A rotor for reducing torque ripple of a synchronous reluctance motor

Abstract

The application discloses a rotor for reducing torque ripple of a synchronous reluctance motor and belongs to the technical field of synchronous reluctance motors. The rotor is composed of a first lamination and a second lamination formed by the same punching sheet, and there are multiple layers of magnetic barriers under each pole. For the first lamination, the tail ends of the outer layer and the inner layer magnetic barriers on the left side of the q-axis are respectively offset by an angle of Delta theta 1 and Delta theta 2 relative to the other side. The second lamination is obtained by horizontally turning the first lamination by 180 degrees, and the shape of the magnetic barrier under the single pole of the second lamination is mirror-symmetrical about the q-axis compared with the first lamination. The torque harmonic amplitude and phase of the two laminations are different, and the synchronous reluctance motor can have a larger average torque and reduce torque ripple by superimposing and combining in a certain proportion. The application can realize the suppression of torque harmonics of specific frequencies and reduce the torque ripple of the motor. The application has important significance for improving the performance of the synchronous reluctance motor and expanding the application thereof.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synchronous reluctance motors, and more particularly to a rotor for reducing torque ripple of a synchronous reluctance motor. BACKGROUND

[0002] In recent years, energy crisis has become one of the problems that the world is generally concerned about. According to the data of the total electricity consumption of the whole society released by the National Energy Administration from January to June 2022, the cumulative total electricity consumption of the whole society in China is 40977 billion kilowatt-hours, an increase of 2.9% over the same period. Among them, the industrial electricity consumption accounts for about 70% of the total electricity consumption. The main electric equipment for industrial production is induction motor, which accounts for about 70%-80% of industrial electricity consumption. Therefore, developing high-efficiency motors has important significance for promoting energy saving and emission reduction and realizing green economic development in China.

[0003] The rotor of the synchronous reluctance motor has no squirrel cage structure, which significantly reduces the rotor loss and improves the efficiency of the motor. Compared with the induction motor, the synchronous reluctance motor has lower loss, higher efficiency and torque density at the same power level, and is expected to replace the induction motor and become the main force of the new generation of industrial motors. However, the synchronous reluctance motor generally has the problems of large torque ripple and obvious vibration and noise, which has become one of the hotspots of current research on synchronous reluctance motors.

[0004] In previous studies, the main methods for reducing the torque ripple of the synchronous reluctance motor include: 1. Rotor skewing, which has been widely used, but still has the problem of output torque loss, resulting in reduced torque density of the motor; 2. Design and optimization of the geometry parameters of the rotor barrier, but due to the complex structure of the rotor of the synchronous reluctance motor, the design of the barrier is difficult, and this method generally has the problem of long optimization time; 3. Reasonable selection of slot-pole combination and barrier layer number, but this method has little effect on the suppression of torque ripple. Therefore, the problem of torque ripple of the synchronous reluctance motor needs further research. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a rotor for reducing the torque ripple of a synchronous reluctance motor, which aims to improve the suppression effect of torque ripple and reduce the design optimization time.

[0006] To achieve the above object, the application provides a rotor for reducing torque ripple of a synchronous reluctance motor, which selects a tail angle of a rotor magnetic barrier by using a magnetic circuit equivalent model, adopts a rotor lamination mirror combination mode to reduce amplitude of main sub-harmonic waves, and further reduce torque ripple of the motor.

[0007] Taking a double-layer magnetic barrier synchronous reluctance motor as an example, assuming that the outer magnetic barrier q-axis angles are θ1 and θ1', the inner magnetic barrier q-axis angles are θ2 and θ2', ignoring stator slotting, and assuming a linear model, the torque expression based on the equivalent magnetic circuit model of the synchronous reluctance motor is obtained as follows:

[0008]

[0009] wherein:

[0010]

[0011]

[0012] ε3=aε1 (4)

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] In the formula, D is an outer diameter of the rotor, L is a motor stack length, g is an air gap length, p is a rotor pole pair number, K is a νth line current density amplitude, tblb1 and tblb2 are width and length ratios of the outer and inner magnetic barriers, respectively, and α is a current phase angle. stk ν i ​​​

[0019] It is found by formula (1) that the torque characteristic is related to the tail end angle of the magnetic barrier, and the amplitude and phase of each harmonic torque can be further obtained, and appropriate angle combination will make the motor have lower torque ripple compared with the case of symmetric shape of the magnetic barrier, and the average torque changes slightly.

