Description:ROTOR ASSEMBLY FOR PMSR-MOTOR
TECHNICAL FIELD
Generally, the present disclosure relates to a permanent magnet synchronous reluctance motor. Particularly, the present disclosure relates to a rotor assembly of a permanent magnet synchronous reluctance motor.
BACKGROUND
Recently, traction motors are increasingly being used due to adoption of electric vehicles. AC motors are one of the good options to serve as traction motor in electric vehicles due to their high performance and efficiency. The permanent magnet synchronous motor (PMSM) has a higher efficiency. However, their drawbacks include eddy current loss at high speed, and a reliability risk because of the possible breaking and demagnetization of magnets due to higher temperature. On the other hand, the reluctance motors (RM) can deliver high power density at low cost, making them attractive for electric automobile applications; however, these motors experience high torque ripple when operated at low speed, and subsequent noise due to torque ripple.
Permanent magnet Synchronous reluctance motor (PMSRM) comes out to be a viable option which combines the advantages of Permanent magnet synchronous motor (PMSM) and Reluctance motor (RM), thus delivering high power density, high efficiency, and wide speed regulation range, while maintaining low torque ripples and high reliability factor.
Due to the above advantages, the PMSRM are being used in various high-power applications such as electric vehicles. The PMSRM is a reliable and effective solution for modern automotive propulsion systems. It is to be understood that the motors used in the automobile application are highly power dense and have multiple mechanical components including stator assembly, rotor assembly, casing. Furthermore, each of the mechanical component of the PMSRM may further have multiple sub-components which increases the manufacturing and assembling complexity of the PMSRM. Such as the rotor assembly comprises a shaft, a rotor core, permanent magnets and so on. Furthermore, there may be other additional components in particular rotor assemblies. Typically, each of the mechanical component of the rotor is manufactured separately and then assembled together to form the mechanical assembly of the rotor. The separate manufacturing of the mechanical components may create variations in the dimensions of the components. As understood, the manufacturing processes/machines used for the manufacturing of the mechanical components may have error/tolerances. Such tolerance may lead to inaccuracy in dimension of the manufactured mechanical components. During the assembly process, when the multiple components are stacked together, the inaccuracies of the dimensions may add up leading to assembly fouling (improper assembly of components) of the rotor. Conventionally, washers are used to overcome such dimensional variations. However, the washers are ineffective to a great extent when the variation in the dimension is greater than the width of the washer. Moreover, the washers may deform due to uneven distribution of forces during the operation of the rotor. Such variation in the dimension may lead to vibration of the components of the rotor and thus leading to failure of the motor. Furthermore, the magnetic field generate by the rotor assembly may be disturbed due to the vibration of the rotor components leading to reduced motor efficiency. As a result, the electric motor may suffer from decreased performance, increased energy consumption, and reliability issues.
Therefore, there exists a need for an improved rotor assembly of permanent magnet synchronous reluctance motor that overcomes the one or more problems as set forth above.
SUMMARY
An object of the present disclosure is to provide a rotor assembly of a Permanent Magnet Synchronous Reluctance Motor.
In accordance with an aspect of the present disclosure there is provided a rotor assembly of a Permanent Magnet Synchronous Reluctance Motor. The rotor assembly comprises a rotor shaft, a rotor core and at least one spacer spring. The rotor core is mounted on the rotor shaft. The at least one spacer spring is mounted on the rotor shaft along with the rotor core. The at least one spacer spring is configured to restrict axial movement of the rotor core on the rotor shaft.
The present disclosure provides a rotor assembly for Permanent Magnet Synchronous Reluctance Motor (PMSRM). The rotor assembly, as disclosed by the present disclosure is advantageous in terms of stable operation of the rotor assembly. The rotor assembly, as disclosed by the present disclosure beneficially comprises a spacer spring configured to restrict axial movement of the rotor core on the rotor shaft for preventing vibrations of the rotor components during the operation of the rotor assembly. Furthermore, the rotor assembly of the present disclosure is advantageous in terms of accommodating manufacturing errors of the rotor assembly components. Beneficially, the rotor assembly of the present disclosure increases operational life of the motor. Beneficially, the rotor assembly of the present disclosure reduces maintenance cost of the motor.
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 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 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.
