A skew-pole wound rotor for a brushless doubly-fed motor

Abstract

This utility model relates to the field of brushless doubly-fed motor technology, and more particularly to a skew-pole wound rotor for use in brushless doubly-fed motors. The skew-pole wound rotor includes a rotor body and coils. Large and small teeth protrude from the outer periphery of the rotor body. These large and small teeth are evenly distributed along the circumference of the rotor body, alternating, and spacers are provided between adjacent large and small teeth. The centerline of the spacers is inclined relative to the axis of the rotor body. Coils are wound on the large teeth, while no coils are wound on the small teeth. The coil span is smaller than the coil pole pitch, and the coils are self-closing, with no overlap between them. This utility model improves the electromagnetic performance and reduces harmonic content of the brushless doubly-fed motor by optimizing the rotor winding structure.

Description

Technical Field

[0001] This utility model relates to the field of motor technology, and in particular to a slanted-pole wound rotor for use in a brushless doubly fed motor. Background Technology

[0002] Brushless doubly fed motors are powered by grid power and frequency converter power separately. They are reliable in operation, require less capacity frequency converter power, and can use different voltage levels. They can operate as motors with variable frequency speed regulation and are also suitable as generators for wind or hydropower variable speed constant frequency power generation.

[0003] The stator of a brushless doubly-fed motor has two sets of windings with different pole pairs. The key to its good performance lies in the rotor. From a working principle perspective, there are various types of rotor structures, such as those using wound windings. However, these rotor structures mostly suffer from problems such as low conductor utilization, high harmonic content, and low power density. Although existing technologies have proposed some solutions to these problems, the wound winding structure still suffers from complex manufacturing processes and high processing costs. Utility Model Content

[0004] The purpose of this invention is to propose a skew-pole wound rotor for a brushless doubly fed motor, which improves the electromagnetic performance and reduces the harmonic content of the brushless doubly fed motor by optimizing the rotor winding structure.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A skewed-pole wound rotor for a brushless doubly-fed motor, wherein the stator windings of the brushless doubly-fed motor have pole pairs p1 and p2, and the equivalent pole pair number p of the skewed-pole wound rotor is... r =p1+p2;

[0007] The skew-pole wound rotor includes a rotor body and coils;

[0008] The outer periphery of the rotor body protrudes to form large and small teeth;

[0009] The large and small teeth are evenly distributed along the circumference of the rotor body, and a tooth groove is provided between adjacent large and small teeth. The center line of the tooth groove is inclined relative to the axis of the rotor body.

[0010] The large tooth is wound with a coil, while the small tooth is not wound with a coil.

[0011] The span y of the coil r The pole pitch τ of the coil is smaller than r Furthermore, the coils are self-closing connections, and there is no overlap between the coils.

[0012] Preferably, the winding coefficient of the coil satisfies:

[0013] k r =k yν k sk

[0014] Where, k yν k is the short-range coefficient. sk This is the tooth cogging coefficient.

[0015] Preferably, the short distance coefficient The cogging coefficient

[0016] Where v is the order of the higher harmonics that the target weakens;

[0017] y r The span of the coil;

[0018] τ r τ is the polar moment corresponding to the pole pairs p1 or p2. r =Z r / p r Z r The number of turns of the coil;

[0019] b sk The deflection angle of the center line of the tooth groove relative to the axis of the rotor body.

[0020] Preferably, p1 = 1 and p2 = 3;

[0021] The span y of the coil r =0.8τ r ;

[0022] The number of turns Z of the coil r =p r =p1+p2=4;

[0023] The number of grooves in the tooth is 2Z. r =2*4=8;

[0024] The number of large teeth and the number of small teeth are both 8 / 2 = 4.

[0025] Preferably, the deflection angle b sk = 4π / 15.

[0026] One of the above technical solutions has the following beneficial effects:

[0027] 1. Performance Improvement: The skewed pole structure weakens harmonic magnetic fields and reduces torque pulsation, significantly improving the smoothness of motor operation, reducing mechanical vibration and noise, and extending the service life of the motor; the design of the equivalent pole pair number enhances the coupling effect between the rotor and stator magnetic fields, improving the motor's operating efficiency and power density.

