An asymmetric hybrid surface-embedded salient pole permanent magnet motor

Abstract

This invention discloses an asymmetric hybrid surface-embedded-salient pole permanent magnet motor, belonging to the field of permanent magnet motor technology. It includes an outer stator core with an air gap in the middle and an inner hybrid surface-embedded-salient pole permanent magnet rotor. Three-phase armature windings are mounted on the stator core, and a shaft is surrounded by the rotor and located on the motor's central axis. The rotor includes rotor salient pole teeth, a rotor yoke, an inner air slot, permanent magnets, and an outer slot. The permanent magnets are placed in the outer slot, offset at an angle relative to the central axis of the outer slot. This invention combines the advantages of surface-embedded permanent magnet motors (simple structure, high permanent magnet utilization, high power density) and salient pole motors (high reluctance torque). By utilizing the asymmetric distribution of the permanent magnets, the peak values ​​of the permanent magnet torque and reluctance torque components can reach their maximum values ​​at similar current angles, improving torque component utilization and thus increasing torque density.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of permanent magnet motors, and particularly relates to a non-symmetrical hybrid surface-embedded salient pole type permanent magnet motor. BACKGROUND

[0002] With the deterioration of the ecological environment and the depletion of global energy, vigorously developing the new energy automobile industry has become a key measure concerning the development of the national economy. With the increasing demand of users for electric vehicles, the built-in permanent magnet synchronous motor (PMSM) is widely used in electric vehicles due to its high power density, high efficiency and better control accuracy, including Toyota Prius 2017, BMW i3 and Tesla Model 3 and other models.

[0003] The expensive rare earth permanent magnet material used in the permanent magnet motor is not conducive to the promotion and development of electric vehicles, so it is crucial to improve the utilization rate of permanent magnets. The rotor of the traditional built-in motor usually adopts a symmetrical structure, and the d-axis difference angle of the permanent magnet torque and the reluctance torque is about 45 degrees of electrical angle, resulting in a decrease in the utilization rate of the two, which limits the overall power density of the motor. Therefore, a kind of magnetic axis offset permanent magnet motor is proposed, which can reduce the d-axis difference angle of the permanent magnet torque and the reluctance torque, thereby realizing the improvement of the torque density. However, in order to make up for the decline of the reluctance torque peak value in the offset process, the reluctance structure of this kind of motor is increasingly complex, which increases the manufacturing and control difficulty of the motor. SUMMARY

[0004] In view of the defects of the prior art, the purpose of the present application is to provide a lightweight non-symmetrical hybrid surface-embedded salient pole type permanent magnet motor which can effectively solve the problem of low utilization rate of torque components in traditional built-in permanent magnet motors and the problem of complex structure of existing magnetic axis offset motors.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A non-symmetrical hybrid surface-embedded salient pole type permanent magnet motor, the motor comprising a stator core with an air gap in the middle and a hybrid surface-embedded salient pole type permanent magnet rotor, the stator core having an array of several three-phase armature windings, the motor having a rotating shaft at the center axis, the rotor being arranged around the rotating shaft;

[0007] The stator core comprises stator teeth, a stator yoke and stator slots, one end of the stator teeth being close to the rotor, the other end of the stator teeth away from the rotor being connected with the stator yoke, and the stator slots being located between two adjacent stator teeth.

[0008] Further, the three-phase armature windings are double-layer distributed windings, and the three-phase armature windings are wound on the stator teeth through the stator slots.

[0009] Further, the rotor is divided into two layers, the outer layer of the rotor comprises rotor salient pole teeth, surface-embedded permanent magnets and rotor outer slots, the surface-embedded permanent magnets are located on the rotor outer slots, the angle alpha exists between the central axis of the surface-embedded permanent magnets and the central axis of the rotor outer slots, and the surface-embedded permanent magnets do not completely fill the rotor outer slots, the non-permanent magnet part of the rotor outer slots is air, and the rotor outer slots are symmetrically arranged between two adjacent rotor salient pole teeth.

[0010] Further, the inner layer of the rotor is a symmetrical rotor core composed of rotor inner slots and rotor yokes, and the central axes of the rotor inner slots and the rotor outer slots coincide.

