Description:PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.
 
A STATOR FOR AN OUTER-ROTOR BRUSHLESS DIRECT CURRENT (BLDC) MOTOR AND METHOD THEREOF

TECHNICAL FIELD
[0001] Embodiments of the present disclosure generally relate to stator assemblies and more particularly relate to a stator for an outer-rotor Brushless Direct Current (BLDC) motor and method thereof.

BACKGROUND
[0002] Generally, permanent magnet Brushless Direct Current (BLDC) motors are fundamental components in electric mobility, including electric scooters, motorcycles, hub motor systems, industrial drives, and other electromechanical applications. Such motors rely on electromagnetic interaction between stator windings and rotor permanent magnets to generate torque. The geometric configuration of the stator teeth, slot openings, airgap region, and winding distribution significantly influences torque production, cogging characteristics, efficiency, and overall operational smoothness. The ability of these motors to deliver high torque with minimal ripple and vibration is essential for ensuring ride quality, efficiency, and system reliability.
[0003] Currently, in order to obtain higher torque output, conventional BLDC motor designs primarily focus on rotor-oriented modifications, such as increasing magnet strength, altering magnet shapes, increasing pole count, or adopting complex magnet arrangements. However, the use of high-energy rare-earth magnets increases material cost and may lead to magnetic circuit saturation. Further, shaping magnets into sinusoidal or skewed profiles requires complex machining or grinding processes, which increase manufacturing difficulty and production expense. Additionally, increasing magnet strength or pole count may intensify cogging torque and harmonic effects, thereby affecting smooth motor operation.
[0004] The conventional motors typically implement skew structures on the rotor magnets or stator cores in order to reduce cogging torque. While skewing may reduce torque ripple to some extent, however, results in a reduction in average torque output and introduces structural complexity in the lamination assembly. Step-skewed cores and offset slot openings require additional manufacturing processes such as bonding, welding, or caulking, thereby increasing production cost and assembly complexity. Moreover, such approaches do not fundamentally optimize the airgap permeance distribution responsible for cogging phenomena.
[0005] Further, existing motor designs may adopt fractional-slot configurations or specific pole-slot combinations to improve electromagnetic performance. However, the conventional solutions may primarily emphasize winding configuration or rotor topology without coordinated optimization of stator. As a result, conventional stator structures may exhibit high torque ripple, elevated copper and iron losses, inefficient magnetic energy utilization, and increased material consumption. In addition, reliance on rotor-based improvements increases magnet usage and overall manufacturing costs.
[0006] Consequently, there is a need in the art for an improved stator for an outer-rotor Brushless Direct Current (BLDC) motor and method thereof, to address at least the aforementioned issues in the prior arts.

SUMMARY
[0007] This summary is provided to introduce a selection of concepts, in a simple manner, which is further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the subject matter nor to determine the scope of the disclosure.
[0008] An aspect of the present disclosure provides a stator for an outer-rotor Brushless Direct Current (BLDC) motor. The stator includes a laminated stator core defining a central axis and comprising a plurality of circumferentially distributed stator teeth extending radially outward and separated by a corresponding plurality of stator slots. Further, the stator includes a plurality of concentrated windings disposed in the plurality of stator slots. The plurality of stator slots and a number of poles of permanent magnets associated with an outer rotor positioned radially outward of the stator include a fractional-slot concentrated winding configuration with a number of slots per pole of a pre-defined value. A plurality of coils of each of the plurality of concentrated windings are concentrated corresponding to each of the plurality of stator teeth. Each of the plurality of stator teeth includes a tooth body extending radially from a stator yoke and a tooth tip disposed at a radially outer end of the tooth body including an airgap region defining a slot opening. The tooth tip comprises a tooth lip with a pre-determined tooth lip height corresponding to a radial direction relative to the airgap region. The tooth tip defines a slot opening width of the slot opening circumferentially at the airgap region and the tooth lip height radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip. The slot opening width and the tooth lip height are dimensioned to define an airgap permeance profile along a circumferential direction of the stator.
[0009] Another aspect of the present disclosure provides a method of configuring a stator for an outer-rotor Brushless Direct Current (BLDC) motor. The method includes forming a laminated stator core defining a central axis, the laminated stator core including a plurality of circumferentially distributed stator teeth extending radially outward from a stator yoke and separated by a corresponding plurality of stator slots. Further, the method includes forming each of the plurality of stator teeth with a tooth body extending radially from the stator yoke and a tooth tip disposed at a radially outer end of the tooth body adjacent an airgap region. Furthermore, the method includes forming a slot opening between adjacent tooth tips, the slot opening comprising a slot opening width measured circumferentially at the airgap region. The method further includes forming each tooth tip with a tooth lip comprising a predetermined tooth lip height measured radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip. Further, the method includes dimensioning the slot opening width and the predetermined tooth lip height to establish an airgap permeance profile along a circumferential direction of the stator. Furthermore, the method includes associating the plurality of stator slots with a number of poles of permanent magnets of an outer rotor positioned radially outward of the stator causing the plurality of stator slots and the number of poles establish a fractional-slot concentrated winding configuration with a number of slots per pole of a predefined value. Additionally, the method includes disposing a plurality of concentrated windings within the plurality of stator slots causing coils of each concentrated winding concentrated corresponding to respective stator teeth.
