Combined magnetic pole type permanent magnet synchronous motor and method based on magnetic field offset principle

Abstract

The invention relates to a combined magnetic pole type permanent magnet synchronous motor and a method based on the principle of magnetic field offset, belonging to the field of permanent magnet motors. The invention solves the problem that the difference between the current angle corresponding to the maximum value of the permanent magnet and reluctance torque of the existing built-in permanent magnet synchronous motor is large, and the motor cannot output the designed permanent magnet torque and the maximum value of the reluctance torque at the same time. In the invention, n layers of d-axis direction permanent magnet slots are embedded and arranged on each pole of the rotor core with the d-axis as the symmetry axis, and a q-axis direction permanent magnet slot is opened at each end of the d-axis direction permanent magnet slot, and the q-axis direction permanent magnet slot extends to the surface of the rotor core, and the n d-axis direction permanent magnet slots are connected with the q-axis direction permanent magnet slots located at the ends thereof, and the slots all penetrate the entire motor along the axial direction, and the d-axis direction permanent magnet is placed in the d-axis direction permanent magnet slot, and the q-axis direction permanent magnet is placed in the q-axis direction permanent magnet slot; the magnetic field of the d-axis direction permanent magnet and the magnetic field of the q-axis direction permanent magnet symmetrical at both ends are synthesized to achieve magnetic field offset.

Description

Technical Field

[0001] The invention relates to a combined magnetic pole type permanent magnet synchronous motor topology structure based on a magnetic field offset principle, and belongs to the field of permanent magnet motors. Background Art

[0002] Permanent magnet synchronous motors are widely used in industrial fields such as transportation electrification because of their high power density, torque density and efficiency. However, with the continuous development of transportation equipment in the field of new energy, higher requirements are placed on the torque and speed range of motors. At this time, built-in permanent magnet synchronous motors are more often used as core power components for electric vehicles due to their wide speed regulation range, ability to utilize reluctance torque, and high mechanical strength. The armature d-axis inductance is much larger than that of surface-mounted permanent magnet synchronous motors of the same specifications, so the motor speed range can be greatly improved through weak magnetic control strategies. And because its permanent magnets are placed in the permanent magnet slots inside the rotor core, the mechanical strength and safety reliability are better than surface-mounted magnets fixed by bonding, and higher speeds and greater torques can be output. The reluctance torque of the motor can be improved by reasonably designing the rotor magnetic circuit structure, thereby further improving the torque density of the motor. However, the existing built-in permanent magnet synchronous motors cannot simultaneously output the designed permanent magnet torque and reluctance torque maximum values ​​because the current angles corresponding to the peak values ​​of the permanent magnet torque and reluctance torque differ by 45°, resulting in a problem of torque waste. The principle of magnetic field offset is to achieve the angle offset between the permanent magnet flux and inductance of the motor through the special design of the motor topology, which is reflected in the torque characteristics to reduce the current angle difference between the permanent magnet and the reluctance torque peak point, thereby increasing the output torque of the motor. Some scholars have proposed to use asymmetric rotor structure to achieve the magnetic field offset effect, but this will lead to problems such as difficulty in ensuring rotor dynamic balance, complex processing and assembly, and affected reluctance torque peak.

[0003] Therefore, in view of the above shortcomings, it is necessary to provide a symmetrical motor topology that can realize the magnetic field offset effect to reduce the difference between the current angles corresponding to the reluctance torque and the permanent magnet torque. This is the research focus for further improving the torque density and other performance of the drive motor. Summary of the invention

[0004] In view of the problem that the difference between the current angle corresponding to the maximum value of the permanent magnet and reluctance torque of the existing built-in permanent magnet synchronous motor is large, and the motor cannot output the designed permanent magnet torque and reluctance torque maximum value at the same time, the present invention provides a combined magnetic pole type permanent magnet synchronous motor and method based on the magnetic field offset principle. The structure uses two permanent magnet groups with orthogonal magnetic fields to synergistically synthesize the permanent magnetic field of the motor rotor, thereby realizing the flexible adjustment of the relative position relationship between the motor flux linkage and inductance distribution; and increasing the output torque of the motor without adopting a complex topology and without increasing the amount of additional materials.

