CN110022013B - A rotor with inclined magnetic poles and asymmetrical salient poles and a high-performance permanent magnet motor - Google Patents

Abstract

The disclosure proposes a rotor with inclined magnetic poles and asymmetric salient poles and a high-performance permanent magnet motor. The inclined poles of the magnetic poles are implemented within one pole pitch, and the salient poles are arranged on one side of the magnetic poles, which has asymmetry in the circumferential direction. The rotor design of the high-performance permanent magnet motor can not only reduce the torque ripple, but also effectively avoid the drop of the output torque after reducing the torque ripple, realize the low torque ripple and high torque density operation of the motor, and greatly improve the performance of the motor. Specifically: 1) Reduce cogging torque; 2) Generate sinusoidal or quasi-sinusoidal back electromotive force to reduce torque ripple; 3) There is no axial overlap between adjacent magnetic poles to avoid excessive torque density attenuation; asymmetrical salient pole rotor structure , so that the maximum value of the reluctance torque and the permanent magnet torque are superimposed at the same or similar current phase angle, so as to make up for the torque loss caused by the magnetic pole inclination by increasing the utilization rate of the two torque components, and ensure that the motor is low Torque ripple while maintaining high torque density.

Description

A rotor with inclined magnetic poles and asymmetrical salient poles and a high-performance permanent magnet motor

technical field

The present disclosure relates to the relevant technical field of permanent magnet motors, in particular, to a rotor with inclined magnetic poles and asymmetric salient poles and a high-performance permanent magnet motor.

Background technique

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

With the development of rare earth permanent magnet materials, permanent magnet motors are widely used in various fields such as electric vehicles, wind power generation, and ship propulsion due to their significant advantages such as high efficiency, high power density, and high reliability. Due to the various structures of permanent magnet motors, the optimal design of the structure of permanent magnet motors can maximize the performance of permanent magnet motors in all aspects.

According to the placement position of the permanent magnet on the rotor, it is mainly divided into surface-mounted permanent magnet motors, surface-embedded permanent magnet motors and built-in permanent magnet motors. Among them, the surface-embedded permanent magnet motor has a saliency effect compared with the surface-mounted permanent magnet motor, so the electromagnetic torque not only has the permanent magnet torque, but also generates the reluctance torque, thus producing higher torque density and Efficiency, and has good field-weakening speed regulation performance; compared with the embedded permanent magnet motor, the structure is simple and the manufacturing cost is lower; therefore, the surface embedded permanent magnet motor has very good performance because of its better comprehensive performance. application prospects.

However, surface embedded permanent magnet motors also have problems: 1) Although the electromagnetic torque of surface embedded permanent magnet motors includes two torque components, permanent magnet torque and reluctance torque, there is no such torque component in traditional designs. is fully utilized because the permanent magnet torque and reluctance torque reach their maximum values with a current phase angle difference of 45 degrees. 2) Due to the saliency effect, the surface embedded permanent magnet motor will produce higher torque ripple. Methods for suppressing torque ripple of permanent magnet motors have been widely studied, such as rotor circumferential segmentation, rotor pole arc cutting, oblique poles, rotor surface slotting, asymmetric magnetic barriers, etc. In particular, the oblique pole technique is an effective method to suppress torque ripple, and many literatures have conducted in-depth discussions and researches on this method. At first, it was concluded from the simulation analysis that the magnetic poles of the offset motor can weaken the cogging torque, and then some scholars put forward some methods for determining the offset angle on the basis of theoretical analysis. With the continuous improvement of the method, its effect is getting better and better. But the skewed pole method has some disadvantages, such as reducing the torque density of the motor. For the motor, the torque density is often more important than the torque ripple, so it is worth further study to improve the problem of the reduction of the torque density of the permanent magnet motor caused by the oblique pole of the permanent magnet. However, current literature shows that motor design techniques that reduce torque ripple while maintaining torque density are difficult to achieve.