[0011] The beneficial effects of the present application are as follows:

[0012] 1. Under the premise of a certain amount of permanent magnets, the asymmetric distribution of permanent magnets can make the permanent magnet torque and the reluctance torque component reach the maximum value under similar current angles, improve the utilization rate of torque components, and improve the torque output capacity; in addition, under the premise of requiring a certain output torque, the amount of permanent magnets can be reduced, although the permanent magnet torque component is reduced, the maximum values of the permanent magnet torque and the reluctance torque component are close to each other, the proportion of the reluctance torque is improved, the weak magnetic speed expansion capability of the motor is enhanced, and it is beneficial to be applied in the field of electric vehicles;

[0013] 2. Compared with the existing magnetic shaft offset motor, the motor of the present application combines the advantages of high permanent magnet torque of the surface-embedded permanent magnet motor and high reluctance torque of the salient pole motor, and the obtained hybrid magnetic pole motor has high permanent magnet torque and reluctance torque and has the advantages of simple structure of both, and has the characteristics of "high torque density and light weight". BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0015] Figure 1 It is a schematic diagram of the cross-sectional structure of the motor of the present application;

[0016] Figure 2 It is a schematic diagram of the motor no-load magnetic force line distribution and permanent magnet d-axis and reluctance d-axis of the present application;

[0017] Figure 3 It is a motor output torque separation diagram of the present application. DETAILED DESCRIPTION

[0018] 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.

[0019] An asymmetric hybrid surface-embedded-salient pole permanent magnet motor, such as Figure 1 As shown, the motor includes a stator core 1 with an air gap in the middle and a hybrid surface-embedded-salient pole permanent magnet rotor 2. Several three-phase armature windings 3 are arrayed on the stator core 1. A rotating shaft 4 is provided at the central axis of the motor. The rotor 2 is arranged around the rotating shaft 4. The rotating shaft 4 is used to pass through and fix the hybrid surface-embedded-salient pole permanent magnet rotor. The motor is also provided with a housing, in which the stator, rotor and rotating shaft 4 are all located inside the housing.

[0020] The stator core 1 includes stator teeth 1.1, stator yoke 1.2, and stator slots 1.3. One end of the stator teeth 1.1 is close to the rotor 2, and the end of the stator teeth 1.1 away from the rotor 2 is connected to the stator yoke 1.2. The stator slots 1.3 are located between two adjacent stator teeth 1.1. The stator teeth 1.1 and stator slots 1.3 are evenly arranged around the central axis of the stator. The number of stator slots 1.3 and stator teeth 1.1 is the same, both being 24. The three-phase armature winding 3 is a double-layer distributed winding, and the three-phase armature winding 3 passes through the stator slots 1.3 and is wound on the stator teeth 1.1.

[0021] The hybrid surface-embedded-salient permanent magnet rotor 2 is divided into inner and outer layers. The outer layer of rotor 2 includes rotor salient pole teeth 2.1, surface-embedded permanent magnets 2.4, and rotor outer slots 2.5. The surface-embedded permanent magnets 2.4 are located on the rotor outer slots 2.5. There is an angle α between the central axis of the surface-embedded permanent magnets 2.4 and the central axis of the rotor outer slots 2.5. The surface-embedded permanent magnets 2.4 do not completely fill the rotor outer slots 2.5. The non-permanent magnet medium in the rotor outer slots 2.5 is air. The rotor outer slots 2.5 are symmetrically arranged between two adjacent rotor salient pole teeth 2.1. The embedded permanent magnet 2.4 is radially magnetized, and the magnetization directions of two adjacent embedded permanent magnets 2.4 are opposite. The inner layer of the rotor 2 is a symmetrical rotor core composed of the rotor inner slot 2.3 and the rotor yoke 2.2. The rotor core has a high saliency ratio, that is, a high difference between the cross-axis inductance and the direct-axis inductance, so it can provide high reluctance torque. The central axis of the rotor inner slot 2.3 and the rotor outer slot 2.5 coincides, and the number of embedded permanent magnets 2.4 is the same as that of the two, which is twice the number of rotor pole pairs pr.

[0022] Theoretically, when the rotor pole pair number pr and the offset angle α satisfy:

[0023] pr×α=45°

[0024] The magnetic axis offset effect is most significant, and the total torque is maximized.

[0025] In the embodiment, the number of surface-embedded permanent magnets 2.4 is four, and the number of rotor inner slots 2.3 and rotor outer slots 2.5 is also four. The permanent magnets used are neodymium-iron-boron permanent magnets. The number of stator slots 1.3 is twenty-four, and the armature winding 3 is a double-layer distributed design.

[0026] Please refer to Figure 2 and Figure 3 , the operation principle of the asymmetric hybrid surface-embedded salient pole permanent magnet motor of the embodiment is as follows:

[0027] For the permanent magnet magnetic field part, the magnetic path of the permanent magnet flux is from the N pole of the permanent magnet to the air gap, the stator tooth, the stator yoke, the stator tooth, the air gap, the S pole of the permanent magnet, and then back to the N pole of the permanent magnet through the rotor yoke to form a closed path. Due to the rotation of the rotor, the magnetic path rotates with the rotor. At the same time, the stator is supplied with three-phase current to form a rotating magnetic field with the same speed as the rotor. The interaction of the stator and rotor magnetic fields produces a permanent magnet torque to drive the rotor to rotate constantly. At the same time, for the magnetic resistance part, the difference between the cross-axis and direct-axis inductances is large due to the difference between the cross-axis and direct-axis magnetic paths of the rotor, thereby generating a magnetic resistance torque.