[0005] The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle of the present invention comprises a stator core 1, a stator winding 2, a rotor core 3 and a rotating shaft 8; the armature winding 2 is arranged on the stator core 1, and the rotor core 3 is fixed on the rotating shaft 8 and is located inside the stator core 1;

[0006] On each pole of the rotor core 3, n layers of d-axis permanent magnet slots 4 are embedded and arranged with the d-axis as the symmetry axis. The slots are connected from the two ends of the rotor core 3 surface on both sides of the d-axis axis to the near-center direction of the d-axis axis. A q-axis permanent magnet slot 6 is opened at each end of the d-axis permanent magnet slot 4. The q-axis permanent magnet slot 6 extends to the surface of the rotor core 3. The n d-axis permanent magnet slots 4 are connected with the two q-axis permanent magnet slots 6 located at the ends thereof. The n d-axis permanent magnet slots 4 and the 2n q-axis permanent magnet slots 6 all run through the entire motor in the axial direction. The d-axis permanent magnet 5 is placed in the d-axis permanent magnet slot 4, and the q-axis permanent magnet 7 is placed in the q-axis permanent magnet slot 6, where n is between 2 and 5.

[0007] The magnetic field shift is achieved by combining the magnetic field of the d-axis permanent magnet 5 and the magnetic field of the q-axis permanent magnet 7 symmetrical at both ends.

[0008] Preferably, the d-axis direction permanent magnet slot 4 is a straight-line, V-shaped or U-shaped structure. When the d-axis direction permanent magnet slot 4 is a straight-line, a d-axis direction permanent magnet 5 is embedded in each d-axis direction permanent magnet slot 4; when the d-axis direction permanent magnet slot 4 is a V-shaped, two d-axis direction permanent magnets 5 are symmetrically placed in each d-axis direction permanent magnet slot 4 with the d-axis axis as the axis of symmetry; when the d-axis direction permanent magnet slot 4 is a U-shaped, two or three d-axis direction permanent magnets 5 are embedded in each d-axis direction permanent magnet slot 4. If two d-axis direction permanent magnets 5 are embedded, they are symmetrically placed on both sides of each d-axis direction permanent magnet slot 4; if three d-axis direction permanent magnets 5 are embedded, in addition to being symmetrically placed on both sides of each d-axis direction permanent magnet slot 4, another d-axis direction permanent magnet 5 is embedded on the bottom side;

[0009] The q-axis direction permanent magnet slot 6 is a straight-line, V-shaped or U-shaped structure. When the q-axis direction permanent magnet slot 6 is a straight-line, a q-axis direction permanent magnet 7 is embedded in each q-axis direction permanent magnet slot 6; when the q-axis direction permanent magnet slot 6 is a V-shaped, two q-axis direction permanent magnets 7 are symmetrically placed on both sides of each q-axis direction permanent magnet slot 6; when the q-axis direction permanent magnet slot 6 is a U-shaped, two or three q-axis direction permanent magnets 7 are embedded in each q-axis direction permanent magnet slot 6. If two q-axis direction permanent magnets 7 are embedded, they are symmetrically placed on both sides of each q-axis direction permanent magnet slot 6; if three q-axis direction permanent magnets 7 are embedded, in addition to being symmetrically placed on both sides of each q-axis direction permanent magnet slot 6, another q-axis direction permanent magnet 7 is embedded on the bottom side.

[0010] Preferably, the rule for determining whether the magnetization directions are the same is: whether the magnetic flux generated by the permanent magnet after magnetization simultaneously enters the air gap from the rotor or enters the rotor from the air gap;

[0011] The magnetizing direction of the d-axis permanent magnet 5 is perpendicular to the long side of the d-axis permanent magnet 5 , the magnetizing direction of the d-axis permanent magnet 5 under each pole is the same, and the magnetizing directions of the d-axis permanent magnets 5 of adjacent poles are opposite;

[0012] The magnetizing direction of the q-axis permanent magnet 7 is perpendicular to the long side of the q-axis permanent magnet 7; all the q-axis permanent magnets 7 under each pole are divided into two groups with the d-axis axis as the boundary, wherein the magnetizing direction of a group of q-axis permanent magnets 7 on the rotor rotation direction side is the same as that of the d-axis permanent magnet 5 under the pole, and the magnetizing direction of a group of q-axis permanent magnets 7 on the opposite side of the rotor rotation direction is opposite to that of the d-axis permanent magnet 5 under the pole; the magnetizing directions of two adjacent groups of q-axis permanent magnets 7 of adjacent poles are the same.

[0013] Preferably, when the permanent magnet slot 6 in the q-axis direction is a straight line, no magnetic bridge is arranged on the surface side of the permanent magnet 7 in the q-axis direction close to the rotor core 3; when the permanent magnet slot 6 in the q-axis direction is a V-shaped or U-shaped structure, a magnetic bridge is arranged on the surface side of the permanent magnet 7 in the q-axis direction close to the rotor core 3.

