Dual three-phase asymmetric stator type dual permanent magnet vernier motor

Abstract

The invention discloses a dual three-phase asymmetric stator type dual permanent magnet vernier motor which comprises a stator and a rotor. The stator comprises a stator iron core and stator permanent magnets, the stator iron core is formed by alternately arranging a plurality of umbrella-shaped armature teeth and quasi-rectangular armature teeth in the circumferential direction, and the consequent pole array permanent magnets which are magnetized outwards in the radial direction are pasted to openings in the two sides of each umbrella-shaped armature tooth respectively. A sector-ring-shaped auxiliary groove is formed between the umbrella-shaped armature teeth and the stator permanent magnets, and the auxiliary groove is filled with a non-magnetic-conductive material. The rotor comprises a rotor iron core and a rotor ferrite, the rotor iron core is similar to a gear in shape, the rotor ferrite is embedded in the rotor iron core by adopting a Halbach-based consequent pole array, and the length of the rotor ferrite is larger than the length of the rotor iron core and the length of the stator iron core. According to the invention, the torque density and the permanent magnet utilization rate are improved by using additional working harmonic waves generated by an asymmetric design and a double-permanent-magnet structure and an unequal-length structure.

Description

Technical Field

[0001] The present invention relates to a dual permanent magnet motor, in particular to a dual three-phase asymmetric stator type dual permanent magnet vernier motor, belonging to the technical field of permanent magnet motors. Background Art

[0002] With the rapid development of rare earth permanent magnet materials and power electronics technology, permanent magnet synchronous motors with characteristics such as high power density and high efficiency have broad application prospects in many fields such as electric vehicles, rail transit, and agricultural machinery equipment.

[0003] The dual permanent magnet vernier motor is a motor with permanent magnets distributed on both the stator and the rotor and having a high torque density. Its unique double-sided excitation structure has maximally utilized the distribution of the excitation source. Therefore, how to further improve the torque density of the motor has become a research hotspot for many scholars. The literature "Design and analysis of novel asymmetric-stator-pole flux reversal PM machine (IEEE Transactions on Industrial Electronics, 67(1): 101-114, 2020)" proposes a flux reversal motor with asymmetric stator poles. Compared with the traditional flux reversal motor, although the torque density of this motor has been improved, the internal space of the motor is still not fully utilized, and there is a large interpolar leakage flux. The literature "A novel dual-permanent-magnet-excited machine with non-uniformly distributed permanent-magnets and flux modulation poles on the stator (IEEE Transactions on Vehicular Technology, 69(7): 7104-7115, 2020)" proposes a dual permanent magnet vernier motor with non-uniformly distributed stator poles. Due to the large number of pole pairs of the permanent magnets on the stator and rotor of this motor, the eddy current loss increases, resulting in a decrease in its efficiency.

[0004] The purpose of this patent is to design a novel permanent magnet vernier motor with a dual permanent magnet and dual winding structure, simple and compact mechanical structure, and capable of further improving the torque density and the utilization rate of permanent magnets. Summary of the Invention

[0005] In view of the deficiencies and drawbacks of the prior art, the present invention proposes a dual-three-phase asymmetric stator type dual permanent magnet vernier motor. The motor adopts a dual permanent magnet combined with a dual winding structure to improve the torque density. On this basis, the concept of alternating poles and asymmetric design are introduced to reduce the amount of permanent magnets used and improve the utilization rate of permanent magnets. At the same time, by setting ferrite with a Halbach array between adjacent rotor teeth, the working harmonics in the air-gap magnetic density are enhanced, thereby further improving the torque density of the motor.

