Surface-embedded permanent magnet biased synchronous reluctance motor

Abstract

A surface-embedded permanent magnet biased synchronous reluctance motor includes a stator core with an air gap in the middle and an inner surface-embedded permanent magnet biased synchronous reluctance rotor, three-phase armature windings are arranged on the stator core, and a rotating shaft is located on the central axis of the motor. The stator core includes stator teeth, a stator yoke, and stator slots formed between adjacent stator teeth. The surface-embedded permanent magnet biased synchronous reluctance rotor includes surface-embedded permanent magnets, a rotor yoke, rotor teeth, and an asymmetric reluctance unit composed of three layers of U-shaped magnetic barriers. The present application can combine the advantages of high permanent magnet torque of surface-embedded permanent magnet motor and high reluctance torque of synchronous reluctance motor, realize the comprehensive improvement of permanent magnet torque peak and reluctance torque peak, and further use the asymmetric design in the rotor to realize the shift of the magnetic axis, so that the current angles corresponding to the peak values of the permanent magnet and reluctance torque components are close to each other, the utilization rate of torque components is improved, and the torque density is improved.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet motors, specifically relating to a surface-mounted permanent magnet biased synchronous reluctance motor. Background Technology

[0002] With the promotion and development of electric vehicles, built-in permanent magnet synchronous motors are widely used in electric vehicles due to their advantages such as high power density, high efficiency, and better control precision. However, the high cost of rare-earth permanent magnet materials used in permanent magnet motors makes their manufacturing cost too high, which is not conducive to the promotion and development of electric vehicles. Therefore, improving the utilization rate of permanent magnets is crucial. Traditional built-in motors can provide high reluctance torque, but compared with traditional surface permanent magnet motors, their permanent magnet torque is relatively low. Moreover, their rotors usually adopt a symmetrical structure, and the d-axis difference between permanent magnet torque and reluctance torque is approximately 45 degrees, resulting in a decrease in the utilization rate of both and limiting the overall power density of the motor. To address this, a type of magnetic shaft offset permanent magnet motor has been proposed. This type of motor can reduce the d-axis difference angle between permanent magnet torque and reluctance torque, thereby improving torque density. Currently, motors with magnetic shaft offset effects have relatively low permanent magnet utilization rates and relatively low peak permanent magnet torque. Furthermore, to compensate for the decrease in peak torque during offset, the topology of such motors is becoming increasingly complex, increasing the difficulty of motor design, analysis, and manufacturing. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide an embedded permanent magnet biased synchronous reluctance motor, which solves the problems of low torque component utilization in traditional built-in permanent magnet motors and insufficient peak torque component in existing magnetic shaft offset motors.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] An embedded permanent magnet biased synchronous reluctance motor includes a stator core with an air gap in the middle and an embedded permanent magnet biased synchronous reluctance rotor on the inner side. The stator core has a three-phase armature winding and a shaft surrounded by the embedded permanent magnet biased synchronous reluctance rotor and located on the motor's central axis. The stator core includes stator teeth, a stator yoke, and stator slots formed between adjacent stator teeth. The embedded permanent magnet biased synchronous reluctance rotor includes embedded permanent magnets, a rotor yoke, rotor teeth, and an asymmetric reluctance unit composed of three layers of U-shaped magnetic barriers.

[0006] Furthermore, the embedded permanent magnets of the surface-mounted permanent magnet biased synchronous reluctance rotor are embedded in the outer periphery of the rotor and are evenly distributed, and there is an angle α between the axis of the surface-mounted permanent magnets and the defined motor d-axis.

[0007] Furthermore, the embedded permanent magnets are radially magnetized, and the magnetization directions of adjacent embedded permanent magnets are opposite.

[0008] Furthermore, the asymmetric reluctance unit of the surface-mounted permanent magnet biased synchronous reluctance rotor is composed of three layers of asymmetric U-shaped air slot structure. One side of the asymmetric reluctance unit is close to the inner side of the surface-mounted permanent magnet body, and the other side is close to the outer diameter of the rotor.

[0009] Furthermore, the rotor yoke of the surface-mounted permanent magnet biased synchronous reluctance rotor is located between the asymmetric reluctance unit and the rotating shaft, and the rotor teeth of the surface-mounted permanent magnet biased synchronous reluctance rotor are located between adjacent asymmetric reluctance units and the surface-mounted permanent magnet.

