Double-stator electrically-excited bearingless Vernier magnetor

Abstract

This invention discloses a dual-stator electrically excited bearingless vernier reluctance motor, comprising a rotor, an inner stator, an outer stator, a torque winding, and a suspension winding. The axes of the inner and outer stators differ in phase by an angle δ. Each of the inner and outer stators has a set of three-phase concentrated windings, namely a torque winding and a suspension winding. Torque current and DC bias current are injected into the torque winding, and suspension current and DC bias current are injected into the suspension winding. Compared with traditional bearingless motors, the dual-stator electrically excited bearingless vernier reluctance motor of this invention injects DC bias current into the torque winding and suspension winding, that is, it uses zero-sequence current excitation to replace permanent magnets, avoiding irreversible demagnetization of permanent magnets due to excessive temperature. Furthermore, by setting the angle δ, it effectively weakens the magnetic coupling between the suspension current magnetic field and the torque current magnetic field, which has high theoretical and practical value.

Description

Technical Field

[0001] This invention belongs to the field of motor manufacturing and control technology, specifically relating to a dual-stator electrically excited bearingless vernier reluctance motor. Background Technology

[0002] With the continuous advancements in high-speed drives and sealed transmissions, high-speed motors have become a significant trend in modern motor development, creating an urgent need for bearingless motor technology. Traditional mechanical bearings have numerous limitations, making ordinary motors unable to meet the demands of long-term high-speed operation. Liquid and air-floating bearings have large control systems, occupying significant space and increasing costs. While magnetic bearings offer advantages such as no mechanical wear, no need for lubrication, and strong environmental adaptability due to their sealing system, magnetic bearing motor systems also suffer from drawbacks including complex overall structure, low power density, and difficulty in significantly increasing critical speed and power capacity. Therefore, bearingless motors have emerged as a solution.

[0003] Bearingless motors achieve both rotation and self-levitation by embedding the levitation windings within the stator slots. This significantly reduces friction between the shaft and bearings during rotation, improving efficiency and enabling high-speed operation, making them highly valuable for industrial applications. There are three main types of bearingless motors: bearingless induction motors, bearingless permanent magnet motors, and bearingless vernier reluctance motors. Among these, bearingless vernier reluctance motors offer advantages such as simple structure, reliable operation, high power density, small size, light weight, and good control performance, making them a hot research topic in the field of bearingless motors today.

[0004] Based on the placement of the permanent magnets, the bearingless vernier reluctance motors currently under research are mainly divided into two categories: rotor permanent magnet bearingless motors and stator permanent magnet bearingless motors. For both types of motors, the embedding of permanent magnets will lead to a decrease in the mechanical strength of the rotor or stator, and the permanent magnets themselves occupy a certain amount of space, which will greatly increase the motor's losses and costs. Summary of the Invention

[0005] To overcome the technical problems / defects caused by the embedding of permanent magnets in existing bearingless vernier reluctance motors, this invention provides a dual-stator electrically excited bearingless vernier reluctance motor. This dual-stator electrically excited bearingless vernier reluctance motor injects DC bias current into the torque winding and suspension winding, that is, it uses zero-sequence current excitation to replace permanent magnets, avoiding the irreversible demagnetization of permanent magnets due to excessive temperature, and effectively solving the technical problems / defects caused by permanent magnets. However, since torque windings and suspension windings are set on the inner and outer stators, there is coupling between the magnetic field of the suspension current and the magnetic field of the torque current generated by them. In order to reduce the coupling effect, the technical solution of this invention sets an angle δ between the axes of the inner and outer stators, which has a significant effect and has high theoretical and practical value.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A dual-stator electrically excited bearingless vernier reluctance motor includes at least a rotor, an inner stator, an outer stator, a torque winding, and a suspension winding;

[0008] The rotor is sandwiched between the inner stator and the outer stator, and the phase angle between the axes of the inner stator and the outer stator is δ, where the value of δ is [0, π / 3].

[0009] There are air gaps between the inner and outer stators and the rotor. The rotor has rotor teeth facing the outer stator and the inner stator on its inner and outer sides. One of the torque winding and the suspension winding is located on the inner stator and the other is located on the outer stator.

