Electric machine

Abstract

The present invention discloses an electric machine (100). The electric machine (100) has a stator (102) and a rotor (104). A plurality of flux barrier groups (108) is formed on the rotor (104). A plurality of magnet groups (110) are accommodated in the plurality of flux barrier groups (108). Each magnet group (e.g., 402) has a first magnet set (430) and a second magnet set (440) accommodated in a first flux barrier (322), and similarly, a third magnet set (450) and a fourth magnet set (460) accommodated in a second flux barrier (324). Each of the first magnet set (430), the second magnet set (440), the third magnet set (450), and the fourth magnet set (460) has a first magnet (432, 442, 452, 462) accommodated along the direction of a D-axis and a second magnet (434, 444, 454, 464) accommodated in a Q-axis.

Description

ELECTRIC MACHINECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Indian Non-provisional patent application 202411022417, filed on 22ndMarch 2024 which is incorporated herein in its entirety by this reference thereto.FIELD OF INVENTION

[0002] The present disclosure relates to an electric machine and, more particularly to a Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSRM), with increased torque and improved reluctance to magnetic flux.BACKGROUND

[0003] A reluctance motor is a type of electric motor used in multiple applications, such as power tools, washing machines, vehicles, for example, Electric Vehicles (EVs), and the like. Similar to every other motor, reluctance motors also have a stator and a rotor. The stator includes windings over multiple projections forming multiple electromagnetic poles. The rotor also includes multiple projections forming induced non-permanent magnetic poles through magnetic reluctance. It is to be noted that the rotor is generally a ferromagnetic rotor without any windings. The rotor generates torque through magnetic reluctance. Magnetic reluctance is the reluctance of the magnetic material indicating its ability to oppose the flow of magnetic flux. Generally, the magnetic flux created by the field windings follows the path of least magnetic reluctance. The rotor rotates to align itself with the magnetic field to minimize reluctance and maximize torque.

[0004] Synchronous Reluctance Motor (SynRM) is a type of reluctance motor that has an equal number of stator and rotor poles. The rotor has multiple projections that introduce internal flux barriers that direct the magnetic flux along a direct axis (D-axis). The windings on the stator create a rotating magnetic field, and the rotor poles get attracted towards the stator poles and rotate at synchronous speed. Nowadays, the requirements for security, range, power density, and torque of motors that are used in several applications such as EVs are rising steadily. Existing reluctance motors, provide low power density, low torque density, and low efficiency due to high rotor mass.

[0005] To address the above-mentioned problems, a Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSRM) has been introduced in the market. A PMaSRM is a type of SynRM that has permanent magnets accommodated in the rotor. Conventionally, there exist different types of PMaSRMs having different arrangements for the permanent magnets in the rotor. However, the torque generated by conventional PMaSRMs is still less and has a scope for improvement. Moreover, the magnets positioned on the rotor of some of the conventional PMaSRMs are arranged only in the direction of the D-axis. The positioning of the magnets only along the direction of the D-axis has certain drawbacks such as the increase in the magnetic reluctance at all speeds of the motor. As a consequence of the increase in magnetic reluctance at all speeds, the output torque also decreases which is a result of magnetic torque and reluctance torque. Also, most of these machines are constructed with single 3- phase windings which deliver lower power compared to the proposed machine.SUMMARY

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0007] In order to solve the foregoing problems and to provide other advantages, one aspect of the present invention is to provide an electric machine. The electric machine includes a stator and a rotor. The stator includes a plurality of slots formed therein. The rotor is adapted to rotate within the stator. The rotor includes a plurality of magnet groups accommodated circumferentially within a plurality of flux barrier groups formed on the rotor. At least one magnet group of the plurality of magnet groups includes a plurality of magnet sets. At least one magnet set has at least one first magnet arranged along the direction of a D-axis. The at least one magnet set also has at least one second magnet arranged along the direction of a Q-axis. The at least one first magnet is positioned at a first predetermined angle with respect to the corresponding at least one second magnet in the at least one magnet set. The plurality of magnet sets includes a first magnet set and a second magnet set accommodated in a first flux barrier of at least one flux barrier group of the plurality of flux barrier groups. The first flux barrier is formed in proximity to a periphery of the rotor. The plurality of magnet sets includes a third magnet set and a fourth magnet set accommodated in a second flux barrier of the at least one flux barrier group. The second flux barrier is formed parallelly towards an outer side of thefirst flux barrier.

