Rotor with magnetic positioning tab system

Abstract

A rotor for an electric machine includes a rotor core having one or more cavities inside the rotor core, the cavities defined by a wall of the rotor core. Laminations are stacked together to form the rotor core, and the laminations define the cavities. One or more bodies, which may be magnets, extend within the cavities. A subset of the laminations each includes a tab system having at least one tab configured to bias the body into a seating position against the wall and to retain the bodies in the seating position within the cavity.

Description

introduction

[0001] The present invention relates to electrical machines and their rotors, and more particularly to a rotor having a plurality of internal cavities adapted to receive permanent magnets, the rotor having features for positioning the magnets in desired positions in their slots for high performance operation.

[0002] A rotor, e.g., for an interior permanent magnet (IPM) or synchronous reluctance (SR) machine, comprises a rotor core mounted around the rotating shaft. Such a segmental rotor typically consists of a series of stacked laminations forming a core body. The core body usually contains cavities that act as flux barriers, which influence the operating characteristics of the machine. The individual laminations of the core body are disc-shaped with a central opening for mounting on a rotating shaft. The flux barriers are distributed around the shaft opening, may have ends located on the outer circumference of the lamination, and may extend toward the shaft opening. The cavities of the flux barriers may or may not contain the magnets.

[0003] The physical dimensions, number, and positioning of flux barrier cavities affect the performance of an electrical machine. Flux barriers can be placed in an optimal position to achieve optimal performance. This can result in the flux barriers being designed and positioned so that only thin structural elements remain that support portions of the rotor core. These thin sheet metal elements can limit the power and speeds achievable by the electrical machine without unduly stressing the rotor core or without unduly increasing the element size, especially if the magnets are not optimally positioned. Because the magnets are located within the flux barrier cavities, maintaining balance is challenging.

[0004] Accordingly, it is desirable to provide economical rotors for electrical machines that achieve high performance without equilibrium fluctuations. Furthermore, other desirable features and characteristics of the present invention will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. Description

[0005] In various embodiments, a rotor for an electric machine includes a rotor core with one or more cavities inside the rotor core. The cavities are defined by a wall defined by the rotor core. Laminations are stacked together to form the rotor core, and the laminates define the cavities. One or more bodies may extend within the cavities. A subset of the laminates includes a tab system with one or more tabs that bias the body into a seating position against the wall and retain the body in the seating position within the cavity.

[0006] In further embodiments, the body is a magnet.

[0007] In further embodiments, the body has chamfered corners, and there is only a single tab on each of the sheets in the subset of sheets. The single tab engages the body at one of the chamfered corners.

[0008] In further embodiments, the body has chamfered corners. Individual sheets have a single tab that extends into the cavity and engages the body at one of the chamfered corners. The wall includes an angled portion that engages the body at another of the chamfered corners.

[0009] In further embodiments, there is a first tab that engages the body at a first side of the body and a second tab that engages the body at a second side of the body. The first side and the second side share a common corner of the body.

[0010] In other embodiments, the tab is not present on a majority of the individual laminates.

[0011] In further embodiments, the wall defines a stop on one side of the body. The tab is arranged on another side of the body. The two sides are opposite each other, so that the tab preloads the body against the stop.

[0012] In further embodiments, the tab defines an interference fit between the body and the wall to create the preload.

[0013] In further embodiments, the wall comprises a radially inner lateral wall portion, a radially outer lateral wall portion, a radially inner tip, and a radially outer tip, all of which define the cavity. The preload urges the body against the radially outer lateral wall portion and toward the radially outer tip.

[0014] In further embodiments, the rotor can alternate between being in a stationary state and operating by rotating at a speed state. The preload is adjusted to maintain the body in the sitting position in both the stationary state and the speed state.

[0015] In a number of additional embodiments, a rotor for an electric machine comprises a rotor core having cavities within the rotor core. The cavities are defined by a wall of the rotor core. Laminations are stacked together to form the rotor core, the laminations together defining the cavities. A body, which may be a magnet, extends within at least some of the cavities. A subset of the laminations includes a tab system having one or more tabs that bias the body into a seating position against the wall and hold the body in the seating position.