[0006] The technical solution of the present invention is as follows: A dual-three-phase asymmetric stator type dual permanent magnet vernier motor, comprising a stator and a rotor, both the stator and the rotor are salient pole structures. The stator includes a stator core, a dual-three-phase winding and stator permanent magnets. The stator core is composed of a number of umbrella-shaped armature teeth and rectangular-like armature teeth arranged alternately in the circumferential direction. The rectangular-like armature teeth are composed of a single piece of iron core, and the umbrella-shaped armature teeth are composed of a "permanent magnet + iron core + permanent magnet" sandwich array. One stator permanent magnet is pasted at each of the two open ends on both sides. The stator permanent magnets are pasted at the two open ends on both sides of the umbrella-shaped armature teeth and are magnetized radially outward with the same polarity. A fan-shaped auxiliary slot is opened between the umbrella-shaped armature teeth and the stator permanent magnets, and the auxiliary slot is filled with a non-magnetic material or no filler; the dual-three-phase windings are respectively wound on the umbrella-shaped armature and the rectangular-like armature teeth, and the dual-three-phase windings are concentrated windings: The rotor includes a rotor core and rotor ferrite. The shape of the rotor core is similar to a gear. The rotor ferrite is embedded in the rotor core by an alternating pole array based on Halbach. The length of the rotor ferrite is greater than the lengths of the rotor core and the stator core; both the stator core and the rotor core are laminated from silicon steel sheets.

[0007] A further feature of the present invention is that: the umbrella-shaped armature teeth are inverted "T" shaped in the circumferential cross-section, and slot openings are made in a fan shape on both sides of the tooth ends.

[0008] A further feature of the present invention is that: the stator permanent magnets are pasted in a tile shape at the two open ends on both sides of the umbrella-shaped armature teeth. A fan-shaped auxiliary slot is opened between the umbrella-shaped armature teeth and the stator permanent magnets, and the auxiliary slot is filled with a non-magnetic material such as epoxy resin or no filler.

[0009] A further feature of the present invention is that: the stator permanent magnets adopt high coercivity rare earth permanent magnet materials such as neodymium iron boron magnets, and are magnetized radially outward with the same polarity; the rotor ferrite adopts low coercivity permanent magnet materials such as ferrite magnets, and is embedded in the rotor core by a Halbach array composed of radial and parallel magnetization. The magnetic focusing direction of the rotor ferrite is radially directed towards the stator, and the length of the rotor ferrite is greater than the lengths of the rotor core and the stator core.

[0010] A further feature of the present invention is that the arc lengths of the two ferrite materials with radial and parallel magnetization are tr0 = (0.25 - 0.5) * τ and tr1 = (0 - 0.25) * τ respectively, where τ is the pole pitch.

[0011] A further feature of the present invention is that the double three-phase winding adopts a concentrated winding structure and is wound around the umbrella-shaped armature teeth and the rectangular-like armature teeth respectively. The windings wound around the umbrella-shaped armature teeth are the A1 phase, B1 phase, and C1 phase respectively, and the phase differences between the A1 phase and the B1 phase, the A1 phase and the C1 phase, and the B1 phase and the C1 phase are 120°; the windings wound around the rectangular-like armature teeth are the A2 phase, B2 phase, and C2 phase respectively, and the phase differences between the A2 phase and the B2 phase, the A2 phase and the C2 phase, and the B2 phase and the C2 phase are 120°; the phase differences between the A1 phase and the A2 phase, the B1 phase and the B2 phase, and the C1 phase and the C2 phase are 30°.

[0012] A further feature of the present invention is that according to the double-sided excitation structure and the double-sided magnetic field modulation effect, the equivalent armature winding pole pair number Pa, the stator tooth number Ns, the stator permanent magnet pole pair number Ps, the rotor tooth number Nr, and the rotor ferrite pole pair number Pr satisfy the following relationship:

[0013]

[0014] In the formula, p is the pole pair number in a unit stator symmetric period, and s is the slot number in a unit stator symmetric period.

[0015] A double three-phase asymmetric stator type dual permanent magnet vernier motor of the present invention has the following beneficial effects:

[0016] 1) The double three-phase asymmetric stator type dual permanent magnet vernier motor of the present invention adopts a dual permanent magnet and double salient pole structure. The combination of its unique double-sided flux modulation effect and the double three-phase winding structure can maximize the torque density of the motor.

[0017] 2) The double three-phase asymmetric stator type dual permanent magnet vernier motor of the present invention combines the concept of alternating poles with asymmetric design to generate additional working harmonics to improve torque, and introduces a Halbach array in the rotor ferrite to enhance the effective air-gap harmonics, improving the utilization rate of permanent magnets while further increasing the torque density.

