Claims:WE CLAIM:
1. A method (200) of attaching permanent magnets (101) to a rotor (103) of an electric machine, said method (100) comprising:
connecting a mould (106) against an inner surface of said rotor (103), said mould (106) defines an internal space;
attaching a protective cover (105) to an inner surface of said mould (106);
arranging a plurality of permanent magnets (101) inside said internal space defined by said mould (106);
bonding said protective cover (105) with said plurality of permanent magnets (101) and said plurality of permanent magnets (101) with said inner surface of said rotor (103) using a bonding agent; and
disconnecting said mould (106) from said inner surface of said rotor (103),
wherein,
said protective cover (105) completely covers said plurality of permanent magnets (101) on said rotor (103) of said electrical machine, and thereby protects said plurality of permanent magnets (101) from environmental factors.

2. The method (200) as claimed in claim 1, wherein said protective cover (105) is adapted to protect said permanent magnets from environmental factors such as temperature, dust, pollution, and moisture entering into said plurality of permanent magnets.

3. The method (200) as claimed in claim 1, wherein said mould (106) includes an open side which is arranged such that said open side is connected against said inner surface of said rotor (103) of said electric machine.

4. The method (200) as claimed in claim 1, wherein said plurality of magnets (101) includes at least one south pole magnet and a north pole magnet disposed adjacent to each other, said protective cover (105) is configured to cover a space defined between said north and south poles.

5. The method (200) as claimed in claim 1, wherein said protective cover (105) is made-up of at least one of glass reinforced plastic (GRP sheets) and polyester resin.

6.The method (200) as claimed in claim 1, wherein said bonding agent is at least a thermosetting adhesive, said bonding agent is at least PU glue, said bonding agent is configured to fill all the spaces defined between the said plurality of magnets and said mould (106).

7. A permanent magnet rotor assembly (100) for an electric machine, comprising;
a plurality of permanent magnets (101) having a surface portion mounted on an inner surface of a rotor (103) for magnetically interacting therewith,
a protective cover (105) formed with at least one open side connected to said inner surface of said rotor (103), said cover (105) arranged such that said cover (105) completely encloses said plurality permanent magnets (101); and
an adhesive agent (or bonding agent) bonding said protective cover (105) to said plurality of magnets (101) and said plurality of magnets (101) to said inner surface of said rotor (103) of said electric machine.
8. The rotor arrangement (100) as claimed in claims 6, wherein said electric machine at least a wind turbine having a generator.
, Description:TECHNICAL FIELD
[001] The present disclosure generally relates generally to electric machines, and more specifically, to a method of attaching permanent magnets to a rotor or a stator of an electrical machine.
BACKGROUND
[002] Various types of electric machines include permanent magnets. For example, a direct current (DC) motor may include a plurality of permanent magnets coupled to an exterior surface of a rotor core. For example, if a rotor of a diameter in the range of 2-6 m is in use, then a magnet typically of 1-3 cm in height and 10-20 cm wide is used. A permanent magnet usually comprises a number of magnet pieces, each with a weight in the region of 10-15 kg/for large magnets. Conventional methods of mounting magnets usually involve attaching each magnet to a steel base of the same width as the magnet, for instance using an adhesive layer, and attaching this unit to the rotor by covering it with a U-shaped steel housing and soldering each housing along its lower edges onto the rotor. The housings ensure that the magnets are protected from corrosion and from mechanical impact. However, this approach is inflexible and expensive, since it requires a steel base for each magnet, a closely-fitting housing for each magnet, and a time-consuming soldering step. Another disadvantage is the additional weight contribution on account of the steel bars.
[003] Typically, the plurality of permanent magnets are coupled to the exterior surface of the rotor core using an adhesive and/or a retaining ring. The plurality of permanent magnets must be coupled to the rotor core such that the permanent magnets remain coupled to the rotor core even when high speed rotation of the rotor exerts forces on the permanent magnets tending to separate the permanent magnets from the rotor core. Magnets attached to the rotor core with the adhesive are known to have bonding issues. Specifically, magnets have been known to detach from the rotor core during periods of high RPM motor operation. In end user applications, environmental factors such as temperatures and humidity as well as other corrosive elements affect integrity of a rotor having magnets attached thereto with an adhesive. It is not uncommon to see bonding failures either at a test facility or in the end use application due to aforementioned factors.
[004] Therefore, there exists a need for a method of attaching permanent magnets to a rotor or a stator of an electrical machine, which obviates the aforementioned drawbacks.
OBJECTS
[005] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
[006] An object of the present disclosure is to provide a method of attaching permanent magnets to a rotor or a stator of an electrical machine.
[007] Another object of the present disclosure is to provide a permanent magnet rotor assembly for use in an electric machine.
[008] Still another object of the present disclosure is to provide the method which is suitable for electric generator of wind turbine, hydro turbines, and other electrical machines.
[009] Still another object of the present disclosure is to provide the permanent magnet rotor assembly which includes a protective cover for protecting the permanent magnet against corrosion caused by tropical environment.
[010] Still another object of the present disclosure is to provide the permanent magnet rotor assembly which includes the protective cover for protecting the permanent magnet against environmental factors such as as temperature, dust, pollution, and moisture.
[011] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[012] The embodiments of the invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[013] Figures 1a and 1b depicts a front view and a top view of a permanent magnet rotor assembly, according to the embodiment as disclosed herein;
[014] Figures 2a and 2b depict images of permanent magnet rotor assembly, according to the embodiment as disclosed herein; and
[015] Figure 3 depicts a flowchart indicating a method of attaching permanent magnets to a rotor or a stator of an electrical machine.
DETAILED DESCRIPTION
[016] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. Referring now to the drawings and more particularly to Figure 1 through Figure 3, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[017] For the purpose of this description and ease of understanding, the assembly and method thereof is explained herein below in conjunction with the electric machine such as wind turbine and hydro turbine application. However, it is also within the scope of the invention to use this assembly and the method in any other electric machines without otherwise deterring the intended function as can be deduced from the description and corresponding drawings.
[018] As discussed herein, the permanent magnets are assembled to the rotor of the wind turbine. The permanent magnets coupled to the rotor surface are subjected to environmental factors whereby the permanent magnets tend to damage. Owing to such damage, the wind turbine tends to produce disrupted electric supply. Therefore, a protection is necessary for the permanent magnets of the rotor. So, it is essential to have a protective cover for the magnets mounted on the rotor surface.
[019] Figures 1a and 1b depicts a front view and a top view of a permanent magnet rotor assembly, according to the embodiment as disclosed herein and Figures 2a and 2b depict images of permanent magnet rotor, according to the embodiment as disclosed herein. In an embodiment, the electric machine considered herein is a wind turbine. The electric machine includes a stator (not shown), a plurality of winding, a rotor (103), and a plurality of permanent magnets (101) mounted to an inner surface of the rotor (103).
[020] The permanent magnet rotor assembly (100) includes the plurality of permanent magnets (101) each having a first surface portion mounted on the inner surface of the rotor (103). The permanent magnets (101) are disposed on the surface of the rotor (103) so that the magnets interacting magnetically with the stator (not shown) thereby. The plurality of magnets (101) includes at least one south pole magnet and a north pole magnet disposed adjacent to each other. Further, each of the permanent magnets (101) includes a second surface which is configured to adhere with a protective cover (105).
[021] The protective cover (105) is formed such that the cover (105) includes at least one open side which is connected to the inner surface of the rotor (103). The cover (105) is arranged above the plurality of permanent magnets (101) such that the cover (105) completely encloses the plurality permanent magnets (101). The protective cover (105) is made up of at least one of glass reinforced plastic (GRP sheets) and polyester resin. The protective cover (105) is adapted to protect the permanent magnets from environmental factors such as temperature, dust, pollution, and moisture entering into said plurality of permanent magnets.

