A stator slotted type double permanent magnet vernier motor and its design method

Abstract

This invention discloses a stator slotted type dual permanent magnet vernier motor and its design method. The motor structure includes a stator and a rotor. The stator includes a stator core, windings, and stator permanent magnets, while the rotor includes a rotor core and rotor permanent magnets. Each stator tooth is split into two smaller teeth for modulation, and the stator permanent magnets are respectively embedded in each split tooth. The rotor adopts a salient pole structure for modulation, and the rotor permanent magnets are respectively embedded in the rotor salient pole teeth. Air slots are sequentially spaced in the stator teeth, penetrating the stator core. Three-phase single-layer fractional-slot concentrated windings are wound on each slotted stator tooth. The design method of this invention starts from the harmonic contribution components of the original structure to torque. By directionally increasing the equivalent winding factor of the main operating wave and decreasing the equivalent winding factor of the lower harmonics through slotting within the stator phases, the amplitude of the main operating wave of the armature magnetic field is increased, while the non-operating waves such as lower harmonics are reduced.

Description

Technical Field

[0001] This invention relates to a stator slotted double permanent magnet vernier motor and its design method, belonging to the field of motors. The stator employs an interphase air slot structure design, giving the motor advantages such as high torque density, low torque ripple, low loss, and high power factor, making it suitable for applications in aerospace, marine propulsion, and other fields. Background Technology

[0002] Dual permanent magnet vernier motors have permanent magnets distributed on both the stator and rotor, achieving higher torque density than ordinary permanent magnet vernier motors while maintaining the same motor size. This makes them suitable for low-speed, high-torque applications such as wind power generation, oil field extraction, and radar turntables. However, their unique dual-side excitation structure already maximizes the distribution of excitation sources, making further improvements in torque density a hot research topic. Furthermore, vernier motors operate based on magnetic field modulation mechanisms and utilize multiple harmonics, typically requiring fractional-slot concentrated windings. This inevitably introduces low-order harmonics and other non-operating waves, increasing motor losses and torque ripple, which is detrimental to normal motor operation.

[0003] Chinese invention patent application number CN2021110283979.8, entitled "A Stator Modular Magnetic Field Modulation Motor with Low Harmonic Loss," discloses a structure that uses stator modular technology to reduce motor losses. However, while reducing motor losses, this structure inevitably increases the magnetic reluctance of the operating wave, resulting in a certain sacrifice in motor torque. Summary of the Invention

[0004] This invention addresses the shortcomings and defects of existing technologies by proposing a stator-slotted dual permanent magnet vernier motor and its design method. Starting from the harmonic torque contribution components of the original motor structure, it increases the equivalent winding factor of the main operating wave and decreases the equivalent winding factor of lower harmonics by directionally increasing the stator phase slots, thereby increasing the amplitude of the main operating wave in the armature magnetic field and decreasing the amplitude of lower harmonics. This invention effectively improves the motor's torque density, reduces torque ripple, and lowers motor losses while keeping other dimensional parameters unchanged, while also improving the motor's power factor.

[0005] To achieve the above objectives, the technical solution of the motor of the present invention is as follows: a stator slotted type double permanent magnet vernier motor, characterized in that: the motor includes a stator core, a rotor core, a stator permanent magnet, a rotor permanent magnet, and an armature winding, with an air gap between the stator and the rotor; the stator core includes 12 split teeth, each split tooth being split into 2 smaller teeth, participating in the modulation process, and 12 continuous pole stator permanent magnets are respectively embedded in each split tooth; the rotor core includes 19 salient pole teeth, participating in the modulation process, and 19 continuous pole rotor permanent magnets are respectively embedded in the rotor salient pole teeth; the stator core is sequentially spaced with air slots, the air slots penetrating the stator core, and three-phase single-layer fractional slot concentrated windings are respectively wound on each slotted stator tooth.

[0006] Furthermore, all stator and rotor permanent magnets are radially magnetized, with the magnetization direction pointing outwards from the center, so that the stator and rotor magnetic fields are positively superimposed to obtain optimal performance.