[0010] Torque current and DC bias current are injected into the torque winding, and suspension current and DC bias current are injected into the suspension winding.

[0011] The purpose of setting an angle δ between the axes of the inner stator and the outer stator in the technical solution of the present invention is to reduce the coupling between the magnetic field of the levitation current and the magnetic field of the torque current.

[0012] Further optionally, the optimal value of the δ angle is: the δ angle is the angle when the partial derivative of the mutual inductance flux linkage between the torque winding and the suspension winding with respect to the δ angle is equal to 0;

[0013] The mutual inductance flux is calculated based on the mutual inductance between the torque winding and each phase suspension winding.

[0014] Specifically, the process for obtaining the optimal value of the preferred angle δ in the technical solution of this invention is as follows:

[0015] Calculate the mutual inductance between the torque winding and the suspension windings of each phase;

[0016] Then, the mutual inductance flux linkage between the torque winding and the suspension winding is calculated based on the mutual inductance between the torque winding and each phase suspension winding.

[0017] The partial derivative of the mutual inductance flux with respect to the angle δ is taken, and the angle δ corresponding to the partial derivative being equal to 0 is the optimal angle δ.

[0018] When the torque winding and suspension winding on the electrodes are symmetrically distributed, as long as the coupling between the torque winding and the suspension current is minimized, the coupling between the torque current and the suspension current can be minimized.

[0019] Therefore, when both the torque winding and the suspension winding are three-phase windings symmetrically distributed, the partial derivative of the mutual inductance flux linkage between any phase A, B, or C torque winding and the suspension winding with respect to angle δ is calculated. When the partial derivative is equal to 0, the angle δ is... Where, θ s The phase angle of the levitation current;

[0020] Among them, the mutual inductance flux ψ between the A-phase torque winding and the suspension winding Ats Represented as:

[0021] ψ Ats =M Ats i As +M ABts i Bs +M ACts i Cs

[0022] In the formula, M Ats M ABts M ACts These represent the mutual inductance between the A-phase torque winding and the A, B, and C-phase suspension windings, respectively. As i Bs i Cs The phase currents of the three-phase floating windings A, B, and C;

[0023] The mutual inductance M between phase A torque winding and phases A, B, and C suspension windings Ats M ABts M ACts Represented as:

[0024] M Ats =L m1 ·cosδ

[0025] M ABts =L m1 ·cos(δ+2π / 3)

[0026] M ACts =L m1 ·cos(δ-2π / 3)

[0027] In the formula, L m1 It is the magnetizing inductor.

[0028] Further optionally, the torque winding includes: a concentrated winding At1, a concentrated winding Bt1, a concentrated winding Ct1, a concentrated winding At2, a concentrated winding Bt2, and a concentrated winding Ct2.

[0029] Among them, the concentrated windings At1 and At2 are radially opposite to each other and together form the A-phase torque winding; the concentrated windings Bt1 and Bt2 are radially opposite to each other and together form the B-phase torque winding; the concentrated windings Ct1 and Ct2 are radially opposite to each other and together form the C-phase torque winding; the A, B, and C three-phase torque windings are arranged in space in a counterclockwise direction with a mechanical angle difference of 120°.

[0030] Further optionally, the suspension winding includes: a centralized winding As1, a centralized winding Bs1, a centralized winding Cs1, a centralized winding As2, a centralized winding Bs2, and a centralized winding Cs2.

[0031] Among them, the concentrated windings As1 and As2 are radially opposite to each other and together form the A-phase suspension winding; the concentrated windings Bs1 and Bs2 are radially opposite to each other and together form the B-phase suspension winding; the concentrated windings Cs1 and Cs2 are radially opposite to each other and together form the C-phase suspension winding; the A, B, and C three-phase suspension windings are arranged in space in a counterclockwise direction with a mechanical angle difference of 120°.

[0032] Alternatively, the rotor may be provided with a non-magnetic material structural layer.

[0033] The rotor has a non-magnetic material layer in the middle to reduce the coupling between the magnetic field of the levitation current and the magnetic field of the torque current, which would affect the motor's operating performance.

