Asymmetric rotor suitable for double-groove triangular wave modulation of induction motor

Abstract

The invention discloses an asymmetric rotor suitable for double-groove triangular wave modulation of an induction motor, and the rotor comprises a rotor iron core, the rotor iron core is provided with a plurality of convex grooves, the convex grooves of the rotor are of a straight groove structure, and the rotor with double distributed grooves is modulated in the spatial position. The rotor slot spacing and the rotor slot width are changed by using a triangular wave function, so that the space position angle of the rotor is arranged according to a triangular wave function mode. According to the scheme, the arrangement mode of the rotor slots is changed through double-slot modulation and triangular wave modulation, on the premise that notching is facilitated, electromagnetic noise and additional loss of the motor can be reduced, synchronous additional torque can be eliminated, the starting performance can be improved, and meanwhile it is guaranteed that the running performance of the motor is basically not affected. The structure is simple, the electromagnetic noise and additional loss of the motor are reduced, the synchronous additional torque is eliminated, the starting performance is obviously improved, and the universality is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of motor production-related equipment, and in particular to an asymmetric rotor with double slots and triangular wave modulation suitable for an induction motor. Background Art

[0002] Squirrel-cage induction motors typically use skewed slots to mitigate the additional losses and noise caused by harmonic magnetic fields. In cast aluminum rotors without slot insulation, skewed slots generate induced potentials and transverse currents between adjacent rotor bars, leading to additional losses. The skewed slots also affect the motor's starting performance. High-voltage, high-power induction motor rotors with skewed slots induce significant torsional torque, which in turn causes torsional vibration and compromises the rotor's mechanical strength. Straight slots in induction motor rotors also generate significant electromagnetic vibration and noise. Therefore, there is an urgent need for new rotor structures that can effectively mitigate the negative effects of skewed slots, such as increased electromagnetic noise and reduced starting performance. Summary of the Invention

[0003] The present invention proposes a double-slot triangular wave modulated asymmetric rotor suitable for an induction motor, which aims to solve the problems existing in the background technology, reduce the electromagnetic noise of the induction motor, and improve the starting performance of the induction motor.

[0004] The present invention provides an asymmetric rotor with double slots and triangular wave modulation suitable for an induction motor, comprising a rotor core with a plurality of rotor slots formed thereon. The rotor slots are convex slots, and rotor teeth are formed between any two adjacent convex slots.

[0005] Beneficial effects:

[0006] By modifying the rotor slot arrangement through a dual-slot triangular wave modulation method, the invention reduces motor electromagnetic noise and parasitic losses, improves starting performance, and substantially maintains the motor's operating performance while facilitating machining of the rotor slots. This invention boasts a simple structure, significantly reduces motor electromagnetic noise and parasitic losses, and improves starting performance, offering broad versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A diagram showing a rotor slot distribution structure of an asymmetric rotor with double-slot triangular wave modulation suitable for an induction motor after double-slot modulation according to an embodiment of the present invention;

[0008] Figure 2 A diagram showing a rotor slot distribution structure of an asymmetric rotor with double-slot triangular wave modulation suitable for an induction motor according to an embodiment of the present invention after double-slot triangular wave modulation;

[0009] Figure 3 is the spatial distribution of air gap magnetic density;

[0010] Figure 4 is the FFT (Fast Fourier Decomposition) of the air gap magnetic density spatial distribution. DETAILED DESCRIPTION

[0011] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention, and are not to be construed as limiting the present invention.

[0012] The following description uses the YKK5004-6 high-voltage induction motor as an example. This motor has a rated output power of 900 kW, a rated voltage of 10 kV, and six poles. Its stator outer diameter is 850 mm, its stator inner diameter is 590 mm, its rotor inner diameter is 350 mm, its air gap is 1.8 mm, its stator core has 72 straight slots, and it has a double-layer winding. For this high-voltage induction motor, the stator structure remains unchanged; only the rotor slot distribution is modulated with a two-slot triangular wave to achieve an uneven rotor slot distribution.

