Design method of bearing-free permanent magnet synchronous motor with inclined plane connection parallel magnetizing combined magnetic poles

Abstract

The invention discloses a design method of a bearingless permanent magnet synchronous motor with inclined plane connection and parallel magnetization combined magnetic poles, and belongs to the technical field of novel special alternating current motor optimization design. Stator teeth / grooves of the BL-PMSM are uniformly distributed along the circumference of the stator, and the stator teeth / grooves are designed by pear-shaped grooves and parallel teeth; constructing a four-pole torque winding and a two-pole suspension winding; and finally, constructing a symmetric arc-bottom trapezoidal main magnetic pole and an asymmetric trapezoidal auxiliary magnetic pole by adopting a high-residual-magnetism material and a low-residual-magnetism material respectively, carrying out seamless inclined plane connection on the main magnetic pole and the auxiliary magnetic pole, and constructing an integrated parallel magnetizing integral sector ring magnetic pole structure by taking a pole-arc coefficient occupied by the width of an inclined plane connection region as one of structural parameter variables. And constructing a quadrupole permanent magnet inner rotor structure of the BL-PMSM according to an N and S polarity alternating sequence. The inclined plane connection combined magnetic pole structure can effectively avoid local fusion of air gap flux density waveforms, reduces pulsation rates of torque and suspension force, and is suitable for the technical field of high-speed permanent magnet synchronous motor magnetic suspension rotation driving.

Description

Technical Field

[0001] The invention relates to the technical field of AC motor optimization design, and in particular to a design method for a bearingless permanent magnet synchronous motor with parallel magnetized combined magnetic poles connected by inclined surfaces. Background Art

[0002] The bearingless permanent magnet synchronous motor (BL-PMSM) is a new type of magnetic levitation motor that is composed of an additional set of suspension windings that differ from the torque winding (motor winding) by one pair of magnetic poles embedded in the stator core of the traditional permanent magnet synchronous motor. By applying the same frequency of excitation current to the two sets of windings, a stable and controllable radial magnetic levitation force can be generated while obtaining a stable electromagnetic torque, thereby realizing the bearingless magnetic levitation rotation of the motor. This motor has broad application prospects in high-tech fields such as flywheel energy storage, sealed pumps, life sciences, and aerospace.

[0003] Literature and search results show that the electromagnetic performance of BL-PMSM driven by sinusoidal current is closely related to the sinusoidality of the air gap flux density; the development of BL-PMSM started late, and its current optimized pole optimization structure mainly includes Halbach permanent magnet array, unequal amplitude modulated pole structure and combined pole; Chinese scholars applied the combined poles in traditional permanent magnet synchronous motors to BL-PMSM and conducted a series of studies, which can reduce torque pulsation and suspension force pulsation while ensuring the output performance of the motor, but the integrated radial magnetization method of the combined poles adopted is not conducive to significantly improving the sinusoidality of the air gap flux density of BL-PMSM.

[0004] In order to improve the electromagnetic torque and radial magnetic levitation force characteristics of BL-PMSM, the present invention will address the defects existing in the domestic existing technical research and propose a new structure of "bearingless permanent magnet synchronous motor with inclined plane connection, parallel magnetization combined poles" which can effectively improve the sinusoidality of air gap magnetic density and reduce torque pulsation and levitation force pulsation. Summary of the invention

[0005] The purpose of the present invention is to provide a design method for a bearingless permanent magnet synchronous motor with parallel magnetized combined poles connected by inclined surfaces, and proposes a new structure of parallel magnetized combined poles connected by inclined surfaces. In order to improve the sinusoidality of its air gap magnetic field, an integrated parallel magnetization method is adopted; the middle main pole of the combined pole adopts a symmetrical arc bottom trapezoidal structure, and the auxiliary poles symmetrically distributed on both sides adopt an asymmetrical trapezoidal structure, and together with the middle main pole, they form a fan ring permanent magnet structure after seamlessly connecting with the inclined surface. The boundary area between the main pole and the auxiliary pole of the same combined pole occupies a certain width (which can be characterized by the pole arc coefficient of the inclined surface connection area), which will make the synthetic residual magnetic flux density change continuously in the boundary area, thereby effectively avoiding the step-like mutation of the air gap magnetic field, thereby further improving the degree of consistency between the rising / falling area in the air gap magnetic field waveform and the sine waveform.