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 rotor assembly of a Permanent Magnet Synchronous Reluctance Motor, in accordance with an embodiment of the present disclosure.
Figure 2 illustrates a perspective view of a rotor shaft of a rotor assembly, in accordance with an embodiment of the present disclosure.
Figure 3 illustrates a perspective view of a locking plate of a rotor assembly, in accordance with an embodiment of the present disclosure.
Figure 4 illustrates a perspective view of a rotor assembly of a Permanent Magnet Synchronous Reluctance Motor, in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an 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.
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 recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a rotor assembly and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in 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 minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein 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.
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 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, 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 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, reference is made to the accompanying drawings and 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.
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 with unnecessary detail.
As used herein, the terms “electric motor”, “motor”, “permanent magnet synchronous reluctance motor”, “PMSR motor”, “IPM-SynRM” and “PMSRM” are used interchangeably and refer to electric motors capable of being implemented in an industrial or automobile application, such as on the work machine or other vehicle. The permanent magnet synchronous reluctance motor is a type of hybrid electric motor that combines the features of Permanent Magnet Synchronous Motor (PMSM) and Reluctance Motor (RM). The PMSRM has permanent magnets in the rotor, which generates a constant magnetic field, and the PMSRM relies on the principle of magnetic reluctance to create a rotating field within the motor. It would be appreciated that combination of technologies allows the PMSRM to achieve higher efficiency and better performance than other types of electric motors. In general, the stator of the PMSRM typically contains three-phase windings, which are used to generate alternating current that powers the electric motor. Typically, the rotor is made of iron or other magnetic materials, contains the permanent magnets that generate the magnetic field. It would be appreciated that the PMSRM can be modified to comprise active cooling system, such as a liquid cooling system. It would be appreciated that such cooling system would employ a coolant liquid circulating through the well-defined coolant flow paths (such as stator jackets) inside the motor to dissipate the heat generated by the electric motor during operation.
As used herein, the terms “electric vehicle”, “EV”, and “EVs” are used interchangeably and refer to any vehicle having stored electrical energy, including the vehicle capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source. Additionally, it is to be understood that the ‘electric vehicle’ as used herein includes electric two-wheeler, electric three-wheeler, electric four-wheeler, electric pickup trucks, electric trucks and so forth.
As used herein, the terms “rotor” and “rotor assembly” are used interchangeably and refer to the rotating part of the motor which is typically made of iron or other magnetic materials. It contains the permanent magnets and the reluctance core that generate the magnetic field used to drive the rotor. The rotor converts electrical energy supplied to the stator into mechanical energy. The rotor assembly may generate magnetic torque, reluctance torque or a combination thereof.
As used herein, the terms “stator” and “stator assembly” are used interchangeably and refer to the stationary part of a motor which provides a magnetic field that drives the rotating armature. The stator may act as a field magnet.
As used herein, the term “motor shaft”, “shaft” and “rotor shaft” are used interchangeably and refer to a cylindrical rotating component of the motor that transmits mechanical power from the motor to the driven load. The motor shaft extends from the rotor and protrudes out of the motor casing.
As used herein, the term “rotor core”, “rotor stack” and “stack” are used interchangeably and refer to rotor core that houses the components associated with the rotor of the motor. The rotor core may typically comprise permanent magnets integrated into the structure, typically embedded within the laminated steel core. The rotor core generates magnetic torque and reluctance torque wherein the permanent magnets provide magnetic torque by interacting with the stator's magnetic field and the flux barriers in the rotor core create a difference in magnetic reluctance, contributing to reluctance torque, which helps align the rotor with the rotating magnetic field in the stator. It is to be understood that the core is typically made of laminated steel to minimize eddy current losses and improve efficiency. Alternatively, the rotor core may be non-laminated. Furthermore, the permanent magnets are placed within the rotor, often in a V-shape or similar configuration, to optimize the distribution of the magnetic field.
As used herein, the term “spacer spring” refers to a component of the rotor assembly that is designed to apply consistent axial force on the rotor stack, ensuring that the stack remains properly aligned and under the desired preload. Furthermore, it is to be understood that the spacer spring occupies an axial space on the rotor shaft accommodating any dimension errors of the rotor core. Furthermore, the spacer spring compress or expand slightly, exerting force along the axis of the rotor.
