Novel doubly-fed vernier motor

Abstract

The invention discloses a novel doubly-fed vernier motor, and belongs to the technical field of vernier motors, the novel doubly-fed vernier motor comprises a stator, a rotor and an air gap, the air gap is arranged between the stator and the rotor, the stator comprises stator teeth, stator slots and stator windings, the stator slots are arranged between the adjacent stator teeth, the stator windings are arranged in the stator slots, and the stator windings are arranged in the stator slots. The stator winding comprises a stator slot and a stator winding, the rotor comprises a rotor slot and a rotor winding, the rotor slot is arranged on the surface of the rotor, the rotor winding is arranged in the rotor slot, and both the stator winding and the rotor winding are double-layer windings. According to the novel doubly-fed vernier motor, different numbers of pole pairs of the stator winding and the rotor winding are set, and the stator slots with larger openings are matched, so that a magnetic gear effect is generated, the magnetic field modulation capability of the motor is improved, the average torque and the operation efficiency of the motor are improved, and the service life of the motor is prolonged. And the motor has the advantages of wide rotating speed range and adjustable power factor.

Description

Technical Field

[0001] The present invention relates to the technical field of vernier motors, and in particular to a novel double-fed vernier motor. Background Art

[0002] A brushed doubly-fed motor, also known as an AC-excited motor, has a set of windings on its stator and rotor, respectively. Depending on the winding connection method, it can flexibly operate in a variety of operating modes, including synchronous, asynchronous, and doubly-fed. In doubly-fed mode, the stator winding is directly connected to the grid, while the rotor winding is connected to a back-to-back AC inverter via brushes and slip rings. The rotor windings of a brushed doubly-fed motor typically have a low voltage, and the power flowing through them is also related to the motor's slip, resulting in a relatively small converter capacity. Brushed doubly-fed motors offer a simple structure, durability, high capacity, a wide speed range, and four-quadrant operation. They are widely used in wind power generation, pumped hydro storage, and flexible power conditioners.

[0003] The key to improving the torque density of brushless doubly-fed motors lies in improving the stator-rotor topology and optimizing motor parameters. Conventional structural optimization involves changing the rotor winding arrangement, such as using a special distributed winding, to reduce air-gap magnetomotive force harmonics and improve operating efficiency. However, this approach lacks innovation in the doubly-fed motor's topology and fails to significantly improve torque density. Summary of the Invention

[0004] The purpose of the present invention is to provide a new type of doubly fed vernier motor. By setting different pole pairs of the stator and rotor windings and coordinating the stator slots with larger openings, a magnetic gear effect is generated, thereby improving the magnetic field modulation capability of the motor, thereby improving the average torque and operating efficiency of the motor. In addition, the motor has the advantages of a wide speed range and an adjustable power factor.

[0005] To achieve the above objectives, the present invention provides a novel doubly-fed vernier motor, comprising a stator, a rotor, and an air gap, wherein the air gap is provided between the stator and the rotor, the stator comprising stator teeth, stator slots, and stator windings, the stator slots being provided between adjacent stator teeth, the stator windings being provided within the stator slots, the rotor comprising rotor slots and rotor windings, the rotor slots being provided on the rotor surface, the rotor windings being provided within the rotor slots, and both the stator winding and the rotor winding being double-layer windings;

[0006] The number of pole pairs of the motor stator winding is different from that of the rotor winding. The stator teeth with larger openings are used to form a magnetic field modulation effect. The number of main pole pairs of the stator is p s The number of main pole pairs of the rotor is p r and the stator slot number Z s There is a certain mathematical relationship between them, namely p s +pr =Z s , p s 、p r Are positive integers and are not equal.

[0007] Preferably, the pole-slot matching of the stator and rotor should satisfy: Zs = mk·GCD(Zs,2ps), Zr = nk·GCD(Zr,2pr), where k = 1, 2, 3, ..., m and n are the phase numbers of the stator and rotor windings respectively, and GCD is the greatest common divisor.

[0008] Preferably, the number of stator winding pole pairs ps of the magnetic field modulation permanent magnet motor is usually set to be small (ps=1-2), and the number of stator slots Zs and the number of rotor winding pole pairs pr are set to be large to obtain a higher average torque.

[0009] Preferably, the stator slots are flat-bottomed slots, and the slotting ratio of the stator slots is greater than 0.3 and less than 0.9.

