Motor stator
By forming grooves inside the motor stator slots, the problems of decreased magnetic flux density and magnetic saturation are solved, the winding space and magnetic flux density are increased, and the overall performance of the motor is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DELTA ELECTRONICS INC(CN)
- Filing Date
- 2025-04-28
- Publication Date
- 2026-05-05
AI Technical Summary
The flat-bottom design of existing motor stators leads to a decrease in magnetic flux density and space utilization, and is also prone to magnetic saturation problems.
A groove is formed inside the stator slot, with the groove width being approximately half the diameter of the winding. By setting the groove at the outer end of the stator teeth, the winding space is increased, and magnetic saturation is avoided through the design of the inner and outer sides, thereby increasing the magnetic flux density.
The increased winding space improves magnetic flux density and space utilization, while avoiding magnetic saturation and optimizing the overall performance of the motor.
Smart Images
Figure CN224204833U_ABST
Abstract
Description
Technical Field
[0001] This case relates to a motor stator, particularly a motor stator with grooves formed inside the stator slots to provide additional winding space and increase magnetic flux density. Background Technology
[0002] In conventional motors, the stator slots are typically designed with a flat bottom to facilitate wiring and ensure neat winding.
[0003] The yoke width of a motor stator primarily depends on the magnetic saturation condition in the magnetic circuit design. Generally, the region with the smallest yoke width has the highest magnetic flux density and has a significant impact on magnetic reluctance and the overall performance of the motor. In the aforementioned flat-bottomed motor stator design, as the yoke width gradually increases, the magnetic flux density decreases, leading to a reduction in the space utilization of the motor stator. However, excessively reducing the yoke width can also cause magnetic saturation.
[0004] In view of this, it is necessary to provide a motor stator with grooves formed inside the stator slots to provide additional winding space and increase magnetic flux density, while avoiding magnetic saturation, so as to solve the deficiencies of the prior art. Utility Model Content
[0005] One objective of this invention is to provide a motor stator with grooves formed inside the stator slots. The grooves are located at the radially outer ends of the stator teeth, such as the yoke or the shoe portion, to increase the stator slot space and facilitate the placement of additional windings. The width of the grooves is approximately half the diameter of the winding wire, for example, between 0.05 mm and 1.50 mm. This not only allows for the placement of additional windings but also prevents magnetic saturation caused by excessively narrow outer ends.
[0006] Another objective of this invention is to provide a motor stator with grooves formed inside the stator slots. The grooves are formed, for example, by two inner surface structures, with the inner surface near the teeth being flat, allowing for neat winding arrangement and facilitating an increase in the number of windings, thus improving space utilization efficiency. The width of the outer end gradually increases from both ends towards the center. The inner surfaces of the grooves near the two ends of the outer end are approximately parallel to the outer peripheral surface of the motor stator, ensuring that the width of the outer end is approximately consistent near both ends, thereby increasing the overall magnetic flux density of the motor stator while avoiding magnetic saturation. Furthermore, the tooth width in the stator teeth is, for example, between 1.8 and 2.5 times the minimum width of the outer end to achieve optimal magnetic flux density.
[0007] To achieve the aforementioned objective, this invention provides a motor stator including a plurality of stator teeth. Each of the plurality of stator teeth includes a tooth portion, an inner end portion, and an outer end portion. The tooth portion extends along a first direction, has inner and outer ends opposite to each other, and is configured for winding with a wire. The first direction is perpendicular to the circumferential direction. The inner end portion is connected to the inner end of the tooth portion and protrudes outward from two opposite sides of the inner end. The outer end portion is connected to the outer end of the tooth portion and includes an outer body and two outer extension ends. The outer body protrudes outward from two opposite sides of the outer end. The tooth portion is connected between the inner end portion and the outer body. The two outer extension ends are respectively disposed on two opposite sides of the outer body. The outer body includes a first inner surface facing the inner end portion and is connected between the tooth portion and the outer extension ends. The outer extension ends protrude circumferentially and form a first width relative to the first inner surface. The first width is smaller than the diameter of the winding wire.
[0008] In one embodiment, the first width is half the diameter of the winding wire.
[0009] In one embodiment, the first width is between 0.05 mm and 1.50 mm.
[0010] In one embodiment, the inner end is a boot portion and the outer end is a yoke portion. Multiple stator teeth are connected to each other through the outer ends.