As used herein, the term “rotor magnets”, “plurality of magnets”, and “magnets” are used interchangeably and refer to the permanent magnets attached inside or on surface of the rotor core to generate magnetic field that interacts with the rotating magnetic field of the stator assembly resulting in rotational motion.
As used herein, the term “hollow section” refers to voids in the rotor core that are designed to accommodate the rotor magnets. The hollow sections may be cut-through sections with both ends open. Alternatively, the hollow sections may be closed at one end. It is to be understood that the plurality of the rotor magnets may be secured inside the hollow sections by various means.
As used herein, the term “locking plates” refers to disc like components of the rotor assembly that are placed on the ends of the rotor core to secure the plurality of the magnets inside the hollow sections of the rotor core.
As used herein, the term “first locking mechanism” refers to a combination of a slit and flange or any similar mechanism configured to secure the position of the rotor core on the rotor shaft. It is to be understood that the first locking mechanism prevents slipping of the rotor core on the rotor shaft.
As used herein, the term “second locking mechanism” refers to a combination of a notch and projection or any similar mechanism configured to secure the position of the locking plates on the rotor core. It is to be understood that the second locking mechanism prevents slipping of the locking plates on the rotor core.
As used herein, the term “locking ring” refers to a component of the rotor assembly configured to secure the spacer spring on the rotor shaft. The locking ring may be a snap ring or may be a circlip.
Figure 1, in accordance with an embodiment describes a rotor assembly 100 of a Permanent Magnet Synchronous Reluctance Motor. The rotor assembly 100 comprises a rotor shaft 102, a rotor core 104 and at least one spacer spring 106. The rotor core 104 is mounted on the rotor shaft 102. The at least one spacer spring 106 is mounted on the rotor shaft 102 along with the rotor core 104. The at least one spacer spring 106 is configured to restrict axial movement of the rotor core 104 on the rotor shaft 102.
The present disclosure provides a rotor assembly 100 for Permanent Magnet Synchronous Reluctance Motor (PMSRM). The rotor assembly 100, as disclosed by the present disclosure is advantageous in terms of stable operation of the rotor assembly 100. The rotor assembly 100, as disclosed by the present disclosure beneficially comprises a spacer spring 106 configured to restrict axial movement of the rotor core 104 on the rotor shaft 102 for preventing vibrations during the operation of the rotor assembly 100. Furthermore, the rotor assembly 100 of the present disclosure is advantageous in terms of accommodating manufacturing errors of the rotor assembly 100. Beneficially, the rotor assembly 100 of the present disclosure increases operational life of the motor. Beneficially, the rotor assembly 100 of the present disclosure reduces maintenance cost of the motor.
In an embodiment, the rotor shaft 102 may act as central component for the rotor assembly 100. Beneficially, other components of the rotor assembly 100 are mounted on the rotor shaft 102. Beneficially, the rotor shaft 102 may be designed to accommodate the components of the rotor assembly 100. It is to be understood that the rotor shaft 102 may comprise particular design features according to particular component to be accommodated. Beneficially, the rotor shaft 102 may be made of a high torsional strength material.
In an embodiment, the rotor shaft 102 and the rotor core 104 comprise a first locking mechanism 112a, 112b to restrict a relative rotational motion between the rotor shaft 102 and the rotor core 104. It is to be understood that the first locking mechanism 112a, 112b comprises a slit 112a and a corresponding flange 112b that locks in the slit 112a. Beneficially, the first locking mechanism 112a, 112b secures the rotor core 104 on the rotor shaft 102 to prevent relative rotational motion between the rotor shaft 102 and the rotor core 104. In other words, the first locking mechanism 112a, 112b prevents slipping of the rotor core 104 on the rotor shaft 102.
In an embodiment, the rotor core 104 comprises a plurality of rotor magnets 108, wherein the plurality of rotor magnets 108 are embedded inside the rotor core 104. Beneficially, the plurality of rotor magnets 108 generate a magnetic torque by interacting with magnetic field generated by the stator assembly.
In an embodiment, the rotor core 104 comprises a plurality of hollow sections 104a configured to receive the plurality of rotor magnets 108 within. Beneficially, the plurality of rotor magnets 108 are securely accommodated in the plurality of hollow sections 104a. In an implementation, the hollow sections 104a may be open at both ends. In another implementation, the hollow sections 104a may be open at one end and closed at another end.