[0006] To achieve the above object, the present invention provides a design method for a bearingless permanent magnet synchronous motor with parallel magnetization combined magnetic poles and inclined plane connection, comprising the following steps:

[0007] S1. Construct stator teeth / slots of BL-PMSM with inclined planes and parallel magnetized combined poles, evenly arrange stator teeth / slots of BL-PMSM along the circumference of the stator, and arrange 24 stator teeth / slots in a pear-shaped stator slot structure and a parallel stator tooth structure;

[0008] S2, constructing the stator winding of the BL-PMSM with inclined plane connection and parallel magnetization combined magnetic poles, placing two sets of conductors in each stator slot designed in step S1 to form a torque winding conductor and a suspension winding conductor, and after numbering each torque winding conductor and suspension winding conductor, constructing a four-pole stator torque winding in the inner layer of the slot and a two-pole stator suspension winding in the outer layer of the slot;

[0009] S3. Construct the overall structure of the inclined-connected combined magnetic poles of the BL-PMSM inner rotor, use high remanence material and low remanence material to construct symmetrical arc-bottom trapezoidal main magnetic poles and asymmetrical trapezoidal auxiliary magnetic poles respectively, connect the main and auxiliary magnetic poles seamlessly with an inclined surface, and use the pole arc coefficient occupied by the width of the connecting inclined surface area as one of the structural parameter variables to construct an integrated parallel magnetized inclined-connected combined magnetic pole overall fan ring structure, and then construct the permanent magnet four-pole inner rotor structure of the BL-PMSM in the alternating order of N and S polarities.

[0010] Preferably, in step S1, the steps of constructing the stator teeth / slots of the BL-PMSM with inclined planes connected to parallel magnetized combined magnetic poles are specifically as follows:

[0011] S11, adopting the structure of outer stator and inner rotor, 24 stator teeth / slots are evenly arranged along the inner surface of the stator core;

[0012] S12. Number the stator slots with a slot pitch of 15° from 1 to 24 in a counterclockwise direction.

[0013] Preferably, in step S12, the stator slot width is b s0 , the width of the stator slot body close to the stator slot shoulder is b s1 , is the width of the stator slot bottom b s2 , the stator slot height is h s0 , the height of the groove shoulder is h s1 , stator slot depth is h s2 ; The bottom of the pear-shaped groove is a semicircular arc structure, and the radius of the arc at the bottom of the groove is b s2 / 2 , and the center of the circle is located at the intersection of the middle axis of the stator slot and the boundary lines of the stator slot body and the stator slot bottom.

[0014] Preferably, in step S2, constructing the stator winding of the BL-PMSM with inclined-plane connection and parallel magnetization combined magnetic poles specifically includes the following steps:

[0015] S21. Two sets of conductors are placed in the 24 stator slots, with the torque winding conductors embedded in the inner layer of the slots and the suspension winding conductors embedded in the outer layer of the slots, and the 24 conductors of the torque winding and the suspension winding are numbered No. 1, No. 2, No. 3, No. 4, ..., No. 23, No. 24 in a counterclockwise order, and the numbers of the torque winding conductors and the suspension winding conductors are consistent with the corresponding stator slot numbers;

[0016] S22, constructing a four-pole torque winding in the inner layer of the slot, connecting the No. 1 torque winding conductor and the No. 7 torque winding conductor end to end to obtain a No. 1 torque coil, and connecting the No. 2 torque winding conductor and the No. 8 torque winding conductor end to end to obtain a No. 2 torque coil;

[0017] Then connect the No. 1 torque coil and the No. 2 torque coil in series to obtain the No. 1 "torque coil group";

[0018] Connect the torque winding conductor No. 13 and the torque winding conductor No. 19 end to end to obtain the torque coil No. 3, connect the torque winding conductor No. 14 and the torque winding conductor No. 20 end to end to obtain the torque coil No. 4, and then connect the torque coil No. 3 and the torque coil No. 4 in series to obtain the "torque coil group" No. 2;

[0019] Connect the No. 1 "torque coil group" and the No. 2 "torque coil group" in series to obtain the "A-phase four-pole torque winding";

[0020] S23, constructing a two-pole suspension winding in the outer layer of the slot, connecting the No. 1 suspension winding conductor and the No. 13 suspension winding conductor end to end to obtain a No. 1 suspension coil, connecting the No. 2 suspension winding conductor and the No. 14 suspension winding conductor end to end to obtain a No. 2 suspension coil, connecting the No. 3 suspension winding conductor and the No. 15 suspension winding conductor end to end to obtain a No. 3 suspension coil, and connecting the No. 4 suspension winding conductor and the No. 16 suspension winding conductor end to end to obtain a No. 4 suspension coil;

[0021] Then, the No. 1 suspension coil, the No. 2 suspension coil, the No. 3 suspension coil, and the No. 4 suspension coil are connected in series in sequence to obtain a "U-phase two-pole suspension winding".

[0022] Preferably, in step S22, according to the construction steps of "A-phase four-pole torque winding", B-phase and C-phase torque windings are constructed, and the A-phase, B-phase and C-phase torque windings of the stator are staggered by 120 electrical degrees in electrical space.