[0011] In one embodiment, the inner end is a yoke and the outer end is a boot. Multiple stator teeth are connected to each other through the inner ends.
[0012] In one embodiment, the first inner surface is a plane and is perpendicular to the first direction.
[0013] In one embodiment, the outer peripheral surface of the motor stator has a second width between it and the first inner surface. The second width gradually increases from both ends of the outer body towards the center.
[0014] In one embodiment, the motor stator includes N stator teeth. N is 9, 12, 15, or 18.
[0015] In one embodiment, the end portion includes a second inner surface. The second inner surface faces the inner end portion, and a first angle is formed between the first inner surface and the second inner surface. The first angle is less than 180°.
[0016] In one embodiment, the first angle = 180° - (360° / 2N).
[0017] In one embodiment, a third width exists between the outer peripheral surface of the motor stator and the second inner surface. The third width is not greater than the second width.
[0018] In one embodiment, the tooth has a fourth width. The fourth width is between 1.8 and 2.5 times the third width.
[0019] In one embodiment, the motor stator includes an insulating layer disposed between the stator teeth and the winding. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the motor stator and winding structure according to the first embodiment of this case;
[0021] Figure 2 This is a schematic diagram of the stator teeth and winding structure of the first embodiment of this case;
[0022] Figure 3 This is a schematic diagram of the stator teeth in the first embodiment of this case;
[0023] Figure 4 This is a schematic diagram of the motor stator and winding structure according to the second embodiment of this case;
[0024] Figure 5 This is a schematic diagram of the stator teeth and winding structure of the second embodiment of this case;
[0025] Figure 6 This is a schematic diagram of the stator teeth in the second embodiment of this case.
[0026] [Symbol Explanation]
[0027] 1, 1a: Motor stator
[0028] 10, 10a: Stator teeth
[0029] 11: Teeth
[0030] 111: Inner End
[0031] 112: External end
[0032] 12, 12a: Inner end
[0033] 13, 13a: Outer end
[0034] 131: Outer body
[0035] 131a: First inner surface
[0036] 132: Outer extension end
[0037] 132a: Second inner surface
[0038] 20: Outer perimeter
[0039] 30: Insulation layer
[0040] 9: Winding
[0041] C: Axis
[0042] W1: First width
[0043] W2: Second width
[0044] W3: Third Width
[0045] W4: Fourth Width
[0046] X, Y: Axes
[0047] θ1: First angle Detailed Implementation
[0048] Some typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different forms, all of which do not depart from the scope of this invention, and the descriptions and drawings herein are for illustrative purposes only and not for limiting the invention. For example, if the following description of this invention places a first feature on or above a second feature, it indicates that it includes embodiments where the first and second features are in direct contact, and also includes embodiments where additional features can be placed between the first and second features, so that the first and second features may not be in direct contact. Furthermore, different embodiments in this invention may use repeated reference numerals and / or markings. These repeated reference numerals and / or markings are for simplification and clarity purposes and are not intended to limit the relationships between the various embodiments and / or the described appearance structures. Moreover, to facilitate the description of the relationship between one component or feature in the drawings and another component(s) or feature(s), spatially related terms such as "inner," "outer," "left," "right," "upper," "lower," and similar terms may be used. In addition to the orientations illustrated in the accompanying drawings, spatially relevant terms are used to cover different orientations of the device in use or operation. The device may be positioned in other orientations (e.g., rotated 90 degrees or located in other orientations), and the spatially relevant terms used will be interpreted accordingly. When a component is referred to as being "connected" or "coupled" to another component, it may be directly connected to or coupled to the other component, or there may be intervening components. Although the numerical ranges and parameters of the broad scope of this application are approximate, the values are stated as precisely as possible in specific examples. It should be understood that although terms such as "first," "second," etc., may be used in the claims to describe different components, these components should not be limited by these terms, and the components described accordingly in the embodiments are represented by different component symbols. These terms are used to distinguish different components; for example, a first component may be referred to as a second component. Similarly, a second component may also be referred to as a first component without departing from the scope of the embodiments. The term "and / or" in the specification includes any or all combinations of one or more of the related listed items. The term "approximately" refers to an average value within a standard error range generally accepted by those skilled in the art. Unless explicitly stated in the operational / working examples or otherwise, all numerical ranges, quantities, values, and percentages (e.g., angles, durations of time, temperatures, operating conditions, quantity ratios, etc.) disclosed herein should be understood to be modified by the terms "approximately" or "substantially" throughout the embodiments. Therefore, unless otherwise stated, the numerical parameters stated herein and in the claims are approximate values that may vary as needed. For example, the significant digits of each numerical parameter should be interpreted at least by applying ordinary rounding. Ranges may be expressed herein as from one endpoint to another or between two endpoints. Unless otherwise stated, all ranges disclosed herein include endpoints.
