CN117650656A

CN117650656A - Segmented magnet array and motor

Info

Publication number: CN117650656A
Application number: CN202211079495.2A
Authority: CN
Inventors: 张维
Original assignee: Taicang Boze Drive System Co ltd
Current assignee: Taicang Boze Drive System Co ltd
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2024-03-05

Abstract

The invention relates to a segmented magnet array and an electric machine. The segmented magnet array comprises a first magnet segment and a second magnet segment, which are alternately arranged along the circumferential direction to form a magnetic ring, the first magnet segment and the second magnet segment having different magnetization directions from each other, wherein the first magnet segment and the second magnet segment are anisotropic magnets of different orientations from each other. The motor comprises a stator and a rotor, wherein the rotor is configured as a segmented magnet array as described above. The segmented magnet array according to the invention can achieve 95% of the ideal halbach magnet array performance while the weight of copper wire used by the motor is significantly reduced and the motor cogging torque and torque ripple are reduced.

Description

Segmented magnet array and motor

Technical Field

The invention relates to the field of motors, in particular to a permanent magnet motor. In particular, in a first aspect, the invention relates to a segmented magnet array for a rotor of an electric machine. In a second aspect, the invention relates to a permanent magnet motor comprising the segmented magnet array.

Background

Halbach (Halbach) magnet arrays are suitable for use in motor rotors due to their relatively high local magnetic flux density. Such magnet arrays typically employ sinusoidal magnetization, thereby increasing motor torque, reducing cogging torque and torque ripple of the motor, and increasing the sound vibration harshness (NVH) performance of the motor.

The halbach magnet arrays used in electrical machines in current practice are typically in the form of integrally sintered magnetic rings. The magnet array of this arrangement has the following disadvantages: the manufacturing cost is high, the remanence Br is low, and the ideal performance of the halbach magnet array cannot be achieved. It is desirable to retrofit existing arrangements of halbach magnet arrays to achieve as much as possible the performance of the ideal halbach magnet array.

Disclosure of Invention

The object of the present invention is to overcome the above-mentioned drawbacks of the prior art designs.

In a first aspect, the present invention provides a segmented magnet array comprising a first magnet segment and a second magnet segment, the two magnet segments being alternately arranged in a circumferential direction to form a magnetic ring, the first magnet segment and the second magnet segment having different magnetization directions from each other. According to the invention, the first and second sections are anisotropic magnets oriented differently from each other. According to an embodiment, the magnet is a sintered ferrite, the remanence Br is 0.4-0.48T, and the Hcb is 170-280kA/m (normal temperature).

According to an embodiment, the segmented magnet array is configured as a halbach magnet array.

According to an embodiment, the first magnet segment and the second magnet segment are configured as sectors or as trapezoids of four points of sector connection.

According to an embodiment, the sum of the inner arc angles of the first magnet segment and the second magnet segment is equal to the sum of the outer arc angles of the first magnet segment and the second magnet segment.

According to an embodiment, the ratio of the inner arc angles of the first magnet segment and the second magnet segment is 0.8-0.85.

According to an embodiment, the ratio of the outer arc angles of the first magnet segment and the second magnet segment is 1.5-2.

According to an embodiment, the pole pitch of the segmented magnet array is 360 degrees/sum of inner arc angles of the first and second magnet segments or sum of outer arc angles of the first and second magnet segments.

According to an embodiment, the magnet segments of the segmented magnet array are held together by plastic over-molding or by gluing, while the rotor back iron is optional. In this way, the segmented magnet array according to the invention is easy to manufacture compared to prior halbach magnet arrays in the form of magnetic rings.

In a second aspect, the invention provides an electric machine comprising a stator and a rotor configured as a segmented magnet array as described above. According to an embodiment, the rotor is an outer rotor.

According to a preferred embodiment, the ratio of the rotor outer diameter to the stator outer diameter is 1.15-1.35 and/or the ratio of the radial thickness to the pole pitch of the magnetic steel is 0.6-0.75.