Contents of the invention

In order to solve the above problems, the present disclosure proposes a rotor with inclined magnetic poles and asymmetric salient poles, which is applied to permanent magnet motors such as surface embedded permanent magnet motors, which can not only reduce torque ripple, but also effectively avoid The problem of output torque drop after pulsation.

The second aspect of the present disclosure also proposes a permanent magnet motor based on a rotor with inclined magnetic poles and asymmetric salient poles, which effectively combines magnetic pole offset and asymmetric salient pole rotors to achieve low torque ripple and high torque of the motor Density operation, effectively improve the performance index of the motor.

The disclosure adopts the following technical solutions:

One or more embodiments provide a rotor with inclined magnetic poles and asymmetrical salient poles, including a rotor core and magnetic poles disposed on the rotor core, each magnetic pole comprising salient poles and rotor poles alternately disposed on the rotor core Slots. Segmented permanent magnets are arranged in the rotor slots, and each segment of permanent magnets is extended and arranged along the direction of the rotating shaft, and is sequentially arranged in dislocation according to a set angle on the circumference of the rotor core.

One or more embodiments provide a permanent magnet motor with tilted rotor poles and asymmetric salient poles, including the above-mentioned rotor with tilted magnetic poles and asymmetric salient poles, a stator and a rotating shaft, the rotor and the stator are coaxially arranged , the rotor is arranged inside the stator through the rotating shaft, and there is a gap between the rotor and the stator.

In the present disclosure, the tilted magnetic pole obtained by using the permanent magnet segmental dislocation method can effectively weaken the cogging effect, reduce the cogging torque, and reduce the harmonic content of the back electromotive force when applied to the permanent magnet motor, and generate sinusoidal or quasi-sinusoidal back electromotive force And reduce the torque ripple, making the motor output torque more stable.

Compared with the prior art, the beneficial effects of the present disclosure are:

This disclosure proposes a permanent magnet motor based on a rotor with inclined magnetic poles and asymmetric salient poles, so that the torque ripple of the surface-embedded permanent magnet motor is reduced while the torque density is not reduced. Specifically: 1) This disclosure By using the magnetic pole segment dislocation method, the cogging effect can be effectively weakened, the cogging torque can be reduced, and the harmonic content of the back electromotive force can be reduced at the same time, and the sinusoidal or quasi-sinusoidal back electromotive force can be generated to reduce the torque ripple, making the output torque of the motor more accurate. 2) Magnetic pole segmental dislocation is realized within a magnetic pole pitch, so that adjacent magnetic poles do not overlap in the axial direction, and excessive torque density attenuation is avoided; 3) By using an asymmetrical salient pole rotor structure, the reluctance torque and The maximum value of the permanent magnet torque is superimposed at the same or similar current phase angle, which is smaller than the 45-degree current phase angle in the traditional design, so as to compensate for the torque caused by the magnetic pole skew by increasing the utilization of the two torque components Loss, to ensure low torque ripple of the motor while maintaining high torque density.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and not to limit the present application.

Fig. 1 is a schematic structural diagram of an existing traditional surface-embedded permanent magnet motor;

Fig. 2 is a schematic diagram of the oblique poles of the rotor in Embodiment 1 of the present disclosure;

Fig. 3 is a schematic diagram of an equivalent magnetic pole and an equivalent salient pole in Embodiment 1 of the present disclosure;

4 is a schematic diagram of the influence of the asymmetric rotor on the torque of the motor in Embodiment 2 of the present disclosure;

Fig. 5 is a three-dimensional schematic diagram of the motor rotor in Embodiment 1 of the present disclosure;

Fig. 6 is a top view of the structure of the permanent magnet motor according to Embodiment 2 of the present disclosure;

Fig. 7 is a schematic diagram of the back EMF comparison between the traditional motor (basic model) and the example motor (proposed model) according to the embodiment of the present disclosure;

Fig. 8 is a schematic diagram of the cogging torque comparison between the example motor of Embodiment 2 of the present disclosure and the conventional motor;

