DESC:SURFACE PERMANENT MAGNET MOTOR
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202221056419 filed on 30/09/2022, the entirety of which is incorporated herein by a reference. 5
TECHNICAL FIELD
The present disclosure generally relates to an electrical motor. Particularly, the present disclosure relates to a surface permanent magnet motor.
BACKGROUND
Permanent magnet motors are widely used in multiple industrial and automotive 10 applications. The stator is a stationary part of the permanent magnet motor and consists of a stator core, and a stator winding. The main function of the stator is to generate a rotating magnetic field. The stator structure is generally a tooth-yoke integrated structure, and the manufacturing cost is high. Meanwhile, the tooth-yoke integrated structure makes winding the stator coil difficult and increases damage to 15 insulation during the winding process. Thus, the winding arrangement in a tooth-yoke integrated structure is complex, and hence installing windings in the desired location in such a stator is a difficult task.
Generally, the formed coil is of an inverted trapezoidal structure, the upper side of the formed coil is wide, the lower side of the formed coil is narrow, and the tooth 20 part of the integrated iron core is also wide at the upper side and narrow at the lower side of the formed coil. Hence, during the coil insertion process, the coil is inserted from the narrow end, the process becomes complex and may result in damage to the insulation.
Furthermore, while the coil is inserted from the narrow end of the slot, the slot fill 25 factor is lower as the wider portion of the slot is not completely utilized. Specialized
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coil designs, such as wave windings or overlapping windings, are specifically designed to fit within the slot dimensions more efficiently than traditional windings to increase the slot fill factor. However, the usage of specialized coil designs leads to increased heat generation within the stator.
Moreover, the surface permanent magnet motors suffer from the problem of magnet 5 falloff during the operation of the motor. Usually, the magnets are securely bonded or attached to the rotor through adequate adhesives and bonding techniques. The mechanical stresses and vibrations within the rotor result in the occurrence of magnet fall-off. Furthermore, the magnet falloff causes mechanical damage to the components of the motor. Traditionally, a magnet cover is utilized to prevent the 10 magnet falloff. However, the magnet cover increases the air gap between the rotor assembly and the stator assembly resulting in reduced efficiency of the rotor.
Therefore, there exists a need for an improved motor that overcomes one or more problems associated as set forth above.
SUMMARY 15
An object of the present disclosure is to provide a surface permanent magnet motor with an improved design.
In accordance with the first aspect of the present disclosure, there is provided a surface permanent magnet motor comprising a stator assembly, a rotor assembly, and a shaft for mounting the rotor assembly. The stator assembly comprises a stator 20 ring and a teeth ring. The teeth ring is removably accommodated within the stator ring. The rotor assembly comprises a rotor core and a plurality of magnets mounted on the rotor core.
The present disclosure provides a surface permanent magnet motor with an improved design. The motor as disclosed in the present disclosure is advantageous 25 in terms of providing higher flux density by reducing the air gap. The air gap is further reduced by eliminating the requirement of a magnet sleeve that holds the
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magnet along the rotor assembly. Furthermore, the disclosed surface permanent magnet motor facilitates the assembling and maintenance process by reducing the complexity of assembly. The disclosed motor is advantageous in terms of preventing magnet falloff. The disclosed motor is advantageous in terms of providing an improved fill factor for the stator assembly. 5
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being 10 combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended 15 drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers. 20
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figure 1 illustrates an exploded view of a surface permanent magnet motor, in accordance with an embodiment of the present disclosure.
Figure 2 illustrates an exploded view of a stator assembly, in accordance with an 25 embodiment of the present disclosure.
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Figure 3 illustrates an exploded view of a rotor assembly, in accordance with another aspect of the present disclosure.
Figure 4 illustrates a perspective view of a rotor assembly, in accordance with another aspect of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an 5 item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing. 10
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also 15 possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a surface permanent magnet motor and is not intended to represent the only forms that may be developed or utilized. The description sets forth the various structures and/or functions in 20 connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein 25 are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
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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 particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives 5 falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, or system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed 10 or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, 15 reference is made to the accompanying drawings 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 20 present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the description 25 with unnecessary detail.
As used herein, the terms “motor”, “surface permanent magnet motor”, “SPM motor”, “permanent magnet motor” and “SPM” are used interchangeably and refer to type of synchronous electric motor in which the permanent magnets are attached
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to the surface of the rotor, in a radial or axial arrangement. The magnets may be attached to the rotor by means of adhesives or mechanical fasteners. The magnets generate a magnetic field that interacts with the magnetic flux generated by the stator windings to produce the rotational motion of the rotor. The permanent magnet motor has high efficiency, and compact design and is suitable for applications such 5 as electric vehicles (EVs) and robotics.