[0008] In an aspect, the at least one second magnet in the first magnet set and the third magnet set, respectively in one magnet group are accommodated parallelly with the at least one second magnet in the second magnet set and the fourth magnet set, respectively in an adjacent magnet group. The at least one second magnet in the second magnet set and the fourth magnet set, respectively in one magnet group are accommodated parallelly with the at least one second magnet in the first magnet set and the third magnet set, respectively in an adjacent magnet group.

[0009] In an aspect, the at least one first magnet and the at least one second magnet in each of the first magnet set and the second magnet set are accommodated with a first predefined spacing. The at least one first magnet and the at least one second magnet in each of the third magnet set and the fourth set are accommodated with a second predefined spacing. The second predefined spacing is such that the at least one second magnet (454) in the third magnet set (450) is in line with the at least one second magnet (434) in the first magnet set (430), and the at least one second magnet (464) in the fourth magnet set (460) is in line with the at least one second magnet (444) in the second magnet set (440).

[0010] In an aspect, the at least one first magnet and the at least one second magnet of each of the plurality of magnet sets are configured to provide a minimum magnetic reluctance path from the stator to the rotor.

[0011] In an aspect, the first flux barrier is split into a first groove accommodating the first magnet set and a second groove accommodating the second magnet set, and the second flux barrier is split into a third groove accommodating the third magnet set and a fourth groove accommodating the fourth magnet set. Herein, each of the first groove, the second groove, the third groove, and the fourth groove has a V-shape and includes at least one holder to hold the plurality of magnet sets in the first flux barrier and the second flux barrier

[0012] In an aspect, each of the first flux barrier and the second flux barrier, has an oblique U-shape facing outwards from a center of the rotor.

[0013] In an aspect, the rotor includes a first predefined count of magnetic poles generated upon operation of the electric machine. Herein, the first predefined count comprises ten.

[0014] In an aspect, the stator includes a second predefined count of the plurality of slots comprising stator windings. Herein, the second predefined count comprises twelve.

[0015] In an aspect, the Q-axis makes a second predefined angle with the D-axis. Herein, the first predefined angle is based at least on the second predefined angle, and a first orientation of the at least one first magnet and a second orientation of the at least one second magnet within the at least one magnet group.

[0016] In an aspect, the at least one first magnet and the at least one second magnet of the plurality of magnet groups are of the same size and shape.

[0017] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.BRIEF DESCRIPTION OF THE FIGURES

[0018] The invention itself, together with further features and advantages, will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments of the present disclosure are now described, by way of example only wherein like reference numerals represent like elements and in which:

[0019] Figure 1 illustrates a perspective view of an electric machine, in accordance with an embodiment of the invention;

[0020] Figure 2 illustrates a perspective view of a stator of the electric machine of Figure 1, in accordance with an embodiment of the invention;

[0021] Figure 3 illustrates a perspective view of a rotor of the electric machine of Figure 1, in accordance with an embodiment of the invention;

[0022] Figure 4A illustrates a front view of the rotor of the electric machine depicting an arrangement of a plurality of magnet groups within the rotor, in accordance with an embodiment of the invention;

[0023] Figure 4B illustrates a front view of a magnet group of the plurality ofmagnet groups of Figure 4A, in accordance with an embodiment of the invention;

[0024] Figure 4C illustrates a front view of three adjacent magnet groups of the plurality of magnet groups of Figure 4A, in accordance with an embodiment of the invention;

[0025] Figure 4D illustrates a front view of two magnet sets of the magnet group of Figure 4C, in accordance with an embodiment of the invention;

[0026] Figure 5 illustrates a perspective view of the rotor revealing an interior view of the plurality of magnet groups accommodated within the rotor, in accordance with an embodiment of the invention;

[0027] Figure 6 illustrates a simulation result from a Finite Element Analysis (FEA) of the electric machine of Figure 1 depicting a flow of magnetic flux between the stator and the rotor of the electric machine, in accordance with an embodiment of the invention; and

[0028] Figure 7 illustrates a graphical representation of a variation of total torque with total speed of the electric machine, in accordance with an embodiment of the invention.

[0029] The drawings referred to in this description are not to be understood as being drawn to scale except if specifically noted, and such drawings are only exemplary in nature.DETAILED DESCRIPTION

[0030] While the invention is susceptible to various modifications and alternative forms, a 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 invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention.

[0031] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device, or method 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 device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises. . . a” does not, without more constraints, preclude the existence of other elements or additional elementsin the system or apparatus.

[0032] For a better understanding of this invention, a reference would now be made to the embodiment illustrated in the accompanying figures and description below. Further, in the following figures, the same reference numerals are used to identify the same components in various views.