[0014] The present invention also provides another technical solution, a method for offsetting the magnetic field of a motor. The method is implemented based on the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle. The method is:

[0015] The permanent magnets in the d-axis direction jointly generate the d-axis magnetic field, and the permanent magnets in the q-axis direction jointly generate the q-axis magnetic field, and the d-axis magnetic field and the q-axis magnetic field are in orthogonal directions;

[0016] The synthesis of the d-axis and q-axis magnetic fields generated by the two sets of permanent magnets realizes the offset of the motor rotor magnetic field. The direction of the synthetic magnetic field is controlled by adjusting the amplitude relationship of the d-axis and q-axis magnetic fields, so that the motor has different degrees of magnetic field offset capability, thereby improving the electromagnetic torque of the motor.

[0017] The magnetic field offset angle β of the motor is adjusted by designing various parameters to characterize the offset capability:

[0018]

[0019] Where:

[0020] b di is the permanent magnet working point of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, b qi is the permanent magnet working point of the i-th q-axis permanent magnet 7 under each q-axis magnetic field, B dj is the saturation magnetic flux density of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, Bqi is the saturation flux density of the permanent magnet 7 in the i-th q-axis direction under each q-axis magnetic field, W dj is the width of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, W qi is the width of the i-th q-axis permanent magnet 7 under each q-axis magnetic field, n d is the number of permanent magnets in the layer closest to the center of the circle under each d-axis magnetic field. When the permanent magnet slot 4 in the d-axis direction is in a straight line, n d is 1; when the permanent magnet slot 4 in the d-axis direction is V-shaped, n d is 2; when the permanent magnet slot 4 in the d-axis direction is a U-shaped structure, n d is 2 or 3;

[0021] Motor electromagnetic torque T e Under the action of magnetic field offset angle β, the improvement is:

[0022] T e =T pp cos(α+β-90°)+T rp sin(2α)

[0023] Where: T pp is the peak value of the permanent magnet torque current angle curve of the motor, T rp is the peak value of the reluctance torque torque-current angle curve of the motor, and α is the current electrical angle under the rotor magnetic field orientation.

[0024] Preferably, when the d-axis magnetic field and the q-axis magnetic field are equal, β=45°, and the motor output torque reaches a maximum value.

[0025] Beneficial effects of the present invention: The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle of the present invention is arranged on the motor rotor core with two groups of permanent magnets generating magnetic fields in the orthogonal directions of the d-axis and the q-axis. The magnetic field of any direction required for the operation of the motor can be flexibly synthesized by the combination of the two permanent magnetic fields. Different from the way in which the asymmetric built-in permanent magnet synchronous motor realizes the magnetic field offset by adding a special asymmetric magnetic barrier, the two magnetic fields of the combined magnetic poles can naturally realize the offset of the magnetic field by synthesis, reducing the difference between the current angles corresponding to the peak values ​​of the permanent magnet torque and the reluctance torque to even 0, thereby improving the torque density of the motor. Since the permanent magnet generating the q-axis magnetic field is located at the end position of the permanent magnet slot to which the permanent magnet generating the d-axis magnetic field belongs, the combination of the two permanent magnets will not affect the magnetic flux path of the motor armature reaction and the motor salient pole ratio, that is, the permanent magnet flux linkage and the motor inductance are decoupled in the positional relationship, and the motor topology can be flexibly made to have permanent magnet flux linkages and motor inductances with various relative angle relationships to meet various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a structural schematic diagram of a combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle of the present invention;

[0027] Figure 2 yes Figure 1 A partial enlarged view of

[0028] Figure 3 It is a schematic diagram of the magnetization direction of the permanent magnet of the motor of the present invention;

[0029] Figure 4 yes Figure 3 A partial enlarged view of

[0030] Figure 5 It is a torque current angle curve comparison diagram of the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle of the present invention and the conventional built-in permanent magnet synchronous motor. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0034] Specific implementation method 1: The following is combined Figures 1 to 5 The present embodiment is described. The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle described in the present embodiment comprises a stator core 1, a stator winding 2, a rotor core 3 and a rotating shaft 8; the armature winding 2 is arranged on the stator core 1, and the rotor core 3 is fixed on the rotating shaft 8 and is located inside the stator core 1;

[0035] On each pole of the rotor core 3, n layers of d-axis permanent magnet slots 4 are embedded and arranged with the d-axis as the symmetry axis. The slots are connected from the two ends of the rotor core 3 surface on both sides of the d-axis axis to the near-center direction of the d-axis axis. A q-axis permanent magnet slot 6 is opened at each end of the d-axis permanent magnet slot 4. The q-axis permanent magnet slot 6 extends to the surface of the rotor core 3. The n d-axis permanent magnet slots 4 are connected with the two q-axis permanent magnet slots 6 located at the ends thereof. The n d-axis permanent magnet slots 4 and the 2n q-axis permanent magnet slots 6 all run through the entire motor in the axial direction. The d-axis permanent magnet 5 is placed in the d-axis permanent magnet slot 4, and the q-axis permanent magnet 7 is placed in the q-axis permanent magnet slot 6.

