An electric motor and a compressor

Abstract

This utility model relates to an electric motor, specifically an electric motor and a compressor. The motor satisfies the following condition: (μ0×hcj / Bm)×100≤N×a×Wt / t≤(μ0×hcj / Bm)×2000; where N is the number of turns in a single stator winding, Wt is the shortest width of the stator teeth, t is the thickness of a single permanent magnet, a is the angle between permanent magnets in the same pole, Bm is the saturation magnetic flux density of the stator material, μ0 is the permeability of free space, and hcj is the intrinsic coercivity of the permanent magnet material. Compared with the prior art, this utility model addresses the deficiency of existing technologies that only reflect the influence of a few structures in the motor on demagnetization resistance. This solution proposes the relationship between the number of coil turns, the shortest width of the teeth, the thickness of the permanent magnet, the angle between the permanent magnets, and the demagnetization resistance. By adjusting the motor structure, the motor's demagnetization resistance can be improved, and the amount of permanent magnets used can be reduced.

Description

Technical Field

[0001] This utility model relates to an electric motor, specifically to an electric motor and a compressor. Background Technology

[0002] Permanent magnet synchronous motors, as the core power source of high-efficiency energy conversion devices, have been widely used in refrigeration compressors, new energy vehicle drive systems, and industrial equipment.

[0003] Rare earth permanent magnet materials, especially neodymium iron boron (NdFeB), are frequently used as permanent magnets in permanent magnet synchronous motors due to their excellent magnetic properties; moreover, they have become key materials for improving motor power density. According to the International Energy Agency, permanent magnet motors consume more than 35% of the world's total rare earth materials. However, due to the uneven distribution of global rare earth resources and the environmental pressures inherent in rare earth mining, the industry is forced to achieve synergistic optimization of magnetic material usage and motor performance through technological innovation, in order to meet current technical requirements while minimizing the amount of permanent magnets used.

[0004] For example, CN220797895U discloses an electric motor, a compressor, and a refrigeration device. The electric motor includes a stator and a rotor. The stator includes a stator core and windings. The stator core has stator slots, and the windings are wound on the stator core and located in the stator slots. The rotor includes a rotor core and multiple permanent magnets. The rotor core has multiple per-pole magnet slots, and the permanent magnets are located within each per-pole magnet slot. The number of stator slots is 15, the number of rotor poles is 10, the intrinsic coercivity of the permanent magnet is hcj, the included angle of each per-pole magnet slot is α, the thickness of the permanent magnet along the magnetization direction is h, hcj ≤ 1800 kA / m, 11*α / hcj ≤ h ≤ 50*α / hcj, where α / hcj is the demagnetization factor. This design primarily considers the included angle of the magnet slots, the thickness of the permanent magnet along the magnetization direction, and the intrinsic coercivity of the permanent magnet, aiming to reduce the use of heavy rare earth elements and lower the cost of the magnets while ensuring that demagnetization requirements are met. However, in actual motor structures, in addition to the thickness of the permanent magnet along the magnetization direction, several other structural parameters affect the motor's demagnetization resistance, including the structural parameters of the stator, rotor, and permanent magnet.

[0005] Therefore, the conclusions put forward by existing studies only consider the influence of single or few structural factors on the resistance to demagnetization, and lack research on the influence of multiple structural parameters, making it difficult to objectively demonstrate the correlation between the resistance to demagnetization and the motor structure. Utility Model Content

[0006] The purpose of this invention is to provide a motor and a compressor to solve at least one of the aforementioned problems, thereby overcoming the shortcomings of existing technologies that only reflect the influence of a few structures in the motor on its demagnetization resistance. This solution further proposes the relationship between the number of coil turns, the shortest tooth width, the thickness of the permanent magnet, and the included angle of the permanent magnet and its demagnetization resistance. This allows for the improvement of the motor's demagnetization resistance while reducing the amount of permanent magnet used by adjusting various aspects of the motor's structure.

[0007] The objective of this utility model is achieved through the following technical solution:

[0008] The first aspect of this utility model discloses an electric motor, including stator laminations, rotor laminations, permanent magnets, and stator windings;

[0009] The stator laminations are stacked to form a stator, and the stator is provided with stator slots spaced apart circumferentially, with teeth formed between the stator slots;

[0010] The rotor laminations are stacked to form a rotor, and the rotor is provided with pairs of magnet slots spaced apart along the circumferential direction. Each pair of magnet slots is composed of a pair of magnet slots arranged in a V-shape.