[0033] While the present invention is illustrated in the context of an electric machine (e.g., synchronous electric motor), however, aspects and features thereof can be used with other types of machines as well. The terms “electric machine”, “electric motor”, “synchronous electric motor”, “Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSRM)”, and “PMaSRM” have been interchangeably used throughout the description.

[0034] Figure 1 illustrates a perspective view of an electric machine (100), in accordance with an embodiment of the invention. An example of the electric machine (100) as shown in Figure 1 is a Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSRM). The PMaSRM is a type of synchronous reluctance motor having a stator (e.g., poly-phase, two 3-phase stators, a 6-phase stator, or a dual stator) (also referred to as the stator (102)) and a rotor (also referred to as the rotor (104)). The synchronous reluctance motor generates a Rotating Magnetic Field (RMF), that runs at a predetermined speed by converting electrical currentAC) supplied to the stator (102) to mechanical energy (i.e., rotational energy). These motors can also run at different speeds based on changes in supply frequency which is controlled by a motor controller. Furthermore, these machines can also work in regeneration mode to deliver power back to a power source such as a battery pack (which is not explained here because it is not the scope of this invention).

[0035] The stator (102) has a plurality of slots (shown in Figure 2) that allow stator windings (106) to pass through therein. In a non-limiting implementation, the stator windings (106) can be of two 3-phase concentrated winding sets with a star or a delta connection. The stator windings (106) (also called armature winding) are excited by two 3-phase supplies. In an embodiment, the two 3-phase winding sets can have a 30-degree displacement between them. It is to be noted that having a 6-phase motor provides redundancy in a case when one supply system fails (i.e., one of the two 3-phase supplies) as well as provides more power input / output of the machine.

[0036] The rotor (104) is positioned inside the stator (102). In one non-limitingimplementation, the rotor (104) is made up of multiple steel laminations arranged adjacent to each other to reduce eddy current losses. In another non-limiting implementation, the rotor (104) is a single, solid, and cylindrical metal piece with a predefined thickness. In an embodiment, the metal piece may be composed of a ferromagnetic material. The rotor (104) has a plurality of flux barrier groups (108) that are configured to accommodate a plurality of magnet groups (110) in the rotor (104). The plurality of magnet groups (110) includes but is not limited to a plurality of permanent magnets of equal size and shape. The rotor (104) also has a shaft (112) connected to at least one device (not shown in Figure 1) that requires mechanical energy. For example, the shaft (112) of the rotor (104) can be connected to the wheels of a vehicle, for example, an electric vehicle (e.g., an electric scooter).

[0037] Upon supplying the 6-phase supply to the stator windings (106), RMF is generated around the stator (102). The north pole of the rotating magnetic field in the stator (102) and the south pole of the plurality of magnet groups (110) should create a magnetic locking, similarly, the south pole of the RMF in the stator (102) and the north pole of the plurality of magnet groups (110) creates the magnetic locking. Upon magnetic locking, that is locking of the north pole of the RMF in the stator (102) with the south pole of the plurality of magnet groups (110), and also the south pole of the RMF in the stator (102) with the north pole of the plurality of magnet groups (110), the rotor (104) will rotate at the synchronous speed of the RMF. As per Ampere’s principle, the magnetic locking generates a torque that allows the rotor (104) to start rotating. The shaft (112) of the rotor (104) transfers the torque to the other device, which requires mechanical energy. The detailed working of the electric machine (100) is not further explained, as it is a well-known art in the electric machines.

[0038] It should be noted that the plurality of magnet groups (110) accommodated in the plurality of flux barrier groups (108) creates a difference of reluctance in the rotor (104). This allows a low reluctance portion of the rotor (104) to get magnetically locked with the RMF generated in the stator (102). Thus, the arrangement and accommodation of the plurality of magnet groups (110) in the plurality of flux barrier groups (108) generate a low reluctance path for magnetic linkage so that more flux passes through the rotor (104). This increases the torque (also called the reluctance torque) induced on the rotor (104).