[0036] The magnetic field shift is achieved by combining the magnetic field of the d-axis permanent magnet 5 and the magnetic field of the q-axis permanent magnet 7 symmetrical at both ends.

[0037] n is a positive integer, and the specific number can be determined according to actual conditions. The larger n is, the more flexible the implementation of the magnetic field offset is, but the design and processing is more complicated. Generally, n is between 2 and 5.

[0038] In this embodiment, n layers of d-axis permanent magnet slots 4 are arranged inside the rotor core 3, and this part is realized by using the existing technology. The d-axis permanent magnet slots 4 are of a straight, V-shaped or U-shaped structure. When the d-axis permanent magnet slots 4 are of a straight, each d-axis permanent magnet slot 4 is embedded with a d-axis permanent magnet 5; when the d-axis permanent magnet slots 4 are of a V-shaped, the d-axis axis is used as the axis of symmetry, and two d-axis permanent magnets 5 are symmetrically placed in each d-axis permanent magnet slot 4; when the d-axis permanent magnet slots 4 are of a U-shaped, each d-axis permanent magnet slot 4 is embedded with two or three d-axis permanent magnets 5. If two d-axis permanent magnets 5 are embedded, they are symmetrically placed on both sides of each d-axis permanent magnet slot 4; if three d-axis permanent magnets 5 are embedded, in addition to being symmetrically placed on both sides of each d-axis permanent magnet slot 4, another d-axis permanent magnet 5 is embedded on the bottom side; Figure 1 , 2 The permanent magnet slot 4 in the d-axis direction is V-shaped.

[0039] The innovation of this embodiment is that a q-axis permanent magnet slot 6 is provided at each end of the d-axis permanent magnet slot 4, and the q-axis permanent magnets 7 symmetrically arranged in the slots at both ends are used to construct an offset magnetic field to improve the motor performance.

[0040] The q-axis direction permanent magnet slot 6 is a straight-line, V-shaped or U-shaped structure. When the q-axis direction permanent magnet slot 6 is a straight-line, a q-axis direction permanent magnet 7 is embedded in each q-axis direction permanent magnet slot 6; when the q-axis direction permanent magnet slot 6 is a V-shaped, two q-axis direction permanent magnets 7 are symmetrically placed on both sides of each q-axis direction permanent magnet slot 6; when the q-axis direction permanent magnet slot 6 is a U-shaped, two or three q-axis direction permanent magnets 7 are embedded in each q-axis direction permanent magnet slot 6. If two q-axis direction permanent magnets 7 are embedded, they are symmetrically placed on both sides of each q-axis direction permanent magnet slot 6; if three q-axis direction permanent magnets 7 are embedded, in addition to being symmetrically placed on both sides of each q-axis direction permanent magnet slot 6, another q-axis direction permanent magnet 7 is embedded on the bottom side. Figure 1 , 2 The permanent magnet slot 6 in the q-axis direction is V-shaped.

[0041] The magnetization requirements for each permanent magnet when configuring the offset magnetic field, the rule for whether the magnetization directions are the same in this embodiment is: whether they enter the air gap from the rotor or enter the rotor from the air gap at the same time;

[0042] The magnetizing direction of the d-axis permanent magnet 5 is perpendicular to the long side of the d-axis permanent magnet 5 . The magnetizing directions of the d-axis permanent magnet 5 under each pole are the same, and the magnetizing directions of the d-axis permanent magnets 5 of adjacent poles are opposite; see Figure 3 As shown, the rotor rotates counterclockwise. The figure shows the magnetization under one pole. The magnetization directions of the two groups of d-axis permanent magnets 5 on the left and right sides of the d-axis are perpendicular to their own long sides, and the combined direction is from the rotor into the air gap. The left side of the d-axis is the rotor rotation direction side, and the right side of the d-axis is the opposite side of the rotor rotation direction.

[0043] The magnetization direction of the q-axis permanent magnet 7 is perpendicular to the long side of the q-axis permanent magnet 7; according to the division rule of each pole area of ​​a conventional motor, all q-axis permanent magnets 7 under each pole are divided into two groups with the d-axis axis as the boundary, wherein the magnetization direction of a group of q-axis permanent magnets 7 on the rotor rotation direction side is the same as that of the d-axis permanent magnet 5 under the pole, and the magnetization direction of a group of q-axis permanent magnets 7 on the opposite side of the rotor rotation direction is opposite to that of the d-axis permanent magnet 5 under the pole; the magnetization directions of two adjacent groups of q-axis permanent magnets 7 of adjacent poles are the same. See Figure 3 , 4 The q-axis permanent magnet slot 6 is V-shaped, with the q-axis axis as the symmetry axis. Two q-axis permanent magnets 7 are symmetrically placed in each q-axis permanent magnet slot 6, and their magnetization directions are perpendicular to their own long sides. The direction of the synthetic magnetic field of the left q-axis permanent magnet group is from the rotor to the stator through the air gap, while the direction of the synthetic magnetic field of the right q-axis permanent magnet group is from the stator to the rotor through the air gap.