[0013] Figure 1 A diagram showing a rotor slot distribution structure of an asymmetric rotor with double-slot triangular wave modulation suitable for an induction motor after double-slot modulation according to an embodiment of the present invention; Figure 2 FIG. 1 is a diagram showing the rotor slot distribution structure of an asymmetric rotor with double-slot triangular wave modulation suitable for an induction motor according to an embodiment of the present invention after double-slot triangular wave modulation. Figure 1 and Figure 2 As shown, the asymmetric rotor includes a rotor core, which is provided with a plurality of rotor slots. The rotor slots are convex slots, which are beneficial to improving the starting performance of the motor. A rotor tooth portion is formed between any two adjacent convex slots. When the slot depth is large, the punching sheet utilization area is larger, which can effectively reduce aluminum consumption and improve the efficiency of the motor. The rotor core is provided with a plurality of rotor slots.

[0014] In one embodiment, the asymmetric rotor is a cast aluminum rotor, and the rotor core is provided with 72 convex slots distributed in a double-slot sinusoidal wave modulation pattern.

[0015] In one embodiment, the rotor slots are closed straight slots or semi-closed straight slots, and the convex slots have different widths to ensure that the ratio of the slot width to the tooth width on the outer diameter of the rotor is the same.

[0016] In one embodiment, the rotor slot is a convex slot, the upper half of which is a parallel slot structure and the lower half of which is a parallel tooth structure.

[0017] In one embodiment, the rotor slots are first modulated as a double slot and then modulated as a triangular wave to obtain unevenly distributed rotor slots, including:

[0018] Phase 1: Dual-slot modulation for evenly distributed rotor slots: Two different rotor slots are combined into one rotor.

[0019] The first stage can specifically include: a. Determine the rated power, rated voltage, and number of poles of the motor. By consulting the typical product data sheet of the motor, determine the stator outer diameter, rotor outer diameter, rotor inner diameter, and number of stator slots of the motor. At this time, there are multiple options for the number of rotor slots. Different options have different effects on various performance of the motor. Combining two different rotor slots into one rotor can combine the excellent performance of the two rotor slot distributions. b. Define two different stator and rotor slot combinations Qs:Qr1 and Qs:Qr2, where the number of stator slots Qs remains unchanged. The number of slots Qr1 and Qr2 differ between the two rotors. One of the rotors has fewer stator slots Qr1 than the number of stator slots Qs, and the other has more stator slots Qr2 than the number of stator slots Qs. The slot shape and radial depth of each part of the two rotor slots are the same, and only the slot width is different. The slot width of the rotor with a larger number of slots is smaller. The rotor slots of the two stator and rotor slot combinations are combined according to the ratio Qr1:Qr2 of the rotor slot numbers of their respective slot combinations. After the combination, the total number of rotor slots is Qr = (Qr1+Qr2) / 2, which is equal to the number of stator slots. This eliminates the cogging effect that is obvious in the symmetrical rotor slot structure, effectively suppresses the main noise source caused by parasitic induction waves - type 2 radial force waves, and obtains better noise characteristics.

[0020] The following is a specific example: the number of stator slots Qs is fixed to 72, and two slot combinations 72 / 56 and 72 / 88 are selected, that is, Qr1 is selected as 56 and Qr2 is selected as 88. Figure 1 As shown, the total number of rotor slots after combination is Qr = (Qr1+ Qr2) / 2 = (56+88) / 2 = 72 = Qs, Qr1: Qr2 = 56:88 = 7:11, so the rotors with two slot combinations are combined in a ratio of 7:11, and a total of 4 groups are combined to form the modulated rotor slots. In the two slot combinations, the rotor slots of the same slot combination are 360° / 88 = 4.09° and 360° / 56 = 6.43° apart, respectively, and the rotor slots of different slot combinations are (360°-40×4.09°-24×6.43°) / 4 = 5.26° apart.

[0021] The second stage: Modulate the spatial position of the double-slot rotor, use the triangular wave function to obtain the spatial position of each rotor slot in this stage, and change the rotor slot pitch again so that the rotor spatial position angle is arranged in the manner of the triangular wave function, thereby changing the situation where the rotor slot pitch of the traditional induction motor is equal. The expression of the spatial position angle of each rotor slot after modulation is:

[0022] ,

[0023] Where, is the rotor slot spatial position angle, is the number of rotor slots, and is the modulation coefficient, and their values ​​are generally integer multiples of the number of motor poles.

[0024] The expression of the width of each rotor slot after modulation is:

[0025] ,

[0026] Where, For the The rotor slot width, is the first rotor slot width.