[0039] Figure 2 illustrates a perspective view of the stator (102) of the electric machine (100) of Figure 1 , in accordance with an embodiment of the invention. The stator (102) includes various parts such as a frame (202), a stator core (204), a plurality of slots (206), thestator windings (106) (see, Figure 1), cooling mechanisms (not shown in Figure 2), etc. The frame (202) is the outer part of the electric machine (100) and is made up of cast iron for smallsized machines, and welded steel for large-sized machines. The stator core (204) includes a plurality of projections formed towards an inner surface of the stator core (204). The stator (102) has a predefined count of the plurality of slots (206) that are formed due to the plurality of projections. The stator windings (106) of two 3-phase concentrated winding are wound around the plurality of projections and through the plurality of slots (206). These windings are supplied with the two 3-phase AC power supply. In some embodiments, a predefined count of the plurality of slots (206) as shown in Figure 2 is about twelve. In some other embodiments, the predefined count of the plurality of slots (206) can be any number less than or greater than twelve, without limiting the scope of the invention. However, a greater number of slots (206) is difficult in terms of manufacturability. The stator core (204) of the stator (102) is constructed with a thin silicon lamination and insulated by a surface coating, to minimize the eddy current and hysteresis losses.

[0040] Figure 3 illustrates a perspective view of the rotor (104) of the electric machine (100) of Figure 1, in accordance with an embodiment of the invention. The rotor (104) is adapted to rotate within the stator (102) due to magnetic reluctance developed within the electric machine (100). The rotor (104) is formed with the plurality of flux barrier groups (108). In one embodiment, the plurality of flux barrier groups (108) include flux barrier groups (302, 304, 306, 308, 310, 312, 314, 316, 318, and 320). At least one flux barrier group (302) of the plurality of flux barrier groups (108) includes a first flux barrier (322) and a second flux barrier (324). The first flux barrier (322) is formed in proximity to a periphery (325) of the rotor (104). The second flux barrier (324) is formed parallelly towards an outer side (327) of the first flux barrier (322). The plurality of magnet groups (110) is accommodated circumferentially within the plurality of flux barrier groups (108), with one magnet group being accommodated within one flux barrier group. It is to be noted that the plurality of magnet groups (110) includes a plurality of magnet sets (shown in Figure 4A). At least one magnet set includes at least one first magnet and at least one second magnet (shown in Figure 4A) arranged within the plurality of flux barrier groups (108). The arrangement of the plurality of magnet groups (110) is explained in Figure 4A. The first flux barrier (322) includes a first groove (326) and a second groove (328). The second flux barrier (324) includes a third groove (330) and a fourth groove (332). The first groove (326) in the first flux barrier (322) includes a first holder (334). The second groove (328) in the first flux barrier (322) includes a second holder (336). Each of the firstholder (334) and the second holder (336) is configured to hold the at least one second magnet within the first flux barrier (322). The first holder (334) and the second holder (336) prevent the magnets (the corresponding at least one second magnet) from slipping and dropping out of the rotor (104).

[0041] Each of the first groove (326), the second groove (328), the third groove (330), and the fourth groove (332) accommodate two magnets (z.e., the at least one first magnet and the at least one second magnet). The length of the first flux barrier (322) is less than the second flux barrier (324). Thus, in the first flux barrier (322), the magnets are positioned close to each other and hence, only one holder, that is the first holder (334) and the second holder (336) is sufficient to hold its respective the first magnet (e.g., 432, 442) and the second magnet (e.g., 434, 444) shown in Figure 4A. In the case of the second flux barrier (324), each magnet (e.g., a first magnet (452)) needs to be held by its respective holders (e.g., the third holder (338)). The third groove (330) in the second flux barrier (324) includes a third holder (338), and a fourth holder (340). The fourth groove (332) in the second flux barrier (324) includes a fifth holder (342), and a sixth holder (344). Each of the third holder (338), and the fourth holder (340), is configured to hold at least one magnet of the plurality of magnet groups (110) within the second flux barrier (324). They prevent the magnets from slipping and dropping out of the rotor (104). Each of the fifth holder (342), and the sixth holder (344) are configured to hold at least one magnet of the plurality of magnet groups (110) within the second flux barrier (324). They prevent the magnet from slipping and dropping out of the rotor (104).

[0042] It should be noted that to explain the structure of the plurality of flux barrier groups (108), the flux barrier group (302) is taken as an example. The explanation of the structure of the other flux barrier groups (304, 306, 308, 310, 312, 314, 316, 318, and 320) is similar to the flux barrier group (302), hence the arrangement and positioning of other flux barrier groups (304, 306, 308, 310, 312, 314, 316, 318, and 320) are not explained in the present disclosure for the sake of brevity.