Fig. 9 is a schematic diagram of torque separation when the permanent magnet of the motor in Example 2 of the embodiment of the present disclosure is not approaching the salient pole;

Fig. 10 is a schematic diagram of torque separation when the permanent magnet of the motor in Example 2 of the embodiment of the present disclosure approaches the salient pole;

Fig. 11 is a schematic diagram of the permanent magnet torque comparison between the example motor and the traditional motor according to Embodiment 2 of the present disclosure;

Fig. 12 is a schematic diagram of the electromagnetic torque comparison between the example motor of Embodiment 2 of the present disclosure and the traditional motor;

Among them: 1. Stator, 2. Stator winding, 3. Salient pole, 3-1, First side of salient pole, 3-2, Second side of salient pole, 4. Permanent magnet, 5. Rotor, 5-1, Rotor Slot, 5-2, rotor core, 6, magnetic pole axis, 7, rotating shaft, 8, first end face, 9, second end face.

Detailed ways:

The present disclosure will be further described below in conjunction with the accompanying drawings and embodiments.

It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof. It should be noted that, in the case of no conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other. The embodiments will be described in detail below in conjunction with the accompanying drawings.

Example 1

In the technical solutions disclosed in one or more embodiments, as shown in Figures 5 and 6, an asymmetrical rotor with inclined magnetic poles and salient poles includes a rotor core 5-2 and a Each magnetic pole includes salient poles 3 and rotor slots 5-1 alternately arranged on the rotor core, and segmented permanent magnets 4 are arranged in the rotor slots 5-1, and each segment of permanent magnets 4 is arranged along the rotating shaft 7 The directions are extended and arranged, and are sequentially arranged in dislocation according to a set angle on the circumference of the rotor iron core 5-2. In this disclosure, the tilted magnetic poles obtained by using the 4-stage dislocation method of permanent magnets can effectively weaken the cogging effect and reduce the cogging torque when applied to permanent magnet motors, and at the same time reduce the harmonic content of back electromotive force to generate sinusoidal or quasi-sinusoidal countermeasures. The electromotive force reduces the torque ripple, making the output torque of the motor more stable.

As shown in Figure 1, it is a traditional symmetrical rotor structure. The permanent magnets of the existing symmetrical rotor structure extend from one end face of the rotor to the other end face according to the rotating shaft. If the geometric centerline of each magnetic pole is defined as the magnetic pole axis 6. The permanent magnet is symmetrical to the magnetic pole axis. The extension and arrangement of each segment of permanent magnets 4 along the rotation axis means that the permanent magnets are arranged from the first end surface 8 to the second end surface 9 according to the rotation axis direction. Arranging in sequence on the circumference of the rotor iron core according to the set angle misalignment means that the permanent magnets 4 of each segment are staggered by a certain angle in the circumferential direction of the rotor iron core, which can be the structure shown in Figures 2 and 5 . Referring to Fig. 2 for illustration, a magnetic pole includes a rotor slot 5-1 and a salient pole 3. After the permanent magnets are staggered and arranged in sections, the permanent magnets 4 in Fig. 2 are asymmetrical with respect to the magnetic pole axis 6, forming a non-symmetrical permanent magnet 4. Symmetrical structure.

As a further improvement, the shape of the permanent magnets 4 in each segment can be the same, and the radial projection can be a rectangle. When projecting a rectangle in the radial direction, the cogging torque can be minimized by step biasing, and the permanent magnets of each segment are arranged along the rotation axis in a segmented shape, and are sequentially arranged at a set angle on the circumference of the rotor core. After dislocation arrangement, they form a ladder shape, which can be the structure shown in FIG. 5 .

As a further improvement, at least one side surface of the salient pole extends along the direction of the rotation axis. As shown in FIG. 5 , the second side 3 - 2 of the salient poles in the figure extends along the direction of the rotating shaft, presenting a straight up and down state, and the permanent magnets of different two rotor slots 5 - 1 do not overlap in the axial direction.