[0011] The stator winding is disposed in the stator slot of the stator, and the stator winding is wound around the stator teeth;

[0012] The permanent magnet is disposed in the magnetic slot of the rotor;

[0013] The motor satisfies: (μ0×hcj / Bm)×100≤N×a×Wt / t≤(μ0×hcj / Bm)×2000;

[0014] in:

[0015] N is the number of turns of a single stator winding in the stator, Wt is the shortest width of the stator teeth, t is the thickness of a single permanent magnet in the rotor, and a is the included angle between permanent magnets in the same pole of the rotor, in radians.

[0016] Bm is the saturation magnetic flux density of the stator material, μ0 is the vacuum permeability, and hcj is the intrinsic coercivity of the permanent magnet material.

[0017] In the inequality, Bm and hcj are both material performance parameters, which are constants once the material is determined; μ0 is a constant with a value of 4π × 10⁻⁶. -7 N / A 2 .

[0018] Preferably, in the motor,

[0019] The number of slots Q on the stator and the number of pole pairs P on the rotor satisfy the following condition: Q:P = 3:2.

[0020] Preferably, the motor is selected from one of a 12-pole 18-slot motor, a 10-pole 15-slot motor, an 8-pole 12-slot motor, and a 6-pole 9-slot motor.

[0021] Preferably, in the motor,

[0022] The outer diameter D of the stator punching sheet constituting the stator satisfies: 80 mm ≤ D ≤ 120 mm.

[0023] Preferably, in the motor,

[0024] The shortest width Wt of the tooth part of the stator satisfies: 3 mm ≤ Wt ≤ 9 mm.

[0025] Limiting the structural parameters of the stator of the motor can ensure a high motor efficiency when the magnetic field density of the stator is within a suitable range.

[0026] Preferably, in the motor,

[0027] The thickness t of a single permanent magnet provided in the rotor satisfies: 0.8 mm ≤ t ≤ 3 mm.

[0028] Increasing the thickness of the permanent magnet can significantly improve the anti-demagnetization ability of the motor, but it will also lead to an increase in cost; therefore, selecting a suitable thickness can ensure sufficient anti-pushing ability and reduce the motor cost.

[0029] Preferably, in the motor,

[0030] The included angle a between the permanent magnets in the same pole of the rotor satisfies: in radian measure, 0 rad < a ≤ π rad (i.e., in degree measure, 0° - 180° and not 0°).

[0031] Preferably, in the motor,

[0032] The range of the saturation magnetic flux density Bm of the material of the stator is 1.7 T - 2.5 T.

[0033] The increase in Bm means that the silicon steel sheet of the motor is less likely to reach saturation, and more permanent magnets can be used under the same amount of silicon steel sheet to improve the motor efficiency, but more permanent magnets mean an increase in cost; therefore, when selecting the material of the stator (stator punching sheet), the silicon steel sheet within this range can better balance the motor efficiency and cost. More preferably, the range of the saturation magnetic flux density Bm of the material of the stator is 1.8 T - 2.2 T.

[0034] Preferably, in the motor,

[0035] The range of the intrinsic coercive force hcj of the material of the permanent magnet is 1,200,000 A / m - 2,500,000 A / m.

[0036] Increasing the intrinsic coercivity hcj can significantly improve the motor's resistance to demagnetization, but it also increases the cost of the permanent magnet. Therefore, when selecting permanent magnet materials, materials within this range offer a good balance between demagnetization resistance and cost. More preferably, the intrinsic coercivity hcj of the permanent magnet material is in the range of 1,300,000 A / m to 2,000,000 A / m, i.e., the permanent magnet grade is H, SH, or UH.

[0037] The second aspect of this utility model discloses a compressor.

[0038] The compressor includes any of the motors described above.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] If N×a×Wt× / t is less than (μ0×hcj / Bm)×100, the utilization rate of the magnet material in the permanent magnet is low, or the intrinsic coercivity of the magnet material in the permanent magnet is too high, resulting in performance waste and increased motor cost. If N×a×Wt× / t is greater than (μ0×hcj / Bm)×2000, the permanent magnet is prone to partial irreversible demagnetization during motor operation, resulting in permanent degradation of permanent magnet performance and affecting motor efficiency.

[0041] In the inequality proposed in this scheme, the number of coil turns N, the included angle of the permanent magnet a, the shortest width of the tooth Wt, and the thickness of the permanent magnet t are all structural parameters, μ0 is a constant, and hcj and Bm are material parameters (once the material is determined, its value is determined, which is equivalent to a constant; the material can be a conventional commercially available product, and this scheme does not make any improvements to the material). Therefore, this inequality is an inequality about the synergistic effect between structural parameters, which can reflect the influence of the motor structure on the anti-demagnetization ability, and thus can realize the improvement of the motor's anti-demagnetization ability by adjusting the motor structure while reducing the amount of permanent magnet used. Attached Figure Description

[0042] Figure 1 This is a schematic cross-sectional view of the motor structure;

[0043] In the figure: 1-stator lamination; 2-rotor lamination; 11-stator slot; 12-tooth section; 21-magnet slot. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0045] Unless otherwise specified, all materials used in the following description are suitable commercially available products, and any matters not covered herein shall be handled using existing technology.