[0044] The two groups of permanent magnets on the rotor in the d-axis and q-axis directions can generate magnetic fields in two orthogonal directions. By adjusting the relative amplitude relationship of the two magnetic fields, a permanent magnetic field in a specific direction can be synthesized, thereby achieving the effect of magnetic field offset.

[0045] Whether to arrange a magnetic bridge of a corresponding shape on the side of the q-axis permanent magnet 7 close to the surface of the rotor core 3 can be determined according to the specific shape of the q-axis permanent magnet 7. Generally, a "one"-shaped permanent magnet does not arrange a magnetic bridge, while a V-shaped permanent magnet and a U-shaped permanent magnet arrange a magnetic bridge. When the q-axis permanent magnet slot 6 is a one-shaped structure, the q-axis permanent magnet 7 is not arranged with a magnetic bridge on the side of the surface of the rotor core 3. When the q-axis permanent magnet slot 6 is a V-shaped or U-shaped structure, the q-axis permanent magnet 7 is arranged with a magnetic bridge on the side of the surface of the rotor core 3.

[0046] The d-axis direction permanent magnet 5 and the q-axis direction permanent magnet 7 are composed of one or more permanent magnets, and can also be further divided into multiple permanent magnets along the axial direction.

[0047] Working principle: When the motor of the present invention works normally, two groups of permanent magnets arranged on the motor rotor core that generate magnetic fields in orthogonal directions of the d-axis and the q-axis form a pair of combined magnetic poles. The combination of the two permanent magnetic fields can flexibly synthesize the magnetic field in any direction required for the operation of the motor, thereby realizing the magnetic field offset effect, reducing the difference in current angles corresponding to the peak points of the permanent magnet torque and the reluctance torque to even 0, thereby improving the torque density of the motor; compared with the conventional built-in permanent magnet synchronous motor, the torque current angle curve of the motor changes, the difference is as follows: Figure 5 As shown, the electromagnetic torque output by the motor is improved. Different from the way that the asymmetric built-in permanent magnet synchronous motor realizes magnetic field offset, without adding special asymmetric magnetic barriers, the two magnetic fields of the combined magnetic poles can naturally realize magnetic field offset by synthesis, and because the permanent magnet that generates the q-axis magnetic field is located at the end position of the permanent magnet slot to which the permanent magnet that generates the d-axis magnetic field belongs, it will not affect the magnetic flux path of the motor armature reaction and the motor salient pole ratio, that is, the permanent magnet flux linkage and the motor inductance are decoupled in positional relationship, and the motor topology with various relative positional relationships of permanent magnet flux linkage and motor inductance can be flexibly realized to meet various needs. At the same time, since the permanent magnet magnetic field is synthesized by the magnetic fields in two orthogonal directions, under the same air gap magnetic field strength, the rotor core saturation of the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle is greatly reduced, which helps to further improve the torque performance of the motor.

[0048] Taking n=4, the d-axis permanent magnet slots 4 and the q-axis permanent magnet slots 6 are V-shaped structures as an example, a specific embodiment is given, the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle of the present invention, such as Figure 1As shown, it is composed of a stator core 1, a stator winding 2, a rotor core 3, a d-axis direction permanent magnet slot 4, a d-axis direction permanent magnet 5, a q-axis direction permanent magnet slot 6, a q-axis direction permanent magnet 7 and a rotating shaft 8; the rotor core 3 is fixed on the rotating shaft 8 and is located inside the stator core 1, and the armature winding 2 is arranged on the stator core 1;