As a further improvement, as shown in FIG. 5 , the salient pole 3 is arranged in an asymmetric structure, the first side 3-1 of the salient pole interacts with the segmented permanent magnets arranged obliquely in a stepped manner, and the second side 3-1 of the salient pole interacts in a stepped manner. 2 extending along the direction of the rotation axis, and the first side 3-1 of the salient pole is in contact with one side of each permanent magnet.

A rotor slot 5-1 is formed between two adjacent salient poles. The structure of the rotor slot 5-1 is determined by the structure of the salient poles. When one side of the salient pole is set in a stepped shape to match the structure of the permanent magnet 4, the rotor The structure of the groove 5-1 is to form a space where the permanent magnet can be arranged, which is adapted to the stepped shape on one side of the salient pole. It is set to form a stepped structure. The other side leaves space for the permanent magnet to tilt.

Optionally, the permanent magnets at both ends of the segmented permanent magnet 4 along the direction of the rotation axis are respectively arranged in contact with the salient poles 3 . That is, in the illustrated position in FIG. 3 , the uppermost section of permanent magnet is arranged in contact with the uppermost end of the left salient pole 3 , and the lowermost section of permanent magnet is arranged in contact with the lowermost end of the right salient pole 3 .

As shown in Figure 3, the inclination angle of the segmented permanent magnets 4 determines the degree of staggering of the permanent magnets. The method for determining the inclination angles of two adjacent permanent magnets 4 is: the cogging torque is determined by the rotor permanent magnets 4 and the stator The cogging torque is minimized by step biasing due to the interaction between the cogging structures. The inclination angles of two adjacent permanent magnets 4 are equal to:

In the formula, θ _skewing is the inclination angle between two adjacent steps, HCF is the greatest common divisor function, Q is the number of stator slots, p is the number of pole pairs, n is the number of offset steps of the stepped permanent magnet, and the number of offset steps Subtract 1 from the number of segments, n=6 in FIG. 3 .

As shown in Figure 3, the two-dimensional equivalent diagram of the permanent magnet 4 and the asymmetrical salient pole 3 with the rotor tilted is obtained. In the figure, the angle of each oblique pole is θ _skew , and θ _dq in the figure is the electrical angle between the direct axis and the quadrature axis. In the figure, θ _m is the radian angle of a section of permanent magnet. In the figure, θ _pm is the total pole pitch angle (radian) between the one-pole permanent magnet 4 and the salient pole 3. In the figure, θ _r(i) is the maximum salient pole arc angle. In the figure, d _e is the direct axis, and q _e in the figure is the quadrature axis. In the figure, the stepped permanent magnet 4 interacts with the first side 3 - 1 of the salient pole 3 in a stepped manner, and the second side 3 - 2 of the salient pole 3 is linear and extends along the direction of the rotation axis 7 .

Further, to prevent severe torque degradation, within a permanent magnet pole pitch, create a constraint

nθ _skewing +θ _m ≤θ _pm (2)

In the formula, θ _m is the pitch angle between adjacent permanent magnets, and θ _pm is the pole pitch angle of the permanent magnets.

Further, as shown in Figure 2, it is a schematic diagram of rotor magnetic pole segmented oblique poles, the number of segments n of the permanent magnet can be set, and the rotor magnetic pole segmented into 7 ends in this embodiment 1 is only a numerical value for convenience of explanation and setting. According to the formula (1) and formula (2), it can be obtained that the offset angle of the permanent magnets in two adjacent sections of the segmented offset rotor described in Example 1 is 5 degrees.

Example 2

This embodiment provides a permanent magnet motor with tilted rotor magnetic poles, including a rotor, a stator and a rotating shaft, the rotor and the stator are coaxially arranged, the rotor is arranged inside the stator through the rotating shaft, and there is a gap between the rotor and the stator, so The rotor adopts the rotor with inclined magnetic poles and asymmetry described in Embodiment 1.

As shown in FIG. 6 , the stator includes a stator core and a stator slot, and a stator winding 2 is arranged in the stator slot, and a radial gap 18 is formed between the stator winding 2 and the outer periphery of the rotor 5 .