In an embodiment, the rotor assembly 100 comprises a pair of locking plates 110a, 110b, wherein each of the locking plate 110a, 110b is mounted on the rotor shaft 102 adjacent to the rotor core 104 in a mutually opposite axial direction. In an embodiment, the pair of locking plates 110a, 110b is configured to lock the plurality of rotor magnets 108 inside the rotor core 104 to prevent axial movement of the plurality of rotor magnets 108 inside the rotor core 104. Beneficially, the pair of locking plates 110a, 110b secures the plurality of rotor magnets 108 inside the rotor core 104.
In an embodiment, the pair of locking plates 110a, 110b is configured to provide weight balancing to the rotor assembly 100. Beneficially, the pair of locking plates 110a, 110b may be designed to balance weight on both axial ends of the rotor assembly 100.
In an embodiment, the pair of locking plates 110a, 110b and the rotor core 104 comprise a second locking mechanism 114a, 114b to restrict a relative rotational motion between the pair of locking plates 110a, 110b and the rotor core 104. It is to be understood that the second locking mechanism 114a, 114b comprises a projection 114a and a corresponding notch 114b in which the projection 114a locks in. Beneficially, the second locking mechanism 114a, 114b secures the pair of locking plates 110a, 110b on the rotor core 104 to prevent relative rotational motion between the pair of locking plates 110a, 110b and the rotor core 104. In other words, the second locking mechanism 114a, 114b prevents slipping of the pair of locking plates 110a, 110b on the rotor core 104.
In an embodiment, the at least one spacer spring 106 is configured to exert a compressive force on the at least one locking plate 110a, 110b to restrict movement of the rotor core 104 in the axial direction on the rotor shaft 102. It is to be understood that during the manufacturing of the rotor core 104, there may occur error in the dimension of the rotor core 104, causing either increased or decreased length of the rotor core 104. To accommodate such error, the spacer spring 106 would occupy the vacant space on the rotor shaft 102 meant for the rotor core 104 and exert a compressive force on the at least one locking plate 110a, 110b to restrict movement of the rotor core 104 in the axial direction on the rotor shaft 102. It is to be understood that when the dimension of the rotor core 104 is more than required, the spacer spring 106 compresses to accommodate such change in dimension of the rotor core 104. Similarly, when the dimension of the rotor core 104 is less than required, the spacer spring 106 expands to accommodate such change in dimension of the rotor core 104. Beneficially, the at least one spacer spring 106 is made of material suitable for providing elasticity.
In an embodiment, the rotor assembly 100 comprises at least one locking ring 116 configured to lock the at least one spacer spring 106 on the rotor shaft 102. Beneficially, the at least one locking ring 116 secures the at least one spacer spring 106 on the rotor shaft 102. In an alternative embodiment, the at least one spacer spring 106 is self-locking interference fit on the rotor shaft 102.
Figure 2, in accordance with an embodiment describes perspective view of the rotor shaft 102. The rotor shaft 102 comprises the slit 112a to accommodate the corresponding flange 112b of the rotor core 104. The at least one spacer spring 106 is positioned on the rotor shaft 102. Furthermore, the at least one locking ring 116 configured to lock the at least one spacer spring 106 on the rotor shaft 102.
Figure 3, in accordance with an embodiment describes perspective view of the locking plate 110a, 110b. The locking plate 110a, 110b is mounted on the rotor shaft 102 adjacent to the rotor core 104 in a mutually opposite axial direction. Furthermore, the locking plate 110a, 110b is configured to lock the plurality of rotor magnets 108 inside the rotor core 104 to prevent axial movement of the plurality of rotor magnets 108 inside the rotor core 104. Furthermore, the locking plate 110a, 110b comprises the projection 114a that locks in the notch 114b to lock the locking plate 110a, 110b with the rotor core 104.