[0034] Alternatively, the rotor may employ a straight slot or a skewed slot structure.

[0035] Further optionally, both the inner stator and the outer stator have 6 poles, the rotor has 10 poles on the side facing the inner stator, and the rotor has 11 poles on the side facing the outer stator.

[0036] Beneficial effects

[0037] 1. The dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention solves the technical problems / defects caused by the embedding of permanent magnets in existing bearingless vernier reluctance motors by injecting torque current and DC bias current into the torque winding and floating current and DC bias current into the floating winding, that is, by excitation through the injected zero-sequence current (injecting DC bias current into the torque winding and the floating winding).

[0038] 2. The technical solution of this invention sets an angle δ between the axes of the inner stator and the outer stator, which can effectively reduce the coupling between the levitation current magnetic field and the torque current magnetic field. Furthermore, to obtain the optimal value of the angle δ, the partial derivative of the mutual inductance flux linkage between the torque winding and the levitation winding is calculated with respect to the angle δ based on the motor structure. The angle δ is then calculated when this partial derivative equals 0, at which point the coupling between the levitation current magnetic field and the torque current magnetic field is minimized to the greatest extent possible. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention;

[0040] Figure 2 This is an equivalent circuit model diagram of a dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention, wherein (a) corresponds to the torque winding equivalent circuit diagram and (b) corresponds to the suspension winding equivalent circuit diagram.

[0041] Figure 3 This is a schematic diagram of the axial offset of the inner and outer stators of the dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention.

[0042] The accompanying figure is labeled as follows:

[0043] 1. Rotor; 2. Torque winding; 3. Floating winding; 4. Inner stator; 5. Outer stator; 6. Non-magnetic material structural layer. Detailed Implementation

[0044] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0045] Example 1:

[0046] This embodiment provides a dual-stator electrically excited bearingless vernier reluctance motor, comprising: a rotor 1, an inner stator 4, an outer stator 5, a torque winding 2, and a suspension winding 3; wherein, the rotor 1 is sandwiched between the inner stator 4 and the outer stator 5, and there are air gaps between the inner stator 4, the outer stator 5, and the rotor 1; the inner and outer sides of the rotor 1 are provided with rotor teeth facing the outer stator 5 and the inner stator 4; one of the torque winding 2 and the suspension winding 3 is provided on the inner stator 4, and the other is provided on the outer stator 5.

[0047] In this embodiment, the rotor 1, inner stator 4, and outer stator 5 are preferably all salient pole structures. The torque winding 2 is disposed on the inner stator 4, and the suspension winding 3 is disposed on the outer stator 5, thereby injecting torque current and DC bias current into the torque winding 2, and injecting suspension current and DC bias current into the suspension winding 3.

[0048] To reduce the coupling between the magnetic field of the levitation current and the magnetic field of the torque current, a non-magnetic structure layer 6 is provided in the middle of the rotor 1. Furthermore, as... Figure 3 As shown, an angle δ is set between the axes of the inner stator 4 and the outer stator 5, and the value of this angle is in the range of [0, π / 3].

[0049] In order to minimize the coupling effect between the levitation current magnetic field and the torque current magnetic field in this embodiment, the following reasoning is made based on the motor structure in this embodiment:

[0050] like Figure 3 The diagram shows the axis offset of the inner and outer stators 5. From the diagram, the flux linkage equations of each phase winding of the motor can be written:

[0051]

[0052] In the formula, ψ At ,ψ Bt ,ψ Ct ψ represents the flux linkage of the three-phase torque windings A, B, and C in the torque winding; As ,ψ Bs ,ψ Cs L represents the flux linkage of the three-phase suspension windings A, B, and C in the suspension winding. At ,L Bt ,L Ct L is the self-inductance of the three-phase torque windings A, B, and C. As ,L Bs ,L Cs i is the self-inductance of the three-phase floating windings A, B, and C. At i Bt i Ct Let i be the phase current of the three-phase torque windings A, B, and C. As i Bs i Cs Let ψ be the phase current of the three-phase floating windings A, B, and C. fAt ,ψ fBt ,ψ fCt ψ is the excitation flux linkage of the three-phase torque windings A, B, and C. fAs ,ψ fBs ,ψ fCs The excitation flux linkage is for the three-phase suspension windings A, B, and C.