[0010] Furthermore, the embedded permanent magnets and the asymmetric magnetoresistive units are grouped together, with the number being twice the number of rotor pole pairs.

[0011] Furthermore, the three-phase armature winding is a double-layer distributed winding that passes through the stator slots and is wound around the stator teeth.

[0012] The beneficial effects of this invention are:

[0013] 1. This invention can be based on a surface-mounted permanent magnet motor with high permanent magnet torque, combined with a multi-layer synchronous reluctance structure, to further expand the peak reluctance torque of the motor, providing further advantages for field weakening speed regulation. At the same time, the number of permanent magnets in the proposed motor is significantly reduced compared to traditional permanent magnet assisted synchronous reluctance motors, greatly reducing the time required for permanent magnet assembly and thus improving motor production efficiency.

[0014] 2. In traditional symmetrical motors, the current angles corresponding to the maximum values ​​of the two torque components differ by 45 electrical degrees. However, under the premise of a certain amount of permanent magnets, this invention utilizes the fully biased design of permanent magnets and the auxiliary effect of the asymmetrical distribution of multi-layer reluctance structures to enable the permanent magnet torque and reluctance torque components to reach their maximum values ​​at similar current angles, thereby improving the utilization rate of torque components and enhancing torque output capability.

[0015] 3. Due to the complete bias of the permanent magnets, most of the permanent magnet flux in each permanent magnet of the motor rotor is only through the magnetic circuit provided by the asymmetric reluctance unit. The permanent magnet flux is only through the reluctance corresponding to one permanent magnet, which reduces the weakening of the permanent magnet flux and helps to improve the utilization rate of the permanent magnets. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the cross-sectional structure of the motor according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the distribution of the motor's unloaded magnetic field lines and the d-axis of the permanent magnet and the reluctance magnet in an embodiment of the present invention.

[0019] Figure 3 This is a motor torque separation diagram according to an embodiment of the present invention.

[0020] Reference numerals: 1. Stator core; 11. Stator tooth; 12. Stator yoke; 13. Stator slot; 2. Surface-mounted permanent magnet biased synchronous reluctance rotor; 21. Surface-mounted permanent magnet; 22. Rotor yoke; 23. Rotor tooth; 24. Asymmetric reluctance unit; 3. Three-phase armature winding; 4. Shaft. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0023] like Figure 1-2 As shown, one embodiment of the present invention provides an embedded permanent magnet biased synchronous reluctance motor, including a stator core 1 with an air gap in the middle, an embedded permanent magnet biased synchronous reluctance rotor 2 disposed in the middle of the inner side of the stator core 1, a three-phase armature winding 3 disposed on the stator core 1, and a rotating shaft 4 surrounded by the embedded permanent magnet biased synchronous reluctance rotor 2 and located on the central axis of the motor.

[0024] The stator core 1 includes stator teeth 11, stator yoke 12, and stator slots 13 formed by adjacent stator teeth 11; one end of the stator teeth 11 is close to the surface-mounted permanent magnet biased synchronous reluctance rotor 2, and the other end of the stator teeth 11 away from the surface-mounted permanent magnet biased synchronous reluctance rotor 2 is connected to the stator yoke 12. Stator slots 13 are formed between adjacent stator teeth 11, and the stator teeth 11 and stator slots 13 are evenly distributed around the central axis of the stator; the three-phase armature winding 3 is a double-layer distributed winding that passes through the stator slots 13 and is wound on the stator teeth 11.

[0025] The surface-mounted permanent magnet biased synchronous reluctance rotor 2 includes a surface-mounted permanent magnet 21, a rotor yoke 22, rotor teeth 23, and an asymmetric reluctance unit 24 composed of three layers of U-shaped magnetic barriers.

[0026] The embedded permanent magnets 21 of the surface-mounted permanent magnet biased synchronous reluctance rotor 2 are embedded in the outer circumference of the rotor and are evenly distributed. The axis of each embedded permanent magnet 21 has an angle α with the defined motor d-axis. This arrangement allows for the offset of the permanent magnet axis, significantly bringing the current angle corresponding to the peak permanent magnet torque closer to the current angle corresponding to the peak reluctance torque. The embedded permanent magnets 21 are radially magnetized, and adjacent embedded permanent magnets 21 are magnetized in opposite directions.