[0023] Preferably, in step S23, according to the construction step of "U-phase two-pole suspension winding", V-phase and W-phase suspension windings are constructed, and the U-phase, V-phase and W-phase suspension windings of the stator are staggered by 120 electrical degrees in electrical space.

[0024] Preferably, in step S3, constructing the inclined-plane connected parallel magnetized combined magnetic pole structure of the BL-PMSM inner rotor specifically includes the following steps:

[0025] S31, construct a surface-mounted inclined-plane connected parallel magnetized combined magnetic pole topology structure, each combined magnetic pole is composed of three permanent magnets of equal thickness, and the middle main magnetic pole is composed of high remanence permanent magnetic material to form an "arc bottom trapezoidal" symmetrical structure;

[0026] Two asymmetric trapezoidal auxiliary magnetic poles are symmetrically arranged on both sides of the main magnetic pole using permanent magnetic materials with relatively low remanence. The two auxiliary magnetic poles are seamlessly connected with the main magnetic pole on an inclined surface to form an overall fan ring structure of "inclined combined magnetic poles".

[0027] S32, setting parameter variables of the combined magnetic pole, setting the overall pole arc coefficient α1 of the combined magnetic pole, the pole arc coefficient α2 of the main magnetic pole, the pole arc coefficient α3 corresponding to the width of the junction area between the main and auxiliary magnetic poles, and the permanent magnet thickness hm as "structural parameter variables";

[0028] Under the premise that each parameter variable satisfies the relationship of "α1>α2+α3", the overall structure of the combined magnetic pole can be changed by changing the size of the four permanent magnet structural parameter variables α1, α2, α3 and hm;

[0029] The permanent magnet thickness hm parameter is generally selected within the range of 2.5 to 3.5 times the air gap length; at the same time, the main magnetic pole residual flux density Brm and the auxiliary magnetic pole residual flux density Brs on both sides of the combined magnetic pole are set as "magnetization parameter variables", which satisfy the relationship of "Brm>Brs";

[0030] S33, determining the limiting condition of the pole arc coefficient α3 corresponding to the width of the junction area between the main and auxiliary magnetic poles, when the interface between the main magnetic pole and the auxiliary magnetic pole is tangent to the outer diameter of the rotor, the pole arc coefficient α3 obtains the maximum value;

[0031] S34, performing integrated parallel magnetization on the magnetic combination poles after the inclined surfaces are connected, and performing integrated parallel magnetization on the four combined magnetic pole permanent magnet structures after the inclined surfaces are connected along the center lines of the main magnetic poles in the order of alternating N and S polarities, to obtain two inclined surfaces connected parallel magnetized combined magnetic pole permanent magnet N poles and two inclined surfaces connected parallel magnetized combined magnetic pole permanent magnet S poles;

[0032] S35. In the order of alternating N and S polarities, the combined magnetic poles are evenly pasted on the outer surface of the rotor core to form a permanent magnet four-pole inner rotor with inclined surfaces connecting parallel magnetized combined magnetic poles.

[0033] Preferably, in step S33, the constraint relation of α3 is as follows:

[0034]

[0035] According to formula (1), the maximum value of the pole arc coefficient α3 occupied by the inclined surface connection area between the main magnetic pole and the auxiliary magnetic pole can be obtained:

[0036]

[0037] In the formula (1) and (2), Rm is the outer diameter of the rotor permanent magnet, and Rr is the outer diameter of the rotor core;

[0038] By changing the six parameter variables and combining the magnetizing method of the rotor permanent magnet, the air gap magnetic field distribution characteristics and radial magnetic flux density amplitude generated by the inclined plane connecting parallel magnetizing combined magnetic poles can be determined.

[0039] Therefore, the design method of the bearingless permanent magnet synchronous motor with parallel magnetization combined magnetic poles connected by inclined planes according to the present invention has the following beneficial effects:

[0040] (1) Compared with the traditional tile-type combined magnetic pole structure, the inclined-connected parallel magnetized combined magnetic pole topology structure of the present invention can effectively avoid the local drastic change of the air gap magnetic flux distribution waveform. In addition, the integrated parallel magnetization method can further improve the torque and suspension force control characteristics of the bearingless permanent magnet synchronous motor, and effectively reduce the torque pulsation rate and suspension force pulsation rate.