The stator slots are arranged at equal intervals along the circumferential direction on the inner periphery of the stator 1 , and extend from the side of the stator core to the direction of the rotating shaft in a convex shape. The stator can be a common six-slot structure.

In Embodiment 2, by using an asymmetrical salient pole rotor structure, the maximum values of the reluctance torque and the permanent magnet torque are superimposed at the same or similar current phase angle, thereby making up for it by increasing the utilization rate of the two torque components The torque loss caused by the magnetic pole slant ensures low torque ripple of the motor while maintaining high torque density.

The principle of achieving the above effect by using a rotor with inclined magnetic poles and asymmetrical salient poles described in Example 1 of the permanent magnet motor is as follows:

Create an asymmetric rotor structure as shown in Figure 4 to make the rotor permanent magnet 4 approach the rotor salient pole 3, so that the maximum value of the reluctance torque and the permanent magnet torque are superimposed at the same current phase angle, thereby obtaining the maximum output torque. The upper figure in Figure 4 shows that when the rotor of the permanent magnet motor is a symmetrical rotor, the maximum values of the reluctance torque and the permanent magnet torque cannot be superimposed at the same current phase angle, but have a difference of 45 electrical degrees, so that the torque utilization rate did not reach the maximum. The lower figure in Fig. 4 illustrates that when the rotor structure in Embodiment 1 is adopted, the rotor permanent magnet 4 approaches the rotor salient pole 3, so that the maximum value of the reluctance torque and the permanent magnet torque are superimposed at the same current phase angle, thus The maximum output torque is obtained by increasing the utilization rate of the two torque components. The implementation example 2 uses an asymmetrical rotor to make up for the torque loss caused by the skewed magnetic poles, so as to ensure low torque ripple of the motor while maintaining high torque density.

The goal of determining the asymmetric rotor design is the maximum average torque, and the constraint variables are the width of the rotor permanent magnet 4, the width of the rotor salient pole 3, and the offset angle of the rotor permanent magnet 4 to the rotor salient pole 3. That is, how to set the value of the above constraint variables can make full use of the torque component to obtain the maximum electromagnetic torque. The method of freezing magnetic permeability can be used to first obtain the total torque generated by all excitations, then remove the permanent magnet to obtain the reluctance torque, and finally obtain the permanent magnet torque by subtracting the reluctance torque from the total torque, and transform the constraint The value of the variable is observed through the finite element software to see if it meets the design goal.

The effect of the improved structure of the present embodiment has not been described, and a simulation analysis has been carried out, which is as follows:

The simulation uses a permanent magnet motor with 4 magnetic poles and 6 stator slots as an example motor or a proposed model. According to the total electrical angle of the permanent magnet misalignment at both ends of the rotor extending along the direction of the rotating shaft is 30°. According to the number of segments, the misalignment of two adjacent permanent magnets of the same magnetic pole is set at 5°. The permanent magnets after segmented oblique poles approach the salient poles of the rotor to form an asymmetric rotor structure, so that the maximum values of the reluctance torque and permanent magnet torque are superimposed at the same or similar current phase angles to increase the electromagnetic torque. Solved the problem of the torque density drop of permanent magnet motors due to skewed poles. The basic motor and base model are conventional motors with a symmetrical rotor structure.

As shown in Figures 7-12, the basic model shown in the figure is the traditional motor before improvement, and the proposed model is the improved motor. Due to the segmental inclined pole setting of the rotor magnetic pole, the back EMF of the motor can be seen as shown in Figure 7. The back EMF of the example motor is obviously more sinusoidal than the traditional motor. As shown in Figure 8, the cogging torque of the motor can be seen. The cogging torque of the motor in this example is obviously smaller than that of the traditional motor. Figure 9 shows the torque separation characteristic diagram of the traditional motor. When the permanent magnet torque and the reluctance torque reach their maximum values, the current phase angle differs by 45 degrees, and the two torque components are not fully utilized; as shown in Figure 10. The torque separation characteristic diagram of this embodiment shows that the permanent magnet torque and the reluctance torque reach the maximum value respectively, and the current phase angle differs by 30 degrees, which improves the utilization rate of the two torque components, and the torque lost due to the oblique pole is obtained compensate. The optimized design of the salient poles of the rotor can further reduce the current angle of the difference between the maximum values of the two torque components, and further increase the output torque.