[0016] In further embodiments, the body has chamfered corners. The subset of sheets comprises individual sheets, each of which comprises only one tab that engages the body at one of the chamfered corners.

[0017] In further embodiments, the magnet has chamfered corners. A single tab is located on each lamination in the subset of laminations. The tab engages the body at one of the chamfered corners. The wall includes an angled portion that engages the body at another of the chamfered corners. The wall has a radially outer lateral wall portion, and the tab urges the magnet against the angled portion and the radially outer lateral wall portion.

[0018] In further embodiments, the magnet comprises a first and a second side. A first tab engages the magnet on the first side, and a second tab engages the magnet on the second side. The first side and the second side share a common corner of the magnet.

[0019] In further embodiments, the subset of sheets is a minority of the sheets, so that the tabs are not included on a majority of the sheets.

[0020] In further embodiments, the wall defines a stop on a first side of the magnet. The tab is arranged on a second side of the magnet. The first side is opposite the second side, so that the tab exerts a bias on the magnet to position it against the stop.

[0021] In further embodiments, the tab defines an interference fit between the magnet and the wall to create the preload. A gap is defined between the wall and the magnet adjacent to the tab.

[0022] In further embodiments, the rotor rotates about an axis. To define the cavity, the wall includes a radially inner lateral wall portion, a radially outer lateral wall portion farther from the axis than the radially inner lateral wall portion, a radially inner tip, and a radially outer tip farther from the axis than the radially inner tip. The preload urges the magnet against the radially outer lateral wall portion and toward the radially outer tip.

[0023] In further embodiments, the rotor alternates between a stationary state and a speed state. The preload is adjusted to hold the magnet in its seated position in both the stationary and speed states.

[0024] In a number of other embodiments, a rotor for an electric machine includes a rotor core having cavities inside the rotor core. The cavities are defined by a wall of the rotor core. Laminations are stacked together to form the rotor core and define the cavities. A magnet extends within each of at least some of the cavities. Each lamination in a first subset of the laminations includes a tab system having a tab configured to bias the magnet into a seating position against the wall and to hold the magnet in the seating position. Each lamination in a second subset of the laminations does not include a tab. Short description of the characters

[0025] The exemplary embodiments are described below in conjunction with the following drawings, wherein like numerals indicate like elements: Fig. 1 is a schematic diagram of parts of an electrical machine in accordance with various embodiments; Fig. Figure 2 is a fragmentary cross-sectional view taken generally along line 2-2 of the electrical machine of Fig. 1 in accordance with various embodiments; Fig. 3 is a plan view of the surface of a lamination of the rotor of Fig. 2 according to various embodiments; Fig. Figure 4 is a fragmentary, schematic sectional view of a portion of the rotor of Fig. 2 over a part of a sheet, according to various embodiments; Fig. Figure 5 is a fragmentary, schematic sectional view of another part of the rotor of Fig. 2 over a part of a sheet with tabs, according to various embodiments; Fig. Figure 6 is a fragmentary, schematic sectional view of another part of the rotor of Fig. 2 over a part of a sheet without tabs, according to various embodiments; Fig. Figure 7 is a schematic perspective view of a magnet of the rotor of Fig. 2 in accordance with various embodiments; Fig. Figure 8 is a schematic cross-sectional view of a magnet of the rotor of Fig. 2 in accordance with various embodiments; Fig. Figure 9 is a fragmentary, schematic sectional view of a portion of the rotor of Fig. 2 over a part of the rotor core in a state before insertion of the magnet, according to various embodiments; and Fig. 10 is a fragmentary, schematic sectional view of another part of the rotor of Fig. 9 over a part of the rotor core in a state in which the magnet is inserted, according to various embodiments. Detailed description

[0026] The following detailed description is merely exemplary and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.

[0027] In Fig. 1 schematically illustrates selected components of an electric machine 20 including a stator assembly 22 and a rotor assembly 24 configured to rotate about an axis 25. In the figure, the rotor assembly 24 is shown external to the stator assembly 22 for clarity. In this embodiment, the electric machine 20 is configured as a motor, in which the current in the rotor assembly 24, which produces torque, is induced by the magnetic field created by the excitation of the stator assembly 22. In a number of embodiments, the electric machine 20 is an alternating current machine suitable for use in applications requiring regulated speed control, such as a vehicle traction motor, although this description is not limited to these applications.

