Rotor and motor

Abstract

The utility model provides a rotor and a motor, and belongs to the technical field of motors. Wherein the rotor comprises an iron core and a permanent magnet, a plurality of slotted hole groups are annularly distributed on the iron core at intervals, each slotted hole group comprises at least one slotted hole, the slotted holes penetrate through the iron core along the axial direction, the end part of at least one slotted hole in each slotted hole group extends to the periphery of the iron core, and a polymer coating layer is arranged on the periphery of the iron core; the number of the permanent magnets is multiple, and the multiple permanent magnets are correspondingly arranged in the slotted holes. According to the utility model, no magnetic isolation bridge is arranged at the periphery of the rotor, so that the problem of magnetic leakage can be reduced, and the permanent magnetic flux of the rotor can be improved. The polymer coating layer can reduce the problem that the permanent magnets are thrown out at a high rotating speed, and compared with a carbon fiber coating sleeve arranged on the periphery of the rotor, the polymer coating layer can reduce the cost. Therefore, the magnetic flux leakage problem can be improved on the basis of reducing the cost, the torque of the motor is improved, and the power density of the motor is increased.

Description

TECHNICAL FIELD

[0001] The utility model relates to motor technical field, especially a rotor and motor. BACKGROUND

[0002] The magnetic bridge in the rotor core is mainly used for separating the magnetic circuit of different magnetic poles, and is usually a relatively narrow part. In the magnetic field environment of the motor, the magnetic bridge provides a high-magnetic-resistance path, so that the magnetic flux line can smoothly pass through the air gap on the basis of ensuring the strength, instead of self-leakage in the rotor core. In this way, most of the magnetic flux is limited in the main magnetic circuit of the motor, reducing the leakage and related losses.

[0003] With the development of the motor towards high speed, the magnetic bridge is prone to breakage under high speed conditions. Therefore, the magnetic bridge is usually not set too narrow in the prior art, but this leads to more opportunities for the magnetic flux line to bypass the magnetic bridge, thereby generating leakage.

[0004] Therefore, the related art proposes a method of canceling the magnetic bridge between adjacent permanent magnets and fixing by plastic isolation to reduce leakage, but this technology needs to set a carbon fiber sleeve outside the rotor core, which not only has high cost, but also has complex process. SUMMARY

[0005] In view of the above problems, the utility model provides a rotor and motor, aiming to reduce leakage on the basis of reducing cost.

[0006] In the first aspect, the utility model provides a rotor, which comprises a core and a permanent magnet, a plurality of slot hole groups are annularly and spacedly distributed on the core, each slot hole group comprises at least one slot hole, the slot hole penetrates the core along the axial direction, the end of at least one slot hole in the slot hole group extends to the outer periphery of the core, and a polymer coating layer is arranged on the outer periphery of the core; a plurality of permanent magnets are arranged in the slot holes.

[0007] In some embodiments, the thickness of the polymer coating layer is less than or equal to 0.5 mm.

[0008] In some embodiments, the rotor further comprises a polymer fixing member, which is filled in the slot hole to fix the permanent magnet.

[0009] In some embodiments, the polymer coating layer and the polymer fixing member are integrally formed.

[0010] In some embodiments, the polymer of the polymer coating layer contains one of epoxy resin, acrylate resin, silicone resin, phenolic resin, unsaturated polyester resin and polyurethane resin.

[0011] In some embodiments, the slot group is provided with one slot hole, and both ends of the slot hole extend to the outer periphery of the core.

[0012] In some embodiments, the slot group is provided with a plurality of slot holes, and the plurality of slot holes are distributed at intervals along the radial direction of the core, and both ends of the plurality of slot holes extend to the outer periphery of the core.

[0013] In some embodiments, the slot hole is selected from one of a straight slot, a V-shaped slot, and a U-shaped slot; or, the slot hole is selected from one of a combination of a straight slot and a V-shaped slot, a combination of a straight slot and a U-shaped slot, and a combination of a V-shaped slot and a U-shaped slot; or, the slot hole is selected from a combination of two or more V-shaped slots and U-shaped slots.