[0043] Figure 4A illustrates a front view of the rotor (104) of the electric machine (100) depicting an arrangement of the plurality of magnet groups (110) within the rotor (104), in accordance with an embodiment of the invention. Each flux barrier group, (302, 304, 306, 308, 310, 312, 314, 316, 318, and 320) of the plurality of flux barrier groups (108) is accommodated with respective magnet groups (402, 404, 406, 408, 410, 412, 414, 416, 418, and 420) of the plurality of magnet groups (110). Thus, the plurality of magnet groups (110)accommodated circumferentially within the plurality of flux barrier groups (108) formed on the rotor (104). It is to be noted that for the explanation of the arrangement of the plurality of magnet groups (110), the magnet group (402) is taken as an example. The structure and arrangement of the magnet group (402) are explained with reference to Figure 4B. The arrangement and accommodation of the other magnet groups (404, 406, 408, 410, 412, 414, 416, 418, and 420) are similar to that of the magnet group (402), hence for the sake of brevity, they are not explained in this disclosure.

[0044] Figure 4B illustrates a front view of the magnet group (402) of the plurality of magnet groups (110) of Figure 4A, in accordance with an embodiment of the invention. Figure 4B is explained with respect to the magnet group (z.e., magnet group (402)). The magnet group (402) includes a plurality of magnet sets, such as a first magnet set (430), a second magnet set (440), a third magnet set (450), and a fourth magnet set (460). Each magnet set (e.g., the first magnet set 430) in the plurality of magnet sets (430, 440, 450, 460) includes the first magnet (e.g., 432) and the second magnet (e.g., 434). As may be understood, the first magnet set (430) has the first magnet (432) and the second magnet (434). The first magnet (432) in the first magnet set (430) is accommodated in the first groove (326) of the first flux barrier (322) along a direction of a direct axis (D-axis). The second magnet (434) in the first magnet set (430) is accommodated in the first groove (326) of the first flux barrier (322), along the direction of a quadrature axis (Q-axis).

[0045] The first magnet (432) is positioned at a first predetermined angle (A) with respect to the second magnet (434) in the first magnet set (430). The first magnet (432, 442) and the second magnet (434, 444) in each of the first magnet set (430) and the second magnet set (440) are accommodated with a first predefined spacing. Similarly, the first magnet (452, 462) and the second magnet (454, 464) in each of the third magnet set (450) and the fourth magnet set (460) are accommodated with a second predefined spacing. A portion of the first groove (326) that is not accommodated with the first magnet (432) and the second magnet (434) of the first magnet set (430) forms a first air gap (436) having the first predefined spacing. The first air gap (436) is of high reluctance to the RMF of the stator (102).

[0046] Similarly, the second magnet set (440) has the first magnet (442) and the second magnet (444). The first magnet (442) in the second magnet set (440) is accommodated in the second groove (328) of the first flux barrier (322) along the direction of the D-axis. The second magnet (444) in the second magnet set (440) is accommodated in the second groove(328) of the first flux barrier (322), along the direction of the Q-axis. The first magnet (442) is positioned at the first predetermined angle (A) with respect to the second magnet (444) in the second magnet set (440). A portion of the second groove (328) that is not accommodated with the first magnet (442) and the second magnet (444) of the second magnet set (440) forms a second air gap (446) having the first predefined spacing. The second air gap (446) is of high reluctance to the RMF of the stator (102).

[0047] Further, the third magnet set (450) accommodated in the second flux barrier (324) has the first magnet (452) and the second magnet (454). The first magnet (452) in the third magnet set (450) is accommodated in the third groove (330) of the second flux barrier (324) along the direction of the D-axis. The second magnet (454) in the third magnet set (450) is accommodated in the first groove (326) of the second flux barrier (324), along the direction of the Q-axis. The first magnet (452) is positioned at the first predetermined angle (A) with respect to the second magnet (454) in the third magnet set (450). A portion of the third groove (330) that is not accommodated with the first magnet (452) and the second magnet (454) of the third magnet set (450) forms a third air gap (456) having the second predefined spacing. The third air gap (456) is of high reluctance to the RMF of the stator (102).

[0048] Furthermore, the fourth magnet set (460) accommodated in the second flux barrier (324) has the first magnet (442) and the second magnet (444). The first magnet (442) in the second magnet set (440) is accommodated in the second groove (328) of the second flux barrier (324) along the direction of the D-axis, and the second magnet (444) in the second magnet set (440) is accommodated in the second groove (328) of the second flux barrier (324), along the direction of the Q-axis. The first magnet (442) is positioned at the first predetermined angle (A) with respect to the second magnet (444) in the magnet set (440). A portion of the fourth groove (332) that is not accommodated with the first magnet (462) and the second magnet (464) of the fourth magnet set (460) forms a fourth air gap (466) having the second predefined spacing. The fourth air gap (466) is of high reluctance to the RMF of the stator (102).