[0010] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0011] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0012] FIG. 1 illustrates an exemplary schematic diagram representation of a stator for an outer-rotor Brushless Direct Current (BLDC) motor, in accordance with an embodiment of the present disclosure;
[0013] FIG. 2 illustrates an exemplary schematic diagram representation of an enlarged sectional view of a portion of a stator shown in FIG. 1, in accordance with an embodiment of the present disclosure;
[0014] FIG. 3 illustrates an exemplary schematic diagram representation of an exploded view of a motor components along with a stator, in accordance with an embodiment of the present disclosure;
[0015] FIG. 4 illustrates an exemplary schematic diagram representation of sectional view of circumferential stator segments of a stator, in accordance with an embodiment of the present disclosure;
[0016] FIG. 5 illustrate exemplary graphical diagram representations of graphs for simulation results of a stator, in accordance with an embodiment of the present disclosure; and
[0017] FIG. 6 illustrates an exemplary flow diagram representation of a method for configuring a stator for an outer-rotor brushless direct current (BLDC) motor, in accordance with an embodiment of the present disclosure.
[0018] Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
DETAILED DESCRIPTION
[0019] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
[0020] In the present document, the word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or implementation of the present subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
[0021] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[0022] The terms “comprises”, “comprising”, “includes”, “including” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
[0024] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
[0025] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the invention. In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0026] In the present disclosure, terms such as “upper”, “lower”, “left”, “right”, “front”, “rear”, “vertical”, “horizontal”, “side”, “bottom”, and the like, may refer to an orientation or a positional relationship based on that shown in the drawings, and are merely relational terms, which are used for convenience in describing structural relationships of various components or elements of the present invention, and do not denote any one of the components or elements of the present disclosure, and are not to be construed as limiting the present invention.
[0027] In the present disclosure, terms such as “fixedly attached”, “movably coupled”, “connected”, “coupled”, and the like are to be construed broadly and refer to either a fixed connection, or a movable, or an integral or removable connection; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the terms in the present disclosure can be determined according to circumstances by a person skilled in the relevant art or the art and is not to be construed as limiting the present disclosure.
[0028] Embodiments of the present disclosure provide a stator for an outer-rotor brushless direct current motor and method thereof. The stator includes a laminated stator core defining a central axis and comprising a plurality of circumferentially distributed stator teeth extending radially outward and separated by a corresponding plurality of stator slots. Further, the stator includes a plurality of concentrated windings disposed in the plurality of stator slots. The plurality of stator slots and a number of poles of permanent magnets associated with an outer rotor positioned radially outward of the stator include a fractional-slot concentrated winding configuration with a number of slots per pole of a pre-defined value. A plurality of coils of each of the plurality of concentrated windings are concentrated corresponding to each of the plurality of stator teeth. Each of the plurality of stator teeth includes a tooth body extending radially from a stator yoke and a tooth tip disposed at a radially outer end of the tooth body including an airgap region defining a slot opening. The tooth tip comprises a tooth lip with a pre-determined tooth lip height corresponding to a radial direction relative to the airgap region. The tooth tip defines a slot opening width of the slot opening circumferentially at the airgap region and the tooth lip height radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip. The slot opening width and the tooth lip height are dimensioned to define an airgap permeance profile along a circumferential direction of the stator. Thereby enabling a compact, high-efficiency, and low-cogging torque stator suitable for outer-rotor BLDC motors.
[0029] Referring now to the drawings, and more particularly to FIG. 1 through FIG. 6 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments, and these embodiments are described in the context of the following exemplary system and/or method.
[0030] FIG. 1 illustrates an exemplary schematic diagram representation of a stator 100 for an outer-rotor Brushless Direct Current (BLDC) motor (not shown), in accordance with an embodiment of the present disclosure. Further, FIG. 1 may include a part (a) and a part (b). Further, the part (a) may represent the detailed internal structure/components of the stator 100,and the part (b) may represent the stator 100, depicting a coil overhang 118 configuration. Further, the stator 100 includes primary components such as, a stator yoke 102, plurality of slot liners 104, a stator teeth 106, a plurality of stator slots 108, a plurality of concentrated windings 110, an airgap region 112, a circumferential stator segments 114 (individually referred to as a circumferential stator segment 114-1, 114-2 and 114-3, and collectively referred to as the circumferential stator segments 114), a rotor area 116 and a coil overhang 118.
[0031] Further, the stator yoke 102 forms an annular stator core and serves as a primary low-reluctance magnetic return path adapted to close magnetic flux loops between stator poles and to link magnetic fields generated by the plurality of concentrated windings 110 with permanent magnets positioned at the rotor area 116. The stator yoke 102 may be manufactured using materials, for example, but not limited to, laminated non-oriented silicon steel sheets such as electrical steel grades M19, M27, 50W470, 35W270, or equivalent materials, and the like. Each lamination may include a thickness, for example, within a range of 0.35 mm to 0.5 mm together with inter-lamination insulation structured to reduce eddy current losses. The laminated structure provides a magnetic backbone and a mechanical foundation for a stator assembly.
[0032] The stator teeth 106 or a plurality of circumferentially distributed stator teeth 106 (herein after interchangeably referred to as the stator teeth 106 or the plurality of circumferentially distributed stator teeth 106) extends radially outward from the stator yoke 102 and forms individual magnetic poles of the stator. Each of the plurality of stator teeth 106 concentrates magnetic flux and directs magnetic flux across airgap region 112 towards permanent magnets located at rotor area 116 to generate torque. Each of the plurality of stator teeth 106 further serves as a core about a plurality of coils of each of the plurality of concentrated windings 110, the plurality of coils disposed with a non-overlapping arrangement corresponding to the plurality of stator teeth 106.