[0007] Furthermore, based on the bilateral excitation structure and bidirectional magnetic field modulation effect, the equivalent armature winding pole pair number mP w Number of stator teeth N s Number of permanent magnets in stator P s Rotor teeth number N r Number of permanent magnets in rotor P r The following relationship must be satisfied:

[0008]

[0009] Furthermore, air slots are opened in the stator core. The air slots are located in the center of the stator teeth, penetrate the stator core, and are connected to the stator permanent magnets. The number of air slots is half the number of stator teeth. The two adjacent stator teeth with slots do not have air slots, and the two adjacent stator teeth without slots have air slots, and so on at intervals.

[0010] Furthermore, the armature winding adopts a three-phase fractional slot concentrated winding, with each phase coil wound on an air-slotted stator tooth, and no coil wound on an unslotted stator tooth (slotted within the phase).

[0011] The technical solution of the design method of the present invention is as follows: a design method for a stator slotted type dual permanent magnet vernier motor, comprising the following steps:

[0012] Step 1: Based on the harmonic contribution torque components of the original motor structure, identify the working harmonics that contribute significantly to the positive torque of the motor.

[0013] Step 2: Based on the initial magnetomotive force function, derive the changes in the equivalent winding factors of each harmonic of the initial armature magnetic field after slotting within and between phases.

[0014] Step 3: Based on the magnetic field modulation theory, determine the changes in the harmonic content of the armature magnetic field of the in-phase slotted and inter-phase slotted armature after modulation by the rotor salient pole teeth, and select a better slotted structure in combination with the results of Step 1.

[0015] Step 4: Optimize the grooving parameters.

[0016] Furthermore, step 1 specifically includes: using Maxwell's stress tensor method to analyze the contribution of each order of harmonics in the original structure to the torque, and finding the harmonics that contribute the most to the positive torque of the motor. For the motor, the 19th and 24th working waves contribute the main torque of the motor.

[0017] Furthermore, step 2 specifically includes: stator air slots have two structures: in-phase slots and inter-phase slots. Based on the initial armature magnetomotive force functions of the two structures, the changes in the equivalent winding factors of each harmonic of the initial armature magnetic field after in-phase slotting and inter-phase slotting can be derived. For the motor, in-phase slotting can increase the equivalent winding factors of the 5th and 19th harmonics and decrease the equivalent winding factor of the 1st harmonic. Stator slotting has no significant effect on the permanent magnet magnetomotive force.

[0018] Furthermore, step 3 specifically includes: the change in the equivalent winding factor is positively correlated with the content of the initial armature magnetic field harmonics; the larger the equivalent winding factor of the harmonics, the larger the amplitude of the initial armature magnetic flux density of the harmonics; according to the magnetic field modulation theory, the 5th harmonic of the initial armature magnetic field will be modulated into the 24th harmonic by the 19 salient pole teeth of the rotor; the larger the amplitude of the 5th harmonic before modulation, the larger the amplitude of the 24th harmonic after modulation; combined with step 1, for the motor, the use of in-phase slotting can increase the main working harmonics contributing torque in the armature magnetic field and reduce non-working waves such as low-order harmonics, thereby increasing torque density, reducing torque pulsation, and reducing losses.

[0019] Furthermore, step 4 specifically includes: performing parameter scanning on the slot width. An excessively large slot width will cause saturation of the stator teeth, thereby sacrificing torque. The optimal slot width is 3mm.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The present invention has permanent magnets distributed on both the stator and rotor of the motor, and both the stator and rotor are salient pole modulation tooth structures. It also has a double-sided excitation structure and a bidirectional magnetic field modulation effect, which can maximize the torque density of the motor.

[0022] 2. The motor of the present invention can increase the main working harmonics contributing torque in the armature magnetic field by opening air slots in the stator phase, thereby further improving the torque density of the motor.

[0023] 3. The motor of the present invention reduces non-working waves such as low-order harmonics of the armature magnetic field by opening air slots in the stator phase, thereby reducing losses and torque pulsation.

[0024] 4. The motor of the present invention reduces the self-inductance of the motor and improves the power factor of the motor by opening air slots in the stator phase.