As shown in Figure 11, the permanent magnet torque diagram of the motor can be seen. The permanent magnet torque ripple caused by the inclined pole of the motor in this example is smaller than that of the traditional motor, which shows the effectiveness of the disclosed magnetic pole tilt technology, but the average torque It also becomes smaller, indicating that there are limitations if the magnetic pole skew technology is simply used. Figure 12 shows the electromagnetic torque comparison diagram. The basic model is the electromagnetic torque of the traditional motor. The proposed model is the electromagnetic torque of the motor in this example. The electromagnetic torque ripple of the motor in this example is significantly smaller than that of the traditional motor, while maintaining the same value as the basic model. The same output torque indicates that the asymmetric salient pole technology of the present disclosure is effective in increasing the output torque by increasing the utilization rate of torque components.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Although the specific implementation of the present disclosure has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present disclosure. Those skilled in the art should understand that on the basis of the technical solutions of the present disclosure, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present disclosure.

Claims (7)

1. A rotor with inclined magnetic poles and asymmetric salient poles is characterized in that: the permanent magnet rotor comprises a rotor core and magnetic poles arranged on the rotor core, wherein each magnetic pole comprises salient poles and rotor grooves which are alternately arranged on the rotor core, sectional permanent magnets are arranged in the rotor grooves, the permanent magnets are identical in shape, are arranged along the direction of a rotating shaft, are staggered and arranged in sequence according to a set angle on the circumference of the rotor core, and are in a step shape;

at least one side surface of the salient pole extends along the rotating shaft direction;

the salient pole first side faces are in step-shaped interaction with the obliquely arranged segment permanent magnets, the salient pole first side faces are in contact with one side of each segment of permanent magnet, and the salient pole second side faces extend along the direction of the rotating shaft.

2. A rotor having a skewed pole and asymmetrical salient pole as claimed in claim 1, wherein: the permanent magnets of each section are radially projected to be rectangular.

3. A rotor having a skewed pole and asymmetrical salient pole as claimed in claim 1 or claim 2, wherein: permanent magnets at two ends of the sectional permanent magnet along the rotating shaft direction are respectively contacted with the first side surface and the second side surface of the salient pole.

4. A rotor having a skewed pole and asymmetrical salient pole as claimed in claim 3, wherein: the inclination angle of dislocation of two adjacent permanent magnets of the same magnetic pole is as follows:

in θ _skewing For the inclination angle between two adjacent permanent magnets, HCF is a greatest common divisor function, Q is the number of stator slots, p is the number of pole pairs, n is the number of step-like permanent magnet offset steps, and the number of offset steps is the number of permanent magnet segments minus 1.

5. A permanent magnet motor with oblique rotor magnetic poles and asymmetric salient poles is characterized in that: comprising a rotor, a stator and a rotating shaft, wherein the magnetic poles of the rotor are inclined and the salient poles of the rotor are asymmetric, the rotor and the stator are coaxially arranged, the rotor is arranged inside the stator through the rotating shaft, and a gap is reserved between the rotor and the stator.

6. A rotor pole-sloped and salient pole-asymmetric permanent magnet machine as defined in claim 5, wherein: the stator comprises a stator core and stator slots, stator windings are arranged in the stator slots, and radial gaps are formed between the stator windings and the periphery of the rotor.

7. A permanent magnet motor of a permanent magnet motor with oblique rotor poles and asymmetrical salient poles as claimed in claim 5, wherein: the stator slots are arranged at equal intervals along the circumferential direction on the inner periphery of the stator, and extend from the stator core side to the rotating shaft direction.

Images