[0033] The plurality of concentrated windings 110 remains directly wound about each of the plurality of stator teeth 106 and adopts a fractional-slot concentrated winding configuration, for example, but not limited to, such as a 30-slot / 28-pole arrangement yielding slots per pole of for example, 1.07. The fractional-slot concentrated winding configuration may modify the phase belt distribution and a manner of magnetomotive force harmonics combination, enabling cancellation of selected harmonic orders that otherwise contribute to torque ripple.
[0034] The fractional-slot concentrated winding arrangement further reduces end-turn length requirements, increases slot fill factor, improves copper utilization, and reduces copper losses with an equivalent conductor cross-section relative to distributed winding configurations. The plurality of stator slots 108 may constitute openings formed between adjacent circumferential stator segments 114 of the laminated stator core. The plurality of stator teeth 106 remains defined between adjacent plurality of stator slots 108, each of the plurality of stator teeth 106 extending radially outward from the stator yoke 102. Each of the plurality of stator teeth 106 may remain integrally formed with corresponding circumferential stator segments 114 and bounded circumferentially by the plurality of stator slots 108. The plurality of stator slots 108 may accommodate the active coil sides of the plurality of concentrated windings 110 and may enable the efficient conductor placement together with thermal dissipation from the plurality of concentrated windings 110 during the motor operation.
[0035] Further, the electrical isolation and mechanical protection of the plurality of concentrated windings 110 occur through insertion of a plurality of slot liners 104 within each of the plurality of stator slots 108. The plurality of slot liners 104 may provide the separation between the plurality of concentrated windings 110 and grounded core material including the stator yoke 102 and the plurality of stator teeth 106. The separation may prevent short circuits, reduces conductor abrasion during conductor placement or vibration, and maintains dielectric strength under voltage stress, partial discharge conditions, and thermal cycling.
[0036] The plurality of slot liners 104 may be formed from materials, for example, but not limited to, such as, Nomex aramid paper, Mylar polyester film, composite laminates including Nomex-Mylar-Nomex (NMN), Dacron-Mylar-Dacron (DMD), Nomex-Kapton-Nomex (NKN), polyimide films including Kapton, or any other flexible high-temperature dielectric materials suitable for Class F or Class H insulation systems, and the like.
[0037] Further, at the radially outer extremity, of the plurality of stator teeth 106, lies the airgap region 112, a narrow annular clearance forming a magnetic interface between the stator 100 and an inner surface of rotor area 116. Further the reduction of cogging torque without modification of rotor magnet geometry occurs through airgap permeance shaping achieved by optimized tooth-tip geometry including a pre-determined tooth lip height, and taper profile together with slot opening configuration.
[0038] The tooth lip with a pre-determined tooth lip height controls local magnetic reluctance and defines an airgap permeance profile encountered by rotating permanent magnets at rotor area 116. Further, the reduction of tooth lip height and introduction of taper along the tooth lip may lower the flux concentration peaks, regulate the magnetic saturation within the plurality of stator teeth 106, and reduce the amplitude of cogging torque through smoother reluctance variation during magnet rotation.
[0039] Further, the stator core encompassing the stator yoke 102, the plurality of stator teeth 106, and the plurality of stator slots 108 may be constructed from circumferential stator segments 114, within an exemplary three-segment arrangement. The segmented stamped lamination structure replaces a single full-ring stamping with three or more arc-shaped segments, enabling efficient nesting of stamped pieces during sheet metal processing and substantial reduction of central circular scrap associated with full-ring die configurations.
[0040] Further, the use of smaller segment dies simplifies die structure and reduces manufacturing and maintenance costs, leading to reduced tooling expenditure. Upon the precise assembly of the circumferential stator segments 114 into a complete annular core, equivalent electromagnetic performance and mechanical integrity remain maintained together with improved material utilization. Further, the rotor area 116 may represent an annular volume located radially outward of airgap region 112 and reserved for an outer permanent magnet rotor (not illustrated in figures). The outer permanent magnet rotor carries permanent magnets along an inner circumferential surface facing radially inward toward the stator under an outer-rotor topology.
[0041] Further, during the stator 100 assembly and coil placement, the stator 100 utilizes the fractional-slot concentrated winding configuration. Further, the each of the plurality of coils undergo positioning directly onto each of the plurality of stator teeth 106 and corresponding plurality of stator slots 108, followed by insulation application and resin impregnation to provide electrical isolation, mechanical reinforcement, vibration damping, and environmental protection.
[0042] The assembled stator 100 stack undergoes alignment with an outer permanent magnet rotor positioned at rotor area 116. The absence of rotor skew simplifies magnet mounting, reduces mechanical assembly complexity and associated costs, and improves overall manufacturability.
[0043] Further, the part (b) of FIG. 1 may represent the stator 100 and depicts coil overhang 118 configuration. Further, the part (b) may illustrate the stator assembly with the plurality of concentrated windings 110 including axially protruding coil overhang 118, also referred to as end turns or end windings, extending beyond axial ends of a stator core stack including the stator yoke 102 and the plurality of stator teeth 106. Further, the coil overhang 118 portions provide electrical connection between coil sides located within the plurality of stator slots 108, complete turns for each phase, and support phase interconnections or lead-outs, enabling full electrical operation of the fractional-slot concentrated winding configuration.