[0049] In one embodiment, the second predefined spacing is such that the at least one second magnet (454) in the third magnet set (450) is in line with the at least one second magnet (434) in the first magnet set (430), and the at least one second magnet (464) in the fourth magnet set (460) is in line with the at least one second magnet (444) in the second magnet set (440). In a non-limiting implementation, the first predetermined angle (A) is calculated with the following formula:A = 90 + (90 / p) Equation (1) where ‘A’ represents the first predetermined angle, ‘p’ represents the number of pairs of poles in the rotor (104).

[0050] In one embodiment, a first predefined count of magnetic poles is generated in the rotor (104), upon operation of the electric machine (100). For example, if the first predefined count includes ten, then the number of the pair of poles corresponds to five. The first predetermined angle (A) (see, Figure 4C) calculated using Equation (1) would be about 108 degrees.

[0051] In geometric terms, the D-axis and the Q-axis are the single -phase representations of the magnetic flux contributed by the three separate sinusoidal phase quantities at the same angular velocity. The D-axis is the axis in the direction of which magnetic flux is produced by the stator windings (106). The Q-axis is the axis on which torque is produced. By convention, the quadrature axis always will lead the direct axis electrically by 90 degrees. In other words, the D-axis is the main flux direction, while the Q-axis is the main torque-producing direction. The angle between the D-axis and the Q-axis varies depending on the number of poles. Thus, the angle (i.e., second predetermined angle (B)) between the Q-axis and P-axis is 18 degrees (i.e., 90 / p) for the number of poles being about five. As a result, the angle between the first magnet (e.g., 432) and the second magnet (e.g., 434) is 108 degrees.

[0052] Figure 4C illustrates a front view of three adjacent magnet groups (402, 404, 406) of the plurality of magnet groups (110) of Figure 4A, in accordance with an embodiment of the invention. The second magnet (434, 454) in the first magnet set (430) and the third magnet set (450), respectively of one magnet group (e.g., magnet group (402)) are in line with the second magnet (444(1), 464(1)) in the second magnet set (440(1)) and the fourth magnet set (460(1)), respectively of the adjacent magnet group (e.g., magnet group (404)). Similarly, the second magnet (444, 464) in the second magnet set (440) and the fourth magnet set (460), respectively of the magnet group (e.g., the magnet group (402)) are in line with the second magnet (434(2), 454(2)) in the first magnet set (430(2)) and the third magnet set (450(2)), respectively of another adjacent magnet group (e.g., magnet group (406)). The first magnet (432, 442) in the first magnet set (430) and the second magnet set (440) of one magnet group (e.g., magnet group (402)) are in line with each other. Similarly, the first magnet (452, 462) in the third magnet set (450) and the fourth magnet set (460) of the same magnet group (e.g., magnet group (402)) are in line with each other. This forms an oblique U-shaped structure inthe at least one magnet group (e.g., magnet group (402)). More specifically, each of the first flux barrier (322) and the second flux barrier (324), has an oblique U-shape facing outwards from a center of the rotor (104).

[0053] It should be noted that the first magnet (432, 442, 452, 462) in the first magnet set (430), the second magnet set (440), the third magnet set (450), and the fourth magnet set (460), respectively are positioned in the direction of the D-axis at a first orientation. In one embodiment, the first orientation is along the width direction of the first magnet (432, 442, 452, 462) in the first magnet set (430), the second magnet set (440), the third magnet set (450), and the fourth magnet set (460). Further, the second magnet (434, 444, 454, 464) in the first magnet set (430), the second magnet set (440), the third magnet set (450), and the fourth magnet set (460), respectively are positioned in the direction of the Q-axis at a second orientation. In one embodiment, the second orientation is along the length direction of the second magnet (434, 444, 454, 464) in the first magnet set (430), the second magnet set (440), the third magnet set (450), and the fourth magnet set (460).

[0054] Figure 4D illustrates a front view of two magnet sets ( / '.<?., the first magnet set (430) and the third magnet set (450)) of the magnet group (e.g., magnet group (402)) of Figure 4C, in accordance with an embodiment of the invention. The angle between the first magnet (432) and the second magnet (434) of the first magnet set (430) accommodated in the first groove (326) of the first flux barrier (322) is arranged in V-shape with the first predetermined angle (A). The first predetermined angle (A) is also applicable to the first magnet (442, 452, 462) and the second magnet (444, 454, 464) in other magnet sets (e.g., the second magnet set (440), the third magnet set (450), and the fourth magnet set (460)) of the magnet group (402). Moreover, the first orientation of the first magnet (432, 442, 452, 462) and the second orientation of the second magnet (434, 444, 454, 464) makes the first predetermined angle (A).