[0049] Each pole of the rotor core 3 is arranged with 4 d-axis permanent magnet slots 4 with the d-axis as the symmetry axis, and the slots are connected from the two ends of the rotor core 3 surface on both sides of the d-axis axis to the near-center direction of the d-axis axis. On the surface of the rotor core 3, the ends of the d-axis permanent magnet slots 4 on both sides of the d-axis axis each have a q-axis permanent magnet slot 6, for a total of 8. The 4 d-axis permanent magnet slots 4 are connected with the 2 q-axis permanent magnet slots 6 located at their ends, and the 4 d-axis permanent magnet slots 4 and the 8 q-axis permanent magnet slots 6 all run through the entire motor along the axial direction; the magnetization direction of the permanent magnet is from the rotor into the air gap or from the air gap into the rotor. Taking one pole as an example, 8 d-axis permanent magnets 5 are placed in the d-axis permanent magnet slots 4, and the magnetization direction of the d-axis permanent magnets 5 is perpendicular to the d-axis permanent magnet slots. The long side of the magnet 5 is taken as a reference to the d-axis axis, and the magnetizing directions of the 8 d-axis permanent magnets 5 under each pole are the same, and the magnetizing directions of the d-axis permanent magnets 5 of adjacent poles are opposite; the q-axis permanent magnet 7 is placed in the q-axis permanent magnet slot 6, and the magnetizing direction of the q-axis permanent magnet 7 is perpendicular to the long side of the q-axis permanent magnet 7. Taking the d-axis axis as a reference, the magnetizing directions of the 16 q-axis permanent magnets 7 on both sides are different, the magnetizing directions of the 8 q-axis permanent magnets 7 on the rotor rotation direction side are the same as the d-axis permanent magnet 5, and the magnetizing directions of the 8 q-axis permanent magnets 7 on the opposite side of the rotor rotation direction are opposite to the d-axis permanent magnet 5. The 16 q-axis permanent magnets 7 are equally divided into two groups by the d-axis axis, and their respective magnetizing directions are the same as an adjacent group of q-axis permanent magnets 7 under adjacent poles.

[0050] In order to reduce the difference between the current angles corresponding to the maximum values ​​of the permanent magnet and reluctance torques of the built-in permanent magnet synchronous motor, so that the motor can simultaneously output the designed permanent magnet torque and reluctance torque maximum values, and at the same time improve the motor torque density and efficiency, the present invention provides a combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle. The structure uses two permanent magnet groups with orthogonal magnetic fields to synergistically synthesize the permanent magnetic field of the motor rotor, thereby achieving flexible adjustment of the relative position relationship between the motor flux linkage and inductance distribution; and increasing the output torque of the motor without using complex topology or increasing the amount of additional materials.

[0051] Specific implementation method 2: The following is combined Figure 3 , 4 This embodiment is described. The magnetic field offset method of the motor described in this embodiment is implemented based on the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle described in claim 3. The method is:

[0052] The permanent magnets in the d-axis direction jointly generate the d-axis magnetic field, and the permanent magnets in the q-axis direction jointly generate the q-axis magnetic field, and the d-axis magnetic field and the q-axis magnetic field are in orthogonal directions;

[0053] The synthesis of the d-axis and q-axis magnetic fields generated by the two sets of permanent magnets realizes the offset of the motor rotor magnetic field. The direction of the synthetic magnetic field is controlled by adjusting the amplitude relationship of the d-axis and q-axis magnetic fields, so that the motor has different degrees of magnetic field offset capability, thereby improving the electromagnetic torque of the motor.

[0054] The magnetic field offset angle β of the motor is adjusted by designing various parameters to characterize the offset capability:

[0055]

[0056] Where:

[0057] b di is the permanent magnet working point of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, b qi is the permanent magnet working point of the i-th q-axis permanent magnet 7 under each q-axis magnetic field, B dj is the saturation magnetic flux density of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, B qi is the saturation flux density of the permanent magnet 7 in the i-th q-axis direction under each q-axis magnetic field, W dj is the width of the jth d-axis permanent magnet 5 in the layer closest to the center of the circle under each d-axis magnetic field, W qi is the width of the i-th q-axis permanent magnet 7 under each q-axis magnetic field, n d is the number of permanent magnets in the layer closest to the center of the circle under each d-axis magnetic field. When the permanent magnet slot 4 in the d-axis direction is in a straight line, n d is 1; when the permanent magnet slot 4 in the d-axis direction is V-shaped, n d is 2; when the permanent magnet slot 4 in the d-axis direction is a U-shaped structure, n d is 2 or 3;

[0058] Motor electromagnetic torque T e Under the action of magnetic field offset angle β, the improvement is:

[0059] T e =T pp cos(α+β-90°)+T rp sin(2α)

[0060] Where: T pp is the peak value of the permanent magnet torque current angle curve of the motor, T rp is the peak value of the reluctance torque torque-current angle curve of the motor, and α is the current electrical angle under the rotor magnetic field orientation.

[0061] In this embodiment, the magnetic field offset angle can be changed by different combinations of the width, working point and saturation magnetic flux density of the d-axis permanent magnet 5 and the q-axis permanent magnet 7. The greater the difference between the two orthogonal permanent magnetic fields generated by the d-axis permanent magnet 5 and the q-axis permanent magnet 7, the weaker the magnetic field offset capability of the motor. When only the d-axis permanent magnet 5 or the q-axis permanent magnet 7 is arranged, the magnetic field offset capability is zero. According to different application requirements, the magnetic field offset angle β of the motor can take different values. When the motor pursues maximum torque output, the two orthogonal permanent magnetic fields generated by the d-axis permanent magnet 5 and the q-axis permanent magnet 7 are generally set to be equal. At this time β is 45°, and the electromagnetic torque of the motor is the sum of the peak values ​​of the permanent magnet torque and the reluctance torque.