[0046] Example

[0047] A type of motor with improved resistance to demagnetization, such as Figure 1 As shown, it includes stator lamination 1, rotor lamination 2, permanent magnets and stator windings;

[0048] The stator laminations 1 are stacked to form a stator, and the stator is provided with stator slots 11 spaced apart along the circumferential direction, and teeth 12 are formed between the stator slots 11;

[0049] The rotor laminations 2 are stacked to form a rotor, and the rotor is provided with pairs of magnet slots spaced apart along the circumference. The pair of magnet slots is composed of a pair of magnet slots 21 arranged in a V-shape.

[0050] The stator winding is disposed in the stator slot 11 of the stator, and the stator winding is wound on the stator tooth portion 12;

[0051] The permanent magnet is disposed in the magnetic slot 21 of the rotor;

[0052] The motor satisfies: (μ0×hcj / Bm)×100≤N×a×Wt / t≤(μ0×hcj / Bm)×2000;

[0053] in:

[0054] N is the number of coil turns of a single stator winding in the stator, Wt is the shortest width of the stator teeth, t is the thickness of a single permanent magnet in the rotor, and a is the included angle between permanent magnets in the same pole of the rotor.

[0055] Bm is the saturation magnetic flux density of the stator material, μ0 is the vacuum permeability, and hcj is the intrinsic coercivity of the permanent magnet material.

[0056] Bm and hcj are the material parameters of the stator and permanent magnet, respectively. Once the stator and permanent magnet materials are determined, these two parameters are constants; μ0 is a constant with a value of 4π × 10⁻⁶. -7 N / A 2 .

[0057] The parameters of the motor also meet the following requirements:

[0058] The relationship between the number of slots Q on the stator and the number of pole pairs P in the rotor is: Q:P = 3:2. This can usually be considered as a 12-pole 18-slot motor, a 10-pole 15-slot motor, an 8-pole 12-slot motor, and a 6-pole 9-slot motor.

[0059] Size meets:

[0060] The outer diameter D of the stator lamination is in the range of 80mm≤D≤120mm;

[0061] The range of the shortest width Wt of the teeth of the stator is 3 mm ≤ Wt ≤ 9 mm;

[0062] The structural parameters of the stator of the motor are limited so that the magnetic field density of the stator can ensure a high motor efficiency within a suitable range.

[0063] The range of the thickness of the permanent magnet is 0.8 mm ≤ t ≤ 3 mm;

[0064] Increasing the thickness of the permanent magnet can significantly improve the demagnetization resistance of the motor, but it will also lead to an increase in cost. Therefore, a suitable thickness needs to be selected.

[0065] The included angle of the permanent magnet ranges from 0 rad < a ≤ π rad in radian measure, which is equivalent to 0° < a ≤ 180° in degree measure.

[0066] The range of the saturation magnetic flux density Bm of the silicon steel sheet material selected for the stator is 1.7 T ≤ Bm ≤ 2.5 T, and more preferably 1.8 T ≤ Bm ≤ 2.2 T, to balance the motor efficiency and cost. This range of the saturation magnetic flux density Bm can basically cover the common silicon steel sheet materials on the market. Therefore, when implementing this solution, only the silicon steel sheet material that meets this range needs to be selected as the stator, and there are no additional restrictions on the stator material.

[0067] The range of the intrinsic coercivity of the material selected for the permanent magnet is 1,200,000 A / m ≤ Hcj ≤ 2,500,000 A / m, and more preferably 1,300,000 A / m ≤ hcj ≤ 2,000,000 A / m, that is, the grade of the permanent magnet material is H, SH or UH, to balance the demagnetization resistance and cost.

[0068] The above stator and permanent magnet can both use suitable commercially available products. This solution does not involve the improvement of materials, and the selection of the stator and permanent magnet belongs to the prior art.

[0069] If N × a × Wt × / t is less than (μ0 × hcj / Bm) × 100, the utilization rate of the magnet material in the permanent magnet is low, or the intrinsic coercivity of the magnet material in the permanent magnet is too high, resulting in performance waste and an increase in the cost of the motor; if N × a × Wt × / t is greater than (μ0 × hcj / Bm) × 2000, the permanent magnet is prone to partial irreversible demagnetization during the operation of the motor, resulting in a permanent decrease in the performance of the permanent magnet and also affecting the motor efficiency.