[0044] Further, the part (b) illustrates increase in overall axial length and depict an as-assembled configuration prior to optional compaction, trimming, or dimensional reduction processes. Further, the subsequent dimensional reduction may decrease axial length to achieve higher power density and improved accommodation within space-constrained applications including hub motors or direct-drive systems.
[0045] Those skilled in the art will recognize that, for simplicity and clarity, the full structure and operation of all data processing systems suitable for use with the present disclosure are not being depicted or described herein. Instead, only so much of the stator 100 as is unique to the present disclosure or necessary for an understanding of the present disclosure is depicted and described. The remainder of the construction and operation of the stator 100 may conform to any of the various current implementations and practices that were known in the art.
[0046] In an embodiment, the stator 100 may include a laminated stator core defining a central axis. The stator 100 may include a plurality of circumferentially distributed stator teeth 106 extending radially outward and separated by a corresponding plurality of stator slots 108. Further, the stator 100 may include a plurality of concentrated windings 110 disposed in the plurality of stator slots 108.
[0047] In an embodiment, the stator 100 may include the plurality of stator slots 108 and a number of poles of the permanent magnets associated with an outer rotor positioned radially outward of the stator 100. Further, the stator 100 may include a fractional-slot concentrated winding configuration with a number of slots per pole of a pre-defined value. Further, the stator 100 may include a plurality of coils of each of the plurality of concentrated windings 110 are concentrated corresponding to each of the plurality of stator teeth 106. As used herein, a fractional-slot concentrated winding configuration denotes a winding arrangement in which a plurality of coils are concentrated around individual stator teeth (or small groups thereof) such that a coil pitch spans substantially one stator tooth, and a number of stator slots divided by a product of a number of rotor poles and a number of phases yields a non integer value (slots per pole per phase q < 1). This configuration produces short end-windings and high slot fill while enabling tailored harmonic content suitable for permanent magnet machines.
[0048] In an embodiment, each of the plurality of stator teeth 106 includes a tooth body extending radially from a stator yoke 102. Further, the plurality of stator teeth 106 includes a tooth tip disposed at a radially outer end of the tooth body comprising an airgap region 112, defining a slot opening. The tooth tip comprises a tooth lip with a pre-determined tooth lip height corresponding to a radial direction relative to the airgap region 112. As used herein, the tooth body denotes a radially extending portion of a stator tooth that projects from a stator yoke toward an airgap region and that carries the majority of the magnetic flux between the stator yoke and a corresponding tooth tip. The tooth body has a circumferential tooth width measured between adjacent stator slots and a radial length measured from an inner surface of the stator yoke to an interface with the tooth tip. As used herein, a tooth tip denotes a radially outer portion of the stator tooth that is integrally formed with, or joined to, the tooth body at a radially outer end thereof and that is disposed adjacent the airgap region facing the rotor. The tooth tip laterally bounds a slot opening between adjacent teeth and defines, together with neighbouring tooth tips, the local geometry of the airgap permeance profile in the circumferential direction.
[0049] The tooth tip may have a tapering profile in a radial cross section, including at least one of a radially outward taper and a radially inward taper, to control flux fringing and local magnetic saturation. In the context of this disclosure, a tooth lip denotes a radially inwardly projecting portion of the tooth tip that partially closes the stator slot at the airgap region. The tooth lip extends circumferentially on each side of the tooth tip so as to reduce an effective slot opening width and to define, together with an inner surface of the tooth tip, a tooth lip height in the radial direction. The tooth lip is configured to influence airgap permeance and magnetic saturation at a radially inner side of the tooth tip.
[0050] As used herein, a tooth lip height is a radial dimension measured between an inner surface of the tooth tip (or tooth lip) and an adjacent surface of the tooth body or stator slot, along a direction parallel to the central axis of the stator. In one implementation, the tooth lip height is defined as a radial distance between an inner surface of the tooth tip at the slot opening and an inner surface of the tooth body at a transition between the tooth body and the tooth tip, and it determines a radial extent of the material that partially closes the slot opening.
[0051] In an embodiment, the tooth tip defines a slot opening width of the slot opening, circumferentially at the airgap region 112. Furthermore, the tooth tip defines the tooth lip height of the tooth lip, radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip. Further, the tooth tip defines slot opening width, and the tooth lip height are dimensioned to define an airgap permeance profile along a circumferential direction of the stator 100.
[0052] As used herein, the slot opening width is the circumferential distance between facing surfaces of two adjacent tooth tips at the airgap region. In particular, the slot opening width is measured along a circular path concentric with a central axis of the stator, at a radial position corresponding to the airgap between the tooth tips and the rotor.
[0053] In an embodiment, the laminated stator core includes a plurality of laminations stacked along an axial direction. Each lamination is formed from a plurality of circumferential stator segments 114. The plurality of circumferential stator segments 114 are configured to be assembled to form a continuous annular stator core. In an embodiment, the slot opening width is dimensioned relative to the tooth lip height, and the tooth tip defines a non-uniform circumferential airgap permeance profile across each slot opening.
[0054] In an embodiment, the tooth tip includes at least one of a radially outward tapering profile and a radially inward tapering profile in a radial cross-section. The plurality of stator teeth 106 including the tooth lip height are configured to control magnetic saturation. Each of the plurality of coils of each of the concentrated windings 110 is located substantially within at least one of a single stator slot and a pair of adjacent stator slots of the plurality of stator slots 108, and comprises a coil pitch of one stator teeth.