[0049] Please refer to Figures 1 to 3 . Figure 1 This is a schematic diagram of the motor stator and winding structure of the first embodiment of this case. Figure 2 This is a schematic diagram of the stator teeth and winding structure of the first embodiment of this case. Figure 3This is a schematic diagram of the stator teeth structure according to the first embodiment of this invention. In this embodiment, the motor stator 1 includes a plurality of stator teeth 10, arranged in a ring around the shaft center C. In this embodiment, the plurality of stator teeth 10 are formed by stacking laminations, for example, but this invention is not limited to this. Each of the plurality of stator teeth 10 includes a tooth portion 11, an inner end portion 12, and an outer end portion 13. The tooth portions 11 of the plurality of stator teeth 10 are radially connected to the corresponding inner end portion 12 and outer end portion 13. In this embodiment, the motor stator 1 is an outer stator, assembled and arranged radially outside the inner rotor (not shown) to form a motor structure. The inner end portion 12 is a boot portion, and the outer end portion 13 is a yoke portion. The plurality of stator teeth 10 are connected to each other through the outer end portions 13. The inner end portions 12 of adjacent stator teeth 10 are spaced apart to form an opening for the winding wire 9 to pass through during the winding operation. In this embodiment, each tooth 11 extends along a first direction (Y-axis direction) between an inner end 12 and an outer end 13, and is configured for winding with a winding thread 9. Each tooth 11 has an inner end 111 and an outer end 112 that are opposite to each other in the radial direction (i.e., the first direction), with the outer end 112 located radially outside the inner end 111. The stator teeth 10 are arranged symmetrically about the tooth 11, for example. In this embodiment, the winding of the winding thread 9 is, for example, arranged in a row along the first direction (Y-axis direction) on the left and right sides of the tooth 11, and then wound sequentially from the inside to the outside in the same manner. The first direction (Y-axis direction) is perpendicular to the circumferential direction. In this embodiment, the inner end 12 is connected to the inner end 111 of the tooth 11 and protrudes outward from the left and right sides of the inner end 111, respectively. The outer end 13 is located radially outside the inner end 12. The outer end portion 13 connects to the outer end 112 of the tooth portion 11 and includes an outer body 131 and two outer extension ends 132. The outer body 131 protrudes outward from the left and right sides of the outer end 112, respectively. The tooth portion 11 is connected, for example, along a first direction (Y-axis direction) between the inner end portion 12 and the outer body 131 of the outer end portion 13. The two outer extension ends 132 are respectively disposed on the left and right sides of the outer body 131. The outer body 131 includes a first inner surface 131a, which faces the inner end portion 12 and connects between the tooth portion 11 and the outer extension ends 132. The outer extension ends 132 protrude circumferentially and form a first width W1 relative to the first inner surface 131a. The first width W1 is smaller than the diameter of the winding 9. Preferably, the first width W1 is approximately half the diameter of the winding 9, for example, the first width W1 is between one-third and two-thirds of the diameter of the winding 9. Specifically, the first width W1 is the vertical distance between the lowest point of the outer extension end 132 and the first inner surface 131a. In this embodiment, the wire diameter of the winding 9 is, for example, between approximately 0.10 mm and 3.00 mm, and the first width W1 is, for example, between approximately 0.05 mm and 1.50 mm. This allows the motor stator 1 to increase magnetic flux density by adding additional windings, thereby increasing space utilization.It should be emphasized that the first width W1 and the applicable winding 9 specifications in this case are not limited to these, but can be adjusted according to actual application requirements.