[0018] 3) The stator poles of the double three-phase asymmetric stator type dual permanent magnet vernier motor of the present invention are treated with auxiliary slots, which can suppress the leakage magnetic flux between the stator poles, thereby increasing the torque and reducing the torque ripple.

[0019] 4) The double three-phase asymmetric stator type dual permanent magnet vernier motor of the present invention adopts a dual permanent magnet structure, and introduces the concept of alternating poles, asymmetric design, and Halbach array, greatly expanding the efficient operation range and reducing the material cost.

[0020] 5) In the rotor ferrite of the dual-three-phase asymmetric stator type dual-permanent magnet vernier motor of the present invention, an unequal length structure is adopted, making the length of the rotor ferrite greater than the lengths of the rotor core and the stator core, so as to make the best use of the internal space of the motor, further enhance the effective air-gap magnetic flux, and thus enhance the torque output ability of the motor. Description of the Drawings

[0021] Figure 1 The topologies of a traditional flux-switching machine and the dual-three-phase asymmetric stator type dual-permanent magnet vernier motor proposed by the present invention are shown: (a) traditional flux-switching machine; (b) the motor of the present invention;

[0022] Figure 2 It is a diagram showing the variation process of the motor of the present invention;

[0023] Figure 3 It is a comparison diagram of the Fourier decomposition of the magnetomotive force generated by the stator permanent magnets of the traditional flux-switching machine and the motor of the present invention;

[0024] Figure 4 It is a comparison diagram of the Fourier decomposition of the air-gap magnetic density of the traditional flux-switching machine and the motor of the present invention;

[0025] Figure 5 It is a comparison diagram of the contribution of harmonics to torque with and without rotor ferrite in the traditional flux-switching machine and the motor of the present invention;

[0026] Figure 6 It is a comparison diagram of the torque with and without rotor ferrite in the traditional flux-switching machine and the motor of the present invention;

[0027] Figure 7 It is the efficiency Map diagram of the traditional flux-switching machine and the motor of the present invention: (a) traditional flux-switching machine; (b) the motor of the present invention;

[0028] Figure 8 It is a cross-sectional view of the unequal length structure of the rotor ferrite of the motor of the present invention;

[0029] In the figure: 1 is the stator core, 11 is the umbrella-shaped armature tooth, 12 is the quasi-rectangular armature tooth; 2 is the dual-three-phase winding; 3 is the stator permanent magnet; 4 is the auxiliary slot; 5 is the rotor core; 6 is the rotor ferrite, 61 is the radially magnetized ferrite, 62 is the parallel magnetized ferrite. Detailed Embodiments

[0030] The present invention will be further described below through specific embodiments.

[0031] A dual-three-phase asymmetric stator type dual-permanent magnet vernier motor, an example of a traditional flux-switching machine and the motor of the present invention is as Figure 1As shown, both motors include a stator and a rotor, and both adopt a slot-pole combination of 12 slots / 34 poles. The traditional flux-reversal motor uses a conventional N-S pole surface-mounted permanent magnet array pasted on the stator surface. Different from the traditional flux-reversal motor, the umbrella-shaped armature teeth (11) and the quasi-rectangular armature teeth (12) in the embodiments of the present invention are different due to the difference in the installation of permanent magnets. The two stator teeth are respectively composed of an iron core and a sandwich array of "permanent magnet + iron core + permanent magnet"; the two stator permanent magnets (3) on the umbrella-shaped armature teeth (11) are both magnetized radially outward with the same polarity, and a fan-shaped auxiliary slot is opened between the two permanent magnets and the middle iron core. The width of the auxiliary slot (4) is 2°, and the auxiliary slot (4) is filled with a non-magnetic material such as epoxy resin or filled with no filler; the stator is alternately arranged by 6 umbrella-shaped armature teeth (11) and 6 quasi-rectangular armature teeth (12) along the circumference. The rotor core (5) is similar to a gear with 17 teeth, and ferrite using a Halbach array is embedded between adjacent rotor teeth. The number of pole pairs of the rotor ferrite (6) is 17, which is composed of two kinds of ferrite magnetized radially (61) and parallelly (62). The magnetic focusing direction of the rotor ferrite (6) is radially pointing to the stator. The maximum circumferential lengths of the two kinds of ferrite magnetized radially (61) and parallelly (62) are tr0 = 5.7 mm and tr1 = 3.1 mm respectively. The length of the rotor ferrite is 10 mm longer than the lengths of the stator core and the rotor core. The double three-phase winding (2) adopts a concentrated winding structure and is respectively wound on the umbrella-shaped armature teeth (11) and the quasi-rectangular armature teeth (12). The windings wound on the umbrella-shaped armature teeth (11) are phase A1, phase B1, and phase C1 respectively, and the phase differences between phase A1 and phase B1, phase A1 and phase C1, and phase B1 and phase C1 are 120°; the windings wound on the quasi-rectangular armature teeth (12) are phase A2, phase B2, and phase C2 respectively, and the phase differences between phase A2 and phase B2, phase A2 and phase C2, and phase B2 and phase C2 are 120°; the phase differences between phase A1 and phase A2, phase B1 and phase B2, and phase C1 and phase C2 are 30°.