According to a preferred embodiment, the motor is an 18 slot 16 pole, 12 slot 14 pole or 12 slot 10 pole motor.

According to a preferred embodiment, harmonics (e.g., third order harmonics or fifth order harmonics) are injected into the stator teeth of the stator. In this way, cogging torque and torque ripple of the motor can be reduced.

With the segmented magnet array according to the invention, the motor is able to achieve 95% of the performance of an ideal halbach magnet array while the weight of copper wire used by the motor is significantly reduced and the motor cogging torque and torque ripple are reduced.

Drawings

Some embodiments of the invention will be explained in more detail in the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a rotor and stator arrangement in the form of a segmented magnet array according to an embodiment of the invention;

FIG. 1A is a schematic illustration of the stator of FIG. 1;

FIG. 2 is a schematic view of two magnet segments of the alternate arrangement of FIG. 1;

FIG. 3 is a schematic magnetization diagram of a segmented magnet array of the rotor of FIG. 1, wherein only half of the magnet array is shown;

FIG. 4 is a schematic diagram comparing the ideal magnetic flux density of a prior art halbach array of magnets in the form of a magnetic ring with the magnetic flux density of the segmented array of magnets of FIG. 1;

FIG. 5 is a schematic diagram comparing the ideal back EMF of a prior art halbach magnet array in the form of a magnetic ring with the back EMF of the segmented magnet array of FIG. 1;

FIG. 6 is a schematic diagram comparing the torque ideal for a motor employing a prior art halbach magnet array in the form of a magnetic ring with the torque of a motor employing the segmented magnet array of FIG. 1;

fig. 7A and 7B are schematic diagrams of magnetic fluxes of a halbach magnet array in the form of a magnetic ring in the prior art and a segmented magnet array in fig. 1, respectively; and

fig. 8A and 8B are schematic diagrams of magnetic field strengths of halbach magnet arrays in the form of magnetic rings in the prior art and segmented magnet arrays in fig. 1, respectively.

In the figures, embodiments of the invention are shown in simplified form for clarity. The figures are not drawn to scale.

Detailed Description

Embodiments of the present invention are described in detail below.

Fig. 1 shows an arrangement of a rotor 10 and a stator 20 of an electric machine, the rotor being an outer rotor, the ratio of the rotor outer diameter R1 to the stator outer diameter R2 being 1.15-1.35, the ratio of the radial thickness D of the magnetic steel to the pole pitch p being 0.6-0.75. In this example, the motor is an 18 slot 16 pole motor. The motor may also be a 12 slot 14 pole or a 12 slot 10 pole motor.

As shown in fig. 1, the rotor 10 is configured as a segmented magnet array including first magnet segments 11 and second magnet segments 12 (different-orientation opposite magnets from each other) configured differently from each other, the two magnet segments being alternately arranged in the circumferential direction to form a magnetic ring. In this case, the first magnet segment and the second magnet segment are configured as sectors, the magnet segments being held together by plastic overmolding or by gluing. Alternatively, the first and second magnet segments are configured as trapezoids with four points of attachment of the segments

Fig. 1A shows a stator tooth 21 into which a third order harmonic or a fifth order harmonic is injected.

Fig. 2 shows two magnet segments arranged alternately. As shown, the sum a1+a2 of the inner arc angles of the first magnet segment 11 and the second magnet segment 12 is equal to the sum a3+a4 of the outer arc angles of the first magnet segment and the second magnet segment, the ratio a1/a2 of the inner arc angles of the first magnet segment and the second magnet segment is 0.8-0.85, and the ratio a3/a4 of the outer arc angles of the first magnet segment and the second magnet segment is 1.5-2. Thus, the pole pitch of the segmented magnet array is 360 degrees per the sum of the inner arc angles of the first and second magnet segments a1+a2 or the sum of the outer arc angles of the first and second magnet segments a3+a4.