[0014] In some embodiments, the slot group is provided with two slot holes, and the two slot holes are distributed at intervals along the radial direction of the core; both the slot I and the slot II of the two slot holes extend to the outer periphery of the core, and both the inner ends of the slot I and the slot II are closed ends.

[0015] In some embodiments, the distance between the outer ends of the slot I and the slot II is greater than the distance between the inner ends.

[0016] In the second aspect, the utility model provides a kind of motor, including the rotor of any one of the above.

[0017] At least one end of at least one slot hole in the utility model can extend to the outer periphery of the core, i.e., the slot hole has an open end, which is equivalent to not setting a magnetic isolation bridge at the outer periphery of the rotor, so as to reduce the problem of magnetic flux leakage, thereby helping to improve the permanent magnet flux of the rotor and increase the torque density of the motor. Since no magnetic isolation bridge is set at the outer periphery of the rotor, in order to reduce the problem of the rotor flinging the permanent magnet at high speed, the utility model sets a polymer cladding layer at the outer periphery of the core, which not only can fix the permanent magnet, but also can reduce the cost compared to setting a carbon fiber cladding sleeve at the outer periphery of the rotor. Therefore, the utility model can improve the problem of magnetic flux leakage and improve the torque of the motor on the basis of reducing the cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a structural schematic view of the rotor (including the polymer cladding layer) in some embodiments of the utility model;

[0019] Figure 2 It is a structural schematic view of the core (excluding the polymer cladding layer and the polymer fixing piece) in some embodiments of the utility model;

[0020] Figure 3 It is a front view of the rotor in some embodiments of the utility model;

[0021] Figure 4Figure 1 is a front view of a rotor according to some embodiments of the present application;

[0022] Figure 5 Figure 2 is a front view of a rotor according to some other embodiments of the present application;

[0023] Figure 6 Figure 3 is a front view of a rotor according to some further embodiments of the present application;

[0024] Figure 7 Figure 4 is a front view of a rotor according to some other embodiments of the present application;

[0025] Figure 8 Figure 5 is a front view of a rotor according to some other embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] 100, rotor; 11, core; 111, slot hole; 1111, slot I; 1112, slot II; 12, permanent magnet; 13, polymer coating layer; 14, polymer fixing member. DETAILED DESCRIPTION

[0028] The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover not exclusive inclusion.

[0030] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0031] In this paper, the "embodiment" means that the specific features, structures or properties described in conjunction with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments of the utility model, the term "and / or" is only a kind of description of the association relationship of associated object, it can exist three kinds of relations, for example A and / or B, it can represent: it exists A alone, A and B exist simultaneously, B exists alone these three cases.In addition, the character " / " in this paper, generally indicates that the associated object before and after is a kind of "or" relation.

[0033] In the description of the embodiments of the utility model, the term "multiple" refers to more than two (including two), and for the same reason, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces). The term "at least one" means one or more.

[0034] In the ideal case, the magnetic flux in the motor should pass through the air gap between the stator and the rotor completely, but in fact, part of the magnetic flux will leak to the external structure or winding of the motor, resulting in leakage flux, at this time, the magnetic bridge is needed to reduce or block the leakage flux between the rotor and the stator, to improve the efficiency and power density of the motor. The magnetic bridge provides a high magnetic resistance path, so that the magnetic flux line can smoothly pass through the air gap based on the strength, instead of self-leakage in the rotor core. In this way, most of the magnetic flux is limited in the main magnetic circuit of the motor, reducing the leakage flux and related losses.

[0035] Based on the above design, the magnetic bridge is usually made of high permeability materials such as silicon steel, soft iron, etc., which can effectively guide the magnetic field and reduce the magnetic field passing. In addition, the magnetic bridge should be as narrow as possible to reduce the leakage flux. However, in order to prevent the magnetic bridge from breaking under high speed conditions, the magnetic bridge cannot be set too narrow, which results in more opportunities for the magnetic flux line to bypass the magnetic bridge, thereby generating leakage flux.