[0027] There are three situations in which the rotor slot spacing size is caused by double-slot modulation. Since the triangular wave modulation distribution is based on the double-slot modulation distribution, the rotor slot angle distribution after double-slot triangular wave modulation is obtained by combining three different triangular wave bands. The rotor slot spatial position angle is solved according to the triangular wave modulation function. The size is 12, The size is set to 0, and the rotor slot width is solved according to the modulated rotor slot width function.

[0028] In one embodiment, the rotor slot distribution should ensure that the ratio of the sum of the slot widths to the sum of the tooth widths on the rotor outer diameter before and after modulation is the same to avoid introducing additional rotor slot harmonics.

[0029] In one embodiment, when the rotor slots utilize dual-slot modulation, the rotor slots of the two slot combinations are combined according to the ratio Qr1:Qr2 of the rotor slot counts of their respective slot combinations. When selecting Qr1 and Qr2, it is preferable to ensure that the total rotor slot count Qr = (Qr1 + Qr2) / 2, which is equal to the number of stator slots, is equal to the total number of rotor slots after combination, to better suppress electromagnetic noise. If the total rotor slot count after combination is not equal to the number of stator slots, fewer slot combinations are available that achieve better noise performance.

[0030] In a specific example, a motor with a double-slot triangular wave modulated rotor ( Figure 2 The rotor structure shown in the figure is operated under rated conditions, and the spatial distribution of the air gap flux density is as follows: Figure 3 As shown, the FFT (Fast Fourier Decomposition) of the air gap magnetic density spatial distribution is as follows Figure 4 As shown in the figure, the magnitude of the high-order magnetic flux density component is expressed as a percentage of the basic component value (taken as 100%). The high-order magnetic flux density component is significantly reduced and the spectrum range is widened, indicating that the harmonic magnetic field content that generates motor electromagnetic noise, additional loss and synchronous additional torque is reduced.

[0031] It should be understood that the orientation or positional relationship indicated in the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0032] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any solution obtained by any technician familiar with the technical field within the technical scope disclosed by the present invention and by equivalent replacement or modification based on the technical solution and inventive concept of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A double-slot triangular wave modulated asymmetric rotor suitable for an induction motor, characterized in that: The invention comprises a rotor core, wherein a plurality of rotor slots are formed on the rotor core, the rotor slots are convex slots, and a rotor tooth portion is formed between any two adjacent convex slots.

2. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 1, characterized in that: The asymmetric rotor is a cast aluminum rotor with 72 convex slots in the rotor core distributed in a double-slot sinusoidal wave modulation pattern.

3. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 1, characterized in that: The rotor slots are closed straight slots.

4. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 1, characterized in that: The rotor slot is a convex slot, the upper part of which is a parallel slot structure and the lower part of which is a parallel tooth structure.

5. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 1, characterized in that: The rotor slots are first modulated as double slots and then modulated as triangular waves to obtain unevenly distributed rotor slots.

6. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 5, characterized in that: Modulation of the rotor slots includes: Phase 1: Double-slot modulation is applied to evenly distributed rotor slots, combining two different rotor slots into one rotor; The second stage: The spatial position of the double-slot rotor is modulated, and the spatial position of each rotor slot in this stage is obtained using a triangular wave function. The rotor slot pitch is changed again so that the spatial position angle of the rotor is arranged according to the triangular wave function, thereby changing the situation where the rotor slot pitch of the traditional induction motor is equal.

7. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 6, characterized in that: Double-slot modulation follows the principle that the total number of rotor slots after modulation is equal to the number of stator slots.

8. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 6, characterized in that: After double-slot modulation, the rotor slot spacing is changed using a triangular wave function so that the rotor's spatial position angle is arranged in the manner of a triangular wave function. The expression for the modulated rotor slot spatial position angle is: ， in, is the rotor slot spatial position angle, is the number of rotor slots, and is the modulation coefficient, and both are integer multiples of the number of motor poles.

9. The double-slot triangular wave modulated asymmetric rotor suitable for an induction motor according to claim 8, characterized in that: The expression of the width of each rotor slot after first double-slot modulation and then triangular wave modulation is: ， in, For the The rotor slot width, is the first rotor slot width.

10. The asymmetric rotor with double slots and triangular wave modulation suitable for induction motor according to claim 6, characterized in that: The rotor slot distribution ensures that the ratio of the sum of the slot widths to the sum of the tooth widths on the rotor outer diameter is the same before and after modulation.

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