[0028] 2. Simplified Structure: The brushless doubly-fed motor eliminates the need for brushes and slip rings, reducing maintenance workload and potential failure points. The coils of the skew-pole wound rotor employ a self-closing, non-overlapping design, further simplifying the rotor winding structure and reducing manufacturing difficulty and cost.

[0029] 3. Flexible control: By adjusting the two pole pair magnetic fields of the stator winding, the motor can achieve a wide range of speed regulation and power control, meet the operating requirements under different working conditions, and improve the application adaptability of the motor and the flexibility of system control. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a slanted-pole wound rotor for a brushless doubly fed motor according to this utility model;

[0031] Figure 2 This is a top view schematic diagram of a slanted-pole wound rotor for a brushless doubly fed motor according to the present invention;

[0032] Figure 3 This is a schematic diagram of the angle of the tooth slots in a slanted-pole wound rotor of a brushless doubly fed motor according to the present invention;

[0033] In the attached diagram: rotor body 1, large tooth 2, small tooth 3, tooth groove 4, coil 5. Detailed Implementation

[0034] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0038] like Figure 1-3 As shown, a skew-pole wound rotor for a brushless doubly-fed motor is disclosed. The stator windings of the brushless doubly-fed motor have pole pairs p1 and p2, and the equivalent pole pair number p of the skew-pole wound rotor is also disclosed. r =p1+p2;

[0039] The skew-pole wound rotor includes a rotor body 1 and a coil 5;

[0040] The outer periphery of the rotor body 1 protrudes to form large teeth 2 and small teeth 3;

[0041] The large teeth 2 and small teeth 3 are evenly distributed along the circumference of the rotor body 1, and a tooth groove 4 is provided between adjacent large teeth 2 and small teeth 3. The center line of the tooth groove 4 is inclined relative to the axis of the rotor body 1.

[0042] The large tooth 2 is wound with a coil 5, while the small tooth 3 is not wound with a coil 5.

[0043] The span y of the coil 5 r The pole pitch τ of the coil 5 is smaller than that of the coil 5. r Furthermore, the coils 5 are self-closing connections, and there is no overlap between the coils 5.

[0044] The specific working principle of applying this skew-pole wound rotor to a brushless doubly-fed motor is as follows:

[0045] During the operation of a brushless doubly-fed motor, the rotating magnetic fields generated by the two different pole pair numbers p1 and p2 of the stator windings interact with the skewed-pole wound rotor. The equivalent pole pair number p of the skewed-pole wound rotor is... r =p1+p2, which enables the rotor to achieve efficient coupling with the stator magnetic field.

[0046] like Figure 1-3As shown, large teeth 2 and small teeth 3 are evenly distributed alternately on the circumference of the rotor body 1. Large teeth 2 are wound with coils 5, while small teeth 3 are not. Each large tooth 2 corresponds to one coil 5, and each coil is closed, ensuring that each slot 4 has only one coil side. There is no overlap between the coils, creating a unique magnetic circuit distribution. When the stator magnetic field rotates, the magnetic flux through the coils 5 passing through the large teeth 2 changes, and according to the principle of electromagnetic induction, an induced electromotive force is generated in the coils 5. Due to the span y of the coils 5... r The pole pitch τ of the coil 5 is smaller than that of the coil 5. r This means that by adopting a short-pitch design and self-closing connection with no overlap, the current distribution and magnetomotive force in each coil 5 are effectively controlled, thereby generating a rotor magnetic field that matches the stator magnetic field.

[0047] More importantly, the center line of slot 4 is inclined relative to the axis of rotor body 1, breaking the traditional symmetrical structure of the rotor and making the air gap magnetic field distribution more reasonable. This skewed pole structure can further weaken the harmonic magnetic field and reduce the torque pulsation caused by the slot 4 effect, making the motor run more smoothly. At the same time, by controlling the input of the stator winding, the interaction between the two pole pair magnetic fields is changed, thereby realizing the speed regulation and power transmission of the motor.

[0048] In summary, the beneficial effects of this skew-pole wound rotor include:

[0049] 1. Performance Improvement: The skewed pole structure weakens harmonic magnetic fields and reduces torque pulsation, significantly improving the smoothness of motor operation, reducing mechanical vibration and noise, and extending the service life of the motor; the design of the equivalent pole pair number enhances the coupling effect between the rotor and stator magnetic fields, improving the motor's operating efficiency and power density.