Figure 4, in accordance with an embodiment describes perspective view of the rotor assembly 100. The rotor assembly 100 comprises the rotor shaft 102, the rotor core 104 and the at least one spacer spring 106. The rotor core 104 is mounted on the rotor shaft 102. The at least one spacer spring 106 is mounted on the rotor shaft 102 along with the rotor core 104. The at least one spacer spring 106 is configured to restrict axial movement of the rotor core 104 on the rotor shaft 102. Furthermore, the rotor shaft 102 and the rotor core 104 comprise the first locking mechanism 112a, 112b to restrict the relative rotational motion between the rotor shaft 102 and the rotor core 104. Furthermore, the rotor core 104 comprises the plurality of rotor magnets 108, wherein the plurality of rotor magnets 108 are embedded inside the rotor core 104. Furthermore, the rotor core 104 comprises the plurality of hollow sections 104a configured to receive the plurality of rotor magnets 108 within. Furthermore, the rotor assembly 100 comprises the pair of locking plates 110a, 110b, wherein each of the locking plate 110a, 110b is mounted on the rotor shaft 102 adjacent to the rotor core 104 in the mutually opposite axial direction. Furthermore, the pair of locking plates 110a, 110b is configured to lock the plurality of rotor magnets 108 inside the rotor core 104 to prevent axial movement of the plurality of rotor magnets 108 inside the rotor core 104. Furthermore, the pair of locking plates 110a, 110b are configured to provide weight balancing to the rotor assembly 100. Furthermore, the pair of locking plates 110a, 110b and the rotor core 104 comprise the second locking mechanism 114a, 114b to restrict the relative rotational motion between the pair of locking plates 110a, 110b and the rotor core 104. Furthermore, the at least one spacer spring 106 is configured to exert the compressive force on the at least one locking plate 110a, 110b to restrict movement of the rotor core 104 in the axial direction on the rotor shaft 102. Furthermore, the rotor assembly 100 comprises at least one locking ring 116 configured to lock the at least one spacer spring 106 on the rotor shaft 102.
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 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.
Modifications to embodiments and combination 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”, “is” used to describe and claim the present disclosure are intended to be construed in a 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 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 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 rotor assembly (100) of a Permanent Magnet Synchronous Reluctance Motor (PMSRM), wherein the rotor assembly (100) comprises:
- a rotor shaft (102);
- a rotor core (104) mounted on the rotor shaft (102);
- at least one spacer spring (106) mounted on the rotor shaft (102) along with the rotor core (104),
wherein the at least one spacer spring (106) is configured to restrict axial movement of the rotor core (104) on the rotor shaft (102).
2. The rotor assembly (100) as claimed in claim 1, wherein the rotor shaft (102) and the rotor core (104) comprise a first locking mechanism (112a, 112b) to restrict a relative rotational motion between the rotor shaft (102) and the rotor core (104).
3. The rotor assembly (100) as claimed in claim 1, wherein the rotor core (104) comprises a plurality of rotor magnets (108), wherein the plurality of rotor magnets (108) are embedded inside the rotor core (104).
4. The rotor assembly (100) as claimed in claim 3, wherein the rotor core (104) comprises a plurality of hollow sections (104a) configured to receive the plurality of rotor magnets (108) within.
5. The rotor assembly (100) as claimed in claim 1, wherein the rotor assembly (100) comprises a pair of locking plates (110a, 110b), wherein each of the locking plate (110a, 110b) is mounted on the rotor shaft (102) adjacent to the rotor core (104) in a mutually opposite axial direction.
6. The rotor assembly (100) as claimed in claim 1, wherein the pair of locking plates (110a, 110b) is configured to lock the plurality of rotor magnets (108) inside the rotor core (104) to prevent axial movement of the plurality of rotor magnets (108) inside the rotor core (104).
7. The rotor assembly (100) as claimed in claim 1, wherein the pair of locking plates (110a, 110b) is configured to provide weight balancing to the rotor assembly (100).
8. The rotor assembly (100) as claimed in claim 1, wherein the pair of locking plates (110a, 110b) and the rotor core (104) comprise a second locking mechanism (114a, 114b) to restrict a relative rotational motion between the pair of locking plates (110a, 110b) and the rotor core (104).
9. The rotor assembly (100) as claimed in claim 1, wherein the at least one spacer spring (106) is configured to exert a compressive force on the at least one locking plate (110a, 110b) to restrict movement of the rotor core (104) in the axial direction on the rotor shaft (102).
10. The rotor assembly (100) as claimed in claim 1, wherein the rotor assembly (100) comprises at least one locking ring (116) configured to lock the at least one spacer spring (106) on the rotor shaft (102).