[0025] 5. The design method of the present invention aims to directionally increase or decrease the harmonics of the armature magnetic field. It is not limited to this type of motor and can provide a reference for the design of motors with different structures and different slot pole combinations. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the stator slotted type double permanent magnet vernier motor of the present invention;

[0027] Figure 2 This is a diagram showing the contribution of harmonics to torque in the traditional original structure.

[0028] Figure 3 This is a comparison diagram of the Fourier decomposition of permanent magnet flux density when the permanent magnets of a traditional original structure double permanent magnet vernier motor and a new stator slotted double permanent magnet vernier motor are used individually.

[0029] Figure 4 This is a Fourier decomposition comparison of the armature magnetic flux density of a traditional original structure double permanent magnet vernier motor and a new type of stator slotted double permanent magnet vernier motor when the armature windings act alone.

[0030] Figure 5 This is a schematic diagram showing the variation of torque performance of a novel stator slotted double permanent magnet vernier motor with slotting parameters;

[0031] Figure 6 This is a comparison chart of the load torque of a traditional original structure double permanent magnet vernier motor and a new type of stator slotted double permanent magnet vernier motor.

[0032] Figure 7 This is a comparison chart of the load torque ripple content between a traditional original structure double permanent magnet vernier motor and a new stator slotted double permanent magnet vernier motor.

[0033] Figure 8 and Figure 9 This is a comparison chart of losses between a traditional original structure dual permanent magnet vernier motor and a new type of stator slotted dual permanent magnet vernier motor.

[0034] Figure 10 This is a comparison chart of the power factors of a traditional original structure double permanent magnet vernier motor and a new type of stator slotted double permanent magnet vernier motor.

[0035] In the diagram: 1. Stator core; 2. Rotor core; 3. Stator permanent magnet; 4. Rotor permanent magnet; 5. Armature winding; 6. Air gap; 7. Air slot. Detailed Implementation

[0036] To make the objectives, technical solutions, and effects of this invention clearer, the invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 This is a structural diagram of a stator slotted type dual permanent magnet vernier motor according to the present invention. The selected dual permanent magnet vernier motor has 12 stator slots, 12 stator permanent magnet poles, and 19 rotor permanent magnet poles; wherein 1 is the stator core, 2 is the rotor core, 3 is the stator permanent magnet, 4 is the rotor permanent magnet, 5 is the armature winding, 6 is the motor air gap, and 7 is the stator air slot; the air gap is located between the stator and the rotor, and the air gap thickness is 0.7mm; the stator core includes 12 split teeth, each split tooth is split into 2 small teeth, which participate in the modulation process, and 12 continuous pole stator permanent magnets are respectively embedded in each split tooth; the rotor core includes 19 salient pole teeth, which participate in the modulation process, and 19 continuous pole rotor permanent magnets are respectively embedded in the rotor salient pole teeth.

[0038] All stator and rotor permanent magnets are radially magnetized, with the magnetization direction pointing outwards from the center, so that the stator and rotor magnetic fields are positively superimposed to achieve optimal performance.

[0039] Based on the bilateral excitation structure and bidirectional magnetic field modulation effect, the equivalent armature winding pole pair number mP w Number of stator teeth N s Number of permanent magnets in stator P s Rotor teeth number N r Number of permanent magnets in rotor P r The following relationship must be satisfied:

[0040]

[0041] The stator core has air slots, which are located in the center of the stator teeth, penetrate the stator core, and are connected to the stator permanent magnets. The number of air slots is half the number of stator teeth. The two adjacent stator teeth with slots do not have air slots, and the two adjacent stator teeth without slots have air slots, and so on.

[0042] The armature winding adopts a three-phase fractional slot concentrated winding, with each phase coil wound on an air-slotted stator tooth, and no coil wound on an unslotted stator tooth (slotted within the phase).

[0043] The stator slotted type dual permanent magnet vernier motor design method of the present invention includes the following steps:

[0044] Step 1: Based on the harmonic torque contribution components of the original motor structure, identify the working harmonics that contribute significantly to the positive torque of the motor.