[0055] In an embodiment, each of the plurality of concentrated windings 110 are impregnated with an insulating material such as, but not limited to, epoxy varnish, epoxy resin, polyester varnish, or silicone resin using vacuum pressure impregnation or trickle impregnation techniques to fill inter turn voids and enhance thermal and mechanical integrity, and the like. Each of the plurality of circumferential stator segments 114 includes a portion of each of the plurality of stator teeth 106 and the fractional-slot. The assembled plurality of laminations collectively define a circular stator core comprising the radially outward extending plurality of stator teeth 106.
[0056] FIG. 2 illustrates an exemplary schematic diagram representation of an enlarged sectional view of a portion of a stator 100 shown in FIG. 1, in accordance with an embodiment of the present disclosure. Further, FIG. 2 may include part (a), part (b), and part (c). Further, the part (a) may depict an enlarged sectional view of the stator 100 components with the coil overhang 118, the part (b) may depict an enlarged sectional view of the stator 100 components without the coil overhang 118, and part (c) may depict a further enlarged cross-sectional detail of the tooth assembly.
[0057] Further, the part (a) of the FIG. 1 may include the stator yoke 102, circumferential stator segments 114, with axially protruding coil overhang 118. Further, the coil overhang 118 may protrude axially beyond axial ends of the stator 100 core stack and may connect corresponding plurality of coils of the plurality of concentrated windings 110 disposed within the plurality of stator slots 108. Further, the coil overhang 118 may remain positioned outside the laminated core region at both axial ends of the stator to complete electrical turns of each phase.
[0058] Further, the part (b) of the FIG. 1 may include the plurality of slot liners 104, plurality of stator teeth 106, plurality of stator slots 108, plurality of concentrated windings 110, and airgap region 112. Further, the plurality of concentrated windings 110 may remain confined within an axial length defined by the plurality of stator teeth 106 and the plurality of stator slots 108. Further, the plurality of slot liners 104 may be disposed within the plurality of stator slots 108 to electrically insulate the plurality of concentrated windings 110 from the plurality of stator teeth 106. Further, the airgap region 112 may be defined radially inward of the plurality of stator teeth 106 to enable electromagnetic interaction between stator 100 and rotor.
[0059] Further, the part (c) of the FIG. 1 may include the plurality of stator teeth 106, plurality of stator slots 108 provided with plurality of slot liners 104 and plurality of concentrated windings 110 positioned within the plurality of stator slots 108. Further, each of the plurality of stator slots 108 may be defined between adjacent ones of the plurality of stator teeth 106 and may extend axially along a core length. Further, the plurality of slot liners 104 may be disposed along inner surfaces of the plurality of stator slots 108 to provide electrical insulation between the plurality of concentrated windings 110 and the plurality of stator teeth 106. Further, the plurality of concentrated windings 110 may be accommodated within respective plurality of stator slots 108 in a concentrated configuration around individual ones of the plurality of stator teeth 106, thereby forming phase windings confined within the slot region.
[0060] FIG. 3 illustrates an exemplary schematic diagram representation of an exploded view of a motor components 300 along with stator 100, in accordance with an embodiment of the present disclosure. Further, the exploded view may depict a plurality of motor components arranged along a central shaft axis to represent an assembly sequence and structural interrelationship among the components. Further, the components may include a nut self-locking with collar 302, a locking plate 304, an NCE cover with bearing sub assembly 308, a stator sub assembly 310, a rotor sub assembly with rim 312, a CE cover with bearing sub assembly 314, and a sand guard 316.
[0061] Further, a central stationary shaft may form a fixed, non-rotating axis extending through the center of the motor and may serve as a primary structural reference line for all motor components. Further, the nut self-locking with collar 302 may be positioned toward each end of the central stationary shaft to secure the entire assembly and restrict loosening under vibration or rotational forces. Further, the locking plate 304 may be disposed adjacent each nut self-locking with collar 302 to restrain axial movement and provide positive locking between rotating and stationary parts. Further, the NCE cover with bearing sub assembly 308 may enclose the non-commutating end of the motor, house a bearing supporting the central shaft, and provide protection against environmental contaminants while maintaining smooth rotation. Furthermore, the stator sub assembly 310 may be centrally disposed and may incorporate a segmented stator core including yoke 102, plurality of stator teeth 106, plurality of stator slots 108, plurality of concentrated windings 110, plurality of slot liners 104, and airgap-permeance-shaped tooth tips as described previously. Further, the stator sub assembly 310 may form a stationary electromagnetic element configured to generate a rotating magnetic field.
[0062] Further, the rotor sub assembly with rim 312 may define the outer-rotor structure and may carry permanent magnets along an inner circumferential surface to interact radially with the stator sub assembly 310 across the airgap region 112. Further, the rotor sub assembly with rim 312 may include a rim portion configured for mechanical integration with a driven load, including a wheel rim for hub motor applications.
[0063] Further, the CE cover with bearing sub assembly 314 may enclose the commutating end of the motor, support the shaft via a bearing, and provide structural closure with electrical connections or sensor mounting. Further, the sand guard 316 may shield bearing regions and internal components from ingress of sand, dust, moisture, or other contaminants to enhance durability and reliability.