[0032] Figure 2 This is the change process of the motor structure of the present invention. Different from the traditional flux-reversal motor, the stator permanent magnets of the present invention adopt an alternating-pole permanent magnet array and an asymmetric design scheme, and an auxiliary slot is introduced. An alternating-pole ferrite based on the Halbach array is embedded on the rotor.

[0033] According to the bilateral excitation structure and the bidirectional magnetic field modulation effect, the equivalent armature winding pole pair number Pa, the stator tooth number Ns, the stator permanent magnet pole pair number Ps, the rotor tooth number Nr, and the rotor ferrite pole pair number Pr satisfy the following relationship:

[0034]

[0035] Figure 3 This is a comparison diagram of the Fourier decomposition of the magnetomotive force generated by the stator permanent magnets of a traditional flux-reversal machine and the machine of the present invention. It can be seen from the figure that due to the difference in adjacent stator teeth, the magnetomotive force of the machine of the present invention has odd harmonic components that are odd multiples of 6, such as the 6th, 18th, and 30th harmonics. After being modulated by the rotor teeth, these harmonics will generate some additional harmonics, as shown in Figure 4 shown. Figure 5 This is a comparison diagram of the torque contributions of harmonics with and without rotor ferrite in a traditional flux-reversal machine and the machine of the present invention. It can be seen from the figure that the asymmetric design of the stator poles increases some additional harmonics such as the 6th, 11th, and 18th harmonics to generate torque. In the machine of the present invention, due to the presence of rotor ferrite, the 17th harmonic also contributes to the torque.

[0036] Figure 6 This is a comparison diagram of the torques of a traditional flux-reversal machine and the machine of the present invention with and without rotor ferrite. It can be seen from the figure that the torque of the traditional flux-reversal machine is 5.59 Nm and the torque ripple is 0.8%. The torque of the machine of the present invention without rotor ferrite is 7.53 Nm and the torque ripple is 1.6%. The torque of the machine of the present invention is 10.05 Nm and the torque ripple is 1.26%. When reducing the permanent magnet usage by half, the machine of the present invention without rotor ferrite adopts a scheme combining the asymmetric design of stator poles and the concept of alternating poles, which increases the torque by 34.7%. On this basis, the machine of the present invention introduces an alternating-pole rotor ferrite based on the Halbach array, which further increases the torque by 33.47%. At the same time, due to the presence of the dual-three-phase winding, the torque ripples of the above three machines are all relatively low.

[0037] The optimal slotting width of the auxiliary slot of the machine of the present invention is 2°. Figure 7 This is the efficiency Map diagram of a traditional flux-reversal machine and the machine of the present invention. It can be seen from the figure that under the operating conditions of a rated speed of 300 rpm and a rated peak current of 10 A, the efficiency of the traditional flux-reversal machine is 81.11%, and the efficiency of the machine of the present invention is 87.88%. In addition, the machine of the present invention improves the torque performance in the constant-torque region; in the field-weakening region, the operating range of the high-efficiency region is greatly expanded. Figure 8 This is a cross-sectional view of the unequal-length structure of the rotor ferrite of the machine of the present invention. The length of the rotor ferrite is greater than the lengths of the rotor core and the stator core. Considering the usage of ferrite material, the optimal unequal-length of one end of the rotor ferrite is 5 mm.