[0036] Although the related art proposes a method of canceling the magnetic bridge between adjacent permanent magnets and fixing by plastic isolation to reduce leakage flux, but this technology needs to set a carbon fiber sleeve outside the rotor core, which has the problems of cost increase, etc.

[0037] Based on the above problems, the utility model provides a rotor 100, as shown in Figures 1-8 The utility model discloses a rotor, which comprises a core 11 and a permanent magnet 12, a plurality of slot hole groups are annularly and spacedly distributed on the core 11, each slot hole group comprises at least one slot hole 111, the slot hole 111 penetrates the core 11 along the axial direction, the end of at least one slot hole 111 in the slot hole group extends to the outer periphery of the core 11, and a polymer coating layer 13 is arranged on the outer periphery of the core 11; a plurality of permanent magnets 12 are arranged in the slot holes 111.

[0038] The iron core 11 is an important component of the rotor 100, and its main function is to provide a magnetic field path. For example, in a common induction motor, when the stator winding is connected to an alternating current, a rotating magnetic field is generated. This rotating magnetic field needs to interact with the rotor 100 through the air gap, and the iron core 11 acts as the main path of the magnetic field in the rotor 100 part. In the wound rotor motor, the iron core 11 is also used to support the rotor winding, and at this time the rotor winding is arranged in the slot of the iron core 11 to ensure that the winding can remain stable during the rotation of the motor.

[0039] The iron core 11 is usually made of high magnetic permeability material, which allows the magnetic field to be more concentrated inside the iron core 11, thereby reducing the magnetic resistance. In some embodiments, the iron core 11 is made of silicon steel, which has good magnetic conductivity and can effectively reduce the eddy current loss in the iron core 11. Further, the iron core 11 can be formed by stacking multiple silicon steel sheets.

[0040] The main function of the permanent magnet 12 in the rotor 100 is to generate a magnetic field. On the one hand, the permanent magnet 12 can reduce the energy loss of the motor to some extent, and on the other hand, the high magnetic performance of the permanent magnet 12 allows the motor to generate a strong enough magnetic field in a smaller volume, thereby improving the power density of the motor. The permanent magnet is usually made of magnetic steel material, which can be aluminum-nickel-cobalt magnetic steel, samarium-cobalt magnetic steel, or neodymium-iron-boron magnetic steel.

[0041] The end of at least one slot hole 111 in the slot hole group extends to the outer periphery of the iron core 11, which means that at least one slot hole 111 in the slot hole group has an open end. The open end can be set to one, or each end of the slot hole 111 can be set to an open end. In this way, the outer periphery of the iron core 11 can not be provided with a magnetic isolation bridge, which can reduce the magnetic leakage problem caused by the magnetic isolation bridge being too narrow, thereby improving the rotor efficiency.

[0042] The polymer coating layer 13 can be a polymer sleeve set on the outer periphery of the iron core 11, or a coating layer formed by pouring or injection molding polymer on the outer periphery of the iron core 11. The polymer coating layer 13 can form a wrapping around the iron core 11, which can reduce the problem of the permanent magnet 12 being thrown out at high speed.

[0043] The permanent magnet 12 arranged in the slot hole 111 can be closely matched with the slot hole 111 or gap matched with the slot hole 111. The closely matched permanent magnet 12 and the slot hole 111 refer to that the gap between the permanent magnet 12 and the slot hole 111 is small, so that the space can be used to the maximum extent, and the magnetic field generated by the permanent magnet 12 can effectively pass through the iron core 11 and the air gap to interact with the stator. The gap matched permanent magnet 12 and the slot hole 111 refer to that the size of the permanent magnet 12 is greatly different from the size of the slot hole 111, that is, the gap between the permanent magnet 12 and the slot hole 111 is large. On the one hand, the installation of the permanent magnet 12 is facilitated, and on the other hand, the large gap can provide space for the expansion of the permanent magnet 12 and the iron core 11 when heated, so as to avoid the damage of the permanent magnet 12 due to extrusion, or the excessive pressure on the iron core 11 to cause the deformation of the iron core 11 and other problems.