[0041] (2) The present invention provides specific parameters for the structure of the parallel magnetized combined magnetic poles with inclined surfaces connected, especially setting the pole arc coefficient of the inclined connection area between the main magnetic pole and the auxiliary magnetic poles on both sides as a parameter variable, which greatly facilitates the optimization of the combined magnetic pole structure and also provides convenient conditions for the motor structure optimization analysis based on the intelligent optimization algorithm; by changing the combined magnetic pole structure parameters provided in the present invention, the structure of the combined magnetic pole and the air gap magnetic field distribution characteristics and magnetic flux density amplitude generated by it can be changed quickly and accurately.

[0042] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The overall topology diagram of the BL-PMSM with inclined plane connection parallel magnetization trapezoidal combined magnetic poles of the design method of the bearingless permanent magnet synchronous motor with inclined plane connection parallel magnetization combined magnetic poles of the present invention;

[0044] Figure 2 A schematic diagram of the stator teeth / slots topology structure of a trapezoidal combined magnetic pole type BL-PMSM of the design method of a bearingless permanent magnet synchronous motor with parallel magnetized combined magnetic poles and an inclined plane connection according to the present invention;

[0045] Figure 3It is a schematic diagram of the A-phase four-pole torque winding of the combined magnetic pole type BL-PMSM of the design method of the parallel magnetized combined magnetic pole bearingless permanent magnet synchronous motor of the present invention;

[0046] Figure 4 It is a schematic diagram of the U-phase two-pole suspension winding of the combined magnetic pole type BL-PMSM of the design method of the parallel magnetized combined magnetic pole bearingless permanent magnet synchronous motor of the present invention with inclined plane connection;

[0047] Figure 5 A topological schematic diagram of a surface-mounted inclined-surface-connected parallel-magnetized trapezoidal combined magnetic pole design method for a bearingless permanent magnet synchronous motor with inclined-surface-connected parallel-magnetized combined magnetic poles according to the present invention;

[0048] Figure 6 It is a schematic diagram of the magnetic pole structure when α3 takes the maximum value in the design method of the bearingless permanent magnet synchronous motor with inclined plane connection and parallel magnetization combined magnetic poles of the present invention. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0050] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0051] Example

[0052] The present invention provides a design method for a bearingless permanent magnet synchronous motor with inclined-plane connection and parallel magnetization combined magnetic poles, comprising the following steps:

[0053] S1. Construct stator teeth / slots of BL-PMSM with inclined planes and parallel magnetized combined poles, evenly arrange stator teeth / slots of BL-PMSM along the circumference of the stator, and arrange 24 stator teeth / slots in a pear-shaped stator slot structure and a parallel stator tooth structure;

[0054] S2, constructing the stator winding of the BL-PMSM with inclined plane connection and parallel magnetization combined magnetic poles, placing two sets of conductors in each stator slot designed in step S1 to form a torque winding conductor and a suspension winding conductor, and after numbering each torque winding conductor and suspension winding conductor, constructing a four-pole stator torque winding in the inner layer of the slot and a two-pole stator suspension winding in the outer layer of the slot;

[0055] S3. Construct the inclined-surface connection parallel magnetization combined magnetic pole structure of the inner rotor of BL-PMSM, use high remanence material and low remanence material to construct symmetrical arc-bottom trapezoidal main magnetic poles and asymmetrical trapezoidal auxiliary magnetic poles respectively, connect the main and auxiliary magnetic poles seamlessly with inclined surfaces, and take the pole arc coefficient occupied by the width of the connecting inclined surface area as one of the structural parameter variables to construct an integrated parallel magnetization inclined-surface connection combined magnetic pole overall fan ring structure, and then construct the permanent magnet four-pole inner rotor structure of BL-PMSM in the alternating order of N and S polarities.

[0056] In step S1, the specific steps of constructing the stator teeth / slots of the BL-PMSM with inclined plane connection and parallel magnetization combined magnetic poles are as follows:

[0057] Figure 1 The overall topological structure diagram of the BL-PMSM with parallel magnetized combined poles connected by inclined planes (see the stator winding connection Figure 3-4 ), adopts an outer stator and inner rotor structure. The stator teeth / slots are evenly arranged along the inner surface of the stator core; for a stator core with 24 slots / teeth, the stator slots with a slot pitch of 15° are numbered from 1 to 24 in the counterclockwise direction.

[0058] In order to avoid damaging the insulation layer in the slot, a pear-shaped stator slot structure is adopted. Figure 2 is the pear-shaped slot topology diagram adopted, where b s0 is the stator slot width, b s1 b is the width of the stator slot body close to the stator slot shoulder, s2 is the stator slot bottom width, h s0 is the stator slot height, h s1 is the height of the groove shoulder, h s2 is the stator slot depth; the bottom of the pear-shaped slot is a semicircular arc structure, and the radius of the arc at the bottom of the slot is b s2 / 2, and the center of the circle is located at the intersection of the middle axis of the stator slot and the stator slot body and the stator slot bottom boundary. In order to increase the slot cross-sectional area and motor power density, the stator teeth adopt a parallel tooth structure, that is, the boundaries of adjacent stator slots and their middle stator teeth remain parallel, that is, except for the crown part, the width of the stator tooth body between two adjacent stator slots is equal.