[0045] By using the Maxwell stress tensor method, the contribution of each order of harmonics in the original structure to the torque is analyzed, and the harmonic that contributes the most to the positive torque of the motor is identified. Figure 2 The diagram shows the torque contribution of harmonics to a traditional dual permanent magnet vernier motor. As can be seen from the diagram, the 19th and 24th harmonics contribute the main torque of the motor.

[0046] Step 2: Based on the initial magnetomotive force function, derive the changes in the equivalent winding factors of each harmonic of the initial armature magnetic field after slotting within and between phases.

[0047] There are two structures for stator air-slotted designs: in-phase slotting and inter-phase slotting. Based on the initial armature magnetomotive force function of these two structures, the changes in the equivalent winding factors of each harmonic of the initial armature magnetic field after in-phase slotting and inter-phase slotting can be derived. The equivalent winding factor k of the traditional original structure... w_0 Equivalent winding factor k of stator phase slotted structure w_in Equivalent winding factor k of stator phase-to-phase slotted structure w_out They can be represented as follows:

[0048]

[0049]

[0050]

[0051] Where v represents the harmonic order.

[0052] For the aforementioned motor, in-phase slotting, compared to the traditional original structure, can increase the equivalent winding factor of the 5th and 19th harmonics and decrease the equivalent winding factor of the 1st harmonic, while inter-phase slotting, compared to the traditional original structure, will decrease the equivalent winding factor of the 5th and 19th harmonics; from Figure 3 It can be seen that the stator slots have no significant effect on the permanent magnet magnetomotive force.

[0053] Step 3: Based on the magnetic field modulation theory, determine the changes in the harmonic content of the armature magnetic field of the intraphase slotted and interphase slotted armature after the rotor salient pole teeth modulation, and select a better slotted structure in combination with the results of Step 1.

[0054] The initial armature magnetomotive force of the three-phase motor can be expressed by the following formula:

[0055]

[0056] Among them, F Aw (θ,t), F Bw (θ,t), F Cw (θ,t) represent the initial armature magnetomotive forces of phases A, B, and C, respectively, where θ is the mechanical angle and t is the time variable. m N represents the current amplitude. c mP is the number of turns in the winding. w ω is the number of pole pairs of the equivalent winding. e k is the electric angular frequency.w This is the winding factor.

[0057] In the formula, the change in the equivalent winding factor is positively correlated with the content of harmonics in the initial armature magnetomotive force. The initial armature magnetic field is the product of the initial armature magnetomotive force and the constant uniform air gap coefficient. Therefore, the larger the equivalent winding factor of the harmonics, the larger the amplitude of the initial armature magnetic flux density of that harmonic. According to the magnetic field modulation theory, the initial armature magnetic field will be modulated by the rotor salient pole teeth to generate new harmonics. The rotor modulation operator M... r (θ,t) can be expressed as:

[0058]

[0059] Where v is the harmonic order, θ is the mechanical angle, and N r Ω represents the number of salient pole teeth on the rotor. r Let a be the rotor rotation speed. r0 a rv These are the DC and AC components of the Fourier coefficients, respectively.

[0060] According to the magnetic field modulation theory, the initial armature magnetic field mP w The subharmonic will be N r Each rotor salient pole tooth modulates mP w ±vN r The 5th harmonic in the initial armature magnetic field is modulated into the 24th harmonic by the 19 salient pole teeth of the rotor. The larger the amplitude of the 5th harmonic before modulation, the larger the amplitude of the 24th harmonic after modulation. Combined with step 1, for the motor, in-phase slotting can increase the main working wave contributing torque in the armature magnetic field and reduce non-working waves such as lower harmonics. Figure 4 As shown, this increases torque density, reduces torque ripple, and reduces losses.

[0061] Step 4: Optimize the grooving parameters.

[0062] Perform parameter scanning on the slot width. Figure 5 This reflects the optimization process of slotting parameters. Excessive slotting width will cause saturation of stator teeth, thus sacrificing torque. The optimal slotting width is 3mm.