[0028] The stator assembly 22 is a generally ring-shaped component that can be designed for single-phase power or multi-phase power, such as three-phase. In this embodiment, the stator assembly 22 includes a core 26 consisting of a stack of laminations 28. The laminations 28 can be formed by stampings that are slotted to receive windings (not shown) and can be made of a soft magnetic material such as silicon steel. The laminations 28 can be insulated from one another by a thin non-conductive coating. In other embodiments, a different ferromagnetic material can be used. The stator assembly 22 can include the windings for excitation.

[0029] The rotor assembly 24 includes a core 30 containing a stack of many laminations 32 configured to receive a shaft 34. The laminations 32 may be stamped or otherwise formed. Each lamination 32 may be symmetrical about its center for balance, but other non-symmetrical options may be used while still providing a balanced design. The laminations 32 are made of a ferromagnetic material and may be insulated from each other by a thin non-conductive coating or may be made of another material. End rings 42, 44 are formed at the ends of the core 30. In the present embodiment, the end rings 42, 44 are made of an aluminum material for lightweight performance.The rotor assembly 24 is configured with a number of poles to create the magnetic circuit of the rotor assembly 24, which depends on the angular position of the rotor assembly 24 to interact with the field induced by the stator assembly 22 of the electric machine 20. These poles can be created, at least in part, by flux barriers, as described below. Operation of the electric machine 20 over a wide speed range (speed condition) with mechanical robustness is desirable.

[0030] In Fig. 2, the rotor unit 24 is shown in cross-section and separated from the stator unit 22. One side 48 of one of the laminations 32 is exposed and visible. The lamination 32 contains a series of openings called cavities, which can serve multiple purposes. Distributed around the rotor assembly 24 near its outer periphery 50 are eight cavity groups 51-58, each consisting of two angled layers. The cavities in the cavity groups 51-58 extend through the stacked rotor laminations 32 of the core 30 in a longitudinal direction 59 that is parallel to the axis 25. Accordingly, each cavity in the cavity groups 51-58 has a length in the axial direction (parallel to the axis 25). The cavity groups 51-58 act as barriers to magnetic flux and help define the magnetic poles of the rotor assembly 24. The geometry of the sheets 32 is defined by the position, thickness and shape of the flow barriers.Parameters such as torque density and efficiency are influenced by the rotor topology. The cavities can generally be shaped to easily accommodate permanent magnets to create a magnet-assisted machine.

[0031] In the present embodiment, the rotor assembly 24 has eight poles, but a different number may be used. The cavity groups 51-58 are arranged to surround the shaft 34 and are evenly distributed in the lamination 32 around the shaft 34. The cavity groups 51-58 are arranged near (adjacent) the outer circumference 50 in the radial direction 75. The radial direction 75 is defined along any line from the axis 25 extending outward through the outer circumference 50, e.g., along the surface 48. The reference line 79 represents a radial line. Furthermore, the radial direction 75 is perpendicular to the axis 25 in the longitudinal direction 59.

[0032] In Fig. 3, a lamination 32 of the rotor assembly 24 is schematically illustrated. Each of the cavity groups 51-58 is similar, and the details of the cavity group 51 will be described herein, assuming that the other cavity groups 52-58 contain similar elements. The cavity group 51 includes two layers 81, 82 of flux barriers, referred to as cavities in the present embodiment of the electric machine 20. Layer 81 is a radially outer layer and includes cavities 83 and 84. Layer 82 is a radially inner layer and includes cavities 85 and 86. Thus, the cavity group 51 includes four cavities 83-86, which are shown without bodies / magnets in this view for simplicity. The cavities 83, 84 are arranged at an angle to each other and define a sector-shaped flux path element 88 defined by a remaining generally triangular steel portion of the lamination 32.The magnet cavities 85, 86 are also arranged at an angle to each other. A V-shaped flux path element 90 is defined between the layers 81, 82 by a remaining steel portion of the lamination 32. The layers 81, 82 define structural elements of the remaining steel of the lamination 32 in the form of struts 91, 92 and bridges 93-96. The struts 91, 92 and bridges 93-96 hold the outer portions of the lamination 32, such as the flux path elements 88, 90, together against rotation-induced forces during operation of the electric machine 20. The maximum speed of the electric machine 20 may be limited by the ability of the rotor assembly 24 to maintain structural integrity, including the relatively thin struts 91, 92 and bridges 93-96.

