An unequal tooth width alternating pole permanent magnet synchronous motor

Abstract

The application discloses an unequal-tooth-width alternating-pole permanent magnet synchronous motor, which comprises a stator and a rotor, the stator is embedded with an armature winding, the rotor is provided with alternating-pole V-shaped permanent magnets, each V-shaped permanent magnet is composed of two permanent magnets, the stator is of an unequal-tooth-width structure, the tooth width is composed of armature teeth and auxiliary teeth in a certain proportion, the armature teeth are wound with the armature winding, the armature tooth top circle center angle and the auxiliary tooth top circle center angle are not equal, the V-shaped permanent magnets are embedded into the rotor, forming an alternating arrangement structure of permanent magnet poles and iron core poles, and the V-shaped permanent magnets are provided with magnetic separation grooves at both ends. The unequal-tooth-width structure can maximize the utilization of the armature winding back electromotive force, improve the output torque, the optimized cooperation of the armature tooth top width and the auxiliary tooth top width can effectively reduce the cogging torque and torque ripple, the alternating-pole structure can maintain the output torque unchanged while greatly reducing the consumption of rare earth permanent magnet materials, and the utilization rate of the permanent magnets is remarkably improved.

Description

Technical Field

[0001] This invention relates to permanent magnet synchronous motors, and more particularly to a permanent magnet synchronous motor with alternating poles and unequal tooth widths. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) improve operational reliability and reduce excitation losses by using permanent magnets instead of excitation windings, eliminating the need for brushes and commutators. This increases efficiency and power density. PMSMs are widely used as drive motors in new energy vehicles, with fractional-slot concentrated winding PMSMs being the preferred choice for small new energy recreational vehicles and agricultural vehicles. However, existing PMSMs for small and medium-sized vehicles suffer from the following problems: traditional equal-tooth-width fractional-slot concentrated winding motors have a pitch less than 1 due to near-pole slot matching and phase separation, potentially resulting in a winding coefficient less than 1 and insufficient utilization of the winding back EMF; the double-layer winding structure creates physical contact between adjacent phases, leading to low self-inductance, high short-circuit current, and poor fault tolerance; and rare-earth permanent magnets account for 20%-30% of the total cost. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a permanent magnet synchronous motor with alternating poles and unequal tooth widths, which can maximize the utilization of the armature winding back electromotive force, improve the output torque, and increase the utilization rate of the permanent magnet.

[0004] Technical solution: The present invention provides an unequal tooth width alternating pole permanent magnet synchronous motor, comprising a stator and a rotor, wherein the stator is provided with Z... s Each slot contains an armature winding, and the rotor has p pole pairs. r The rotor is equipped with alternating pole V-shaped permanent magnets, each V-shaped permanent magnet consisting of two permanent magnets; the stator has an unequal tooth width structure, including armature teeth and auxiliary teeth, the tooth widths of the armature teeth and auxiliary teeth are in a certain proportion, armature windings are wound on the armature teeth, and the central angles of the tip circles of the armature teeth and auxiliary teeth are not equal; the V-shaped permanent magnets are embedded inside the rotor, forming a structure in which the permanent magnet poles and the iron core poles are arranged alternately; magnetic isolation slots are provided at both ends of the V-shaped permanent magnets.

[0005] Furthermore, the number of armature teeth and auxiliary teeth is half the number of stator slots, the armature teeth and auxiliary teeth are arranged alternately, and the armature winding is a single-layer concentrated winding.

[0006] Furthermore, the tooth width of the armature tooth is w t1 The tooth width of the auxiliary tooth is w t2 The central angles of the armature tooth tip and the auxiliary tooth tip are α and α, respectively. tt1 and α tt2 Then we have:

[0007] w t1 +wt2 =2w t w t1 / w t2 =k t w t It is a fixed value; α tt1 +α tt2 <720° / (Z) s ).

[0008] Furthermore, k t The value range is 1 to 2.

[0009] Furthermore, the permanent magnet pole embedded in the V-shaped permanent magnet and its adjacent iron core pole form a pair of poles, with the central angle occupied by the pair of poles being 360° / p. r The number of V-shaped permanent magnets is 2p r ;

[0010] Let the central angle of the permanent magnet's poles be α. pm The central angle of the iron core magnetic poles is α. c Then we have α pm +α c =2τ, α pm ≥τ>α c τ is the polar moment.