Fig. 3 shows a schematic magnetization diagram of a segmented magnet array according to the invention, wherein two magnet segments adjacent to each other are magnetized radially, tangentially, and the magnetization directions of successive radially magnetized magnet segments and successive tangentially magnetized magnet segments are each opposite to each other, thereby forming a halbach magnet array in the form of a magnetic ring. For clarity, only half of the segmented magnet array is shown in fig. 3.

The segmented magnet array of the present invention is compared to an ideal halbach magnet array as follows. Fig. 4 shows a schematic diagram of a comparison of ideal magnetic flux density of a halbach magnet array and magnetic flux density of a segmented magnet array of the present invention, fig. 5 shows a schematic diagram of a comparison of ideal back emf of a halbach magnet array and back emf of a segmented magnet array of the present invention, fig. 6 shows a schematic diagram of a comparison of ideal torque of a motor of a halbach magnet array and torque of a motor employing a segmented magnet array of the present invention, fig. 7A and 7B are schematic diagrams of magnetic fluxes of an ideal halbach magnet array and a segmented magnet array of the present invention, respectively, and fig. 8A and 8B are schematic diagrams of magnetic field strengths of an ideal halbach magnet array and a segmented magnet array of the present invention, respectively. In fig. 6, the upper curve is the ideal torque of the motor of the halbach magnet array (4.72 nm in this example) and the lower curve is the torque of the motor employing the segmented magnet array of the present invention (4.52 nm in this example).

As can be seen from fig. 4-8B, the segmented magnet array of the present invention has substantially the same (up to 95%) performance parameters as the ideal halbach magnet array.

In some cases, the features disclosed in this disclosure may be used as such, irrespective of other features. On the other hand, the features disclosed in the present invention can be combined, when necessary, to provide various combinations.

The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting, and therefore, the use of such phraseology and terminology is not intended to exclude from the scope of the invention any equivalent of the characteristics shown and described. Various modifications, variations and alternatives are possible within the scope of the claims. The claims are intended to cover all such equivalents.

Claims

1. A segmented magnet array comprising a first magnet segment and a second magnet segment, the two magnet segments being alternately arranged in a circumferential direction to form a magnetic ring, the first magnet segment and the second magnet segment having mutually different magnetization directions, characterized in that the first magnet segment and the second magnet segment are anisotropic magnets of mutually different orientations.

2. The segmented magnet array of claim 1, wherein the segmented magnet array is configured as a halbach magnet array.

3. A segmented magnet array according to claim 1 or 2, wherein the first and second magnet segments are configured as sectors or as trapezoids of four points of sector connection.

4. A segmented magnet array according to claim 1 or 2, wherein the sum of the inner arc angles of the first and second magnet segments is equal to the sum of the outer arc angles of the first and second magnet segments.

5. The segmented magnet array of claim 4, wherein the ratio of the inner arc angles of the first and second magnet segments is 0.8-0.85.

6. The segmented magnet array of claim 4, wherein the ratio of the outer arc angles of the first magnet segment and the second magnet segment is 1.5-2.

7. A segmented magnet array according to claim 1 or 2, wherein the pole pitch of the segmented magnet array is 360 degrees/sum of the inner arc angles of the first and second magnet segments or sum of the outer arc angles of the first and second magnet segments.

8. A segmented magnet array according to claim 1 or 2, wherein the magnet segments of the segmented magnet array are held together by plastic over-moulding or by gluing.

9. An electric machine comprising a stator and a rotor, characterized in that the rotor is configured as a segmented magnet array according to any one of claims 1-8.

10. The electric machine of claim 9 wherein the rotor is an outer rotor.

11. An electric machine according to claim 9 or 10, characterized in that the ratio of the rotor outer diameter to the stator outer diameter is 1.15-1.35 and/or the ratio of the radial thickness of the magnetic steel to the pole pitch is 0.6-0.75.

12. An electric machine according to claim 9 or 10, characterized in that the electric machine is an 18 slot 16 pole, a 12 slot 14 pole or a 12 slot 10 pole electric machine.

13. An electric machine according to claim 9 or 10, characterized in that the third or fifth order harmonics are injected into the stator teeth of the stator.