[0053] M Ats M ABtsM ACts These represent the mutual inductance between the A-phase torque winding and the A, B, and C-phase suspension windings, respectively; M ABt M ACt These are the mutual inductances between phase A torque winding and phases B and C torque winding, M. ABs M ACs These are the mutual inductances between the A-phase floating winding and the B and C-phase floating windings, respectively, M BAt M BCt M BAts M Bts M BC ts represents the mutual inductance between the B-phase torque winding and the A and C-phase torque windings, as well as the mutual inductance between the A, B, and C three-phase suspension windings. M Bst M BAs These are the mutual inductances between the B-phase suspension winding and the B-phase torque winding, and between the A-phase suspension winding, respectively. M CAt M CBt M CAts M CBts M Cts M CAs M CBs The definition is the same as above.

[0054] Neglecting the effect of the stator and rotor 1 magnetic reluctance on the inductance, the self-inductance and mutual inductance of each winding are independent of the position of rotor 1, thus we have:

[0055] L At =L Bt =L Ct =L As =L Bs =L Cs =L m1 +L sσ

[0056] Among them, L m1 L is the magnetizing inductance of each phase winding. sσ It is a leakage inductance.

[0057] Because the motor has two sets of three-phase windings symmetrically distributed, as long as the coupling between the A-phase torque current and the floating current can be minimized, the coupling between the torque current and the floating current can also be minimized. Figure 3 The mutual inductance expressions between phase A torque winding (2) and each phase suspension winding (3) can be written as follows:

[0058] M Ats =L m1 ·cosδ

[0059] M ABts =L m1 ·cos(δ+2π / 3)

[0060] M ACts =L m1 ·cos(δ-2π / 3)

[0061] Substituting the levitation current, the mutual inductance flux Ψ between the A-phase torque winding (2) and the levitation winding (3) can be calculated. Ats (Since the zero-sequence current serves as excitation, it is not considered here):

[0062] Ψ Ats =M Ats i As +M ABts i Bs +M ABts i Cs

[0063] =L m1 ·cosδ·I S sin(θ S )+L m1 ·cos(δ+2π / 3)·I S sin(θ S -2π / 3)+L m1 ·cos(δ-2π / 3)·I S sin(θ S +2π / 3)

[0064] ψ Ats Taking the partial derivative with respect to δ, we get:

[0065]

[0066] make It can be calculated that:

[0067]

[0068] And θ s The phase angle of the levitation current determines the direction of the levitation force, and its value depends only on the arrangement of the motor windings, therefore it can be considered a constant. Therefore, it can be determined that when... This minimizes the coupling between torque current and floating current.

[0069] like Figure 2 The diagram shows the equivalent circuit model of the dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention. Figure (a) shows the equivalent circuit diagram of the torque winding, and figure (b) shows the equivalent circuit diagram of the levitation winding. In the figures, I... T I represents the torque current amplitude. s I0 is the amplitude of the floating current; I0 is the applied DC bias current; ω0 e θ is the electric angular velocity of rotor 1. sThe phase angle of the levitation current is θ. The torque converter in Figure (a) is a three-phase converter, which can be configured via software to output three-phase AC with DC bias. The zero-sequence current source consists of three sets of DC chopper circuits, capable of outputting three equal DC currents. For Figure (b), since the phase angle θ of the levitation force... s If this is confirmed, then the three floating currents emitted by the floating current source are all DC currents. Therefore, the floating current source, like the zero-sequence current source, is also composed of three sets of DC chopper circuits, but the three current values ​​emitted by it need to be controlled separately.