[0070] Test example

[0071] For a 10-pole 15-slot motor, different values are taken for the six parameters N, a, Wt, Bm, t, and hcj, as shown in Table 1.

[0072] Table 1 Motor parameters of Scheme 1 to 3

[0073]

[0074] In Table 1, the evaluation coefficient K = N × a × Wt × Bm / (μ0 × t × hcj).

[0075] The evaluation coefficient of Scheme 1 is lower than the lower limit of the inequality, Scheme 2 is within the specified range of the inequality, and Scheme 3 is higher than the upper limit of the inequality.

[0076] The three motors were subjected to a demagnetization experiment: First, the back electromotive force of the three motors at room temperature was measured; then, the corresponding motors were heated to 130 degrees Celsius and a d-axis current was applied; then, the motors were allowed to cool to room temperature, and the back electromotive force of the three motors after high-temperature demagnetization was measured under different d-axis currents.

[0077] The maximum demagnetizing current was taken as the d-axis current when the back EMF of the three motors decreased by 1%, and the results are shown in Table 2.

[0078] Average current when back potential decreases by 1% Option 1 >50A Option 2 35A Option 3 <10A

[0079] Table 2 shows that the maximum demagnetizing current of Scheme 1 is greater than 50A, far exceeding the design requirements. This indicates that the thickness and intrinsic coercivity of the permanent magnet are much higher than the design requirements, resulting in significant performance waste. These values ​​can be reduced accordingly to save costs. The maximum demagnetizing current of Scheme 2 is approximately 35A, which meets the design requirements and strikes a good balance between demagnetization resistance and cost. The maximum demagnetizing current of Scheme 3 is less than 10A, far below the design requirements, rendering the motor unusable.

[0080] In summary, the inequality proposed in this scheme can improve the motor's anti-demagnetization capability while reducing the amount of permanent magnets by adjusting the motor structure.

[0081] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. An electric motor, comprising stator laminations (1), rotor laminations (2), permanent magnets, and stator windings; The stator laminations (1) are stacked to form a stator, and the stator is provided with stator slots (11) spaced apart in the circumferential direction, and teeth (12) are formed between the stator slots (11). The rotor laminations (2) are stacked to form a rotor, and the rotor is provided with pairs of magnet slots spaced apart along the circumferential direction. The pairs of magnet slots are composed of a pair of magnet slots (21) arranged in a V-shape. The stator winding is disposed in the stator slot (11) of the stator, and the stator winding is wound around the teeth (12) of the stator. The permanent magnet is disposed in the magnetic slot (21) of the rotor; Its features are, The motor satisfies: (μ0×hcj / Bm)×100≤N×a×Wt / t≤(μ0×hcj / Bm)×2000; in: N is the number of turns of a single stator winding in the stator, Wt is the shortest width of the stator teeth, t is the thickness of a single permanent magnet in the rotor, and a is the included angle between permanent magnets in the same pole of the rotor, in radians. Bm is the saturation magnetic flux density of the stator material, μ0 is the vacuum permeability, and hcj is the intrinsic coercivity of the permanent magnet material.

2. An electric machine as claimed in claim 1, characterized in that In the aforementioned motor, The number of slots Q on the stator and the number of pole pairs P on the rotor satisfy the following condition: Q:P = 3:

2.

3. An electric machine as claimed in claim 2, characterised in that The motor is selected from one of the following: a 12-pole 18-slot motor, a 10-pole 15-slot motor, an 8-pole 12-slot motor, and a 6-pole 9-slot motor.

4. An electric machine as recited in claim 1, wherein In the aforementioned motor, The outer diameter D of the stator laminations that make up the stator must satisfy: 80mm≤D≤120mm.

5. An electric machine as recited in claim 1, wherein In the aforementioned motor, The minimum width Wt of the stator teeth satisfies: 3mm≤Wt≤9mm.

6. An electric machine as recited in claim 1, wherein In the aforementioned motor, The thickness t of a single permanent magnet set inside the rotor satisfies: 0.8mm≤t≤3mm.

7. An electric machine as recited in claim 1, wherein In the aforementioned motor, The included angle α between permanent magnets in the same pole of the rotor satisfies: 0 rad. <a≤π rad。 8. The motor according to claim 1, characterized in that, In the aforementioned motor, The saturation magnetic flux density Bm of the stator material ranges from 1.7T to 2.5T.

9. The motor according to claim 1, characterized in that, In the aforementioned motor, The intrinsic coercivity hcj of the permanent magnet material ranges from 1,200,000 A / m to 2,500,000 A / m.

10. A compressor, characterized in that, The compressor includes the motor as described in any one of claims 1-9.

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