[0033] In Fig. 4, the area of ​​the cavity group 51 is shown in more detail. The cavity 83 is defined by a wall 102, which is part of the laminations 32 and defines the perimeter of the cavity 83 in a plane of the laminations 32. The wall 102 defines the open space of the cavity 83, which contains a body 104. In the present embodiment, the body 104 is a magnet. The cavity 84 is defined by a wall 106, which is part of the laminations 32 and defines the perimeter of the cavity 84 in a plane of the laminations 32. The wall 106 defines the open space of the cavity 83, which contains a body 108. In the present embodiment, the body 108 is a magnet. The cavity 85 is defined by a wall 110, which is part of the laminations 32 and defines the perimeter of the cavity 85 in a plane of the laminations 32. The wall 110 defines the open space of the cavity 85, which contains a body 112. In the present embodiment, the body 112 is a magnet.The cavity 86 is defined by a wall 116, which is a portion of the laminations 32 and defines the perimeter of the cavity 86 in a plane of the laminations 32. The wall 116 defines the open space of the cavity 86, which contains a body 118. In the present embodiment, the body 118 is a magnet. The cavities 83-86, or a portion thereof, may be referred to as magnet slots in such an embodiment.

[0034] In Fig. 5, the surface of cavities 83 and 85 is shown in more detail. It should be understood that the details of cavities 84 and 86 are mirror images of each other. It should also be understood that the details of the cavities in cavity groups 52-58 are also similar to those of cavity group 51. It should also be understood that in some embodiments, not all cavities contain bodies / magnets.

[0035] At cavity 83, wall 102 defines a radially inner tip 120, a radially outer tip 122, a radially inner lateral wall portion 124, and a radially outer lateral wall portion 126 of cavity 83. Wall 102 defines a space 128 into which body 104 fits. In the present embodiment, radially inner tip 120 and radially outer tip 122 are curved to achieve the desired magnetic properties, but in other embodiments, they may be square or angled. For the purposes of the present embodiment, a tip is not necessarily the outermost point of a structure, but rather includes the surrounding portion of the structure that defines its shape. For example, radially outer tip 122 includes all or substantially all of wall 102 from radially inner lateral wall portion 124 to radially outer lateral wall portion 126.Similarly, the radially inner tip 120 comprises all or substantially all of the portion of the wall 102 from the radially outer lateral wall portion 126 to the radially inner lateral wall portion 124.

[0036] The radially inner lateral wall portion 124 is substantially flat and includes a tab 130 located approximately midway between the radially inner tip 120 and the radially outer tip 122. The tab 130 is a portion of the lamination 32 that extends farther into the cavity 83 toward the radially outer lateral wall portion 126 than the remainder of the radially inner lateral wall portion 124. Thus, the tab 130 is a projection into the cavity 83 that engages the body 104 and urges it toward and against the radially outer lateral wall portion 126 with an adjustable biasing force. The force is adjustable by adjusting properties such as the size of the tab 130. In the present embodiment, the tab 130 is formed on a subset of the laminations 32, i.e., a number less than all of the laminations 32 in the rotor core 30.For example, the tab 130 may be present on only a few laminations of the stack length of the rotor core 30 (e.g., approximately 2-5 per cavity) to avoid excessive compression force for inserting the body 104 (magnet) or excessive preload. In other embodiments, more tabs 130 may be used to achieve a desired preload.