[0038] In the description of this specification, the meaning described by reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples" or "some examples" is that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0039] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor, characterized in that: It includes a stator and a rotor, both of which are salient pole structures; the stator includes a stator core (1), a dual three-phase winding (2), and a stator permanent magnet (3). The stator core (1) is composed of a number of umbrella-shaped armature teeth (11) and rectangular-like armature teeth (12) arranged alternately in the circumferential direction. The rectangular-like armature teeth (12) are composed of one piece of iron core, and the umbrella-shaped armature teeth (11) are composed of a "permanent magnet + iron core + permanent magnet" sandwich array. One stator permanent magnet is pasted at each of the two open ends on both sides. The stator permanent magnet (3) is pasted at the two open ends on both sides of the umbrella-shaped armature teeth and is magnetized radially outward with the same polarity. The dual three-phase winding (2) is wound around the umbrella-shaped armature teeth (11) and the rectangular-like armature teeth (12) respectively, and the dual three-phase winding is a concentrated winding; the rotor includes a rotor core (5) and rotor ferrite (6). The shape of the rotor core (5) is similar to a gear. The rotor ferrite (6) is embedded in the rotor core by an alternating pole array based on Halbach. The rotor ferrite adopts an unequal length structure, and its length is greater than the lengths of the rotor core and the stator core. The stator core (1) and the rotor core (5) are both laminated by silicon steel sheets.

2. The dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 1, wherein: The umbrella-shaped armature teeth (11) are in an inverted "T" shape in the circumferential cross-section, and slot openings are processed in a fan-shaped ring at both sides of the tooth ends.

3. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 1, characterized in that: The stator permanent magnet (3) is pasted at the two open ends on both sides of the umbrella-shaped armature teeth in a tile shape. A fan-shaped ring-shaped auxiliary slot is opened between the umbrella-shaped armature teeth (11) and the stator permanent magnet (3), and the auxiliary slot (4) is filled with a non-magnetic material such as epoxy resin or no filler is filled.

4. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 1, characterized in that: The stator permanent magnet (3) adopts a high coercivity rare earth permanent magnet material such as neodymium iron boron magnet, and is magnetized radially outward with the same polarity, and is pasted at the two open ends on both sides of the umbrella-shaped armature teeth by an alternating pole permanent magnet array; the rotor ferrite (6) adopts a low coercivity permanent magnet material such as ferrite magnet, and is embedded in the rotor core by a Halbach array composed of radial (61) and parallel (62) magnetization. The magnetic focusing direction of the rotor ferrite is radially pointing to the stator, and the length of the rotor ferrite is greater than the lengths of the rotor core and the stator core.

5. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 4, characterized in that: The maximum circumferential lengths of the two ferrites magnetized radially (61) and parallelly (62) are tr0 = (0.25 - 0.5)*τ and tr1 = (0 - 0.25)*τ respectively, where τ is the pole pitch.

6. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 1, characterized in that: The dual three-phase winding (2) adopts a concentrated winding structure and is wound around the umbrella-shaped armature teeth (11) and the rectangular-like armature teeth (12) respectively. The windings wound around the umbrella-shaped armature teeth are phase A1, phase B1, and phase C1 respectively, and the phase differences between phase A1 and phase B1, phase A1 and phase C1, and phase B1 and phase C1 are 120°; the windings wound around the rectangular-like armature teeth are phase A2, phase B2, and phase C2 respectively, and the phase differences between phase A2 and phase B2, phase A2 and phase C2, and phase B2 and phase C2 are 120°; the phase differences between phase A1 and phase A2, phase B1 and phase B2, and phase C1 and phase C2 are 30°.

7. A dual-three-phase asymmetric stator type dual permanent magnet vernier motor according to claim 1, characterized in that: According to the bilateral excitation structure and the bidirectional magnetic field modulation effect, the equivalent armature winding pole pair number Pa, the stator tooth number Ns, the stator permanent magnet pole pair number Ps, the rotor tooth number Nr, and the rotor ferrite pole pair number Pr satisfy the following relationship: Where p is the pole pair number in a unit stator symmetry period, and s is the number of slots in a unit stator symmetry period.

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