[0044] Compared with the carbon fiber covering sleeve arranged at the outer periphery of the rotor, the polymer covering layer can reduce the cost, and therefore, the magnetic flux leakage problem can be improved on the basis of reducing the cost.

[0045] According to some embodiments of the present application, the thickness of the polymer covering layer 13 is less than or equal to 0.5 mm.

[0046] Exemplarily, the thickness of the polymer covering layer 13 can be 0.5 mm, 0.45 mm, 0.4 mm, 0.35 mm, 0.3 mm, 0.25 mm, 0.2 mm, 0.15 mm or 0.1 mm. If the polymer covering layer 13 is too thick, interference with the stator can occur.

[0047] According to some embodiments of the present application, the rotor 100 further comprises a polymer fixing member 14, and the polymer fixing member 14 is filled in the slot hole 111 to fix the permanent magnet 12.

[0048] The polymer fixing member 14 can be a component made according to the gap shape and size between the permanent magnet 12 and the slot hole 111, or a fixing member formed by pouring or injection molding the polymer in the slot hole 111. The polymer fixing member 14 can form isolation between adjacent permanent magnets 12, and can further reduce the problem of the permanent magnet 12 being thrown out at high speed.

[0049] According to some embodiments of the present application, the polymer covering layer 13 and the polymer fixing member 14 are integrally formed.

[0050] The integral forming of the polymer cladding layer 13 and the polymer fixing part 14 means that the polymer cladding layer 13 and the polymer fixing part 14 can be formed at one time by injection molding or pouring. In some embodiments, the silicon steel sheets can be arranged to form the core 11 by lamination, then the plurality of permanent magnets 12 are placed one by one into the slot holes 111, the permanent magnets 12 are temporarily fixed by the fixing part such as adhesive tape to ensure the safety clearance between the permanent magnets 12 and the slot holes 111, then the molten polymer is filled into the whole core 11 by injection molding or pouring process, so that the polymer fixing part 14 can be formed between the permanent magnets 12 and the slot holes 111, and the polymer cladding layer 13 can be formed on the outer periphery of the core 11. The integral injection molding or pouring of the polymer cladding layer 13 and the polymer fixing part 14 can simplify the process and further reduce the cost.

[0051] According to some embodiments of the present application, the polymer of the polymer cladding layer 13 contains one of epoxy resin, acrylate resin, silicone resin, phenolic resin, unsaturated polyester resin, and polyurethane resin.

[0052] The epoxy resin, the acrylate resin, the silicone resin, the phenolic resin, the unsaturated polyester resin, and the polyurethane resin all have good fluidity, adhesion, and high temperature resistance, and can meet the injection molding requirements of fixing the permanent magnets in the rotor and fixing the outer periphery.

[0053] According to some embodiments of the present application, the slot hole group is provided with one slot hole 111, and both ends of the slot hole 111 extend to the outer periphery of the core 11.

[0054] Referring to FIGS. 1 and 2, Figure 4 and 5 As shown, the circumferential annular of the core 11 is uniformly distributed with eight slot hole groups, but the number of the slot hole groups is not limited to the specific example in the figure. Each slot hole group is provided with one slot hole 111, and both ends of the slot hole 111 are open ends.

[0055] According to some embodiments of the present application, the slot hole group is provided with a plurality of slot holes 111, which are distributed at intervals along the radial direction of the core 11, and both ends of the plurality of slot holes 111 extend to the outer periphery of the core 11.