[0050] 2. Simplified Structure: The brushless doubly-fed motor eliminates the brush and slip ring structures, reducing maintenance workload and potential failure points. The coils 5 of the skew-pole wound rotor adopt a self-closing, non-overlapping design, further simplifying the rotor winding structure and reducing manufacturing difficulty and cost.

[0051] 3. Flexible control: By adjusting the two pole pair magnetic fields of the stator winding, the motor can achieve a wide range of speed regulation and power control, meet the operating requirements under different working conditions, and improve the application adaptability of the motor and the flexibility of system control.

[0052] To further explain, the winding coefficient of the coil 5 satisfies:

[0053] k r =k yν k sk

[0054] Where, k yν k is the short-range coefficient. sk This is the tooth cogging coefficient.

[0055] Specifically, the winding coefficient of coil 5 is determined by the short-pitch coefficient k. yν and tooth cogging coefficient k sk The product of these factors quantifies the modulation effect of the short-pitch design and skewed pole structure of coil 5 on the magnetomotive force waveform. When the stator magnetic field cuts the rotor coil 5, the short-pitch design changes the phase difference of the induced electromotive force of coil 5, while the tilt of slot 4 changes the air gap magnetic permeability distribution through spatial angular offset. The combined effect of these two factors enables the winding coefficient to suppress target harmonics of specific frequencies (such as the 5th and 7th harmonics) while ensuring the fundamental magnetic field strength.

[0056] To further explain, the short distance coefficient The cogging coefficient

[0057]

[0058] Where v is the order of the higher harmonics that the target weakens;

[0059] y r The span of the coil 5;

[0060] τ r τ is the polar moment corresponding to the pole pairs p1 or p2. r =Z r / p r Z r The number of turns of the coil 5;

[0061] b sk The deflection angle of the center line of the tooth groove 4 relative to the axis of the rotor body 1.

[0062] Specifically, the short distance coefficient k yν Through formula Quantifying the effect of short-pitch windings on fundamental and harmonic electromotive forces. When the span y r Less than the polar distance τ r When the phase difference of the fundamental electromotive force decreases, the phase difference of higher harmonics (such as the vth harmonic) increases proportionally, thereby weakening the harmonic components.

[0063] tooth cogging coefficient k sk Using formula By tilting the spatial phase offset of the tooth groove 4, the second harmonic of the v tooth is phase-cancelled in the air gap.

[0064] In summary, by adjusting the span y r and deflection angle b sk It can achieve targeted suppression of specific harmonics (such as the target weakened V-order harmonic).

[0065] To further clarify, p1 = 1 and p2 = 3;

[0066] The span y of the coil 5 r =0.8τ r ;

[0067] The equivalent pole pair number p of the skew-pole wound rotor r =p1+p2=1+3=4;

[0068] The number of turns Z of coil 5 r =p r =p1+p2=4;

[0069] The number of slots in the tooth groove 4 is 2Z. r =2*4=8;

[0070] The number of large teeth 2 and the number of small teeth 3 are both 8 / 2 = 4.

[0071] The deflection angle b sk = 4π / 15.

[0072] It is known that the setting of large tooth 2 is a necessary requirement for the principle of brushless doubly-fed motors, but setting only large tooth 2 will lead to excessive harmonics in the motor. The magnitude of harmonic content can be characterized by the winding coefficient of coil 5, where the values ​​of the 5th and 7th harmonics are relatively large. Theoretically, to completely eliminate the corresponding harmonics, the winding coefficient of the target harmonic should be designed to be 0. However, in actual engineering, this ideal state is difficult to achieve absolutely, and it can only be suppressed to an acceptable range through optimized design.

[0073] In this patent, the winding coefficient of coil 5 is defined as the product of the short-pitch coefficient and the skew coefficient. Specifically, to suppress the 5th harmonic, small teeth can be added to form a short-pitch structure; to suppress the 7th harmonic, the slot 4 can be set as an inclined structure to form a skew effect. If both short-pitch and skew designs are used, the content of the 5th and 7th harmonics can be significantly reduced, making the magnetomotive force waveform of the motor closer to the ideal sine waveform.