[0020] On the basis of the above design scheme, the tail angle of the rotor magnetic barrier is mirror-symmetrically transformed about the q-axis, and similarly, the torque and the waveform of each harmonic can be obtained, and it is found that there is a phase difference between the main harmonic waveforms corresponding to the two structures, and the combination of the two rotors with a certain stacking ratio or the combination of the two asymmetric magnetic barriers on a single rotor lamination can reduce the harmonic amplitude and further reduce the motor torque ripple.

[0021] Considering the stator slotting, similar conclusions are obtained through simulation analysis, that is, the combination of asymmetric magnetic barrier rotor laminations and their mirror-symmetric structures can reduce the amplitude of main harmonic torque and thus reduce the torque ripple. The ratio of N1 and N2 is inversely proportional to the ratio of the amplitudes of the main harmonics of the first and second laminations obtained by the equivalent magnetic circuit model.

[0022] The application also provides a three-layer magnetic barrier synchronous reluctance motor, assuming that the angles of the outer magnetic barrier on both sides of the q-axis are θ1 and θ1', the angles of the middle magnetic barrier on both sides of the q-axis are θ2 and θ2', and the angles of the inner magnetic barrier on both sides of the q-axis are θ3 and θ3', ignoring the stator slotting, and assuming a linear model, the expression of torque based on the equivalent magnetic circuit model of the synchronous reluctance motor is:

[0023]

[0024] Wherein:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] Through simulation analysis, similar conclusions are obtained as the double-layer magnetic barrier synchronous reluctance motor.

[0037] Compared with the prior art, the above technical scheme conceived by the present application can improve the rotor structure design and optimization speed and has more obvious torque ripple suppression effect by guiding the selection of the magnetic barrier tail end angle based on the theoretical model and reducing the torque harmonics of specific times through the combination of the mirror-symmetrical structure. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of the asymmetric magnetic barrier synchronous reluctance motor stator and rotor structure in an embodiment of the present application;

[0039] Figure 2 is a comparison of the 18th torque harmonics of the asymmetric magnetic barrier design scheme and the symmetric magnetic barrier scheme in an embodiment of the present application;

[0040] Figure 3 is a comparison of the 18th torque harmonic waveforms of the asymmetric magnetic barrier structure and its mirror-symmetrical structure in an embodiment of the present application;

[0041] Figure 4 is a schematic diagram of the quarter rotor structure composed of the asymmetric magnetic barrier laminations and the laminations horizontally flipped in an embodiment of the present application;

[0042] Figure 5 is a comparison of the torque waveforms of different structure synchronous reluctance motors in an embodiment of the present application;

[0043] Figure 6 is a comparison of the torque waveforms of the design scheme and the initial scheme in a non-ideal case in an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical schemes and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0045] The application provides a rotor for reducing torque ripple of a synchronous reluctance motor, which is characterized by the following steps: using a magnetic circuit equivalent model, simply and quickly selecting a tail angle of a rotor magnetic barrier, adopting a rotor lamination mirror combination mode to reduce the amplitude of main harmonics, and further reducing the torque ripple of the motor.