[0063] Figure 6 This diagram compares the load torque of a traditional dual permanent magnet vernier motor with a new type of stator slotted dual permanent magnet vernier motor. The in-phase slotting increases the main working wave contributing torque in the armature magnetic field without negatively impacting the permanent magnet magnetic field. Under the same rated current, the torque of the traditional original structure is 15.5 Nm, while the torque of the new stator slotted structure is 17 Nm, representing a 9.7% increase in torque compared to the traditional original structure.

[0064] Figure 7This chart compares the load torque ripple content of a traditional dual permanent magnet vernier motor with a new stator slotted design. The in-phase slotting reduces the non-working torque ripple caused by the armature magnetic field not contributing to the torque. Under the same conditions, the torque ripple of the traditional original structure is 0.71 Nm, while that of the new stator slotted structure is 0.39 Nm, reducing the torque ripple percentage from 4.6% to 2.3%.

[0065] Figure 8 and Figure 9 This is a comparison of losses between a traditional dual permanent magnet vernier motor with an original structure and a new type of dual permanent magnet vernier motor with a slotted stator. The slotting within the phases reduces the lower harmonics (1st harmonic) of the armature magnetic field. Under the same rated conditions, the iron loss and eddy current loss of the traditional original structure are 48W and 1.83W, respectively, while the iron loss and eddy current loss of the new type of slotted stator structure are 41W and 1.67W, respectively. The new type of slotted stator structure reduces iron loss by 14.6% and eddy current loss by 9% compared to the traditional original structure.

[0066] Figure 10 This chart compares the power factors of a traditional dual permanent magnet vernier motor with a new type of stator slotted dual permanent magnet vernier motor. The in-phase slotting reduces the motor's self-inductance. Under the same rated conditions, the power factor of the traditional original structure is 0.51, while the power factor of the new stator slotted structure is 0.58. The new stator slotted structure improves the power factor by 13.7% compared to the traditional original structure.

[0067] In summary, this invention relates to a stator-slotted dual permanent magnet vernier motor and its design method. The motor structure includes a stator and a rotor. The stator includes a stator core, windings, and stator permanent magnets, while the rotor includes a rotor core and rotor permanent magnets. Each stator tooth is split into two smaller teeth for modulation, and the stator permanent magnets are embedded in each split tooth. The rotor adopts a salient pole structure for modulation, and the rotor permanent magnets are embedded in the rotor salient pole teeth. Air slots are spaced apart in the stator teeth, penetrating the stator core. Three-phase single-layer fractional-slot concentrated windings are wound on each slotted stator tooth. The design method of this invention starts from the harmonic contribution to torque in the traditional original structure. By directionally increasing the equivalent winding factor of the main operating wave and decreasing the equivalent winding factor of lower harmonics through stator phase slotting, the amplitude of the main operating wave of the armature magnetic field is increased, while the amplitude of lower harmonics and other non-operating waves is decreased. Therefore, this invention can effectively improve the torque density of the motor, reduce torque ripple, reduce motor losses, and improve the power factor of the motor. It is suitable for fields with high requirements for motor torque and other performance, such as aerospace and ship propulsion, and has great application prospects.