[0059] In step S2, the specific steps of constructing the stator winding of the BL-PMSM with inclined-connected parallel magnetized combined poles are as follows:

[0060] First, two sets of conductors are placed in the 24 stator slots, with the torque winding conductors embedded in the inner layer of the slots and the suspension winding conductors embedded in the outer layer of the slots, and the 24 conductors of the torque winding and the suspension winding are numbered No. 1, No. 2, No. 3, No. 4, ..., No. 23, No. 24 in counterclockwise order, and the numbers of the torque winding conductors and the suspension winding conductors are consistent with the corresponding stator slot numbers.

[0061] Then, construct the four-pole torque winding in the inner layer of the slot. Connect the No. 1 torque winding conductor and the No. 7 torque winding conductor end to end to obtain the No. 1 torque coil, connect the No. 2 torque winding conductor and the No. 8 torque winding conductor end to end to obtain the No. 2 torque coil, and then connect the No. 1 torque coil and the No. 2 torque coil in series to obtain the No. 1 "torque coil group"; connect the No. 13 torque winding conductor and the No. 19 torque winding conductor end to end to obtain the No. 3 torque coil, connect the No. 14 torque winding conductor and the No. 20 torque winding conductor end to end to obtain the No. 4 torque coil, and then connect the No. 3 torque coil and the No. 4 torque coil in series to obtain the No. 2 "torque coil group"; then connect the No. 1 "torque coil group" and the No. 2 "torque coil group" in series to obtain the "A phase (four-pole) torque winding". Similarly, the B-phase and C-phase torque windings can be constructed; the A-phase, B-phase, and C-phase torque windings of the stator are staggered by 120 electrical degrees (corresponding to a 60-degree mechanical angle) in the electrical space.

[0062] Secondly, construct the two-pole suspension winding of the outer layer of the slot. Connect the No. 1 suspension winding conductor and the No. 13 suspension winding conductor end to end to obtain the No. 1 suspension coil, connect the No. 2 suspension winding conductor and the No. 14 suspension winding conductor end to end to obtain the No. 2 suspension coil, connect the No. 3 suspension winding conductor and the No. 15 suspension winding conductor end to end to obtain the No. 3 suspension coil, connect the No. 4 suspension winding conductor and the No. 16 suspension winding conductor end to end to obtain the No. 4 suspension coil, and then connect the No. 1 suspension coil, the No. 2 suspension coil, the No. 3 suspension coil, and the No. 4 suspension coil in series in sequence to obtain the "U-phase (two-pole) suspension winding". Similarly, the V-phase and W-phase suspension windings can be constructed; the U-phase, V-phase, and W-phase suspension windings of the stator are staggered by 120 electrical degrees (corresponding to a 120-degree mechanical angle) in the electrical space.

[0063] Through the above steps or methods, a four-pole torque winding and a two-pole suspension winding of a BL-PMSM with parallel magnetized combined magnetic poles connected by an inclined plane can be constructed; Figure 3 and Figure 4 They are the stator winding connection diagrams constructed using the A-phase four-pole torque winding and the U-phase two-pole suspension winding as examples.

[0064] In step S3, the specific steps of constructing the inclined plane connection parallel magnetization combined magnetic pole structure of the BL-PMSM inner rotor are as follows:

[0065] First, construct a surface-mounted inclined parallel magnetized magnetic pole topology structure. Figure 5 As shown, each combined magnetic pole is composed of three permanent magnets of equal thickness; the middle main magnetic pole adopts high remanence permanent magnetic material to form an "arc-bottom trapezoidal" symmetrical structure; two auxiliary magnetic poles with asymmetric trapezoidal structures are symmetrically arranged on both sides of the main magnetic pole using permanent magnetic material with relatively low remanence, and the two auxiliary magnetic poles are seamlessly connected with the main magnetic pole at an inclined surface to form an overall fan-ring structure of "inclined combined magnetic pole".

[0066] Then, set the parameter variables of the sloped connection combined magnetic pole. The overall pole arc coefficient α1 (generally 0.7-0.95) of the sloped connection combined magnetic pole, the pole arc coefficient α2 of the main magnetic pole, the pole arc coefficient α3 of the main and auxiliary magnetic pole slope connection junction area, the permanent magnet thickness h m Set as "structural parameter variable"; under the premise that each parameter variable satisfies the relationship of "α1>α2+α3", by changing α1, α2, α3 and h m The size of these four permanent magnet structural parameter variables can change the overall structure of the inclined surface connection combined magnetic pole; in order to obtain better torque and suspension force control characteristics, the permanent magnet thickness h m The parameter is generally selected within the range of 2.5 to 3.5 times the air gap length; at the same time, the main pole residual flux density B of the combined magnetic pole rm and the residual magnetic flux density B of the auxiliary poles on both sides rs Set as "magnetization parameter variable", which satisfies "B rm >B rs "Relational formula.