[0046] Taking a double-layer magnetic barrier synchronous reluctance motor as an example, assuming that the outer magnetic barrier q-axis angles are θ1 and θ1', the inner magnetic barrier q-axis angles are θ2 and θ2', ignoring stator slotting, and assuming a linear model, the expression of torque based on the equivalent magnetic circuit model of the synchronous reluctance motor is obtained as follows:

[0047]

[0048] wherein, D is the outer diameter of the rotor, L is the motor stack length, g is the air gap length, p is the number of rotor pole pairs, K is the current density amplitude of the νth harmonic, tblb1 and tblb2 are the width and length ratios of the outer magnetic barrier and the inner magnetic barrier, respectively, α is the current phase angle. stk ν i

[0049] The relationship between the motor torque performance and the tail end angle of the magnetic barrier is obtained based on the theoretical model, and the angle combination θ1, θ2, θ1' and θ2' with higher output torque and lower torque ripple is obtained through optimization.

[0050] The main parameters of a synchronous reluctance motor are shown in Table 3-1, and the structural schematic diagram is shown in Figure 1 ​​​As shown. Ignoring the stator slots, the stator phase current amplitude is 6.89A. When the magnetic barrier is symmetrical and the angles θ1 and θ2 between the tail ends of the outer and inner magnetic barriers and the q-axis are 20 degrees and 38 degrees respectively, the theoretical average torque of the motor is 37.8Nm and the theoretical torque ripple is 26.5%. Taking the angle between the tail end of the magnetic barrier and the q-axis as a variable for parameter scanning, it is found that when θ1, θ2, θ1' and θ2' are 19, 37, 20 and 36 degrees respectively, the theoretical average torque is 37.6Nm and the theoretical torque ripple is 17.2%, which is reduced by about 35%. The torque harmonics of the two cases and the 18th torque harmonic waveform are compared. Figure 2 As shown in (a) and (b), it can be seen that the asymmetric magnetic barrier design reduces the amplitude of the 18th harmonic, which is the main reason for the reduction of torque ripple.

[0051] After the rotor laminations are flipped horizontally 180 degrees, θ1, θ2, θ1' and θ2' are 20, 36, 19 and 37 degrees respectively. Other parameters remain unchanged. The average torque theoretical value of the motor is 37.6Nm, and the torque ripple theoretical value is 25.7%. The 18th torque harmonic waveform is compared with the structure before flipping. Figure 3 As shown. Combine the two laminates in a certain ratio to keep the total stack length unchanged, as shown Figure 4 As shown, the average torque is 37.6Nm and the torque ripple is 15.2%. Compared with the symmetrical magnetic barrier solution, the torque ripple is reduced by about 41%. The comparison between the finite element simulation and theoretical results is shown in Table 3-2. The torque waveform simulation results of the symmetrical magnetic barrier rotor structure, the two asymmetric magnetic barrier rotor structures and the combined structure are compared. Figure 5 shown.

[0052] Considering the stator slots and saturation, with other conditional parameters unchanged, the tail angles of the magnetic barrier θ1, θ2, θ1' and θ2' are re-selected as 20, 33.5, 17 and 37.5 degrees respectively, so that the 18th harmonic phases of the two asymmetric structures after horizontal flipping are opposite, and the 18th torque harmonic amplitude is reduced by a certain proportion of combination to reduce the torque pulsation. The simulation results are shown in Table 3-3. The structure proposed in the present invention reduces the torque pulsation by about 62% compared with the symmetrical magnetic barrier structure while ensuring a large average torque. The torque simulation waveform comparison is as follows: Figure 6 As shown, the present invention can not only be applied to the design of synchronous reluctance motors with different numbers of magnetic barrier layers and magnetic barrier shapes, but can also be used to guide the rotor structure design of permanent magnet assisted synchronous reluctance motors.

[0053] Table 3-1 Main parameters of motor

[0054] Parameter name Value Stator outer diameter D e / mm]] 155 Stacked length L stk / mm]] 105 Stator inner diameter D si / mm]] 98 Stator slot number Q s ]]> 36 Number of pole pairs p 2 Air gap length g / mm 0.3

[0055] Table 3-2 Comparison of finite element simulation and theoretical results

[0056]

[0057] Table 3-3 Non-ideal case simulation results

[0058]

[0059] It is to be understood that the above description is merely a preferred embodiment of the application and that modifications, improvements and developments thereof within the scope of the present application are intended to be included within the scope of the present application.