[0050] In this embodiment, the first inner surface 131a is, for example, a plane and is perpendicular to the first direction (Y-axis direction), that is, perpendicular to the left and right sides of the tooth 11. A second width W2 exists between the outer peripheral surface 20 of the motor stator 1 and the first inner surface 131a. The second width W2 gradually increases from both ends of the outer body 131 towards the center. The outer peripheral surface 20 of the motor stator 1 is, for example, an annular shape centered on the shaft center C. In this embodiment, the outer extended end 132 includes a second inner surface 132a. The second inner surface 132a is, for example, a plane. The second inner surface 132a faces the inner end 12, and the first inner surface 131a connects to the second inner surface 132a. A first angle θ1 exists between the first inner surface 131a and the second inner surface 132a. The first angle θ1 is less than 180°. By setting the first inner surface 131a and the second inner surface 132a to have an included angle, the first inner surface 131a and the second inner surface 132a form a groove. The grooves formed by the planar structure help to arrange the windings neatly, thereby increasing the number of windings and improving space utilization efficiency.
[0051] In this embodiment, the first angle θ1 between the first inner surface 131a and the second inner surface 132a is 180° - (360° / 2N), where N is the number of stator teeth 10 in the motor stator 1. Since the number of stator teeth 10 in the motor stator 1 in this embodiment is nine, the first angle θ1 between the first inner surface 131a and the second inner surface 132a is 180° - (360° / 18) = 160°. In other embodiments, the number of stator teeth 10 in the motor stator 1 is, for example, twelve, fifteen, or eighteen, and the first angle θ1 is, for example, 165°, 168°, or 170°. It should be emphasized that the number of stator teeth 10 and the first angle θ1 in the motor stator 1 in this embodiment are not limited to these and can be adjusted according to actual application requirements. In this embodiment, a third width W3 exists between the outer peripheral surface 20 of the motor stator 1 and the second inner surface 132a. The third width W3 is not greater than the second width W2. In other words, the width of the outer extension end 132 of the outer end portion 13 (yoke) is not greater than the width of the outer body 131. By designing the angle between the first inner surface 131a and the second inner surface 132a, the second inner surface 132a is approximately parallel to the outer peripheral surface 20, so that the width of the outer extension end 132 of the outer end portion 13 is approximately consistent, thereby increasing the overall magnetic flux density of the motor stator 1 and avoiding magnetic saturation.
[0052] In this embodiment, the tooth 11 has a fourth width W4. The fourth width W4 is, for example, between 1.8 and 2.5 times the third width W3, so that the outer extension end 132 of the outer end 13 has a near-saturation magnetic flux density, improving utilization efficiency. The motor stator 1 also includes, for example, an insulating layer 30 disposed between the stator teeth 10 and the winding 9. In this embodiment, the insulating layer covers, for example, the first inner surface 131a, the second inner surface 132a, the left and right sides of the tooth 11, and the upper side of the inner end 12, to prevent electrical connection between the motor stator 1 and the winding 9. The thickness of the insulating layer 30 is, for example, uniform, ensuring that the winding 9 is neatly arranged.
[0053] Please refer to Figures 4 to 6 . Figure 4 This is a schematic diagram of the motor stator and winding structure of the second embodiment of this case. Figure 5 This is a schematic diagram of the stator teeth and winding structure of the second embodiment of this case. Figure 6This is a schematic diagram of the stator teeth structure according to the second embodiment of this invention. In this embodiment, the motor stator 1a includes a plurality of stator teeth 10a, arranged in a ring around the shaft center C. In this embodiment, the plurality of stator teeth 10a are formed by stacking laminations, for example, but this invention is not limited to this. Each of the plurality of stator teeth 10a includes a tooth portion 11, an inner end portion 12a, and an outer end portion 13a. The motor stator 1a is an inner stator, assembled and arranged radially inside the outer rotor (not shown) to form a motor structure. The tooth portions 11 of the plurality of stator teeth 10a are radially connected to the corresponding inner end portion 12a and outer end portion 13a. In this embodiment, the inner end portion 12a is a yoke portion, and the outer end portion 13a is a boot portion. The plurality of stator teeth 10a are connected to each other through the inner end portions 12a. The outer end portions 13a of adjacent stator teeth 10a are spaced apart to form openings for the winding wire 9 to pass through during the winding operation. In this embodiment, each tooth 11 extends along a first direction (Y-axis direction) between an inner end 12a and an outer end 13a, and is configured for winding with the winding wire 9. Each tooth 11 has an inner end 111 and an outer end 112 that are opposite to each other in the