As used herein, “stator”, “stator structure” and “stator assembly” are used interchangeably and refer to the stationary part of a motor that houses the motor windings, designed to create a rotating magnetic field when an electrical current is applied to the windings. The magnetic field produced by the stator interacts with 10 the permanent magnets on the rotor to induce rotation. The stator acts as a field magnet. The design of the stator is an important factor in deciding the performance of the motor such as its efficiency, power output, and torque.
As used herein, the term “teeth ring” refers to the plurality of stator teeth being arranged in a ring-shaped structure for holding the field windings in the stator 15 assembly. The teeth ring is made of a permeable material, such as laminated iron or steel to shape and concentrate the magnetic field within the stator.
As used herein, the term “stator ring” refers to the circular structure with inward projections to acquire the complementary outward projections of the teeth ring for firmly holding the teeth ring. The stator ring provides a closed magnetic circuit path 20 for the magnetic flux generated in the stator assembly. The stator ring guides and directs the magnetic field lines to interact with the rotor's magnets and serves as a structural support for the motor as well.
As used herein, the term “inner face” refers to the surface area of a teeth ring directed radially inwards towards the rotor. 25
As used herein, the term “outer face” refers to the surface area of the teeth ring directed radially outwards towards the stator ring. The outer face comprises a raised
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or extended portion of teeth, designed to engage and lock on the inner portion of the stator ring.
As used herein, the terms “stator tooth”, and “stator teeth” are used interchangeably and refer to the tooth-like projections or raised portions of the stator core for holding the conductive windings. The stator teeth also help to reduce eddy currents and 5 hysteresis losses in the motor or generator.
As used herein, the term “stator coil” refers to the winding of insulated copper wire wrapped around the stator tooth for generating magnetic flux in the stator assembly.
As used herein, the term “plurality of slots” refers to vertical cutouts in the teeth ring face facing toward the rotor assembly. 10
As used herein, the term “notches” refers to the depressions on the stator ring to accommodate and firmly fit on the complementary locking protrusions of the outer face of the stator teeth.
As used herein, the term “inner surface” refers to the inner cylindrical surface of the stator ring facing the outer face of the teeth ring for confining and directing the 15 magnetic field within the motor. The inner surface is typically made from materials with high magnetic permeability, such as iron or other ferromagnetic alloys, and in addition, contains means for fixing teeth ring in proper location and orientation around the rotor.
As used herein, “rotor” and “rotor assembly” are used interchangeably and refer to 20 the rotating part of the electric motor that generates a magnetic field through permanent magnets, for interacting with the stator’s magnetic field for the generation of the torque on the rotor. The rotor serves as the structural support for the permanent magnets and provides a path for the magnetic flux to circulate within the rotor. The rotor core is often made of ferromagnetic materials like laminated 25 iron or steel sheets. These materials have high magnetic permeability, which helps concentrate and direct the magnetic field. The physical dimensions of the rotor,
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including diameter and length, physical size determine the power output of the motor.
As used herein, the term “rotor core” refers to the central component of the rotor that supports and houses the permanent magnets. The rotor core is typically made from a magnetic material, such as laminated iron or steel to concentrate and direct 5 the magnetic flux generated by the magnets.
As used herein, the term “fastening strip” refers to a metal piece used for accommodating two adjacent magnets on the rotor core in appropriate alignment and location, for assisting in secured fastening of the magnets.
As used herein, the term “fastening means” refers to the mechanisms or components 10 for securely fixing and maintaining the fastening strips in the appropriate location on the rotor core. The choice of fastening means depends on factors such as the motor's design, intended application, and the specific characteristics of the permanent magnets being used.
As used herein, the terms “permanent magnet” and “magnet” are used 15 interchangeably and refer to pieces of permanent magnets held in the curved surface of the rotor’s core to generate constant magnetic flux in the rotor for interaction with the magnetic field of the stator. The magnets are typically made from materials with strong magnetic properties, such as neodymium-iron-boron (NdFeB) or samarium-cobalt (SmCo). 20
As used herein, the term “groove” refers to the shallow, elongated depressions or channels formed into the surface on each side of magnets to accommodate and hold the fastening strips on the curved surface of the rotor core.
Figure 1, in accordance with an embodiment, describes a surface permanent magnet motor 100 comprising a stator assembly 102, a rotor assembly 104, and a 25 shaft 114 for mounting the rotor assembly 104. The stator assembly 102 comprises a stator ring 104 and a teeth ring 106. The teeth ring 106 is removably
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accommodated within the stator ring 104. The rotor assembly 108 comprises a rotor core 110 and a plurality of magnets 112 mounted on the rotor core 110.
