotor 5. ln prior art stators having slots for accommodating form wound wires, the slots are providedwith a structure or arrangement at the opening of the slots towards the radially innerdelimiting surface of the stator core for retaining the form wound wires. Such a structure orarrangement may impair the operational efficiency of the electric machine because of anelectric field build-up at sharp corners or edges of such a structure or arrangement.Moreover, such structures or arrangements add complexity and manufacturing costs and assembling costs to the electric machine.

Since the stator 1 according to the embodiments herein comprises slots 9 having a wedgeshape extending to the radially inner delimiting surface 13 of the stator core 7, a stator1 isprovided having conditions for retaining the form wound wires 11 in a secure manner whilecircumventing the need for a structure or arrangement at the radially inner delimiting surface 13 of the stator core 7 for retaining the form wound wires 11.

Accordingly, due to the wedge shape of the slots 9 according to the embodiments herein, theform wound wires 11 can be mechanically fixated to the stator core 7 in a mannercircumventing the need for a structure or arrangement at the openings 10 of the slots 9 at theradially inner delimiting surface 13 of the stator core 7. Thus, due to these features, a stator 1for an electric machine 3 is provided having conditions and characteristics suitable for beingmanufactured and assembled in a cost-efficient manner. Moreover, a stator 1 for an electric machine 3 is provided having conditions for an improved operational efficiency.

Furthermore, since the need is circumvented for a structure or arrangement at the openings10 of the slots 9, a stator 1 is provided in which the stator core 7 is more suitable for a steelpunching process during manufacturing thereof. Thus, also for this reason, a stator 1 for anelectric machine 3 is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner.

Since the slots 9 according to the illustrated embodiments comprise no structure or arrangement at the openings 10 of the slots 9, the slots 9 may be referred to as open slots 9.

As is indicated in Fig. 2, the width w1 of each slot 9, measured at the radially inner delimitingsurface 13 of the stator core 7, is greater than the width w0 of the form wound wires 11. Dueto these features, the form wound wires 11 can be inserted into the slots 9 via the openings of the slots 9 at the radially inner delimiting surface 13 of the stator core 7. ln this manner, the assembling of the stator 1 is significantly facilitated.

Moreover, as is evident from Fig. 2, the wedge shape of the slots 9 is such that the width w1of the slots 9, measured at the radially inner delimiting surface 13 of the stator core 7, issmaller than a width w2 of the slots 9 measured at a radial distance rd away from the innerdelimiting surface 13 of the stator core 7. Moreover, as is indicated in Fig. 2, the stator1comprises impregnation 21 between the form wound wires 11 and delimiting surfaces 15', 16of the slots 9. The impregnation 21 may comprise a polymeric material configured toelectrically isolate the form wound wires 11 from the stator core 7. Moreover, due to theimpregnation 21 and the wedge shape of the slots 9, the form wound wires 11 are securelyretained in the slots 9 in radial directions of the stator 1 as well as in axial directions of thestator 1. Axial directions of the stator 1 coincides with the rotation axis of the rotor 5 whereas radial directions of the stator 1 is perpendicular to the rotation axis of the rotor 5.

Fig. 3 illustrates a cross section through a portion of an electric machine 3 according to theembodiments illustrated in Fig. 2. The cross section of Fig. 3 is identical to the cross sectionillustrated in Fig. 2 and has been made to be able to explain further features, functions, andadvantages of the stator 1 and the electric machine 3 without adding excess reference signs which would impair the clarity of Fig. 2.

As indicated in Fig. 3, the stator core 7 comprises a number of teeth 15. Apparently, sides15' of two adjacent teeth 15 form the wedge shape of a slot 9. According to the illustrated embodiments, the sides 15' of the teeth 15 are straight sides 15". The stator core 7 comprises the same number of teeth 15 as the number of slots 9. Accordingly, the stator 1according to the embodiments illustrated in Fig. 1 comprises seventy two teeth 15. Thedelimiting surfaces 15', 16 of the slots 9 referred to above thus constitutes two opposingsides 15' of a slot 9 and a radially outer delimiting surface 16 of the slot 9. According to theillustrated embodiments, the radially outer delimiting surface 16 is a straight delimiting surface meeting the two opposing sides 15' at acute angles.

According to the illustrated embodiments, the angle A1 between the sides 15' of two adjacentteeth 15, measured in the plane P perpendicular to the rotation axis of the rotor 5, isapproximately 4 degrees. According to further embodiments, the angle A1 between the sides15' of two adjacent teeth 15, measured in the plane P perpendicular to the rotation axis of therotor 5, may be within the range of 1.5 - 10 degrees or within the range of 3 - 5 degrees.Thereby, the form wound wires 11 can be securely retained in the slots 9 without the need for a structure of arrangement at the openings of the slots 9.