[0070] The working principle of the dual-stator electrically excited bearingless vernier reluctance motor provided by this invention is the same as that of a traditional vernier reluctance motor, following the principle of minimum reluctance, that is, magnetic lines of force always close along the magnetic circuit with the least reluctance. In the dual-stator electrically excited bearingless vernier reluctance motor provided by this invention, the torque current in the torque winding 2 generates a circular rotating magnetic field in the air gap. This circular rotating magnetic field interacts with the stationary magnetic field generated by the DC bias current component, producing an electromagnetic torque of reluctance nature, thereby driving the rotor 1 to rotate. By adjusting the magnitude of the DC bias current, the magnitude of the stationary magnetic field can be changed, thereby changing the no-load back electromotive force of the motor, ultimately achieving torque adjustment and speed regulation. It is worth noting that, based on the distribution of the armature winding, the magnetic field generated by the DC bias current is radially and uniformly distributed in the motor; therefore, the final synthesized magnetic field is zero, having little impact on the normal operation of the motor.

[0071] The levitation force of the dual-stator electrically excited bearingless vernier reluctance motor provided by this invention originates from Maxwell's force, which is the tension generated along the magnetic field path when a magnetic field passes through two media with different permeabilities. When no levitation current is injected into the levitation winding 3 and only a DC bias current component is present, the resultant force of the Maxwell's force on rotor 1 is approximately zero because the magnetic field lines in all angular directions are uniformly distributed in the stator and rotor. Therefore, the radial force on rotor 1 is approximately zero at this time. When a levitation current is injected into the levitation winding 3, the static magnetic field generated by the levitation current causes the magnetic field lines in rotor 1 to be unevenly distributed along the angular direction, and the resultant force of the Maxwell's force on rotor 1 is not zero, thus generating the radial force. Therefore, the magnitude and direction of the radial force on rotor 1 can be controlled by controlling the amplitude and phase of the levitation current.

[0072] In summary, the dual-stator electrically excited bearingless vernier reluctance motor provided by the present invention can control the rotation of the rotor 1 and generate a levitation effect when injecting torque current and DC bias current into the torque winding 2 and levitation current and DC bias current into the levitation winding 3 without permanent magnets.

[0073] Furthermore, in this embodiment, both the inner stator 4 and the outer stator 5 have 6 poles, the rotor 1 has 10 poles on the side facing the inner stator 4, and 11 poles on the side facing the outer stator 5. In other feasible embodiments, the inner stator 4, the outer stator 5, and the rotor 1 can be configured with different numbers of poles according to the motor structure, but this should ensure stable motor operation and stable rotor levitation.

[0074] Based on the structure of both the inner stator 4 and the outer stator 5 being 6-pole structures in this embodiment, the torque winding 2 includes: concentrated windings At1, Bt1, Ct1, At2, Bt2, and Ct2. Concentrated windings At1 and At2 are radially opposite to each other, forming the A-phase torque winding; concentrated windings Bt1 and Bt2 are radially opposite to each other, forming the B-phase torque winding; concentrated windings Ct1 and Ct2 are radially opposite to each other, forming the C-phase torque winding. The A, B, and C phase torque windings are arranged in a counter-clockwise direction with a mechanical angle difference of 120°. The suspension winding 3 includes: concentrated windings As1, Bs1, Cs1, As2, Bs2, and Cs2. Among them, the concentrated windings As1 and As2 are radially opposite to each other and together form the A-phase suspension winding; the concentrated windings Bs1 and Bs2 are radially opposite to each other and together form the B-phase suspension winding; the concentrated windings Cs1 and Cs2 are radially opposite to each other and together form the C-phase suspension winding; the A, B, and C three-phase suspension windings are arranged in space in a counterclockwise direction with a mechanical angle difference of 120°.

[0075] In other feasible embodiments, the winding method of torque winding 2 and suspension winding 3 can be adaptively adjusted, and the present invention does not impose specific limitations on this.

[0076] In other feasible embodiments, the rotor 1 adopts a straight slot or oblique slot structure.

[0077] In summary, this invention introduces the concept of zero-sequence current excitation without permanent magnets into bearingless motors. Replacing existing permanent magnets with zero-sequence current avoids demagnetization of permanent magnets due to excessively high operating temperatures, thus extending the motor's lifespan. Furthermore, by setting an angle δ between the axes of the inner and outer stators, this invention reduces the coupling between the torque current and the suspension current. In addition, separating the torque winding 2 and the suspension winding 3 further addresses the severe magnetic coupling problem in bearingless vernier reluctance motors.