[0056] Referring to FIGS. 1 and 2, Figures 6-8 As shown, the circumferential annular of the core 11 is uniformly distributed with eight slot hole groups, and each slot hole group is provided with two slot holes 111. The provision of two slot holes 111 in each slot hole group can increase the total number of slot holes 111 while keeping the number of slot hole groups unchanged. When the number of slot holes 111 increases, the magnetic field generated by the permanent magnets 12 is more densely distributed in the circumferential direction, which helps to form a magnetic field closer to a sinusoidal distribution in the air gap and reduce the harmonic content of the magnetic field.

[0057] In some embodiments, the two slot holes 111 are arranged at different distances from the outer periphery of the iron core 11 along the radial direction of the iron core 11, and both ends of the two slot holes 111 extend to the outer periphery of the iron core 11, that is, both ends of the two slot holes 111 are open ends.

[0058] According to some embodiments of the present application, the slot hole 111 is selected from one of a straight slot, a V-shaped slot, and a U-shaped slot; or, the slot hole is selected from one of a combination of a straight slot and a V-shaped slot, a combination of a straight slot and a U-shaped slot, and a combination of a V-shaped slot and a U-shaped slot; the slot hole is selected from one of a combination of two or more V-shaped slots and U-shaped slots.

[0059] In some embodiments, referring to FIG. 1, the slot hole 111 is a straight slot, and the slot hole 111 is arranged close to the outer periphery of the iron core 11, and one permanent magnet 12 is arranged in the slot hole 111. Figure 4 When one whole permanent magnet is arranged in the slot hole 111, the magnetic field distribution is relatively simple, the direction and intensity of the magnetic field change relatively smoothly, and a stable magnetic field can be provided, so that the output characteristics of the motor are more stable.

[0060] In some embodiments, referring to FIG. 2, the slot hole 111 is a V-shaped slot, and two permanent magnets 12 are arranged in the slot hole 111, and the two permanent magnets 12 are arranged on the two sides of the V-shaped slot. Figure 5 The two permanent magnets 12 are isolated by a polymer fixing part 14, that is, referring to FIG. 3, the rotor 100 does not have a magnetic isolation bridge arranged before the two permanent magnets 12 and the outer periphery, and the magnetic leakage problem can be further reduced. Figure 5 In some embodiments, referring to FIG. 4, the two slot holes 111 are both V-shaped slots, and two permanent magnets 12 are arranged in the two slot holes 111, respectively, and the two permanent magnets 12 are arranged on the two sides of the V-shaped slot.

[0061] Figure 6 In some embodiments, referring to FIG. 5, the two slot holes 111 are both V-shaped slots, and four permanent magnets 12 are arranged in the slot hole 111 close to the outer periphery of the iron core 11, and the four permanent magnets 12 are symmetrically arranged on the two sides of the V-shaped slot.

[0062] In some embodiments, referring to FIG. 6, the two slot holes 111 are both V-shaped slots, and four permanent magnets 12 are arranged in the slot hole 111 close to the outer periphery of the iron core 11, and the four permanent magnets 12 are symmetrically arranged on the two sides of the V-shaped slot. Figure 7 When a plurality of permanent magnets 12 are arranged in one slot hole 111, permanent magnets 12 with different coercivities can be selected and used in combination.

[0063] In some embodiments, referring to FIG. 7, the two slot holes 111 are both V-shaped slots, and four permanent magnets 12 are arranged in the slot hole 111 close to the outer periphery of the iron core 11, and the four permanent magnets 12 are symmetrically arranged on the two sides of the V-shaped slot. Figure 8 ​As shown, the slot hole 111 close to the outer periphery of the core 11 is a V-shaped slot hole, and the other slot hole 111 is a U-shaped slot hole, two permanent magnets 12 are arranged on the two sides of the V-shaped slot, and one permanent magnet 12 is arranged on each side and in the middle of the U-shaped slot, that is, three permanent magnets are arranged in the U-shaped slot.

[0064] The shape of the slot hole 111 is not limited to the specific examples described above, and different shapes or combinations of the same shape can be selected as needed.