[0068] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A design method of a slotted dual permanent magnet Vernier motor with a stator, characterized in that: The motor comprises a stator core, a rotor core, a stator permanent magnet, a rotor permanent magnet and an armature winding, and an air gap is left between the stator and the rotor; The stator core comprises 12 split teeth, each split tooth is split into two small teeth, participates in the modulation process, and 12 continuous pole stator permanent magnets are embedded in each split tooth respectively; The rotor core comprises 19 salient pole teeth, participates in the modulation process, and 19 continuous pole rotor permanent magnets are embedded in the rotor salient pole teeth respectively; The stator core is spaced apart by air slots in sequence, the air slots pass through the stator core, and three-phase single-layer armature windings are wound on each slotted stator tooth respectively; The air slots are located in the middle of the stator tooth part, pass through the stator core, are connected with the stator permanent magnet, the number of air slots is half of the number of stator teeth, the adjacent two stator teeth of the slotted stator tooth are not provided with air slots, the adjacent two stator teeth of the unslotted stator tooth are provided with air slots, and the slotted stator teeth are spaced apart in sequence; The armature winding adopts three-phase fractional slot concentrated winding, each phase coil is wound on the slotted stator tooth with air slots, and no coil is wound on the unslotted stator tooth, that is, the slot is opened in the phase. The design method comprises the following steps: Step 1, using the Maxwell stress tensor method, according to the harmonic torque component contribution of the original structure motor, the working harmonic with larger contribution to the motor positive torque is found out; Step 2, according to the initial magnetomotive force function, the change of the equivalent winding factor of each harmonic of the initial armature magnetic field after the slot opening in the phase and between the phases is deduced; The step 2 specifically comprises: the stator open air slot has two structures of intra-phase slotting and inter-phase slotting, the change of the initial armature magnetic field harmonic equivalent winding factor after the intra-phase slotting and the inter-phase slotting can be derived according to the initial armature magnetic motive function of the two structures, the equivalent winding factor k w_0 of the traditional original structure w_in of the stator intra-phase slotting structure w_out can be respectively represented as: ； ； ； Wherein v is the harmonic order; The three-phase initial armature magnetomotive force of the motor can be expressed by the following formula: ； where F Aw (θ, t), F Bw (θ, t), F Cw (θ, t) are the initial armature EMFs of the three phases A, B, C, respectively, θ is the mechanical angle, t is the time variable, I m is the current amplitude, N c is the number of turns, mP w is the equivalent number of pole pairs, ω e is the electrical angular frequency, k w is the winding factor; Step 3, according to the magnetic field modulation theory, the change of the harmonic content of the armature magnetic field after the modulation of the rotor salient pole teeth is judged, and the optimal slotting structure is selected in combination with the result of step 1; Step 4, the slotting parameters are optimized.

2. The design method of a stator slotted dual permanent magnet Vernier motor according to claim 1, characterized in that, All the stator permanent magnets and the rotor permanent magnets are radially magnetized, the magnetization direction is outward away from the center, so that the stator and rotor magnetic fields are positively superimposed to obtain the best performance.

3. The design method of a stator slotted dual permanent magnet Vernier motor as claimed in claim 1, characterized in that, According to the double-sided excitation structure and the bidirectional magnetic field modulation effect, the equivalent armature winding pole pair number mP w , the stator tooth number N s , the stator permanent magnet number P s , the rotor tooth number N r , the rotor permanent magnet number P r Meet the following relationship: 。 4. The method of designing a stator slotted dual permanent magnet Vernier motor as claimed in claim 1, wherein, The specific process of step 1 is: the contribution of each order harmonic to the torque in the original structure is analyzed, and the harmonic with the largest contribution to the motor positive torque is found out. For the motor, the 19th and 24th working waves contribute to the main torque of the motor.

5. The method of designing a stator slotted dual permanent magnet Vernier motor as claimed in claim 1, wherein, Step 2 further comprises: for the motor, the slot opening in the phase can increase the equivalent winding factor of the 5th and 19th harmonics and reduce the equivalent winding factor of the 1st harmonic; the stator slotting has no obvious effect on the permanent magnet magnetomotive force.

6. The method of designing a stator slotted dual permanent magnet Vernier motor as claimed in claim 1, wherein, The specific process of step 3 is: the change of the equivalent winding factor is positively correlated with the content of the initial armature magnetic field harmonic, the larger the equivalent winding factor of the harmonic, the larger the initial armature magnetic field amplitude of the harmonic; according to the magnetic field modulation theory, the 5th harmonic of the initial armature magnetic field will be modulated to the 24th harmonic by the 19 salient pole teeth of the rotor, the larger the amplitude of the 5th harmonic before modulation, the larger the amplitude of the 24th harmonic after modulation; in combination with step 1, for the motor, the slot opening in the phase can increase the main working wave of the armature magnetic field which contributes to the torque and reduce the low-order harmonic and non-working wave, thereby improving the torque density, reducing the torque ripple and reducing the loss.

7. The method of designing a stator slotted dual permanent magnet Vernier motor as claimed in claim 1, wherein, The specific process of step 4 is: the slot width is scanned, too large slot width will cause the saturation of the stator tooth and thus sacrifice the torque, and the optimal slot width is 3mm.

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