[0027] The asymmetric reluctance unit 24 of the surface-mounted permanent magnet biased synchronous reluctance rotor 2 consists of three layers of asymmetric U-shaped air slot structures. One side of the asymmetric reluctance unit 24 is close to the inner side of the surface-mounted permanent magnet 21, and the other side is close to the outer diameter of the rotor. The central axis of the asymmetric reluctance unit 24 has no significant offset from the defined d-axis of the motor, which has the advantage of high reluctance torque of traditional multi-layer synchronous reluctance motors. Moreover, the air slots near the inner side of the permanent magnet are relatively narrow, which can effectively ensure the utilization rate of permanent magnet flux.

[0028] The rotor yoke 22 of the surface-mounted permanent magnet biased synchronous reluctance rotor 2 is located between the asymmetric reluctance unit 24 and the shaft 4. The rotor teeth 23 of the surface-mounted permanent magnet biased synchronous reluctance rotor 2 are located between the adjacent asymmetric reluctance unit 24 and the surface-mounted permanent magnet 21. The asymmetric bias setting of the surface-mounted permanent magnet 21 makes the rotor teeth 23 also asymmetric, resulting in an angle β between the reluctance magnetic axis and the traditional symmetric reluctance magnetic axis. This achieves the offset of the reluctance magnetic axis and plays a certain role in adjusting the current angle corresponding to the peak reluctance torque.

[0029] The rotating shaft 4 is surrounded by the surface-mounted permanent magnet biased synchronous reluctance rotor 2 and passes through the center of the motor.

[0030] In this embodiment, there are four embedded permanent magnets 21, and correspondingly, there are four asymmetric reluctance units 24. The permanent magnets used are neodymium iron boron permanent magnets, there are twenty-seven stator slots 13, and the three-phase armature winding 3 is a double-layer distributed design.

[0031] Invention principle:

[0032] In order to make the current angles corresponding to the peak permanent magnet torque and the peak reluctance torque coincide, the present invention uses the biasing of the embedded permanent magnet 21 to move the permanent magnet axis, i.e. the d-axis corresponding to the permanent magnet torque, toward the reluctance axis, i.e. the d-axis corresponding to the reluctance torque, thereby improving the utilization rate of the permanent magnet torque and reluctance torque of the motor and the peak total torque.

[0033] The embedded permanent magnet 21 and the asymmetric magnetoresistive unit 24 are grouped together, and their number is twice the number of rotor pole pairs pr.

[0034] Theoretically, when the rotor pole pair number pr and the offset angle α satisfy:

[0035] pr×(α-β)=45°

[0036] The peak value of the permanent magnet torque and the peak value of the reluctance torque of the motor are obtained at the same current angle.

[0037] Combination Figure 2 and Figure 3 The operating principle of the surface-mounted permanent magnet biased synchronous reluctance motor in this embodiment is as follows:

[0038] The permanent magnet magnetic field can be divided into two parts. The first part of the permanent magnet flux travels from the N pole of the embedded permanent magnet 21 to the air gap, stator teeth 11, stator yoke 12, stator teeth 11 again, air gap, and the S pole of the embedded permanent magnet 21, then returns to the N pole of the embedded permanent magnet 21 through the rotor yoke 22, forming a closed circuit. The second part of the permanent magnet flux travels from the N pole of the embedded permanent magnet to the air gap, stator teeth 11, stator yoke 12, stator teeth 11, and air gap, then returns to the N pole of the initial embedded permanent magnet 21 through the magnetic path provided by the asymmetric reluctance unit 24, forming a closed circuit. As the rotor rotates, the above magnetic path rotates with the rotor; at the same time, the three-phase current flowing through the stator can form a rotating magnetic field with the same rotational speed as the rotor. The interaction between the stator and rotor magnetic fields generates permanent magnet torque, driving the rotor to rotate constantly. Meanwhile, for the reluctance section, the presence of the designed asymmetric reluctance unit 24 greatly increases the difference between the rotor's quadrature and direct axis magnetic circuits, resulting in a large difference in quadrature and direct axis inductance, thereby generating reluctance torque.