radial direction (i.e., the first direction), and the outer end 112 is located radially outside the inner end 111. The stator teeth 10a are arranged symmetrically about the tooth 11. In this embodiment, the winding method of the winding wire 9 is, for example, to first arrange them in a row along the first direction (Y-axis direction) on the left and right sides of the tooth 11, and then to wind them sequentially from the inside to the outside in the same manner. The first direction (Y-axis direction) is perpendicular to the circumferential direction. In this embodiment, the inner end 12a is connected to the inner end 111 of the tooth 11 and protrudes outward from the left and right sides of the inner end 111 respectively. The outer end 13a is located radially outside the inner end 12a. The outer end portion 13a connects to the outer end 112 of the tooth portion 11 and includes an outer body 131 and two outer extension ends 132. The outer body 131 protrudes outward from the left and right sides of the outer end 112, respectively. The tooth portion 11 is connected, for example, along a first direction (Y-axis direction) between the inner end portion 12a and the outer body 131 of the outer end portion 13a. The two outer extension ends 132 are respectively disposed on the left and right sides of the outer body 131. The outer body 131 includes a first inner surface 131a, which faces the inner end portion 12a and connects between the tooth portion 11 and the outer extension ends 132. The outer extension ends 132 protrude circumferentially and form a first width W1 relative to the first inner surface 131a. The first width W1 is smaller than the diameter of the winding 9. Preferably, the first width W1 is approximately half the diameter of the winding 9, for example, the first width W1 is between one-third and two-thirds of the diameter of the winding 9. Specifically, the first width W1 is the vertical distance between the lowest point of the outer extension end 132 and the first inner surface 131a. In this embodiment, the wire diameter of the winding 9 is, for example, between approximately 0.10 mm and 3.00 mm, and the first width W1 is, for example, between approximately 0.05 mm and 1.50 mm.This allows the motor stator 1a to have additional windings, thereby increasing magnetic flux density and space utilization. It should be emphasized that the first width W1 and the applicable winding specifications 9 are not limited to these and can be adjusted according to actual application requirements.
[0054] In this embodiment, the first inner surface 131a is, for example, a plane and is perpendicular to the first direction (Y-axis direction), that is, perpendicular to the left and right sides of the tooth 11. A second width W2 exists between the outer peripheral surface 20 of the motor stator 1a and the first inner surface 131a. The second width W2 gradually increases from both ends of the outer body 131 towards the center. The outer peripheral surface 20 of the motor stator 1a is, for example, an annular shape centered on the shaft center C. In this embodiment, the outer extended end 132 includes a second inner surface 132a. The second inner surface 132a is, for example, a plane. The second inner surface 132a faces the inner end 12a, and the first inner surface 131a connects to the second inner surface 132a. A first angle θ1 exists between the first inner surface 131a and the second inner surface 132a. The first angle θ1 is less than 180°. By setting the first inner surface 131a and the second inner surface 132a to have an included angle, the first inner surface 131a and the second inner surface 132a form a groove. The grooves formed by the planar structure help to arrange the windings neatly, thereby increasing the number of windings and improving space utilization efficiency.
[0055] In this embodiment, the first angle θ1 between the first inner surface 131a and the second inner surface 132a is 180° - (360° / 2N), where N is the number of stator teeth 10a in the motor stator 1a. Since the number of stator teeth 10a in the motor stator 1a in this embodiment is nine, the first angle θ1 between the first inner surface 131a and the second inner surface 132a is 180° - (360° / 18) = 160°. In other embodiments, the number of stator teeth 10a in the motor stator 1a is, for example, twelve, fifteen, or eighteen, and the first angle θ1 is, for example, 165°, 168°, or 170°. It should be emphasized that the number of stator teeth 10a and the first angle θ1 in the motor stator 1a in this embodiment are not limited to these and can be adjusted according to actual application requirements. In this embodiment, a third width W3 exists between the outer peripheral surface 20 of the motor stator 1a and the second inner surface 132a. The third width W3 is not greater than the second width W2. In other words, the width of the outer extension end 132 of the outer end 13a (boot part) is not greater than the width of the outer body 131. Through the angle design between the first inner surface 131a and the second inner surface 132a, the second inner surface 132a is approximately parallel to the outer peripheral surface 20, so that the width of the outer extension end 132 of the outer end 13a is approximately consistent, thereby increasing the overall magnetic flux density of the motor stator 1a and avoiding magnetic saturation.