[0011] Furthermore, the cores of both the stator and rotor are made of silicon steel sheets or soft magnetic materials.

[0012] Furthermore, the V-shaped permanent magnet is magnetized in parallel.

[0013] Compared with the prior art, the significant advantages of this invention are as follows:

[0014] 1. To address the issue of high cost of permanent magnets in rare-earth permanent magnet synchronous motors, the rotor of this invention adopts an alternating pole structure. In this structure, each pair of permanent magnets is replaced by an iron core, and the remaining permanent magnets are magnetized in the same direction, forcing the magnetic lines of force to enter the air gap from the iron core to form a closed magnetic circuit. The alternating pole structure can maintain the same output torque while reducing the amount of permanent magnets used, saving more than 25% of permanent magnet materials and reducing costs.

[0015] 2. To address the problem that simply replacing a permanent magnet with an iron core may reduce the excitation torque, this invention adjusts the pole arc and the thickness of the permanent magnet to reduce the amount of permanent magnet used without reducing the output torque.

[0016] 3. To address the problem of low back EMF utilization in short-pitch windings and the inability to make changes without altering the stator structure and control method, the stator of this invention adopts an unequal tooth width structure, decoupling the armature teeth and auxiliary teeth. This is achieved by adjusting the central angle of the armature tooth tip and the ratio k of the armature tooth width to the auxiliary tooth width. tTo the optimal value, torque density can be increased by more than 7%. Based on this, by increasing the slot opening width, the torque density can be increased by more than 10%.

[0017] 4. To address the problem of poor fault tolerance performance of double-layer windings, the armature winding of this invention adopts a single-layer winding, and there is physical isolation between the three-phase windings, which improves the fault tolerance performance of the motor. For multi-phase motors, the advantages are even more obvious.

[0018] 5. To address the inherent problem of large cogging torque and torque pulsation in motors with unequal tooth widths, the cogging torque and torque pulsation are suppressed by optimizing three main parameters: the ratio of armature teeth to auxiliary teeth, the combination of tooth tip central angle, and the size of the slot opening. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of the present invention;

[0020] Figure 2 This is a schematic cross-sectional view of the stator portion of the present invention;

[0021] Figure 3 This is a schematic cross-sectional view of the rotor portion of the present invention;

[0022] Figure 4 This is a schematic diagram of the cross-sectional structure of the armature tooth and auxiliary tooth of the present invention;

[0023] Figure 5 This is a schematic diagram of the cross-sectional structure of a single pole of the present invention;

[0024] Figure 6 This is a waveform diagram of the unloaded air gap magnetic flux density of the present invention;

[0025] Figure 7 This is a waveform diagram of the flux linkage of one phase winding of the present invention;

[0026] Figure 8(a) is a comparison of the cogging torque of the embodiment of the present invention and the conventional embedded permanent magnet synchronous motor;

[0027] Figure 8(b) is a comparison of the rated torque of the embodiment of the present invention and the traditional embedded permanent magnet synchronous motor. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] The single-layer winding structure can improve the distribution factor to 1, and there is physical isolation between the two-phase windings, resulting in good fault tolerance. Based on the single-layer winding structure, this invention further adopts an unequal tooth width structure, making the width of the armature teeth greater than the width of the auxiliary teeth, thereby increasing the short-pitch factor to 1. In this way, the total winding factor of the motor can be increased to 1, thus maximizing the utilization rate of the armature winding.

[0030] This invention takes a 12-slot, 10-pole single-layer concentrated winding alternating pole V-type embedded permanent magnet synchronous motor as an example, with the structure as follows: Figure 1 , Figure 2 As shown, the rotor includes a stator 1 and a rotor 2. An armature winding 5 is embedded in the stator 1. The rotor 2 is provided with alternating pole V-shaped permanent magnets 6, each of which consists of two rare earth permanent magnets. The unequal tooth width structure includes armature teeth 3 and auxiliary teeth 4, the tooth widths of which are in a certain proportion. The armature winding 5 is wound on the armature teeth 3, and the central angle of the tip of the armature teeth and the central angle of the tip of the auxiliary teeth are each a certain angle. The V-shaped permanent magnets 6 are embedded inside the rotor 2, forming a structure in which the permanent magnet poles 7 and the iron core poles 8 are arranged alternately. Magnetic isolation slots 9 are provided at both ends of the V-shaped permanent magnets 6.