[022] Further, the permanent magnet rotor assembly (100) includes at least one bonding agent which is filled in the spaces between the protective cover (105) and the plurality of permanent magnets (101), and between the plurality of magnets (101) and the inner surface of the rotor (103). In an embodiment, the bonding agent is at least a thermosetting adhesive like PU glue. However, it is also within the scope of the invention to use any other type of adhesive or bonding agent without otherwise deterring the intended function of bonding as can be deduced from the description and corresponding drawings.
[023] Figure 3 depicts a flowchart indicating a method (200) of attaching permanent magnets to a rotor (or a stator) of an electrical machine. For the purpose of this description and ease of understanding, the method (200) is explained herein below with reference to wind turbine. However, it is also within the scope of this invention to practice/implement the entire steps of the method (200) in a same manner or in a different manner or with omission of at least one step to the method (200) or with any addition of at least one step to the method (200) for any other electric machine, without otherwise deterring the intended function of the method (200) as can be deduced from the description and corresponding drawings. In an embodiment, at step 201, the method (200) includes connecting a mould (106) against an inner surface of said rotor (103), said mould (106) defines an internal space. At step 203, the method (200) includes attaching a protective cover (105) to an inner surface of said mould (106). Further, at step 205, the method (200) includes arranging a plurality of permanent magnets (101) inside said internal space defined by said mould (106). Furthermore, at step 207, the method (200) includes bonding said protective cover (105) with said plurality of permanent magnets (101) and said plurality of permanent magnets (101) with said inner surface of said rotor (103) using a bonding agent. Additionally, at step 209, the method (200) includes disconnecting said mould (106) from said inner surface of said rotor (103). The protective cover (105) completely covers the plurality of permanent magnets (101) on the rotor (103) of said electrical machine, and thereby protects said plurality of permanent magnets (101) from environmental factors.
[024] Process of attaching permanent magnets to the rotor (or a stator) of the electrical machine is explained below herein. Initially, the mould (106) which includes one open side and the internal space is coupled to the inner surface of the rotor (103). After which the protective cover (105) is attached to the inner surface of the mould (106). Subsequently, the plurality of magnets are arranged inside the internal space defined by the mould (106) in a predetermined manner. After arranging the magnets, the thermosetting bonding agent such as PU glue is introduced inside the internal space of the mould (106). The bonding agent bonds the protective cover (105) to the surface of the magnets. Further, the bonding agent bonds the plurality of magnets with the inner surface of the rotor (103). After solidification of the bonding agent, the mould (106) is removed from the surface of the rotor (103). Thus, the protective cover (105) forms a layer on the permanent magnets and protect the magnets from environmental factors.
[025] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.
[026] It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.
[027] Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.
[028] The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.
[029] Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to imply including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.
[030] The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.
[031] The description of the exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top”, and “bottom” as well as derivatives thereof (e.g. “horizontally”, “downwardly”, “upwardly” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion.
[032] These relative terms are for convenience of description and do not require that the corresponding apparatus or device be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected”, refer to a relationship, wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.