[0028] In the traditional symmetric permanent magnet motor theory, the sizes of the permanent magnet torque and the magnetic resistance torque change sinusoidally with the change of the current angle, and the peak value of the permanent magnet torque is obtained when the current angle is 0°, and the peak value of the magnetic resistance torque is obtained when the current angle is 45°. The present application realizes the close of the corresponding current angles at which the two peak torque values are obtained by offsetting the surface-embedded permanent magnets in the rotor outer slots, thereby improving the torque utilization rate and increasing the total torque.

[0029] In the present application, the surface-embedded permanent magnets offset in the rotor outer slots make the permanent magnet magnetic axis offset in the counterclockwise direction, and approach the magnetic resistance magnetic axis, as shown in Figure 2 , Figure 3 , wherein l1 represents the magnetic resistance d-axis, l2 represents the original permanent magnet d-axis, and l3 represents the new permanent magnet d-axis. The present application can ensure that a larger torque is output under the condition of the same amount of permanent magnets.

[0030] In one embodiment, the surface-embedded neodymium-iron-boron permanent magnets can also adopt a surface-mounted form, and the shape of the rotor inner slot can be modified according to requirements. At the same time, the analysis of the present application is also applicable to the concentrated winding form of the armature winding, and still has the torque improvement effect.

[0031] In order to make the maximum current angle of the permanent magnet torque and the reluctance torque close to the same angle, the magnetic axis of the permanent magnet, i.e. the d-axis corresponding to the permanent magnet torque, is offset by the bias of the permanent magnet under the hybrid magnetic pole, and moves towards the direction of the reluctance magnetic axis, i.e. the d-axis corresponding to the reluctance torque, so as to realize the improvement of the utilization rate of the motor permanent magnet torque, reluctance torque and total torque peak. The magnetic axis offset effect of the motor greatly depends on the arc of the rotor outer slot and the arc of the permanent magnet, and the difference between the two will result in the difference of the current angle corresponding to the peak torque and the torque utilization rate.

[0032] Since the surface-embedded permanent magnet motor has the advantage of high permanent magnet torque, the salient pole motor has the advantage of high reluctance torque, and both have simple structure, therefore the application adopts a hybrid magnetic pole motor combining the surface-embedded permanent magnet and the salient pole, realizes the lightweight design of the motor on the basis of torque improvement.

[0033] In the description of the present specification, the description referring to the terms "one embodiment", "example", "specific example" and the like means 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 application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0034] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. An asymmetric hybrid surface-embedded salient pole permanent magnet machine, characterized in that, The motor comprises a stator core (1) with an air gap in the middle and a hybrid surface-embedded salient pole permanent magnet rotor (2), a plurality of three-phase armature windings (3) are arranged on the stator core (1), and a rotating shaft (4) is arranged at the center axis of the motor, and the rotor (2) is arranged around the rotating shaft (4); The stator core (1) comprises stator teeth (1.1), a stator yoke (1.2) and stator slots (1.3), one end of the stator teeth (1.1) is close to the rotor (2), the other end of the stator teeth (1.1) away from the rotor (2) is connected with the stator yoke (1.2), and the stator slots (1.3) are located between two adjacent stator teeth (1.1); The rotor (2) is divided into two layers, the outer layer of the rotor (2) comprises rotor salient pole teeth (2.1), surface-embedded permanent magnets (2.4) and rotor outer slots (2.5), the rotor outer slots (2.5) are symmetrically arranged between two adjacent rotor salient pole teeth (2.1), the surface-embedded permanent magnets (2.4) do not completely fill the rotor outer slots (2.5), the non-permanent magnet part in the rotor outer slots (2.5) is air, and there is an angle α between the center axis of the surface-embedded permanent magnets (2.4) and the center axis of the rotor outer slots (2.5), when the rotor pole pair number pr and the offset angle α satisfy pr×α=45°, the magnetic axis offset effect is most significant, and the total torque is maximized; The inner layer of the rotor (2) is a symmetrical rotor core composed of a rotor inner slot (2.3) and a rotor yoke (2.2), and the center axis of the rotor inner slot (2.3) coincides with that of the rotor outer slot (2.5).

2. An asymmetrical hybrid tabled salient-pole permanent magnet motor according to claim 1, characterized in that, The three-phase armature winding (3) is a double-layer distributed winding, and the three-phase armature winding (3) is wound on the stator teeth (1.1) through the stator slots (1.3).

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