[0010] Preferably, the modulated excitation magnetic field in the air gap includes multiple harmonic components modulated by the stator teeth, and the pole pairs thereof include p r ±Z s 、3p r ±Z s 、5p r ±Z s 、p r ±2Z s 、3p r ±2Z s The modulated armature magnetic field in the air gap contains multiple harmonic components modulated by the stator teeth, and the number of pole pairs includes p s ±Z s 、3p s ±Z s 、5p s ±Z s 、p s ±2Z s 、3p s ±2Z s .

[0011] Therefore, the present invention adopts the above-mentioned new type of doubly fed vernier motor, and by increasing the stator slot opening ratio, sets the stator winding and the rotor winding as double-layer distributed windings, thereby improving the magnetic field modulation capability of this motor, thereby improving the average torque and operating efficiency of the motor, and this motor has the advantages of a wide speed range and adjustable power factor.

[0012] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a cross-sectional view of a novel double-fed vernier motor according to an embodiment of the present invention;

[0014] Figure 2 This is a comparison chart of the average torque and operating efficiency of a doubly-fed vernier motor provided by an embodiment of a novel doubly-fed vernier motor of the present invention and two other traditional doubly-fed motors.

[0015] Reference numerals

[0016] 1. Rotor; 11. Rotor slots; 12. Rotor winding; 2. Air gap; 3. Stator; 31. Stator teeth; 32. Stator slots; 33. Stator winding. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" 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 object being described changes, the relative positional relationship may also change accordingly.

[0019] like Figure 1 As shown, the present invention provides a doubly fed vernier motor, which includes a rotor 1, an air gap 2, and a stator 3 from the inside out. The rotor 1 includes rotor slots 11 and rotor windings 12. The rotor windings 12 serve as excitation units to generate excitation source magnetomotive force. The air gap 2 is a key component for the motor to achieve electromagnetic-mechanical energy conversion. The stator 3 includes stator teeth 31, stator slots 32, and stator windings 33. The stator teeth 31 are magnetic field modulation units that establish a series of magnetomotive force harmonic components. The stator slots 32 are flat-bottomed slots. The stator windings 33 use double-layer distributed windings and are arranged horizontally. They act as a spatial harmonic filter to extract effective air gap 2 magnetic flux density harmonic components for induced flux linkage and electromotive force, and suppress some high-order invalid harmonics.

[0020] Assume that the number of main pole pairs of the rotor winding 12 is p r , the number of main pole pairs of stator winding 33 is p s , stator teeth 31 number is Z s, the three must satisfy the "harmony and modulation" coordination relationship, that is, Z s =p r +p s .

[0021] The stator slots 32 are flat-bottomed, with an opening ratio greater than 0.3 and less than 0.9. The reduced number of slots, combined with increased slot width and depth, creates salient-pole modulation units, enabling coupling of stator magnetic fields with varying pole pairs, thereby utilizing the magnetic gearing effect to increase average torque. Furthermore, the new stator windings 33 save on copper wire length, reducing motor losses and improving operating efficiency.

[0022] The modulated excitation magnetic field within air gap 2 includes multiple harmonic components modulated by stator teeth 31, with pole pairs of pr±Zs, 3pr±Zs, 5pr±Zs, pr±2Zs, and 3pr±2Zs. Similarly, the modulated armature magnetic field within air gap 2 includes multiple harmonic components modulated by stator teeth 31, with pole pairs of ps±Zs, 3ps±Zs, 5ps±Zs, ps±2Zs, and 3ps±2Zs.

[0023] The winding function of the rotor winding 12 is

[0024]

[0025] Where φ is the mechanical angle along the circumference of air gap 2 in the stationary coordinate system, N r is the number of series turns per pole and per phase of the rotor winding, β r is the short-distance mechanical angle, q r is the number of slots per pole and per phase, α r is the slot electrical angle.

[0026] Without considering the air gap modulation, the three-phase rotor winding excitation unit generates a source magnetomotive force, which can be expressed by Fourier expansion of the winding function:

[0027]

[0028] If only the fundamental wave component is considered, the magnetomotive force of the excitation source can be simplified as

[0029]

[0030] For the stator modulation unit, the function C S represents the discontinuous interval occupied by stator tooth 31

[0031]

[0032] ε is the stator slot opening ratio, ε∈[0,1]. Assuming that the stator slot depth is much larger than the air gap width and all magnetic lines of force are distributed in the radial direction, the stator tooth part inverse air gap function gs -1 (φ,θs) is 1 / g, and the stator slot part is 0. Then the unit traveling wave source excitation magnetomotive force after the stator slot modulation operator is:

[0033]

[0034] After Fourier decomposition, the modulated magnetomotive force is

[0035]

[0036] in,

[0037]

[0038] After the unit cosine source excitation magnetomotive force is modulated by the stator teeth, the generated magnetomotive force harmonic components are divided into three categories, and their pole pairs are p r 、Z s -p r and Z s +p r , its amplitude can be converted by three magnetic field coefficients C p 、C sum and C dif The magnetic field conversion coefficient of a doubly-fed vernier motor is independent of the pole pair number and is primarily influenced by the stator slot opening ratio ε. If only fundamental modulation is considered, the magnetic field conversion coefficient is maximized when ε = 0.5, resulting in the maximum average torque.