[0074] For the rotor winding design of a brushless doubly-fed motor with pole pairs p1 and p2, the number of turns of coil 5 on the rotor can be determined to be 4. If the design with 4 turns of coil 5 is used without any optimization, the harmonic content generated by the motor will be very high, as shown in the table below. In this case, the winding factor for all tooth harmonics is 1. With a short-pitch design, it can be observed that the harmonic content decreases with the increase of the number of harmonic pole pairs. Furthermore, by combining a skewed pole design, although the required winding factors for p1 and p2 are reduced, the harmonic content has decreased to a negligible level.

[0075]

[0076] Therefore, compared to conventional designs, the combination of short-pitch and skewed pole design, while sacrificing a small amount of fundamental winding coefficient (reducing from 1 to 0.5710), can achieve complete elimination of the 5th harmonic (winding coefficient of 0), significant suppression of the 7th harmonic (reducing from 0.9511 to 0.0690), and significant reduction of the 11th and higher harmonics (e.g., the 11th harmonic is reduced from 0.5878 to 0.1342, and the 13th harmonic from 0.9511 to 0.1404). This optimized design not only meets the fundamental requirements of brushless doubly-fed motors for large tooth structures, but also overcomes the limitations of single-structure optimization through multi-dimensional process innovation—the short-pitch design uses the slot pitch difference formed by small teeth to cut off the harmonic magnetic circuit, and the skewed pole design uses the slot tilt angle to cause spatial cancellation of the harmonic magnetic field. The synergistic effect of the two significantly improves the sinusoidality of the magnetomotive force waveform.

[0077] From an engineering practice perspective, this solution replaces "ideal elimination" with "controllability reduction," reducing harmonic losses while ensuring that the core performance of the motor (such as power transmission efficiency and speed range) remains unaffected. This approach is particularly suitable for scenarios with stringent requirements for low harmonics and high stability, such as wind power generation. Compared to traditional single-optimization methods, this multi-process collaborative approach to harmonic suppression better balances the "performance-cost-manufacturability" triangle in motor design, providing a quantifiable and replicable solution for the industrial application of brushless doubly-fed motors.

[0078] The technical principles of this utility model have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this utility model and should not be construed as limiting the scope of protection of this utility model in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this utility model without inventive effort, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A skew-pole wound rotor for a brushless doubly-fed motor, wherein the stator windings of the brushless doubly-fed motor have pole pairs p1 and p2, characterized in that: The equivalent pole pair number p of the skew-pole wound rotor r = p1 + p2; The skew-pole wound rotor includes a rotor body (1) and a coil (5); The outer periphery of the rotor body (1) protrudes to form large teeth (2) and small teeth (3); The large teeth (2) and small teeth (3) are evenly distributed along the circumference of the rotor body (1) alternately, and a tooth groove (4) is provided between adjacent large teeth (2) and small teeth (3), and the center line of the tooth groove (4) is inclined relative to the axis of the rotor body (1). The large tooth (2) is wound with a coil (5), while the small tooth (3) is not wound with a coil (5); The span y of the coil (5) r Less than the pole pitch τ of the coil (5) r And the coil (5) is connected from closed, each of the coil (5) has no overlap between each other.

2. A skewed pole winding rotor for a brushless doubly-fed machine according to claim 1, wherein The winding coefficients of the coil (5) satisfy: k r = k yν k sk Where, k yν k is the short-range coefficient. sk This is the tooth cogging coefficient.

3. A skewed pole winding rotor for a brushless doubly-fed machine according to claim 2, wherein the short pitch coefficient the cogging coefficient Where v is the order of the higher harmonics that the target weakens; y r The span of the coil (5); τ r τ is the polar moment corresponding to the pole pairs p1 or p2. r =Z r / p r Z r The number of turns of the coil (5); b sk is the angle of deflection of the center line of the tooth groove (4) with respect to the axis of the rotor body (1).

4. A skewed pole winding rotor for a brushless doubly-fed machine according to claim 3, wherein p1 = 1, p2 = 3; Span of the coil (5) The number of turns Z of the coil (5) r = p r = p1 + p2 = 4; The number of slots 2Z of the tooth slot (4) r = 2 * 4 = 8; The number of large teeth (2) and the number of small teeth (3) are both 8 / 2 = 4.

5. A skewed pole winding rotor for a brushless doubly-fed machine according to claim 4, wherein The deflection angle b sk = 4π / 15.

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