[0064] Further, the plurality of components may be aligned along the central stationary shaft axis, with the stator sub assembly 310 disposed between the NCE cover with bearing sub assembly 308 and the CE cover with bearing sub assembly 314. Further, the rotor sub assembly with rim 312 may circumferentially surround the stator sub assembly 310 to define the outer-rotor topology. Further, the nut self-locking with collar 302 and locking plate 304 may secure end covers and bearing sub-assemblies to the central stationary shaft, and the sand guard 316 may protect bearing interfaces.
[0065] Further, the exploded view may illustrate a modular outer-rotor BLDC motor design, with the stator sub assembly 310 incorporating fractional-slot concentrated windings 110, segmented stamped laminations, and airgap-permeance-shaped tooth tips integrated efficiently with the rotor sub assembly with rim 312, the NCE cover with bearing sub assembly 308, the CE cover with bearing sub assembly 314, the nut self-locking with collar 302, the locking plate 304, and the sand guard 316. Further, the arrangement may provide high torque density, compact construction, simplified assembly, and suitability for applications including electric vehicle hub motors or direct-drive systems.
[0066] FIG. 4 illustrates an exemplary schematic diagram representation of sectional view of circumferential stator segments 114 of a stator 100, in accordance with an embodiment of the present disclosure. Further, FIG. 4 may include part (a), part (b), and part (c). Further, part (a) of the FIG. 4 may depict a first circumferential stator segment 114-1, the part (b) of the FIG. 4 may depict a second circumferential stator segment 114-2, and the part (c) of the FIG. 4 may depict a third circumferential stator segment 114-3.
[0067] Each part may represent one of the three arc-shaped lamination segments which collectively form the complete annular stator core upon assembly. The individual segments may be designed for efficient nesting during the stamping process from sheet metal, reducing material waste compared to full-ring punching and allowing use of smaller, lower-cost dies. Each segment may include identical plurality of stator teeth 106 and plurality of stator slots 108, with shaped tooth tips for airgap-permeance control, and may feature interlocking or alignment elements at the circumferential ends, such as tabs, notches, or dovetail-like cuts, to ensure precise radial and axial alignment when joined into a full ring. The segmented arrangement may preserve electromagnetic performance, maintain magnetic circuit continuity, and provide mechanical strength after assembly, while improving material utilization and supporting scalable manufacturing for high-volume applications including hub motors.
[0068] The three individual circumferential stator segments 114-1, 114-2, and 114-3 may each form an identical 120° arc-shaped lamination. As assembled end-to-end, the segments may establish the complete annular stator core of the outer-rotor BLDC motor. Each segment may include radially outward-protruding plurality of stator teeth 106 with optimized shaped tips for airgap-permeance shaping to reduce cogging torque, and intervening plurality of stator slots 108 for accommodating plurality of concentrated windings 110. The interlocking or alignment features at the ends of each segment may enable precise stacking, radial positioning, and axial joining, ensuring a continuous magnetic path and structural integrity. Dividing the stator into three smaller arc segments instead of a single full-ring stamping may allow efficient nesting of electrical steel sheets during the punching process, reduce central scrap waste, and permit use of simpler, lower-cost segment-specific tooling with easier manufacturing and maintenance.
[0069] FIG. 5 illustrate exemplary graphical diagram representations of graphs 500 of for simulation results of a stator 100, in accordance with an embodiment of the present disclosure. Further, the graphs 500 may include part (a), part (b), part(c) and part (d). Further, the part (a) may include a cogging torque waveform demonstrating an essentially flat profile at approximately zero Newton-meters, with asymmetry caused by fractional-slot concentrated winding, and a peak-to-peak value corresponding to only 0.4% of the peak torque generated by the motor, indicating minimal vibration and precise control.
[0070] Further, the part (b) may depict the no-load back-electromotive force waveform for Phase A along with harmonic components, with optimized stator stamping reducing higher-order space harmonics of the fractional-slot concentrated winding, and the Fast Fourier Transform showing only the fundamental and a fifth harmonic, contributing to reduced torque ripple.
[0071] Further, the part (c) may present the Fast Fourier Transform spectrum of the back-EMF waveform, highlighting dominant fundamental and negligible higher-order harmonics, validating low harmonic content and reduced acoustic noise.
[0072] Further, the part (d) may illustrate the electromagnetic torque waveform under a rated load of for example, 3.6 kW, exhibiting an average torque of for example, 116.0246 Nm with low peak-to-peak ripple, demonstrating stable torque production, smooth operation, and minimal pulsation supported by optimized stator design and ultra-low cogging torque.
[0073] FIG. 6 illustrates an exemplary flow diagram representation of a method 600 for configuring a stator 100 for an outer-rotor brushless direct current (BLDC) motor, in accordance with an embodiment of the present disclosure.
[0074]
[0075] At step 602, the method 600 may include forming a laminated stator core defining a central axis. The laminated stator core includes a plurality of circumferentially distributed stator tooth 106 extending radially outward from a stator yoke 102 and separated by a corresponding plurality of stator slots 108.
[0076] At step 604, the method 600 may include forming each of the plurality of stator tooth 106 with a tooth body extending radially outward from the stator yoke 102 and a tooth tip disposed at the radially outer end of the tooth body adjacent the airgap region 112.
[0077] At step 606, the method 600 may include forming a slot opening between adjacent tooth tips. The slot opening includes a slot opening width measured circumferentially at the airgap region 112.
[0078] At step 608, the method 600 may include forming each tooth tip with a tooth lip including a predetermined tooth lip height measured radially from the inner radial surface of the tooth body and the inner radial surface of the tooth tip.