[0037] The radially outer tip 122 or a portion of the wall 102 adjacent thereto includes a stop 132. The stop 132 may be formed by all of the laminations 32 in the rotor core 30 and extends into the cavity 83, forming a shoulder against which the body 104 can abut to prevent further movement into the radially outer tip 122. In other embodiments, the stop 132 may be included in fewer than all of the laminations 32 in the rotor core 30. Proximate the radially inner tip 120, the wall 102 defines a tab 134 that extends into the cavity 83. The tab 134 is a portion of the lamination 32 that extends further into the cavity 83 toward the stop 132 and toward the radially outer lateral wall portion 126. Consequently, the tab 134 is a projection into the cavity 83 that engages the body 104 and urges it toward and against the stop 132 with an adjustable biasing force.In the present embodiment, the tab 134 is formed on a subset of the laminations 32, ie, on a number that is fewer than all of the laminations 32 in the rotor core 30. For example, the tab 134 is present only on a few laminations of the stack length of the rotor core 30 in order not to cause excessive pressing force for inserting the body 104 (magnet) or excessive preload.

[0038] The body 104, which may be a magnet, extends through the rotor core 30 in a direction parallel to the axis 25 and, as such, has a length that extends axially through the cavity 83. The body 104 has four sides 141-144 and four corners 145-148. Each of the sides 141-144 is flat / planar, and each of the corners 145-148 is substantially square. The tab 130 engages the side 143 and presses (with a preload) the side 141 against the radially outer lateral wall portion 126 of the cavity 83. The tab 134 engages the side 142 at the corner 146 and presses (with a preload) the side 144 at the corner 147 against the stop 132. The corners 146 and 147 have a common side 143 and are adjacent corners around the circumference of the body 104.The preloads caused by the tabs 130 and 134 cause the body 104 to lie in a seating position against the radially outer lateral wall portion 126 and against the stop 132. A gap 157 is created between the body 104 and the radially inner lateral wall portion 156. Due to the action of the tabs 130, 134, the seating position remains the same regardless of whether the rotor unit 24 is in a stationary (non-rotating) state or in a speed (rotating) state.

[0039] Within the cavity 85, the wall 110 defines a radially inner tip 150, a radially outer tip 152, a radially outer side wall portion 154, and a radially inner side wall portion 156 of the cavity 85. The wall 110 defines a space 158 into which the body 112 fits. In the present embodiment, the radially inner tip 150 and the radially outer tip 152 are curved to achieve the desired magnetic properties, but in other embodiments, they may be square or angled.

[0040] The body 112, which may be a magnet, extends in a direction parallel to the axis 25 and, as such, has a length that extends axially through the cavity 85. The body 112 has four sides 161-164. The body 112 has four chamfered corners 165-168. This technically creates eight corner-like elements, but for the purposes of the present embodiment, the four corners 165-168 of the body 112 are chamfered. For example, the corners 165-168 each have a chamfered surface 171-174 located at a 45° angle between the two adjacent right-angled surfaces of the sides 161-164.

[0041] At cavity 85, radially inner lateral wall portion 156 is flat and faces side 163 of body 112. Radially outer lateral wall portion 154 is also flat and faces side 161 of body 112. At or adjacent radially outer tip 152, wall 110 defines an angled portion 180. Angled portion 180 is a portion of wall 110 that is disposed at an angle (e.g., forty-five degrees) to radially inner lateral wall portion 156 and that merges at its other (radially outer) end into radially outer tip 152. Angled portion 180 mates with and faces beveled surface 173 of beveled corner 167.

[0042] The radially inner tip 150, or an adjacent portion of the wall 110, includes a tab 182. The tab 182 is a portion of the sheet 32 ​​that extends further into the cavity 83 toward the angled portion 180 and toward the radially outer lateral wall portion 154 compared to adjacent portions of the wall 110. Thus, the tab 182 is a projection into the cavity 85 that engages the body 112 and urges the body 112 toward and along the angled portion 180 and toward the radially outer lateral wall portion 154 with an adjustable biasing force. The force resulting from the tab 182 acts together with a sliding action of the beveled surface 173 along the angled portion 180, whereby the side 161 of the body 112 is biased against the radially outer lateral wall portion 154 and the body 112 is pressed against the angled portion 180.A gap 159 is created between the body 112 and the radially inner lateral wall portion 124. In the present embodiment, the tab 182 is formed on a subset of the laminations 32, i.e., on a number that is fewer than that of all the laminations 32 in the rotor core 30. For example, the tab 182 is present on only a few (2-5) of the laminations of the stack length of the rotor core 30 in order not to cause excessive pressing force for inserting the body 112 (magnet) or excessive preload. In other embodiments, a larger number of tabs 182 may be used.