[0062] Since the d-axis permanent magnets 5 in the n-layer d-axis permanent magnet slots 4 are in a series magnetic circuit relationship with each other, each d-axis magnetic field generated by them is represented by the magnetic field generated by the d-axis permanent magnet 5 with the largest synthetic width in the layer closest to the center of the circle under each d-axis magnetic field; the q-axis permanent magnets 7 in the 2n q-axis permanent magnet slots 6 are in a parallel magnetic circuit relationship with each other, so each q-axis magnetic field generated by them is represented by the sum of the magnetic fields generated by all the q-axis permanent magnets 7 under each q-axis magnetic field.

[0063] The two magnetic fields of the combined magnetic poles in this embodiment can be synthesized to naturally achieve magnetic field offset, reducing the difference between the current angles corresponding to the peak values ​​of the permanent magnet torque and the reluctance torque to even 0, thereby improving the torque density of the motor.

[0064] From the schematic diagram Figure 5 It can be seen that the electromagnetic torque can be synthesized from the permanent magnet torque and the reluctance torque. Compared with the conventional motor, the electromagnetic torque of the motor using the magnetic field offset method is improved within a wider commonly used current angle range (about 0°-70°), and the maximum electromagnetic torque is also improved. The difference between the peak electromagnetic torques of the two is about 16%, that is, the conventional built-in permanent magnet synchronous motor can improve the electromagnetic torque by about 16% after using the magnetic field offset method.

[0065] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle, comprising a stator core (1), a stator winding (2), a rotor core (3) and a rotating shaft (8); the armature winding (2) is arranged on the stator core (1), and the rotor core (3) is fixed on the rotating shaft (8) and is located inside the stator core (1); It is characterized in that On each pole of the rotor core (3), n layers of d-axis directional permanent magnet slots (4) are embedded and arranged with the d-axis as the symmetry axis. The slots are connected from the two ends of the rotor core (3) surface on both sides of the d-axis axis to the near-center direction of the d-axis axis. A q-axis directional permanent magnet slot (6) is respectively opened at the two ends of the d-axis directional permanent magnet slot (4). The q-axis directional permanent magnet slot (6) extends to the surface of the rotor core (3). The n d-axis directional permanent magnet slots (4) are connected to the two q-axis directional permanent magnet slots (6) located at the ends thereof. The n d-axis directional permanent magnet slots (4) and the 2n q-axis directional permanent magnet slots (6) all penetrate the entire motor in the axial direction. The d-axis directional permanent magnet (5) is placed in the d-axis directional permanent magnet slot (4), and the q-axis directional permanent magnet (7) is placed in the q-axis directional permanent magnet slot (6), where n is between 2 and 5. The magnetic field of the permanent magnet (5) in the d-axis direction and the magnetic field of the permanent magnet (7) in the q-axis direction symmetrical at both ends are synthesized to achieve magnetic field deviation.

2. The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle according to claim 1 is characterized in that: The d-axis direction permanent magnet slot (4) is of a straight, V-shaped or U-shaped structure. When the d-axis direction permanent magnet slot (4) is of a straight shape, one d-axis direction permanent magnet (5) is embedded in each d-axis direction permanent magnet slot (4); when the d-axis direction permanent magnet slot (4) is of a V shape, two d-axis direction permanent magnets (5) are symmetrically placed in each d-axis direction permanent magnet slot (4) with the d-axis axis as the symmetry axis; when the d-axis direction permanent magnet slot (4) is of a U shape, two or three d-axis direction permanent magnets (5) are embedded in each d-axis direction permanent magnet slot (4); if two d-axis direction permanent magnets (5) are embedded, they are symmetrically placed on both sides of each d-axis direction permanent magnet slot (4); if three d-axis direction permanent magnets (5) are embedded, in addition to being symmetrically placed on both sides of each d-axis direction permanent magnet slot (4), another d-axis direction permanent magnet (5) is embedded on the bottom side; The q-axis direction permanent magnet slot (6) is of a straight, V-shaped or U-shaped structure. When the q-axis direction permanent magnet slot (6) is of a straight shape, one q-axis direction permanent magnet (7) is embedded in each q-axis direction permanent magnet slot (6); when the q-axis direction permanent magnet slot (6) is of a V-shaped structure, two q-axis direction permanent magnets (7) are symmetrically placed on both sides of each q-axis direction permanent magnet slot (6); when the q-axis direction permanent magnet slot (6) is of a U-shaped structure, two or three q-axis direction permanent magnets (7) are embedded in each q-axis direction permanent magnet slot (6); if two q-axis direction permanent magnets (7) are embedded, they are symmetrically placed on both sides of each q-axis direction permanent magnet slot (6); if three q-axis direction permanent magnets (7) are embedded, in addition to being symmetrically placed on both sides of each q-axis direction permanent magnet slot (6), another q-axis direction permanent magnet (7) is embedded on the bottom side.