[0039] In the traditional theory of symmetrical permanent magnet motors, the magnitudes of both permanent magnet torque and reluctance torque change sinusoidally with the change of current angle, with the peak permanent magnet torque obtained at a current angle of 0° and the peak reluctance torque obtained at a current angle of 45°. This invention achieves a closer approximation of the current angles corresponding to the two peak torques by completely biasing the embedded permanent magnet 21 around the rotor periphery and by using an asymmetrical design of the multi-layer asymmetrical reluctance unit 24, thereby improving torque utilization and increasing the total torque.

[0040] Compared to traditional surface-mounted permanent magnet motors, the asymmetric reluctance unit 24 added to the motor of this invention, based solely on slotting, significantly increases the peak value of the reluctance torque component. Simultaneously, the number of permanent magnets in the proposed motor is substantially reduced compared to traditional permanent magnet assisted synchronous reluctance motors, greatly reducing the assembly time required for the permanent magnets and thus improving motor production efficiency.

[0041] In this invention, the permanent magnet axis is shifted counterclockwise and brought closer to the reluctance axis by the complete biasing of the surface-mounted permanent magnet. Please refer to [the following text is incomplete and requires further context]. Figure 2 Where, lpm1 represents the original permanent magnet central axis, i.e., the defined motor d-axis; lpm2 represents the central axis of the embedded permanent magnet; lpmrel represents the actual permanent magnet central axis, i.e., the actual permanent magnet axis after offset; α is the theoretical offset angle of the permanent magnet central axis; lr1 is the original reluctance axis; lr2 is the offset reluctance axis; and β is the theoretical offset angle of the reluctance axis. This invention can output greater torque with the same amount of permanent magnets, such as... Figure 3 As shown.

[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A surface-mounted permanent magnet biased synchronous reluctance motor, comprising a stator core (1) with an air gap in the middle and a surface-mounted permanent magnet biased synchronous reluctance rotor (2) on the inner side, characterized in that, The stator core (1) is provided with a three-phase armature winding (3) and a rotating shaft (4) surrounded by the surface-mounted permanent magnet biased synchronous reluctance rotor (2) and located on the central axis of the motor. The stator core (1) includes stator teeth (11), stator yoke (12), and stator slots (13) formed between adjacent stator teeth (11); The surface-mounted permanent magnet biased synchronous reluctance rotor (2) includes a surface-mounted permanent magnet (21), a rotor yoke (22), rotor teeth (23), and an asymmetric reluctance unit (24) composed of three layers of U-shaped magnetic barriers; The embedded permanent magnet (21) of the surface-mounted permanent magnet biased synchronous reluctance rotor (2) is embedded in the outer periphery of the rotor and is evenly distributed, and there is an angle α between the axis of the surface-mounted permanent magnet (21) and the defined motor d axis. The asymmetric reluctance unit (24) of the surface-mounted permanent magnet biased synchronous reluctance rotor (2) is composed of three layers of asymmetric U-shaped air slot structure. One side of the asymmetric reluctance unit (24) is close to the inner side of the surface-mounted permanent magnet (21), and the other side is close to the outer diameter of the rotor.

2. The surface-mounted permanent magnet biased synchronous reluctance motor according to claim 1, characterized in that, The surface-mounted permanent magnet (21) is radially magnetized, and the magnetization directions of adjacent surface-mounted permanent magnets (21) are opposite.

3. The surface-mounted permanent magnet biased synchronous reluctance motor according to claim 1, characterized in that, The rotor yoke (22) of the surface-mounted permanent magnet biased synchronous reluctance rotor (2) is located between the asymmetric reluctance unit (24) and the rotating shaft (4), and the rotor teeth (23) of the surface-mounted permanent magnet biased synchronous reluctance rotor (2) are located between the adjacent asymmetric reluctance unit (24) and the surface-mounted permanent magnet (21).

4. The surface-mounted permanent magnet biased synchronous reluctance motor according to claim 1, characterized in that, The embedded permanent magnet (21) and the asymmetric magnetoresistive unit (24) are distributed in groups, and their number is twice the number of rotor pole pairs.

5. The surface-mounted permanent magnet biased synchronous reluctance motor according to claim 1, characterized in that, The three-phase armature winding (3) is a double-layer distributed winding that passes through the stator slot (13) and is wound on the stator teeth (11).

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