The invention relates to an electrical machine and to a method for assembling the electrical machine. More particularly, the method relates to installing the rotor of the electrical machine into the bore of the stator of the electrical machine.
Sometimes an electrical machine may have to be assembled or repaired at its site of normal operation, i.e. in the field conditions. For example, it may be a case that e.g. bearings of the electrical machine have to be changed and it may be too cumbersome and/or costly to move the whole electrical machine to be repaired elsewhere. Especially, installing a rotor of an electrical machine into the bore of the stator core may be a cumbersome task in field conditions. Especially, assembling a permanent magnet electrical machine may be a challenging task even in workshop circumstances because strong forces caused by the permanent magnets complicate the installation of a rotor including the permanent magnets into the bore of the stator core. In conjunction with permanent magnet electrical machines having surface mounted permanent magnets, there is a considerable risk of damaging the permanent magnets when installing the rotor into the bore of the stator core.
Publications CN101577453, JP2003143786, KR20000007669, JP8168215, and JP2223342 disclose various methods for installing permanent magnets into a rotor of a permanent magnet electrical machine. The installing of the permanent magnets into the rotor into correct positions is a challenging task because of the forces caused by the permanent magnets. However, technical solutions are needed also for overcoming the challenges related to installing of a rotor comprising permanent magnets into the bore of the stator core of a permanent magnet electrical machine. As well, the technical solutions are needed for overcoming the challenges related to installing of a rotor into the bore of the stator core of an electrically magnetized electrical machine in field conditions.
In accordance with the first aspect of the present invention, there is provided a new method for assembling an electrical machine that comprises:
The method for assembling the above-described electrical machine comprises:
As the guide bars are able to keep the rotor centered with respect to the bore of the stator core when the rotor is being slid in the axial direction into the bore of the stator core, the installation of the rotor is a straightforward operation also in field conditions. The method provides advantages especially in conjunction with permanent magnet electrical machines, where forces caused by permanent magnets complicate the installation of the rotor into the bore of the stator core. The risk of damaging the permanent magnets during the installation of the rotor is significantly reduced or even eliminated because the guide bars keep the rotor centered relative to the bore of the stator core. The axial direction mentioned above is the direction of the rotational axis of the rotor.
In accordance with the second aspect of the present invention, there is provided a new electrical machine the rotor of which can be installed using the above-described method. The electrical machine according to the second aspect of the invention comprises:
wherein the mechanical support structure comprises supporting surfaces stationary with respect to the stator and suitable for supporting axially directed guide bars and the rotor comprises sliding surfaces suitable for allowing the rotor to be installed into a bore of the stator core by sliding the rotor in an axial direction along the guide bars which, during the installation, are capable of keeping the rotor sufficiently centered relative to the bore of the stator core, and which, after the installation, are capable of being removed, and wherein the bearings are capable of supporting the rotor with respect to the stator after removal of the guide bars.
The electrical machine can be, for example, a permanent magnet electrical machine wherein the rotor comprises permanent magnets.
A number of exemplifying embodiments of the invention are described in accompanied dependent claims.
Various exemplifying embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.
The verb “to comprise” is used in this document as an open limitation that neither excludes nor requires the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.
The exemplifying embodiments of the invention and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which:
a shows a schematic section view of an electrical machine according to an embodiment of the invention in a situation in which a rotor is being installed,
b shows a schematic section view of the electrical machine shown in
c shows a view of the section taken along the line A-A shown in
d shows a rotor of an electrical machine according to an embodiment of the invention,
a shows a schematic section view of an electrical machine according to an embodiment of the invention in a situation in which a rotor is being installed and
The mechanical support structure 104 comprises supporting surfaces suitable for supporting axially directed guide bars 107, 108, 109 and 110. In the exemplifying construction shown in
The principle of using the guide bars for assisting the installation of the rotor can be implemented with various mechanical arrangements. For example, it is not necessary to provide the mechanical support structure 104 with the threaded holes or with other cavities for the ends of the guide bars. The guide bars are sufficiently supported also, for example, in a case in which there are axially directed grooves on the surface of the mechanical support structure as illustrated in
The above illustrated principle of using the guide bars for assisting the installation of the rotor is advantageous since the guide bars are supported by the same mechanical support structure 104 that is used for arranging the bearings of the rotor. Thus, the guidance for the installation can be co-centric with the bearings 105 and 106 of the rotor.
The guide bars 107-110 which are used for supporting the rotor during installation can also be used for locking the rotor 102 in a fixed position with respect to the stator 101 for example during transportation of the electrical machine, i.e. the guide bars can be used as a transportation support for protecting the electrical machine during transportation e.g. shipping.
In the exemplifying cases described above, the guide bars 107-110 have a circular cross section.
In the exemplifying construction illustrated in
The method comprises:
In a method according to an embodiment of the invention, the first end of each guide bar is pushed into a cavity of the mechanical support structure.
In a method according to an embodiment of the invention, the first end of each guide bar is threaded and is tightened into a corresponding threaded hole of the mechanical support structure.
A method according to an embodiment of the invention further comprises placing, in the optional method phase 303, a support element to second ends of the guide bars for keeping the second ends of the guide bars at pre-determined positions with respect to each other so as to further improve the ability of the guide bars to keep the rotor centered relative to the bore of the stator core.
In a method according to an embodiment of the invention, the rotor comprises permanent magnets.
There is also provided a new method for providing an electrical machine with a transportation support, the electrical machine comprising:
The method for providing the electrical machine with the transportation support comprises:
The specific examples provided in the description given above should not be construed as limiting. Therefore, the invention is not limited merely to the embodiments described above.
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