[0055] Figure 5 illustrates a perspective view of the rotor (104) revealing an interior view of the plurality of magnet groups (110) accommodated within the rotor (104), in accordance with an embodiment of the invention. In a non-limiting implementation, each magnet (e.g., the first magnet (432) and the second magnet (434)) in the rotor (104) is cuboidal in shape. Also, each magnet (e.g., first magnet (432), second magnet (434)) is of the same size and shape, which allows easy manufacturing of the plurality of magnet groups (110) accommodated in the plurality of flux barrier groups (108) of the rotor (104).

[0056] Figure 6 illustrates a simulation result (600) from a Finite Element Analysis (FEA) of the electric machine (100) of Figure 1 depicting a flow of magnetic flux between the stator (102) and the rotor (104) of the electric machine (100), in accordance with an embodiment of the invention. The arrangement of the plurality of magnet groups (110) in the plurality of flux barrier groups (108) creates a varying magnetic reluctance in the rotor (104). Varying magnetic reluctance in the rotor (104), allows the rotor (104) to magnetically link with the RMF of the stator (102). The plurality of magnet groups (110) and a rotor core (604) at the periphery (325) has a low reluctance path so that most of the magnetic flux (602) of the stator (102) passes through the plurality of magnet groups (110) and the rotor (104). The plurality of air gaps (e.g., the first air gap (436), the second air gap (446), etc.,) is of high reluctance to the magnetic flux (602). Thus restricting the magnetic flux (602) to flow through the plurality of air gaps e.g., the first air gap (436), the second air gap (446), etc.,). The lowest reluctance area (606) on the rotor (104) and the high reluctance area (608) on the rotor (104) are shown in Figure 6. The arrangement of the plurality of magnet groups (110) in the plurality of flux barrier groups (108), creates a low reluctance path to the magnetic flux (602), thereby allowing more magnetic flux (602) to pass through. The magnetic flux (602) flows through the plurality of magnet groups (110) and the rotor (104), thereby quickly increasing the magnetic linkage with the rotor (104) to synchronous speed.

[0057] Figure 7 illustrates a graphical representation (700) of a variation of total torque and total speed of the electric machine (100), in accordance with an embodiment of the invention. Figure 7 shows a continuous duty zone of a torque-speed curve (702) and the peak or intermittent torque zone of a torque-speed curve (704) of the electric machine (100) of the present invention. In the continuous duty zone of the torque-speed curve (702), the torque and speed of the electric machine (100) can be produced indefinitely without overheating or damage to the electric machine (100). In the peak (i.e., intermittent) torque zone of the torque- speed curve (704), the highest torque of the electric machine (100) can be produced at a given speed for a limited amount of time (typically a few milliseconds). From Figure 7, it may be observed that, in a non-limiting implementation of the present invention, a maximum torque of the electric machine (100) that can be achieved in the peak duty zone is in the range of about 40 Newton-meter (Nm) to about 50 Nm. Similarly, in the continuous torque zone, the maximum torque that can be achieved would be in the range of about 25 Nm to about 30 Nm. Moreover, when compared to prior art or conventional machines, the torque is observed to be almost doubled in both the continuous duty zone and the peak (i.e., intermittent) torque zone.

[0058] The present invention uses the plurality of magnet groups (110) accommodated in the plurality of flux barrier groups (108), to create varying reluctance in the rotor (104) of the electric machine (100). The varying reluctance in the rotor (104) allows the rotor (104) to achieve the synchronous speed earlier as compared to when the conventional electric machines achieve. Thus, positioning the plurality of magnet groups (110) in the directions of the Q-axis increases magnetic reluctance at all speeds, without decreasing the torque. The present invention increases the output reluctance and torque. The first flux barrier (322) and the second flux barrier (324) in each magnet group (e.g., 402) in the rotor (104) provide maximum torque and power density to the electric machine (100).

[0059] While few embodiments of the present invention have been described above, it is to be understood that the invention is not limited to the above embodiments and modifications may be appropriately made thereto within the spirit and scope of the invention.

[0060] While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the invention herein, whereby 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.