The present disclosure provides a surface permanent magnet motor 100 with an improved design. The motor 100 as disclosed in the present disclosure is advantageous in terms of providing higher flux density by reducing the air gap. The 5 air gap is further reduced by eliminating the requirement of a magnet sleeve that holds the magnet 112 along the rotor assembly 108. Furthermore, the surface permanent magnet motor 100 facilitates the assembling and maintenance process by reducing the complexity of assembly. The motor 100 is advantageous in terms of preventing magnet falloff. The motor 100 is advantageous in terms of providing 10 an improved fill factor of the stator assembly 102.
In an embodiment, the teeth ring 106 comprises a plurality of stator teeth 116, wherein each of the stator tooth 116 comprises an inner face 116a facing towards the rotor assembly 108 and an outer face 116b facing away from the rotor assembly 108. It is to be understood that the plurality of stator teeth 116 are adjacent to one 15 another in the teeth ring 106 for the generation of evenly distributed and desired magnetic field around the rotor assembly 108.
In an embodiment, each of the stator tooth 116 receives a stator coil along the length of the stator tooth 116 from the outer face 116b. It is to be understood that the stator coil is wound around the length of the stator tooth 116 from the outer face 116b to 20 the inner face 116b. Beneficially, such a design of the stator tooth 116 that receives the stator coil from the outer face 116b increases the fill factor of the stator assembly 102.
In an embodiment, the inner face 116a of each of the stator tooth 116 comprises a plurality of slots 120 to reduce cogging torque. It is to be understood that the 25 plurality of slots 120 are designed and positioned such that it reduces the cogging torque during the rotation of the rotor assembly 108.
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In an embodiment, the outer face 116b of each of the stator tooth 116 comprises a locking protrusion 122. Beneficially, the locking protrusion 122 is provided in each stator tooth 116 in appropriate shape and size to achieve a firm assembly 102 with the stator ring 104.
In an embodiment, the stator ring 104 comprises a plurality of notches 124 on inner 5 surface, wherein each of the notch 124 receives the locking protrusion 122 of the stator tooth 116 for removably accommodating the teeth ring 106 within the stator ring 104 to form the stator assembly 102. It is to be understood that the plurality of the locking protrusions 122 removably fits in the notches 124. Beneficially, the removable accommodation of the teeth ring 106 within the stator ring 104 allows 10 for the quick assembly and disassembly of the stator assembly 102.
In an embodiment, the rotor assembly 108 comprises a plurality of fastening strips 126, and wherein each of the fastening strip 126 comprises a fastening means 128. Beneficially, the combination of the plurality of fastening strips 126 and the fastening means 128 enables removable fixing of the plurality of magnets 112 on 15 the rotor core 110 and also prevents the falloff of the plurality of magnets 112 during the operation of the motor 100.
In an embodiment, the plurality of magnets 112 comprises at least one groove 130 on each side of the plurality of magnets 112. In a specific embodiment, the two adjacent magnets 112 receive the fastening strip 128 in the grooves 130 for holding 20 the adjacent magnets 112 together. Beneficially, the fastening strip 128 firmly fits in the grooves 130 for holding the adjacent magnets 112 together on the rotor core 110.
In an embodiment, the plurality of fastening strips 126 are secured on the rotor core 110 along with the plurality of magnets 112 using the fastening means 128 to form 25 the rotor assembly 108. It is to be understood that fastening means 128 are provided on each fastening strip 126 for securing the strips 126 and plurality of magnets 112 together at appropriate positions and orientation on rotor core 110 and beneficially prevents falloff of the plurality of magnets 112.
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Figure 2, in accordance with an embodiment, describes the stator assembly 102. The stator assembly 102 comprises the stator ring 104 and the teeth ring 106. The teeth ring 106 comprises the plurality of stator teeth 116, wherein each of the stator tooth 116 comprises the inner face 116a facing towards the rotor assembly 108 and the outer face 116b facing away from the rotor assembly 108. The inner face 116a 5 of each of the stator tooth 116 comprises a plurality of slots 120 to reduce cogging torque. The outer face 116b of each of the stator tooth 116 comprises a locking protrusion 122. The stator ring 104 comprises a plurality of notches 124 on inner surface, wherein each of the notch 124 receives the locking protrusion 122 of the stator tooth 116 for removably accommodating the teeth ring 106 within the stator 10 ring 104 to form the stator assembly 102.
Figure 3, in accordance with an embodiment, describes an exploded view of the rotor assembly 108. The rotor assembly 108 comprises the rotor core 110, the plurality of magnets 112 mounted on the rotor core 110, and the shaft 114 for mounting the rotor assembly 104. The rotor assembly 108 comprises a plurality of 15 fastening strips 126 and wherein each of the fastening strip 126 comprises a fastening means 128. The plurality of magnets 112 comprises at least one groove 130 on each side of the plurality of magnets 112. The two adjacent magnets 112 receive the fastening strip 128 in the grooves 130 for holding the adjacent magnets 112 together. 20
Figure 4, in accordance with an embodiment, describes the assembled rotor assembly 108. The rotor assembly 108 comprises the rotor core 110 and the plurality of magnets 112 mounted on the rotor core 110 and the shaft 114 for mounting the rotor assembly 104. The plurality of fastening strips 126 are secured on the rotor core 110 along with the plurality of magnets 112 using the fastening means 128 to 25 form the rotor assembly 108.