Claims

1. A rotor for reducing torque pulsation in a synchronous reluctance motor, wherein the rotor has a plurality of sets of slots formed in the punching sheets, wherein the area where each set of slots is located forms a magnetic pole, wherein the slots are magnetic barriers, and the rotor has an asymmetric structure comprising N1 first laminations and N2 second laminations formed from the same punching sheet, wherein the magnetic barriers of each magnetic pole of the first lamination are asymmetric about the magnetic pole axis and intersect at a point with the extension line of the magnetic pole axis, and wherein the shapes of the magnetic barriers under the single poles of the second lamination and the first lamination are mirror-symmetric about the q-axis, characterized in that: The magnetic barrier under each magnetic pole includes an outer magnetic barrier and an inner magnetic barrier. The angles on both sides of the q axis of the outer magnetic barrier are θ1 and θ1 respectively. ' The angles on both sides of the q axis of the inner magnetic barrier are θ2 and θ2 ' , where Δθ1=|θ1 ′ -θ1|, Δθ2=|θ2 ′ -θ2|; The equivalent magnetic circuit model of the synchronous reluctance motor is established as follows: in, D is the outer diameter of the rotor, L stk is the motor stack length, g is the air gap length, p is the number of rotor pole pairs, K ν is the amplitude of the secondary line current density, tblb1 and tblb2 are the ratios of the width and length of the outer and inner magnetic barriers, respectively, and α i is the current phase angle; Based on the theoretical model, the relationship between the motor torque performance and the tail angle of the magnetic barrier is obtained, and the angle combinations θ1, θ2, θ1 with higher output torque and lower torque pulsation are obtained through optimization. ' and θ2 ' .

2. The rotor for reducing torque ripple of a synchronous reluctance motor according to claim 1, characterized in that: The ratio of N1 to N2 is equal to the inverse ratio of the amplitude of the main harmonics of the first lamination and the second lamination obtained by the equivalent magnetic circuit model.

3. A rotor for reducing torque pulsation in a synchronous reluctance motor, wherein the rotor has a plurality of sets of slots formed in the punching sheets, wherein the area where each set of slots is located forms a magnetic pole, wherein the slots are magnetic barriers, and the rotor has an asymmetric structure comprising N1 first laminations and N2 second laminations formed from the same punching sheet, wherein the magnetic barriers of each magnetic pole of the first lamination are asymmetric about the magnetic pole axis and intersect at a point with the extension line of the magnetic pole axis, and wherein the shapes of the magnetic barriers under the single poles of the second lamination and the first lamination are mirror-symmetric about the q-axis, characterized in that: There are outer magnetic barriers, middle magnetic barriers and inner magnetic barriers under each magnetic pole. The angles on both sides of the q axis of the outer magnetic barrier are θ1 and θ1 respectively. ' The angles on both sides of the q-axis of the middle magnetic barrier are θ2 and θ2 ' The angles on both sides of the q axis of the inner magnetic barrier are θ3 and θ3 ' , Δθ1=|θ1 ′ -θ1|, Δθ2=|θ2 ′ -θ2|, Δθ3=|θ3 ′ -θ3|; The equivalent magnetic circuit model of the synchronous reluctance motor is established as follows: in, Based on the theoretical model, the relationship between the motor torque performance and the tail angle of the magnetic barrier is obtained, and the angle combinations θ1, θ2, θ3, and θ1 with higher output torque and lower torque pulsation are obtained through optimization. ' ,θ2 ' and θ3 ' .

4. The rotor for reducing torque ripple of a synchronous reluctance motor according to claim 3, characterized in that: The ratio of N1 to N2 is equal to the inverse ratio of the amplitude of the main harmonics of the first lamination and the second lamination obtained by the equivalent magnetic circuit model.

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