[0056] In this embodiment, the tooth 11 has a fourth width W4. The fourth width W4 is, for example, between 1.8 and 2.5 times the third width W3, so that the outer extension end 132 of the outer end 13a has a near-saturation magnetic flux density, improving utilization efficiency. The motor stator 1a also includes, for example, an insulating layer 30 disposed between the stator teeth 10a and the winding 9. In this embodiment, the insulating layer covers, for example, the first inner surface 131a, the second inner surface 132a, the left and right sides of the tooth 11, and the upper side of the inner end 12a, to prevent electrical connection between the motor stator 1a and the winding 9. The thickness of the insulating layer 30 is, for example, uniform, ensuring that the winding 9 is neatly arranged.
[0057] In summary, this invention provides a motor stator with grooves formed inside the stator slots. The grooves are located at the radially outer ends of the stator teeth, such as the yoke or the shoe portion, to increase stator slot space and facilitate the placement of additional windings. The width of the groove is approximately half the diameter of the winding, for example, between 0.05 mm and 1.50 mm. This not only allows for additional windings but also avoids magnetic saturation due to excessively narrow outer ends. The groove is formed, for example, by two inner surface structures, with the inner surface near the teeth being flat, allowing for neat winding arrangement and increasing the number of windings, thus improving space utilization efficiency. The width of the outer ends gradually increases from both ends towards the center. The inner surfaces of the groove near the two ends of the outer ends are approximately parallel to the outer peripheral surface of the motor stator, ensuring that the width of the outer ends is approximately consistent near both ends, thereby increasing the overall magnetic flux density of the motor stator while avoiding magnetic saturation. Furthermore, the tooth width in the stator teeth is, for example, between 1.8 and 2.5 times the minimum width of the outer ends to achieve optimal magnetic flux density.
[0058] This case may be modified in various ways by those skilled in the art, but all modifications shall not fall outside the scope of protection sought by the appended claims.
Claims
1. A motor stator, characterized in that, It includes a plurality of stator teeth, wherein each of the plurality of stator teeth includes: A toothed portion extends along a first direction, has an inner end and an outer end opposite to each other, and is configured for winding a wire, wherein the first direction is perpendicular to a circumferential direction; An inner end portion, connected to the inner end of the tooth portion, and protruding outward from two opposite sides of the inner end; and An outer end portion is connected to the outer end of the tooth portion and includes an outer body and two outer extension ends, wherein the outer body portion protrudes outward from two opposite sides of the outer end portion, the tooth portion is connected between the inner end portion and the outer body portion, and the two outer extension ends are respectively disposed on two opposite sides of the outer body portion, wherein the outer body portion includes a first inner surface, the first inner surface is facing the inner end portion and is connected between the tooth portion and the outer extension ends, wherein the outer extension ends protrude circumferentially and form a first width relative to the first inner surface, the first width being smaller than the diameter of the winding wire.
2. The motor stator as described in claim 1, characterized in that, The first width is half the diameter of the winding.
3. The motor stator as described in claim 1, characterized in that, The first width is between 0.05mm and 1.50mm.
4. The motor stator as described in claim 1, characterized in that, The inner end is a boot portion, the outer end is a yoke portion, and the plurality of stator teeth are connected to each other through the outer end.
5. The motor stator as described in claim 1, characterized in that, The inner end is a yoke, the outer end is a boot, and the plurality of stator teeth are connected to each other through the inner end.
6. The motor stator as described in claim 1, characterized in that, The first inner surface is a plane and is perpendicular to the first direction.
7. The motor stator as described in claim 1, characterized in that, The motor stator has a second width between an outer peripheral surface and the first inner surface, and the second width gradually increases from the two opposite sides of the outer body toward the center.
8. The motor stator as described in claim 1, characterized in that, The motor stator includes N stator teeth, where N is 9, 12, 15 or 18.
9. The motor stator as described in claim 8, characterized in that, The outer extension includes a second inner surface facing the inner end, and the first inner surface and the second inner surface have a first angle, wherein the first angle is less than 180°.
10. The motor stator as described in claim 9, characterized in that, The first angle = 180° - (360° / 2N).
11. The motor stator as described in claim 9, characterized in that, The motor stator has a second width between an outer peripheral surface and a first inner surface, and a third width between the outer peripheral surface and the second inner surface, wherein the third width is not greater than the second width.
12. The motor stator as described in claim 11, characterized in that, The tooth has a fourth width, which is between 1.8 and 2.5 times the third width.
13. The motor stator as described in claim 1, characterized in that, The motor stator includes an insulating layer disposed between the stator teeth and the winding.