As can be seen in Fig. 2 and Fig. 3, according to the illustrated embodiments, the teeth 15 are wedge shaped in the plane P perpendicular to the rotation axis of the rotor 5. The wedgeshape of the teeth 15 is a result of the wedge shape of the slots 9 and of the number of slots9 circumferentially distributed on the stator core 7. According to the illustrated embodiments,the angle A2 between sides 15' of one tooth 15 of the number of teeth 15 is approximately 2degrees. According to further embodiments, the angle A2 between sides 15' of one tooth 15of the number of teeth 15 may be within the range of 0.5 - 8 degrees or within the range of 1 - 3 degrees.

Even though the stator 1 according to the embodiments explained herein circumvents theneed for a structure or arrangement at the openings 10 of the slots 9, according to someembodiments the stator 1 may comprise elements arranged at the openings 10 of the slots 9so as to further retain the form wound wires 11 in the slots 9. Each of such elements maycomprise a wedge shape corresponding to the wedge shape of a slot 9 and may be provided in a non-electrically conductive material.

Fig. 4 illustrates a vehicle 2 according to some embodiments. According to the illustratedembodiments, the vehicle 2 is a truck. However, according to further embodiments, thevehicle 2, as referred to herein, may be another type of manned or unmanned vehicle forland or water based propulsion such as a lorry, a bus, a construction vehicle, a tractor, a car, a ship, a boat, or the like. 11 The vehicle 2 comprises an electric powertrain 30. The electric powertrain 30 is configured toprovide motive power to the vehicle 2 via Wheels 32 of the vehicle 2. The electric powertrain30 comprises an electric machine 3 according to the embodiments explained with referenceto Fig. 1 - Fig. 3, i.e. an electric machine 3 comprising a stator1 according to theembodiments explained with reference to Fig. 1 - Fig. 3. The electric machine 3 is capable ofproviding motive power to the vehicle 2 via Wheels 32 of the vehicle 2 as Well as providingregenerative braking of the vehicle 2. Thus, according to the illustrated embodiments, theelectric machine 3 is capable of operating as an electric motor as well as an electricgenerator. The electric machine 3 of the vehicle 2 may be referred to as a vehicle propulsion motor/generator 3.

The electric powertrain 30 may be a pure electric powertrain 30, i.e. a powertrain comprisingno internal combustion engine, or a hybrid electric powertrain 30 comprising a combustion engine in addition to the electric machine 3. lt is to be understood that the foregoing is illustrative of various example embodiments andthat the invention is defined only by the appended claims. A person skilled in the art willrealize that the example embodiments may be modified, and that different features of theexample embodiments may be combined to create embodiments other than those describedherein, Without departing from the scope of the present invention, as defined by the appended claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one ormore stated features, elements, steps, components, or functions but does not preclude thepresence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims (2)

1. A stator (1 ) for an electric machine (3), the stator (1) being configured to induce a torqueto a rotor (5) of the electric machine (3), wherein the rotor (5) is configured to rotatearound a rotation axis (ax),and wherein the stator (1) comprises:- a stator core (7) comprising a number of slots (9), and- a number of form wound wires (11) positioned in the slots (9), wherein the slots (9) comprise a wedge shape in a plane (P) perpendicular to therotation axis (ax), and wherein the wedge shape of the slots (9) extends to a radially inner delimiting surface (13) of the stator core (7)_ The stator (1) according to claim 1, wherein the width (w1) of each slot (9), measured at the radially inner delimiting surface (13) of the stator core (7), is greater than the width (w0) of the form wound wires (11)The stator (1) according to claim 1 or 2, wherein the width (w1) of the slots (9),measured at the radially inner delimiting surface (13) of the stator core (7), is smallerthan a width (w2) of the slots (9) measured at a radial distance (rd) away from the inner delimiting surface (13) of the stator core (7)_ The stator (1) according to any one of the preceding claims, wherein the stator core (7) comprises a number of teeth (15), and wherein sides (15') of two adjacent teeth (15) form the wedge shape of a slot (9)The stator (1) according to claim 4, wherein the angle (A1) between the sides (15') oftwo adjacent teeth (15) is within the range of 1.5 - 10 degrees or is within the range of 3 - 5 degreesThe stator (1) according to claim 4 or 5, wherein the teeth (15) are wedge shaped in the plane (P) perpendicular to the rotation axis (ax)_ The stator (1) according to claim 6, wherein the angle (A2) between sides (15') of one tooth (15) of the number of teeth (15) is within the range of 0.5 - 8 degrees or is within the range of 1 - 3 degrees 5. 13 8The stator (1) according to any one of the preceding claims, wherein the stator (1)comprises impregnation (21) between the form wound wires (11) and delimiting surfaces(15', 16) of the slots (9) 9. An electric machine (3) comprising a rotor (5) configured to rotate around a rotation axis(ax), and wherein the electric machine (3) comprises a stator (1) according to any one of the preceding claims 10. The electric machine (3) according to c|aim 9, wherein the electric machine (3) is a vehicle propulsion motor (3) 11. An electric powertrain (30) for a vehicle (2), wherein the powertrain (30) comprises an electric machine (3) according to c|aim 101

2. A vehicle (2) comprising an electric machine (3) according to c|aim 9 or 10 or an electric powertrain (30) according to c|aim 11.