[0031] like Figure 2 As shown, in this embodiment, the stator 1 has 12 tooth slots with parallel tooth profile, and the armature winding 5 is a single-layer winding with alternate teeth.

[0032] A schematic diagram of a pair of armature teeth and auxiliary teeth of the present invention is shown below. Figure 4 As shown, the teeth with armature windings are called armature teeth, and the teeth without armature windings are called auxiliary teeth. The two types of teeth have different widths, with the armature tooth width w being... t1 Greater than the auxiliary tooth width w t2 Among them, w t1 +w t2 =2w t , where w t For a fixed value, w t1 / w t2 =k t In this embodiment, w t =11mm. The central angle of the armature tooth tip is α. tt1 The central angle of the auxiliary tooth tip is α. tt2 , and α tt1 +α tt2 <720° / (Z) s ),Z s This represents the number of stator slots.

[0033] The rotor structure of the present invention is as follows: Figure 3 As shown, five V-shaped permanent magnets 6 are evenly distributed in the rotor core. Each group of permanent magnets is magnetized in the same direction, forming five magnetic poles of the same polarity. The other five cores without embedded permanent magnets form magnetic poles of the same polarity but opposite polarity, constituting a five-pole structure.

[0034] like Figure 5As shown, a pair of magnetic poles consists of a permanent magnet pole embedded with a V-shaped permanent magnet and its adjacent pure iron core pole. The central angle occupied by the pair of poles is 72°. The central angle of the permanent magnet pole is the central angle of one pole of the V-shaped embedded rotor, and it is the central angle from the center line of one rib to the center line of the next rib. This is an adjustable parameter. The central angle of the iron core pole is the pole pitch τ minus the central angle of the permanent magnet. Let the central angle of the permanent magnet pole be α. pm The central angle of the iron core magnetic poles is α. c Then we have:

[0035] α pm +α c =72°

[0036] α pm ≥36°>α c

[0037] like Figure 5 As shown, the two sides of the permanent magnet poles of the V-shaped built-in rotor coincide with the center line of the magnetic rib, and the included angle between the two sides of a pair of poles is equal to the two pole distances of 72°.

[0038] The thickness of the V-shaped permanent magnet is h. mag Width is w mag ;w mag Represented as:

[0039] w mag =A mag / h mag

[0040] Among them, A mag Let be the axial cross-sectional area of ​​each permanent magnet.

[0041] like Figure 5 As shown, a first magnetic bridge with a height of h is provided near the air gap side of the permanent magnet. b Width is w b A second magnetic bridge with a height of h is located near the pivot. σ Width is w σ .

[0042] This invention optimizes the rotor permanent magnet pole center angle α. pm and the thickness h of the permanent magnet mag This invention optimizes the air gap flux of a pair of poles to match the air gap flux density of a traditional V-type built-in permanent magnet motor, while reducing the amount of permanent magnets used to save costs. t α tt1 and α tt2 To improve torque density, the value of α is optimized; tt1 and α tt2 The value of k is used to reduce cogging torque and torque ripple. The winding coefficient of the motor varies with k. tThe value of k first increases to 1 and then decreases, therefore there exists an optimal k. t This maximizes torque density by setting the winding factor to 1; by optimizing α tt1 and α tt2 The value of α can be further increased to improve the amplitude of the back EMF fundamental wave, thereby further increasing the torque density; at the same time, by optimizing α tt1 and α tt2 The value reduces the cogging torque and torque ripple to about half that of traditional embedded motors, effectively avoiding the large torque ripple phenomenon in embedded permanent magnet synchronous motors with unequal tooth width alternating poles.