[0039] Combine Figure 2 It can be seen that compared with conventional brushless doubly fed motors, the doubly fed vernier motor proposed in this application can change the modulation mode of the air gap 2 magnetic field and the torque output characteristics. Taking the doubly fed operating mode as an example, under rated conditions, the average torque of the doubly fed vernier motor with two pairs of poles in the stator 3 and four pairs of poles in the rotor 1 is 418Nm, while the average torque of the doubly fed motor with two pairs of poles is 403Nm, ​​and the average torque of the doubly fed motor with four pairs of poles is 398Nm; the efficiencies of the three are 97.4%, 95.6%, and 95.9%, respectively. It can be seen that while increasing the torque output capacity, the doubly fed vernier motor can also reduce motor losses and improve operating efficiency to a certain extent, and has excellent external characteristics.

[0040] Compared to traditional vernier motors, the doubly-fed vernier motor provided by this invention offers the advantages of a wide speed regulation range and adjustable power factor. The doubly-fed vernier motor has two sets of windings, stator and rotor, connected to a back-to-back converter. By adjusting the frequency of the rotor windings, the motor's speed can be easily adjusted. Using vector control, the motor's active and reactive power can be decoupled, enabling four-quadrant operation, and the power factor can be adjusted over a wide range.

[0041] Therefore, the present invention adopts the above-mentioned new type of doubly fed vernier motor, and by increasing the stator slot opening rate, sets the stator winding and the rotor winding as double-layer distributed windings, thereby improving the magnetic field modulation capability of this motor, thereby improving the average torque and operating efficiency of the motor. In addition, this motor has the advantages of high reliability, strong fault tolerance, wide speed range, and adjustable power factor.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A new type of double-fed vernier motor, characterized by: The invention comprises a stator, a rotor and an air gap, wherein the air gap is provided between the stator and the rotor, the stator comprises stator teeth, stator slots and stator windings, the stator slots are provided between adjacent stator teeth, and the stator windings are provided inside the stator slots, the rotor comprises rotor slots and rotor windings, the rotor slots are provided on the rotor surface, and the rotor windings are provided inside the rotor slots, and both the stator winding and the rotor winding are double-layer windings; The number of pole pairs of the motor stator winding is different from that of the rotor winding. The stator teeth with larger openings are used to form a magnetic field modulation effect. The number of main pole pairs of the stator is p s The number of main pole pairs of the rotor is p r and the stator slot number Z s There is a certain mathematical relationship between them, namely p s +p r =Z s , p s 、p r Are positive integers and are not equal.

2. The novel double-fed vernier motor according to claim 1, characterized in that: The pole slot matching of the stator and rotor should satisfy: Z s =mk·GCD(Z s ,2p s ),Zr=nk·GCD(Z r ,2p r ), where k = 1, 2, 3, …, m and n are the phase numbers of the stator and rotor windings respectively, and GCD is the greatest common divisor.

3. The novel double-fed vernier motor according to claim 1, characterized in that: The number of stator winding pole pairs p of the field modulation permanent magnet motor s Usually set to a smaller value (p s =1~2), number of stator slots Z s and the number of rotor winding pole pairs p r Set it larger to get a higher average torque.

4. The novel double-fed vernier motor according to claim 1, characterized in that: The stator slots are flat-bottomed slots, and the slotting ratio of the stator slots is greater than 0.3 and less than 0.

9.

5. The novel double-fed vernier motor according to claim 1, characterized in that: The modulated excitation magnetic field in the air gap includes multiple harmonic components modulated by the stator teeth, and the pole pairs include p r ±Z s 、3p r ±Z s 、5p r ±Z s 、p r ±2Z s 、3p r ±2Z s The modulated armature magnetic field in the air gap contains multiple harmonic components modulated by the stator teeth, and the number of pole pairs includes p s ±Z s 、3p s ±Z s 、5p s ±Z s 、p s ±2Z s 、3p s ±2Z s .

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