[0078] It should be emphasized that the examples described in this invention are illustrative rather than limiting. Therefore, this invention is not limited to the examples described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solutions of this invention, without departing from the spirit and scope of this invention, whether modifications or substitutions, are also within the protection scope of this invention.

Claims

1. A dual-stator electrically excited bearingless vernier reluctance motor, characterized in that: It includes at least a rotor, an inner stator, an outer stator, a torque winding, and a suspension winding; The rotor is sandwiched between the inner stator and the outer stator, and the center lines of the core teeth of the inner stator and the core teeth of the outer stator are out of phase by an angle of [missing information]. δ horn, δ The range of values ​​for is [0, ... π / 3]; There are air gaps between the inner and outer stators and the rotor. The rotor has rotor teeth facing the outer stator and the inner stator on its inner and outer sides. One of the torque winding and the suspension winding is located on the inner stator and the other is located on the outer stator. Torque current and DC bias current are injected into the torque winding, and suspension current and DC bias current are injected into the suspension winding. The δ The optimal value of the angle is: the mutual inductance flux pair between the torque winding and the suspension winding. δ When the partial derivative of the angle is equal to 0, the corresponding angle is... δ Angle; wherein, the mutual inductance flux is calculated based on the mutual inductance between the torque winding and each phase suspension winding; Both the torque winding and the suspension winding are three-phase windings symmetrically distributed. Calculate the mutual inductance flux linkage between any one of phases A, B, or C's torque winding and the suspension winding. δ Find the partial derivative of the angle, and when the partial derivative is equal to 0, the... δ Angle is ,in, θ s The phase angle of the levitation current; Among them, the mutual inductance flux linkage between the A-phase torque winding and the suspension winding Represented as: ； In the formula, These represent the mutual inductance between the A-phase torque winding and the A, B, and C-phase suspension windings, respectively. The phase currents of the three-phase floating windings A, B, and C are given.

2. The dual-stator electrically excited bearingless vernier reluctance motor according to claim 1, characterized in that: The mutual inductance between phase A torque winding and phases A, B, and C suspension windings Represented as: ； In the formula, L m1 It is the magnetizing inductor.

3. The dual-stator electrically excited bearingless vernier reluctance motor according to any one of claims 1-2, characterized in that: The torque windings include: concentrated winding At1, concentrated winding Bt1, concentrated winding Ct1, concentrated winding At2, concentrated winding Bt2 and concentrated winding Ct2. Among them, the concentrated windings At1 and At2 are radially opposite to each other and together form the A-phase torque winding; the concentrated windings Bt1 and Bt2 are radially opposite to each other and together form the B-phase torque winding; the concentrated windings Ct1 and Ct2 are radially opposite to each other and together form the C-phase torque winding; the A, B, and C three-phase torque windings are arranged in space in a counterclockwise direction with a mechanical angle difference of 120°.

4. The dual-stator electrically excited bearingless vernier reluctance motor according to any one of claims 1-2, characterized in that: The suspended winding includes: a concentrated winding As1, a concentrated winding Bs1, a concentrated winding Cs1, a concentrated winding As2, a concentrated winding Bs2, and a concentrated winding Cs2. Among them, the concentrated windings As1 and As2 are radially opposite to each other and together form the A-phase suspension winding; the concentrated windings Bs1 and Bs2 are radially opposite to each other and together form the B-phase suspension winding; the concentrated windings Cs1 and Cs2 are radially opposite to each other and together form the C-phase suspension winding; the A, B, and C three-phase suspension windings are arranged in space in a counterclockwise direction with a mechanical angle difference of 120°.

5. The dual-stator electrically excited bearingless vernier reluctance motor according to any one of claims 1-2, characterized in that: The rotor is provided with a non-magnetic material structure layer.

6. The dual-stator electrically excited bearingless vernier reluctance motor according to any one of claims 1-2, characterized in that: The rotor adopts a straight slot or oblique slot structure.

7. The dual-stator electrically excited bearingless vernier reluctance motor according to any one of claims 1-2, characterized in that: Both the inner stator and the outer stator have 6 poles. The rotor has 10 poles on the side facing the inner stator and 11 poles on the side facing the outer stator.

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