[0079] At step 610, the method 600 may include dimensioning the slot opening width together, the predetermined tooth lip height to establish an airgap permeance profile along a circumferential direction of the stator 100. The airgap permeance profile helps lower flux concentration peaks, control saturation levels in the stator teeth, and reduce cogging torque magnitude without altering the permanent magnet structure on the outer rotor.
[0080] At step 612, the method 600 may include associating the plurality of stator slots 108 with a number of poles of permanent magnets on an outer rotor positioned radially outward the stator 100 causing the plurality of stator slots (108) and the number of poles establish a fractional-slot concentrated winding configuration with a number of slots per pole of a predefined value. The predefined number of slots per pole includes for example, approximately 1.07 slots per pole when using 30 slots and 28 poles.
[0081] At step 614, the method 600 may including disposing a plurality of concentrated windings 110 within the plurality of stator slots 108 causing coils of each concentrated winding are concentrated corresponding to respective stator teeth 106. Thereby achieving non-overlapping coil placement, shorter end-turn lengths, higher slot fill factor, better copper usage, and reduced copper losses relative to conventional distributed windings.
[0082] In an embodiment, the method 600 may depict the complete sequence for forming the laminated stator core, shaping the tooth tips and slot openings for airgap permeance control, establishing a fractional-slot concentrated winding configuration, and disposing the windings to achieve low cogging torque, reduced torque ripple, improved copper utilization, and enhanced manufacturability.
[0083] The order in which the method 600 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined or otherwise performed in any order to implement the method 600 or an alternate method. Additionally, individual blocks may be deleted from the method 600 without departing from the spirit and scope of the ongoing description. The method 600 describes, without limitation, the implementation of a stator (100) for an outer-rotor brushless direct current (BLDC) motor and method 600 for configuring stator 100. A person of skill in the art will understand that method 600 may be modified appropriately for implementation in various manners without departing from the scope and spirit of the ongoing description.
[0084] Various embodiments of the present disclosure provide a stator and a method for configuring a stator for an outer-rotor brushless direct current (BLDC) motor. The stator includes a laminated stator core defining a central axis, the laminated stator core including a plurality of circumferentially distributed stator teeth extending radially outward from a stator yoke and separated by a corresponding plurality of stator slots. The stator further comprises a plurality of concentrated windings disposed within the plurality of stator slots, the plurality of stator slots and a number of poles of permanent magnets associated with an outer rotor positioned radially outward of the stator comprising a fractional-slot concentrated winding configuration with a predefined number of slots per pole. The plurality of coils of each concentrated winding are concentrated corresponding to respective stator teeth. Each stator tooth includes a tooth body extending radially from the stator yoke and a tooth tip disposed at a radially outer end of the tooth body adjacent an airgap region, the tooth tip defining a slot opening and including a tooth lip having a pre-determined tooth lip height in a radial direction. The slot opening has a width measured circumferentially at the airgap region, and the tooth lip height is measured radially between an inner surface of the tooth body and an inner surface of the tooth tip. The slot opening width and the tooth lip height are dimensioned to define an airgap permeance profile along the circumferential direction of the stator. The laminated stator core further includes a plurality of laminations stacked along an axial direction, each lamination formed from a plurality of circumferential stator segments, the plurality of circumferential stator segments assembled to form a continuous annular stator core. Each tooth tip may comprise at least one of a radially outward tapering profile and a radially inward tapering profile in a radial cross-section, and the plurality of stator teeth including the tooth lip height are configured to control magnetic saturation. Each coil of each concentrated winding is located substantially within a single stator slot or a pair of adjacent stator slots and has a coil pitch of one stator tooth. Each concentrated winding may be impregnated with insulating material. Each circumferential stator segment comprises a portion of the plurality of stator teeth and supports the fractional-slot winding configuration, and the assembled plurality of laminations collectively define a circular stator core comprising the radially outward extending stator teeth. The method of configuring the stator comprises forming the laminated stator core, forming each stator tooth with a tooth body and tooth tip, forming slot openings between adjacent tooth tips, forming tooth lips on each tooth tip, dimensioning the slot opening width and tooth lip height to establish the airgap permeance profile, associating the stator slots with a number of poles of the outer rotor to establish the fractional-slot concentrated winding configuration, and disposing the plurality of concentrated windings within the plurality of stator slots with coils concentrated corresponding to the respective stator teeth.
[0085] The stator configuration for an outer rotor BLDC motor provides electromagnetic advantages by optimizing the stator stamping geometry rather than relying on rotor-side modifications. By defining the slot opening width and tooth lip height to realize a desired airgap permeance profile, the design mitigates inherent BLDC drawbacks such as elevated cogging torque and torque ripple, resulting in smoother torque production, reduced acoustic noise and improved low-speed controllability. In contrast to many conventional approaches that use skewed or specially shaped rotor magnets, the present approach achieves torque-quality improvement predominantly through stator side geometric optimization of the laminated stator core.
[0086] The use of fractional-slot concentrated windings with one-tooth coil pitch and coils substantially confined to individual stator slots or pairs of adjacent slots further enhances performance and efficiency. This winding configuration reduces end turn length and associated copper losses, thereby improving efficiency and torque density for a given machine volume. In addition, the coordinated interaction between the fractional-slot layout and the shaped tooth tips suppresses undesirable space harmonics in the airgap flux density, which contributes to lower torque pulsations and better dynamic response of the BLDC drive.