[0065] According to some embodiments of the present application, the slot hole group is provided with two slot holes 111, which are distributed at intervals along the radial direction of the core 11; both of the two slot holes 111 include slot I 1111 and slot II 1112, and the outer ends of the slot I 1111 and the slot II 1112 extend to the outer periphery of the core 11, and the inner ends of the slot I 1111 and the slot II 1112 are closed ends.

[0066] Reference Figure 1 As shown, the outer ends of the slot I 1111 and the slot II 1112 extend to the outer periphery of the core 11, and the inner ends are closed ends, which means that the outer ends of the slot I 1111 and the slot II 1112 are open ends, and the inner ends are closed ends, that is, the outer periphery of the core 11 is not provided with a magnetic separation bridge, but a magnetic separation bridge is arranged between the slot I 1111 and the slot II 1112, and the magnetic separation bridge arranged between the slot I 1111 and the slot II 1112 can improve the overall strength of the core. In some embodiments, the slot I 1111 and the slot II 1112 can be distributed symmetrically along the radial direction of the core 11.

[0067] According to some embodiments of the present application, the distance between the outer ends of the slot I 1111 and the slot II 1112 is greater than the distance between the inner ends.

[0068] Further reference Figure 1 As shown, the distance between the outer ends of the slot I 1111 and the slot II 1112 is greater than the distance between the inner ends, which means that the slot I 1111 and the slot II 1112 are inclined, and gradually close from the outside to the inside, which can form a relatively narrow magnetic separation bridge between the inner ends of the slot I 1111 and the slot II 1112.

[0069] According to some embodiments of the present application, the present application also provides an electric motor comprising the rotor of any of the above. The specific structure of the rotor is referred to the above embodiments, and since the electrode adopts all the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0070] It should be finally pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A rotor characterized by, The rotor comprises: a core, a plurality of slot groups are annularly and spacedly arranged on the core, each slot group comprises at least one slot hole, the slot hole penetrates the core along the axial direction, and the end of at least one slot hole in the slot group extends to the outer periphery of the core, and the outer periphery of the core is provided with a polymer coating layer; a plurality of permanent magnets are arranged in the slot holes.

2. The rotor of claim 1, wherein The thickness of the polymer coating layer is less than or equal to 0.5 mm.

3. The rotor of claim 1, wherein The rotor further comprises a polymer fixing member, which is filled in the slot hole to fix the permanent magnet.

4. The rotor of claim 3, wherein The polymer fixing member is integrally formed with the polymer coating layer.

5. The rotor of claim 1, wherein The polymer of the polymer coating layer contains one of epoxy resin, acrylate resin, silicone resin, phenolic resin, unsaturated polyester resin and polyurethane resin.

6. A rotor as claimed in any one of claims 1 to 5, characterised in that The slot group is provided with one slot hole, and the two ends of the slot hole extend to the outer periphery of the core.

7. A rotor as claimed in any one of claims 1 to 5 wherein, The slot group is provided with a plurality of slot holes, which are spacedly arranged along the radial direction of the core, and the two ends of the plurality of slot holes extend to the outer periphery of the core.

8. A rotor as claimed in claim 6 or 7, characterised in that The slot hole is selected from one of a straight slot, a V-shaped slot and a U-shaped slot; or The slot hole is selected from one of a combination of a straight slot and a V-shaped slot, a combination of a straight slot and a U-shaped slot, and a combination of a V-shaped slot and a U-shaped slot; or The slot hole is selected from a combination of two or more V-shaped slots and U-shaped slots.

9. A rotor as claimed in any one of claims 1 to 5, characterised in that The slot group is provided with two slot holes, which are spacedly arranged along the radial direction of the core. The two slot holes each comprise a slot I and a slot II, the outer ends of the slot I and the slot II extend to the outer periphery of the core, and the inner ends of the slot I and the slot II are closed ends.

10. The rotor of claim 9, wherein The distance between the outer ends of the slot I and the slot II is greater than the distance between the inner ends.

11. An electric machine characterized by The rotor comprises any one of claims 1-10.

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