Claims

CLAIMS

1. An electric machine (100) comprising: a stator (102) comprising a plurality of slots (206) formed therein; and a rotor (104) adapted to rotate within the stator (102), the rotor (104) comprising a plurality of magnet groups (110) accommodated circumferentially within a plurality of flux barrier groups (108) formed on the rotor (104), at least one magnet group (402) of the plurality of magnet groups (110) comprising a plurality of magnet sets (430, 440, 450, 460), at least one magnet set (430) of the plurality of magnet sets (430, 440, 450, 460) comprising: at least one first magnet (432) arranged along the direction of a D-axis, and at least one second magnet (434) arranged along the direction of a Q- axis, wherein the at least one first magnet (432) is positioned at a first predetermined angle (A) with respect to the corresponding at least one second magnet (434) in the at least one magnet set (430), wherein the plurality of magnet sets (430, 440, 450, 460) comprises a first magnet set (430) and a second magnet set (440) accommodated in a first flux barrier (322) of at least one flux barrier group (302) of the plurality of flux barrier groups (108), the first flux barrier (322) formed in proximity to a periphery (325) of the rotor (104), wherein the plurality of magnet sets (430, 440, 450, 460) comprises a third magnet set (450) and a fourth magnet set (460) accommodated in a second flux barrier (324) of the at least one flux barrier group (302), the second flux barrier (324) formed parallelly towards an outer side (327) of the first flux barrier (322).

2. The electric machine (100) as claimed in claim 1, wherein: the at least one second magnet (434, 454) in the first magnet set (430) and the third magnet set (450), respectively in one magnet group (402) are arranged parallelly with the at least one second magnet (444(1), 464(1)) in the second magnet set (440(1)) and the fourth magnet set (460(1)), respectively in an adjacent magnet group (404), and the at least one second magnet (444, 464) in the second magnet set (440) and the fourth magnet set (460), respectively in one magnet group (402) are arranged parallelly with the at least one second magnet (434(2), 454(2)) in the first magnet set (430(2)) and the third magnet set (450(2)), respectively in an adjacent magnet group (406).

3. The electric machine (100) as claimed in claim 1, wherein: the at least one first magnet (432, 442) and the at least one second magnet (434, 444) in each of the first magnet set (430) and the second magnet set (440) are arranged with a first predefined spacing, the at least one first magnet (452, 462) and the at least one second magnet (454, 464) in each of the third magnet set (450) and the fourth set (460) are arranged with a second predefined spacing, and the second predefined spacing is such that the at least one second magnet (454) in the third magnet set (450) is in line with the at least one second magnet (434) in the first magnet set (430), and the at least one second magnet (464) in the fourth magnet set (460) is in line with the at least one second magnet (444) in the second magnet set (440).

4. The electric machine (100) as claimed in claim 1, wherein the at least one first magnet (432, 442, 452, or 462) and the at least one second magnet (434, 444, 454, or 464) of each of the plurality of magnet sets (430, 440, 450, 460) are configured to provide a minimum magnetic reluctance path from the stator (102) to the rotor (104).

5. The electric machine (100) as claimed in claim 1, wherein the first flux barrier (322) is split into a first groove (326) accommodating the first magnet set (430) and a second groove (328) accommodating the second magnet set (440), and the second flux barrier (324) is split into a third groove (330) accommodating the third magnet set (450) and a fourth groove (332) accommodating the fourth magnet set (460), wherein each of the first groove (326), the second groove (328), the third groove (330), and the fourth groove (332) has a V-shape and comprises at least one holder (334, 336, 338, 340, 342, or 344) to hold the plurality of magnet sets (430, 440, 450, 460) in the first flux barrier (322) and the second flux barrier (324).

6. The electric machine (100) as claimed in claim 1, wherein each of the first flux barrier (322) and the second flux barrier (324), has an oblique U-shape facing outwards from a center of the rotor (104).

7. The electric machine (100) as claimed in claim 1, wherein the rotor (104) comprises a first predefined count of magnetic poles generated upon operation of the electric machine (100), wherein the first predefined count comprises ten.

8. The electric machine (100) as claimed in claim 1, wherein the stator (102) comprises a second predefined count of the plurality of slots (206) comprising stator windings (106), wherein the second predefined count comprises twelve.

9. The electric machine (100) as claimed in claim 1, wherein the Q-axis makes a second predefined angle (B) with the D-axis, wherein the first predefined angle (A) is based at least on the second predefined angle (B), and a first orientation of the at least one first magnet (432, 442, 452, 462) and a second orientation of the at least one second magnet (434, 444, 454, 464) within the at least one magnet group (402).

10. The electric machine (100) as claimed in claim 1, wherein the at least one first magnet (432, 442, 452, 462) and the at least one second magnet (434, 444, 454, 464) of the plurality of magnet groups (110) are of same size and shape.

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