[0043] The tab 182 causes the body 112 to be positioned within the cavity 85 in a seating position that is maintained during the static (non-rotating state) and during the speed (rotating state) of the rotor assembly 24. In this embodiment, the body 112 is a magnet held against the radially outer side wall portion 154. The effect of the tab 182 (which is a single or sole tab within the cavity 85 and the individual laminations 32) is to position the body 112 within the cavity 85 in a seating position that is maintained against the radially outer side wall portion 154 and the angled portion 180 during the stationary (non-rotating state) and during the speed (rotating state) of the rotor assembly 24.The preload provided by the tab 182 is sufficiently large so that the body 112 remains in the same seating position regardless of whether the rotor assembly 24 is in a stationary state or in a speed state.

[0044] During manufacturing, the components of the rotor assembly 24 may be formed, then assembled and balanced before being joined to the remaining parts of the electric machine 20. For example, the rotor assembly 24 may be rotated in a rotor balancing machine, and material may be selectively removed or added to perfect the balance. Rotor balancing studies conducted herein have shown that the body / magnet clearances in the cavities can cause changes in rotor imbalance.Having the bodies / magnets in a seated / final position during balancing in the rotor assembly 24 and the overall movement of the magnets in the laminations during operation in the field, where electromagnetic forces and centrifugal forces can sometimes counteract each other, minimizes any change in balance and its potential impact on noise, vibration and handling (NVH).

[0045] The sheet 32 ​​of the Fig. 4 and Fig. 5 is contained in a first subgroup of the laminations 32 in the rotor core 30, which have at least one tab 130, 134, 182. In Fig. 6 shows a lamination 32 which is included in a second subgroup of laminations 32 in the rotor core. The lamination 32 of Fig. 6 does not include any of the tabs 130, 134, 182, but does include the stop 132. During the manufacture of the sheets 32, for example, by stamping or another process, the sheets 32 in both subassemblies may first be formed with the tabs 130, 134, 182. Then, the tabs 130, 134, 182 may be removed, for example, by stamping, shearing, or another process. As a result, the areas of the removed tabs 130, 134, 182 have cavities that may be referred to as cutouts 131, 135, 183.

[0046] In Fig. 7, the body 112 is schematically shown in its preloaded state. The body 112 has a length 200 in the same direction as the axis 25. The body 112 has a width 202 and a thickness 204. The body 112 has sides 161-164. The body 112 has chamfered corners 165-168 that form chamfered surfaces 171-174. The tabs 182 exert a preload 206 on the body 112 at corner 166. This forces the body 112 against the angled portion 180, and the angled portion 180 of the wall 110 exerts a reaction force 208 on the body 112. Due to the preload 206 and the reaction force 208, the body 112 is preloaded with a force 210 against the radially outer lateral wall portion 154, which exerts an equal and opposite force on the body 112.As a result, the body 112 is held by the forces in a seating position against the radially outer lateral wall portion 154 and does not move in any of the stationary, balanced, or operating states of the rotor assembly 24.

[0047] In Fig. 8, the body 104 is schematically shown in its preloaded state. The body 104 has sides 141-144. The tabs 130 and 134 bias the body 104 against the stop 132 and against the radially outer lateral wall portion 126 with forces 220 and 222, respectively. The body 104 exerts a force 224 on the stop 132 and a force 226 on the radially outer lateral wall portion 126. The stop 132 balances the force 224 with a reaction force, and the radially outer lateral wall portion 126 balances the force 226 with a reaction force. As a result, the forces hold the body 104 in a seated position against the radially outer lateral wall portion 126 and do not move in any of the stationary, balanced, or operating states of the rotor assembly 24.