[0067] Secondly, determine the limiting condition of the pole arc coefficient α3 corresponding to the width of the junction area between the main and auxiliary magnetic poles. The combined magnetic pole structure when the pole arc coefficient α3 in the junction area between the main magnetic pole and the auxiliary magnetic pole takes the maximum value is as follows: Figure 6 As shown in the figure, when the interface between the main magnetic pole and the auxiliary magnetic pole is tangent to the outer diameter of the rotor, the pole arc coefficient α3 reaches its maximum value. At this time, α3 must satisfy the following constraint relationship:

[0068]

[0069] According to formula (1), the maximum value of the pole arc coefficient α3 occupied by the inclined surface connection area between the main magnetic pole and the auxiliary magnetic pole can be obtained:

[0070]

[0071] In the formulas (1) and (2), Rm is the outer diameter of the rotor permanent magnet, and Rr is the outer diameter of the rotor core.

[0072] By changing the six parameter variables and combining the magnetizing method of the rotor permanent magnet, the air gap magnetic field distribution characteristics and radial magnetic flux density amplitude generated by the inclined plane connecting parallel magnetizing combined magnetic poles can be determined.

[0073] Secondly, the magnetic combination poles after the bevel connection are integrated and parallel magnetized as a whole. According to the order of alternating N and S polarities, the four bevel connection combination pole permanent magnet structures are integrated and parallel magnetized along the center line of each main pole, so as to obtain two bevel connection parallel magnetization combination pole permanent magnet N poles and two bevel connection parallel magnetization combination pole permanent magnet S poles.

[0074] Finally, the combined magnetic poles are evenly pasted on the outer surface of the rotor core in the order of alternating N and S polarities, forming a permanent magnet four-pole inner rotor with inclined connection and parallel magnetization combined magnetic poles.

[0075] After the above steps, the overall topological structure of the bearingless permanent magnet synchronous motor with inclined planes connected to parallel magnetized combined magnetic poles of the present invention can be obtained, as shown in FIG. Figure 1 Shown

[0076] The working principle involved in the present invention is as follows:

[0077] (1) According to the working principle of the bearingless motor, the present invention passes the same frequency current into the torque winding and the suspension winding with a difference of one pair of poles, which can generate stable and controllable electromagnetic torque and radial magnetic suspension force. By reasonably controlling the torque current and the suspension current, the stable suspension operation control of the BL-PMSM can be achieved.

[0078] (2) The waveform of the air-gap magnetic field of the motor will directly affect its working characteristics. The traditional combined magnetic poles mainly adopt a tile-type structure with equal or unequal thickness, and adopt vertical surface connection (the pole arc coefficient of the junction area of ​​the main and auxiliary magnetic poles of the same combined magnetic pole is 0). This makes the synthetic residual magnetic flux density have a drastic mutation in the junction area between the main and auxiliary magnetic poles. The trapezoidal combined magnetic poles studied at home and abroad mostly adopt the Halbach array, which is different from the single parallel magnetization method, and the application object is ordinary permanent magnet synchronous motor.

[0079] (3) Aiming at the new type of special motor BL-PMSM, the present invention proposes a new structure of combined magnetic poles with inclined surface connection. In order to improve the sinusoidality of its air gap magnetic field, an integrated parallel magnetization method is adopted; the middle main magnetic pole of the combined magnetic pole adopts a symmetrical arc bottom trapezoidal structure, and the auxiliary magnetic poles symmetrically distributed on both sides adopt an asymmetrical trapezoidal structure, and together with the middle main magnetic pole, they form a fan-ring permanent magnet structure after seamlessly inclined connection. The boundary area between the main magnetic pole and the auxiliary magnetic pole of the same combined magnetic pole occupies a certain width (which can be represented by the pole arc coefficient of the inclined surface connection area), which will make the synthetic residual magnetic flux density change continuously in the boundary area, thereby effectively avoiding the step-like mutation of the air gap magnetic field, thereby further improving the degree of consistency between the rising / falling area in the air gap magnetic field waveform and the sine waveform.