3. The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle according to claim 2 is characterized in that: The rule for whether the magnetization direction is the same is: whether the magnetic flux generated by the permanent magnet after magnetization enters the air gap from the rotor or from the air gap into the rotor at the same time; The magnetization direction of the d-axis permanent magnet (5) is perpendicular to the long side of the d-axis permanent magnet (5), the magnetization direction of the d-axis permanent magnet (5) under each pole is the same, and the magnetization directions of the d-axis permanent magnets (5) of adjacent poles are opposite; The magnetization direction of the q-axis permanent magnet (7) is perpendicular to the long side of the q-axis permanent magnet (7); all q-axis permanent magnets (7) under each pole are divided into two groups with the d-axis axis as the boundary, wherein the magnetization direction of a group of q-axis permanent magnets (7) on the rotor rotation direction side is the same as that of the d-axis permanent magnet (5) under the pole, and the magnetization direction of a group of q-axis permanent magnets (7) on the opposite side of the rotor rotation direction is opposite to that of the d-axis permanent magnet (5) under the pole; and the magnetization directions of two adjacent groups of q-axis permanent magnets (7) of adjacent poles are the same.

4. The combined magnetic pole type permanent magnet synchronous motor based on the magnetic field offset principle according to claim 2 is characterized in that: When the permanent magnet slot (6) in the q-axis direction is in a straight line shape, no magnetic bridge is arranged on the surface side of the permanent magnet (7) in the q-axis direction close to the rotor core (3); when the permanent magnet slot (6) in the q-axis direction is in a V-shaped or U-shaped structure, a magnetic bridge is arranged on the surface side of the permanent magnet (7) in the q-axis direction close to the rotor core (3).

5. A method for shifting the magnetic field of a motor, the method being implemented based on the combined magnetic pole type permanent magnet synchronous motor based on the magnetic field shift principle as claimed in claim 3, characterized in that: The method is: The permanent magnets in the d-axis direction jointly generate a d-axis magnetic field, and the permanent magnets in the q-axis direction jointly generate a q-axis magnetic field. The d-axis magnetic field and the q-axis magnetic field are magnetic fields in orthogonal directions. The synthesis of the d-axis and q-axis magnetic fields generated by the two sets of permanent magnets realizes the offset of the motor rotor magnetic field. The direction of the synthetic magnetic field is controlled by adjusting the amplitude relationship of the d-axis and q-axis magnetic fields, so that the motor has different degrees of magnetic field offset capability, thereby improving the electromagnetic torque of the motor. The magnetic field offset angle β of the motor is adjusted by designing various parameters to characterize the offset capability: Where: b di is the permanent magnet working point of the jth d-axis permanent magnet (5) in the layer closest to the center of the circle under each d-axis magnetic field, b qi is the permanent magnet working point of the i-th q-axis permanent magnet (7) under each q-axis magnetic field, B dj is the saturation magnetic flux density of the jth d-axis permanent magnet (5) in the layer closest to the center of the circle under each d-axis magnetic field, B qi is the saturation magnetic flux density of the permanent magnet (7) in the i-th q-axis direction under each q-axis magnetic field, W dj is the width of the jth d-axis permanent magnet (5) in the layer closest to the center of the circle under each d-axis magnetic field, W qi is the width of the i-th q-axis permanent magnet (7) under each q-axis magnetic field, n d is the number of permanent magnets in the layer closest to the center of the circle under each d-axis magnetic field. When the permanent magnet slot (4) in the d-axis direction is in a straight line, n d is 1; when the permanent magnet slot (4) in the d-axis direction is V-shaped, n d is 2; when the permanent magnet slot (4) in the d-axis direction is a U-shaped structure, n d is 2 or 3; Motor electromagnetic torque T e Under the action of magnetic field offset angle β, the improvement is: T e =T pp cos(α+β-90°)+T rp sin(2a) Where: T pp is the peak value of the permanent magnet torque current angle curve of the motor, T rp is the peak value of the reluctance torque torque-current angle curve of the motor, and α is the current electrical angle under the rotor magnetic field orientation.

6. The method for shifting the magnetic field of a motor according to claim 5, characterized in that: When the d-axis magnetic field and the q-axis magnetic field are equal, β = 45°, the motor output torque reaches its maximum value.

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