[0087] The segmented lamination structure also provides clear manufacturing and assembly benefits. Forming each lamination from circumferential stator segments simplifies tooling for large-diameter outer-rotor stators and facilitates automated winding and impregnation of concentrated coils on individual segments before final assembly into an annular core. This segmented approach may improve dimensional accuracy at the airgap, reduce scrap compared with single piece laminations, and enhance thermal and mechanical robustness after impregnation. Collectively, these advantages make the proposed stator architecture well suited for compact, high torque density outer-rotor BLDC applications that demand smooth, quiet operation and precise control.
[0088] The written description enables any person skilled in the art to make and use the stator and the method, and the scope of the disclosure is defined by the claims, including modifications and equivalent features that do not differ substantially from the literal language of the claims.
[0089] A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the invention. When a single device or article is described herein, it will be apparent that more than one device/article (whether they cooperate) may be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be apparent that a single device/article may be used in place of the more than one device or article or a different number of devices/articles may be used instead of the shown number of devices or programs. The functionality and/or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments of the invention need not include the device itself.
[0090] The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words “comprising”, “having”, “containing”, and “including”, and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
[0091] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.
 
, Claims:CLAIMS:
We claim:
1. A stator (100) for an outer-rotor Brushless Direct Current (BLDC) motor, the stator (100) comprising:
a laminated stator core defining a central axis, comprising a plurality of circumferentially distributed stator teeth (106) extending radially outward and separated by a corresponding plurality of stator slots (108);
a plurality of concentrated windings (110) disposed in the plurality of stator slots (108);
the plurality of stator slots (108) and a number of poles of the permanent magnets associated with an outer rotor positioned radially outward of the stator (100), comprises:
a fractional-slot concentrated winding configuration with a number of slots per pole of a pre-defined value; and
a plurality of coils of each of the plurality of concentrated windings (110) are concentrated corresponding to each of the plurality of stator teeth (106);
wherein each of the plurality of stator teeth (106) comprises:
a tooth body extending radially from a stator yoke (102); and
a tooth tip disposed at a radially outer end of the tooth body comprising an airgap region (112), defining a slot opening, wherein the tooth tip comprises a tooth lip with a pre-determined tooth lip height corresponding to a radial direction relative to the airgap region (112); and
the tooth tip defining:
a slot opening width of the slot opening, circumferentially at the airgap region (112); and
the tooth lip height of the tooth lip, radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip;
wherein the slot opening width, and the tooth lip height are dimensioned to define an airgap permeance profile along a circumferential direction of the stator (100).
2. The stator (100) as claimed in claim 1, wherein the laminated stator core further comprises:
a plurality of laminations stacked along an axial direction;
wherein each lamination is formed from a plurality of circumferential stator segments (114); and
wherein the plurality of circumferential stator segments (114) are configured to be assembled to form a continuous annular stator core.
3. The stator (100) as claimed in claim 1, wherein the slot opening width is dimensioned relative to the tooth lip height, and the tooth tip defines a non-uniform circumferential airgap permeance profile across each slot opening.
4. The stator (100) as claimed in claim 1, wherein the tooth tip comprises at least one of a radially outward tapering profile and a radially inward tapering profile in a radial cross-section.
5. The stator (100) as claimed in claim 1, wherein the plurality of stator teeth (106) including the tooth lip height are configured to control magnetic saturation.
6. The stator (100) as claimed in claim 1, wherein each of the plurality of coils of each of the concentrated windings (110) is located substantially within at least one of a single stator slot and a pair of adjacent stator slots of the plurality of stator slots (108) , and comprises a coil pitch of one stator teeth.
7. The stator (100) as claimed in claim 1, wherein each of the plurality of concentrated windings (110) are impregnated with an insulating material.
8. The stator (100) as claimed in claim 2, wherein each of the plurality of circumferential stator segments (114) comprises a portion of each of the plurality of stator teeth (106) and the fractional-slot.
9. The stator (100) as claimed in claim 2, wherein the assembled plurality of laminations collectively define a circular stator core comprising the radially outward extending plurality of stator teeth (106).
10. A method of configuring a stator (100) for an outer-rotor brushless direct current (BLDC) motor, the method () comprising:
forming a laminated stator core defining a central axis, the laminated stator core comprising a plurality of circumferentially distributed stator tooth (106) extending radially outward from a stator yoke (102) and separated by a corresponding plurality of stator slots (108);
forming each of the plurality of stator tooth (106) with a tooth body extending radially outward from the stator yoke (102), and a tooth tip disposed at a radially outer end of the tooth body adjacent an airgap region (112);
forming a slot opening between adjacent tooth tips, the slot opening comprising a slot opening width measured circumferentially at the airgap region (112);
forming each tooth tip with a tooth lip comprising a predetermined tooth lip height measured radially between an inner radial surface of the tooth body and an inner radial surface of the tooth tip;
dimensioning the slot opening width, the predetermined tooth lip height to establish an airgap permeance profile along a circumferential direction of the stator (100);
associating the plurality of stator slots (108) with a number of poles of permanent magnets of an outer rotor positioned radially outward of the stator (100), causing the plurality of stator slots (108) and the number of poles establish a fractional-slot concentrated winding configuration with a number of slots per pole of a predefined value; and
disposing a plurality of concentrated windings (110) within the plurality of stator slots (108), causing coils of each concentrated winding concentrated corresponding to respective stator teeth (106).