[0043] This invention optimizes the design of a type 120 permanent magnet synchronous motor. The main dimensional parameters after optimization are as follows: k t =1.4, α tt1 =23°, α tt2 =24°, α pm =44°, h mag =3.75mm. In this embodiment, the amount of permanent magnet used is reduced by 25% compared to traditional built-in permanent magnet motors, saving costs.

[0044] like Figure 6 The figure shows the no-load air gap magnetic flux density waveform of the present invention and a traditional embedded permanent magnet synchronous motor. Figure 6 It can be seen that the air gap radial magnetic flux density of the present invention does not have the "zero zone" of the traditional built-in motor, thus improving the utilization rate of the permanent magnet.

[0045] like Figure 7 The figure shows the waveform of the A-phase flux linkage over time in an embodiment of the present invention and a conventional embedded permanent magnet synchronous motor. Figure 7 It can be seen that the amplitude of the unloaded flux linkage of one phase in this embodiment of the invention is higher than that of a traditional built-in permanent magnet synchronous motor.

[0046] Figure 8(a) shows a comparison of the cogging torque of the embodiment of the present invention and the traditional embedded permanent magnet synchronous motor. As shown in Figure 8(a), the cogging torque of the embodiment of the present invention is 50% of that of the original motor, and the average torque is 12% higher under the same phase current conditions. Figure 8(b) shows a comparison of the rated torque of the embodiment of the present invention and the traditional embedded permanent magnet synchronous motor. As shown in Figure 8(b), the torque ripple is reduced by 10%. The present invention not only effectively improves the torque density of the motor, but also solves the problems of excessive cogging torque and torque ripple in permanent magnet motors with unequal tooth widths.

[0047] The unequal tooth width alternating pole permanent magnet synchronous motor of the present invention can also be used as an external rotor structure motor.

[0048] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A permanent magnet synchronous motor with alternating poles and unequal tooth widths, comprising a stator (1) and a rotor (2), characterized in that: The stator (1) has an armature winding (5) embedded on its side, and the rotor (2) has an alternating pole V-shaped permanent magnet (6). Each V-shaped permanent magnet (6) consists of two permanent magnets. The stator (1) has an unequal tooth width structure, including armature teeth (3) and auxiliary teeth (4). The tooth widths of the armature teeth (3) and auxiliary teeth (4) are in a certain proportion. The armature teeth (3) are wound with armature windings (5). The central angles of the armature teeth and the auxiliary teeth are not equal. The V-shaped permanent magnet (6) is embedded inside the rotor (2) to form a structure in which permanent magnet poles (7) and iron core poles (8) are arranged alternately. The V-shaped permanent magnet (6) has magnetic isolation grooves (9) at both ends. The tooth width of armature tooth (3) is w t1 The tooth width of the auxiliary tooth (4) is w t2 The central angles of the armature tooth tip and the auxiliary tooth tip are α and α, respectively. tt1 and α tt2 Then we have: , w t It is a fixed value; Z s k is the number of stator slots; where k t = 1.4, α tt1 = 23º, α tt2 = 24º; The permanent magnet pole (7) embedded in the V-shaped permanent magnet (6) and its adjacent iron core pole (8) form a pair of magnetic poles, and the number of rotor pole pairs is p. r The central angle occupied by a pair of poles is 360° / p r The number of V-shaped permanent magnets is 2p r ; Let the central angle of the permanent magnet's poles be α. pm The central angle of the iron core magnetic poles is α. c Then there is , , α is the polar distance; where α pm = 44º, thickness h of the V-shaped permanent magnet mag = 3.75mm.

2. The unequal tooth width alternating pole permanent magnet synchronous motor according to claim 1, characterized in that, The number of armature teeth (3) and auxiliary teeth (4) is half the number of stator slots, and the armature teeth (3) and auxiliary teeth (4) are arranged alternately. The armature winding (5) is a single-layer concentrated winding.

3. The unequal tooth width alternating pole permanent magnet synchronous motor according to any one of claims 1-2, characterized in that, The cores of both the stator (1) and the rotor (2) are made of silicon steel sheets or soft magnetic materials.

4. The unequal tooth width alternating pole permanent magnet synchronous motor according to any one of claims 1-2, characterized in that, The V-shaped permanent magnet (6) is magnetized in parallel.

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