In an embodiment, the surface permanent magnet motor 100 comprises a stator assembly 102, a rotor assembly 104, and a shaft 114 for mounting the rotor assembly 104. The stator assembly 102 comprises a stator ring 104 and a teeth ring
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106. The teeth ring 106 is removably accommodated within the stator ring 104. The rotor assembly 108 comprises a rotor core 110 and a plurality of magnets 112 mounted on the rotor core 110. Furthermore, the teeth ring 106 comprises a plurality of stator teeth 116, wherein each of the stator tooth 116 comprises an inner face 116a facing towards the rotor assembly 108 and an outer face 116b facing away 5 from the rotor assembly 108. Furthermore, each of the stator tooth 116 receives a stator coil along the length of the stator tooth 116 from the outer face 116b. Furthermore, the inner face 116a of each of the stator tooth 116 comprises a plurality of slots 120 to reduce cogging torque. Furthermore, the outer face 116b of each of the stator tooth 116 comprises a locking protrusion 122. Furthermore, the 10 stator ring 104 comprises a plurality of notches 124 on inner surface, wherein each of the notch 124 receives the locking protrusion 122 of the stator tooth 116 for removably accommodating the teeth ring 106 within the stator ring 104 to form the stator assembly 102. Furthermore, the rotor assembly 108 comprises a plurality of fastening strips 126 and wherein each of the fastening strip 126 comprises a 15 fastening means 128. Furthermore, the plurality of magnets 112 comprises at least one groove 130 on each side of the plurality of magnets 112. Furthermore, the two adjacent magnets 112 receive the fastening strip 128 in the grooves 130 for holding the adjacent magnets 112 together. Furthermore, the plurality of fastening strips 126 are secured on the rotor core 110 along with the plurality of magnets 112 using the 20 fastening means 128 to form the rotor assembly 108.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or 25 electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
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Modifications to embodiments and combinations of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, and “is” used to describe and claim the present disclosure are intended to be construed in a 5 non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other 10 modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings, and the appended claims. In addition to variations 15 and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. ,CLAIMS:We Claim:
1. A surface permanent magnet motor (100), the motor (100) comprising:
- a stator assembly (102) comprising a stator ring (104) and a teeth ring (106);
- a rotor assembly (108) comprising a rotor core (110) and a plurality of 5 magnets (112) mounted on the rotor core (110); and
- a shaft (114) for mounting the rotor assembly (108),
wherein the teeth ring (106) is removably accommodated within the stator ring (104).
2. The motor (100) as claimed in claim 1, wherein the teeth ring (106) 10 comprises a plurality of stator teeth (116), wherein each of the stator tooth (116) comprises an inner face (116a) facing towards the rotor assembly (108) and an outer face (116b) facing away from the rotor assembly (108).
3. The motor (100) as claimed in claim 1, wherein each of the stator tooth (116) receives a stator coil along the length of the stator tooth (116) from the outer face 15 (116b).
4. The motor (100) as claimed in claim 1, wherein the inner face (116a) of each of the stator tooth (116) comprises a plurality of slots (120) to reduce cogging torque.
5. The motor (100) as claimed in claim 1, wherein the outer face (116b) of 20 each of the stator tooth (116) comprises a locking protrusion (122).
6. The motor (100) as claimed in claim 1, wherein the stator ring (104) comprises a plurality of notches (124) on inner surface (132) of the stator ring (104), wherein each of the notch (124) receives the locking protrusion (122) of the stator tooth (116) for removably accommodating the teeth ring (106) within the stator ring 25 (104) to form the stator assembly (102).
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7. The motor (100) as claimed in claim 1, wherein the rotor assembly (108) comprises a plurality of fastening strips (126) and wherein each of the fastening strip (126) comprises a fastening means (128).
8. The motor (100) as claimed in claim 1, wherein the plurality of magnets (112) comprises at least one groove (130) on each side of the plurality of magnets 5 (112).
9. The motor (100) as claimed in claim 1, wherein the two adjacent magnets (112) receive the fastening strip (126) in the grooves (130) for holding the adjacent magnets (112) together.
10. The motor (100) as claimed in claim 1, wherein the plurality of fastening 10 strips (126) are secured on the rotor core (110) along with the plurality of magnets (112) using the fastening means (128) to form the rotor assembly (108).