[0080] Therefore, the present invention adopts the above-mentioned design method of a bearingless permanent magnet synchronous motor with a bevel connection and a combined magnetic pole, which can effectively avoid the local drastic change phenomenon of the air gap magnetic flux distribution waveform. In addition, the integrated parallel magnetization method can further improve the torque and suspension force control characteristics of the bearingless permanent magnet synchronous motor, and effectively reduce the torque pulsation rate and the suspension force pulsation rate. The pole arc coefficient of the bevel connection area between the main magnetic pole and the auxiliary magnetic poles on both sides is set as a parameter variable, which provides great convenience for the optimization of the combined magnetic pole structure and also provides convenience for the motor structure optimization analysis based on the intelligent optimization algorithm; by changing the combined magnetic pole structure parameters given in the present invention, the structure of the combined magnetic pole and the air gap magnetic field distribution characteristics and magnetic flux amplitude generated by it can be quickly and accurately changed.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A design method for a bearingless permanent magnet synchronous motor with parallel magnetized combined poles and inclined surfaces, characterized in that: The following steps are involved: S1. Construct stator teeth / slots of BL-PMSM with inclined planes and parallel magnetized combined poles, evenly arrange stator teeth / slots of BL-PMSM along the circumference of the stator, and arrange 24 stator teeth / slots in a pear-shaped stator slot structure and a parallel stator tooth structure; S2, constructing the stator winding of the BL-PMSM with inclined plane connection and parallel magnetization combined magnetic poles, placing two sets of conductors in each stator slot designed in step S1 to form a torque winding conductor and a suspension winding conductor, and after numbering each torque winding conductor and suspension winding conductor, constructing a four-pole stator torque winding in the inner layer of the slot and a two-pole stator suspension winding in the outer layer of the slot; S3. Construct the inclined-surface connection parallel magnetization combined magnetic pole structure of the inner rotor of BL-PMSM, use high remanence material and low remanence material to construct symmetrical arc-bottom trapezoidal main magnetic poles and asymmetrical trapezoidal auxiliary magnetic poles respectively, connect the main and auxiliary magnetic poles seamlessly with inclined surfaces, and take the pole arc coefficient occupied by the width of the connecting inclined surface area as one of the structural parameter variables to construct an integrated parallel magnetization inclined-surface connection combined magnetic pole overall fan ring structure, and then construct the permanent magnet four-pole inner rotor structure of BL-PMSM in the alternating order of N and S polarities.

2. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 1 is characterized in that: In step S1, the steps of constructing the stator teeth / slots of the BL-PMSM with inclined planes connected and parallel magnetized combined poles are specifically as follows: S11, adopting the structure of outer stator and inner rotor, 24 stator teeth / slots are evenly arranged along the inner surface of the stator core; S12. Number the stator slots with a slot pitch of 15° from 1 to 24 in a counterclockwise direction.

3. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 2 is characterized in that: In step S12, the stator slot width is b s0 , the width of the stator slot body close to the stator slot shoulder is b s1 , is the width of the stator slot bottom b s2 , the stator slot height is h s0 , the height of the groove shoulder is h s1 , stator slot depth is h s2 ; The bottom of the pear-shaped groove is a semicircular arc structure, and the radius of the arc at the bottom of the groove is b s2 / 2 , and the center of the circle is located at the intersection of the middle axis of the stator slot and the boundary lines of the stator slot body and the stator slot bottom.

4. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 1 is characterized in that: In step S2, the stator winding of the BL-PMSM with inclined-connected parallel magnetized combined poles is constructed, which specifically includes the following steps: S21. Two sets of conductors are placed in the 24 stator slots, with the torque winding conductors embedded in the inner layer of the slots and the suspension winding conductors embedded in the outer layer of the slots, and the 24 conductors of the torque winding and the suspension winding are numbered No. 1, No. 2, No. 3, No. 4, ..., No. 23, No. 24 in a counterclockwise order, and the numbers of the torque winding conductors and the suspension winding conductors are consistent with the corresponding stator slot numbers; S22, construct a four-pole torque winding in the inner layer of the slot, connect the No. 1 torque winding conductor and the No. 7 torque winding conductor end to end to obtain the No. 1 torque coil, connect the No. 2 torque winding conductor and the No. 8 torque winding conductor end to end to obtain the No. 2 torque coil, and then connect the No. 1 torque coil and the No. 2 torque coil in series to obtain the No. 1 "torque coil group"; Connect the torque winding conductor No. 13 and the torque winding conductor No. 19 end to end to obtain the torque coil No. 3, connect the torque winding conductor No. 14 and the torque winding conductor No. 20 end to end to obtain the torque coil No. 4, and then connect the torque coil No. 3 and the torque coil No. 4 in series to obtain the "torque coil group" No. 2; Connect the No. 1 "torque coil group" and the No. 2 "torque coil group" in series to obtain the "A-phase four-pole torque winding"; S23, constructing a two-pole suspension winding in the outer layer of the slot, connecting the No. 1 suspension winding conductor and the No. 13 suspension winding conductor end to end to obtain a No. 1 suspension coil, connecting the No. 2 suspension winding conductor and the No. 14 suspension winding conductor end to end to obtain a No. 2 suspension coil, connecting the No. 3 suspension winding conductor and the No. 15 suspension winding conductor end to end to obtain a No. 3 suspension coil, and connecting the No. 4 suspension winding conductor and the No. 16 suspension winding conductor end to end to obtain a No. 4 suspension coil; Then the No. 1 suspension coil, the No. 2 suspension coil, the No. 3 suspension coil and the No. 4 suspension coil are connected in series in sequence to obtain a "U-phase two-pole suspension winding".

5. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 4 is characterized in that: In step S22, according to the construction steps of "A-phase four-pole torque winding", B-phase and C-phase torque windings are constructed, and the A-phase, B-phase and C-phase torque windings of the stator are staggered by 120 electrical degrees in the electrical space.

6. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 4 is characterized in that: In step S23, according to the construction step of "U-phase two-pole suspension winding", V-phase and W-phase suspension windings are constructed, and the U-phase, V-phase and W-phase suspension windings of the stator are staggered by 120 electrical degrees in electrical space.

7. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 1, characterized in that: In step S3, the inclined plane-connected parallel magnetized trapezoidal combined magnetic pole structure of the BL-PMSM inner rotor is constructed, which specifically includes the following steps: S31, construct a surface-mounted inclined-plane connected parallel magnetized combined magnetic pole topology structure, each combined magnetic pole is composed of three permanent magnets of equal thickness, and the middle main magnetic pole is composed of high remanence permanent magnetic material to form an "arc bottom trapezoidal" symmetrical structure; Two asymmetric trapezoidal auxiliary magnetic poles are symmetrically arranged on both sides of the main magnetic pole using permanent magnetic materials with relatively low remanence. The two auxiliary magnetic poles are seamlessly connected with the main magnetic pole on an inclined surface to form an overall fan ring structure of "inclined combined magnetic poles". S32, setting the parameter variables of the inclined surface connection magnetic combination pole, the overall pole arc coefficient α1 of the inclined surface connection magnetic combination pole, the pole arc coefficient α2 of the main magnetic pole, the pole arc coefficient α3 corresponding to the width of the main and auxiliary magnetic pole inclined surface connection junction area, and the permanent magnet thickness hm are set as "structural parameter variables"; Under the premise that all parameter variables satisfy the relationship of "α1>α2+α3", the overall structure of the inclined surface joint combined magnetic pole can be changed by changing the size of the four permanent magnet structure parameter variables α1, α2, α3 and hm. The permanent magnet thickness hm parameter is generally selected within the range of 2.5 to 3.5 times the air gap length; at the same time, the main magnetic pole residual flux density Brm of the combined magnetic pole and the auxiliary magnetic pole residual flux density Brs on both sides are set as "magnetization parameter variables", which satisfy the relationship "Brm>Brs"; S33, determining the limiting condition of the pole arc coefficient α3 corresponding to the width of the junction area between the main and auxiliary magnetic poles, when the interface between the main magnetic pole and the auxiliary magnetic pole is tangent to the outer diameter of the rotor, the pole arc coefficient α3 obtains the maximum value; S34, integrating parallel magnetization on the magnetic combination poles after the bevel connection, and integrating parallel magnetization on the four bevel connection combination pole permanent magnet structures along the center lines of each main pole in the order of alternating N and S polarities, to obtain two bevel connection parallel magnetization combination pole permanent magnet N poles and two bevel connection parallel magnetization combination pole permanent magnet S poles; S35. In the order of alternating N and S polarities, the combined magnetic poles are evenly pasted on the outer surface of the rotor core to form a permanent magnet four-pole inner rotor with inclined surfaces connecting parallel magnetized combined magnetic poles.

8. The design method of the bevel-connected parallel magnetized combined pole bearingless permanent magnet synchronous motor according to claim 7 is characterized in that: In step S33, the constraint relation of α3 is as follows: According to formula (1), the maximum value of the pole arc coefficient α3 occupied by the inclined surface connection area between the main magnetic pole and the auxiliary magnetic pole can be obtained: In the formula (1) and (2), Rm is the outer diameter of the rotor permanent magnet, and Rr is the outer diameter of the rotor core; By changing the six parameter variables and combining the magnetizing method of the rotor permanent magnet, the air gap magnetic field distribution characteristics and radial magnetic flux density amplitude generated by the inclined plane connecting parallel magnetizing combined magnetic poles can be determined.

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