[0048] In Fig. Figure 9 shows a schematic representation of the longitudinally sectioned rotor core 30 in the region of the cavity 83 without the inserted body 104. The laminations 32 comprise a subgroup 138 that includes fewer than all of the laminations 32, and in this embodiment, the laminations 32 comprise two laminations 32 with tabs 130 that extend radially outward and further into the cavity 83 than other laminations 32. In other embodiments, a different number of tabs 130 may be included. The laminations 32 that do not include the tabs 130 together form another subgroup 140. Before the body 104 is inserted into the cavity 83, the tabs 130 are in a straight arrangement that extends radially into the cavity 83. After the body 104 has been inserted into the cavity 83, the tabs 130 on selected sheets 32 can bend and thereby exert a force on the body 104 (see Fig.10). This biases the body 104 against the radially outer lateral wall portion 126. The tabs 130, and hence the tabs 134, 182, are adjusted to apply a selected radially outward preload to their respective bodies 104, 112. In other embodiments, the tabs 130 are configured to apply a preload without interfering with magnet insertion and / or without requiring bending.

[0049] Accordingly, tab systems selectively place the rotor magnets of electric motors in the desired positions within the lamination slots to achieve the desired balancing characteristics. The tab systems position the magnets during the balancing process and during rotor operation. The tab systems minimize magnet movement during and after the balancing process. By minimizing magnet movement, potential changes in the rotor balance are minimized. The tab systems also fix the magnets in a centered seating position. The tab systems can use lamination tabs to apply preload to the chamfer of certain magnets, causing a reaction with the sloped cavity walls at the other end of the magnets. This allows the use of only one tab on the chamfered magnets to apply preload in both directions (along the thickness and width of the magnets).In cases where the magnets do not have a chamfer, two sheets can be used, one applying the preload along the thickness of the magnet and the other applying the preload along the width of the magnet. This positioning of the magnets reduces the initial imbalance of the rotor assembly 24 and reduces the need for additional balancing holes. The magnets are also positioned and preloaded so that they do not move at operating speeds.

[0050] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the description in any way. Rather, the foregoing detailed description is intended to provide one skilled in the art with a convenient guide for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes in the function and arrangement of elements may be made without departing from the scope of the description as set forth in the appended claims and their legal equivalents.

Claims

[1] Rotor for an electrical machine, comprising: a rotor core having at least one cavity inside the rotor core, wherein the at least one cavity is defined by a wall of the rotor core; Laminations stacked together to form the rotor core comprising the at least one cavity; and a body extending in the at least one cavity, wherein a subgroup of the sheets each comprises a tab system with at least one tab, which is configured to bias the body into a sitting position against the wall and hold the body in the sitting position. [2] The rotor of claim 1, wherein the body comprises a magnet. [3] The rotor of claim 1, wherein the body has chamfered corners, wherein the at least one tab comprises only one tab on each of the laminations in the subset of laminations, the one tab engaging the body at one of the chamfered corners. [4] Rotor according to claim 1, wherein: the body includes bevelled corners, which has at least one tab only one tab, which has a tab on one of the bevelled corners that engages the body, the wall includes an angled section that engages the body at another of the beveled corners. [5] Rotor according to claim 1, wherein: the at least one tab comprises a first tab engaging the body on a first side and a second tab engaging the body on a second side, and the first side and the second side share a common corner of the body. [6] The rotor of claim 1, wherein the at least one tab is not present on a majority of the laminations. [7] The rotor of claim 1, wherein the wall defines a stop on a first side of the body, the at least one tab being disposed on a second side of the body, the first side being opposite the second side, such that the at least one tab biases the body against the stop. [8] The rotor of claim 1, wherein the at least one tab is configured to define an interference fit between the body and the wall to establish the preload. [9] Rotor according to claim 1, wherein: the wall has a radially inner lateral wall portion, a radially outer lateral wall portion, a radially inner tip and a radially outer tip defining the cavity, and the preload presses the body against the radially outer lateral wall section and towards the radially outer tip. [10] The rotor of claim 1, wherein the rotor is configured to be in a stationary state and to operate by rotating at a speed condition, the preload being adjusted to maintain the body in the seated position during both the stationary state and the speed condition.

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