Vernier permanent magnet fault-tolerant motor with function multiplexing unit

Abstract

The invention discloses a vernier permanent magnet fault-tolerant motor with a function multiplexing unit, and belongs to the technical field of fault-tolerant motors. Stator slots of the vernier permanent magnet fault-tolerant motor comprise open slots and closed slots; the open slots and the closed slots are equal in number and are arranged in a staggered manner; an auxiliary groove is formed in the face, close to the air gap, of the closed groove. And each closed slot and two adjacent stator teeth jointly form a basic function multiplexing unit. Under the short-circuit fault working condition, the function multiplexing unit changes the direction of a magnetic line of force and the magnetic flux interlinked with the winding so as to form a ring tooth magnetic circuit, the slot leakage inductance is increased so as to increase the winding inductive reactance, and effective suppression of the short-circuit current is realized. Under a normal working condition, the function multiplexing unit realizes mutual counterbalance of magnetic lines in the same direction and integration of magnetic field modulation capability, formation of a ring tooth magnetic circuit can be hindered, a weakened magnetic field modulation effect is compensated, and high torque output of the motor under the normal working condition is ensured. On the basis, the strong fault-tolerant capability and the high torque density of the vernier permanent magnet motor can be cooperatively considered.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault-tolerant motors, and more specifically, relates to a vernier permanent magnet fault-tolerant motor with a function multiplexing unit. Background Art

[0002] With the continuous development of modern engineering machinery equipment industry towards high efficiency, intelligence and greenness, motors have become an important component for providing power sources in the industrial field. Permanent magnet motors have an increasingly wide application market due to their simple structure, high power density, high operating efficiency and flexible control. Among them, a type of vernier permanent magnet motor based on the "magnetic field modulation principle" has gradually attracted attention due to its characteristics of multiple working magnetic field harmonics. It achieves low-speed and high-torque operation without changing the power supply frequency or increasing the number of motor poles and slots. In addition, the magnetic permeance oriented design method based on the working magnetic field harmonics can further improve the upper limit of the output torque of the vernier permanent magnet motor, which can better meet the requirements of high torque density of motors in the field of high-end equipment, and has certain research value.

[0003] In particular, in the fields of high-end equipment such as aerospace, national defense, transportation electrification, and deep-sea exploration, due to the harsh working environment, not only the high-quality operation of the motor body torque density and efficiency must be met, but also the requirements for its fault tolerance performance and high reliability of the drive system have been greatly increased. Affected by unstable factors such as temperature, humidity, pressure, and vibration, the motor will inevitably fail during operation, causing economic losses and threats to personal safety. The main types of motor electromagnetic faults are: winding open circuit, end short circuit and turn-to-turn short circuit, permanent magnet demagnetization, etc. Among them, the probability of winding turn-to-turn short circuit fault is relatively high and difficult to control. When the turn-to-turn short circuit occurs, it is difficult for the permanent magnet motor to achieve fault demagnetization due to the presence of permanent magnets, and a huge demagnetization current is induced in the short-circuited turn, which can usually reach more than ten times or even dozens of times the rated current value. If not intervened in time, it will cause the local temperature rise of the motor to be too high, burn the winding insulation, and in severe cases, cause irreversible demagnetization faults of the permanent magnet. Therefore, the fault-tolerant design of permanent magnet motors has become a research hotspot in many fields.

[0004] At present, the short-circuit resistance design of motors is mainly based on the winding arrangement, modularization and stator slot design. The winding impedance is increased by adopting fractional slot concentrated winding, reducing the number of parallel windings and setting magnetic slot wedges at the slots. However, fault tolerance and power density are usually two contradictory characteristics. In the prior art, patent document CN114465377A discloses a hybrid excitation permanent magnet fault-tolerant motor with short-circuit current suppression capability, such as Figure 1As shown, at least one of the stator core and the rotor core in the motor is a modular structure. The radial air gap between adjacent modules can change the magnetic flux path, reduce the interphase coupling of magnetic lines of force, and improve the short-circuit current suppression capability of the motor. However, the modular structure design is a way to physically isolate the windings of each phase, and has no isolation effect on the winding coils in the same stator slot, so the ability to suppress short-circuit current is limited; at the same time, the radial air gap introduces a magnetic barrier effect, and the permanent magnet placed at the slot will increase the leakage flux, making the torque density of the motor low under normal working conditions. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a vernier permanent magnet fault-tolerant motor with a function multiplexing unit to solve the technical problem that the prior art cannot coordinately take into account the strong fault tolerance and high torque density of the vernier permanent magnet motor.

[0006] In order to achieve the above-mentioned object, the present invention provides a vernier permanent magnet fault-tolerant motor with a function multiplexing unit, wherein the stator and the rotor are coaxially mounted, and an air gap is provided between the rotor and the stator;

[0007] The stator comprises: a stator core and an armature winding; the stator core is provided with stator teeth arranged along the circumferential direction; a stator slot is arranged between two adjacent stator teeth; the armature winding is wound in the stator slot;

[0008] The stator slots include two types: open slots and closed slots; the number of open slots and closed slots is equal and they are staggered; an arc-shaped iron core is arranged at the slot opening of each closed slot, and an auxiliary groove is arranged near the air gap surface;

[0009] A closed slot and two stator teeth adjacent to the closed slot constitute a function multiplexing unit; the function multiplexing unit is used to conduct magnetism to amplify torque under normal working conditions; under short-circuit fault conditions, the direction of the magnetic lines of force and the magnetic flux interlinked with the winding are changed to form a ring tooth magnetic circuit to reduce the short-circuit current.

[0010] Further preferably, the armature winding is a three-phase AC winding, including a double-layer winding coil; the two winding coils in the same closed slot belong to different phases, and the currents passing through them have opposite polarities.

[0011] Further preferably, the coil span of the armature winding is 2.

[0012] Further preferably, the stator teeth are of parallel tooth type.

[0013] Further preferably, the material of the stator core is a soft magnetic material.

[0014] Further preferably, the rotor is arranged inside the stator, and the stator teeth are arranged on the inner side of the stator core to form an outer stator structure; or, the rotor is arranged outside the stator, and the stator teeth are arranged on the outer side of the stator core to form an inner stator structure.

[0015] Further preferably, the number of stator slots Z s , rotor permanent magnet pole pair number P r and armature winding pole pair number P a The following relations are satisfied:

[0016]

[0017] Among them, P a =min{iZ s ±P r |, i∈ positive integer set}, GCD(Z s ,P a ) is Z s and P a The greatest common divisor of .

[0018] Further preferably, the position distribution of each auxiliary groove is determined by the following method:

[0019] Determine whether each harmonic of the motor's armature winding contributes to the motor's back electromotive force and whether the contribution is positive or negative through a motor simulation model, and use the armature winding harmonic that contributes to the back electromotive force as a working harmonic; wherein the motor simulation model is a simulation model of the above-mentioned vernier permanent magnet fault-tolerant motor without auxiliary grooves;

[0020] Based on the magnetic field modulation principle, the pole pairs and phases of the permeance harmonics corresponding to each operating harmonic are calculated respectively, and the phase of the permeance harmonic corresponding to the armature winding harmonic with a negative contribution to the back electromotive force is reversed by 180° as the phase of the permeance harmonic;

[0021] Based on the pole pairs and phases of the permeance harmonics corresponding to each operating harmonic, a spatial permeance waveform having a mapping relationship with the stator tooth structure is constructed;

[0022] Based on the positive and negative information of the spatial magnetic permeability waveform and the stator tooth distribution of the motor simulation model, the starting position and arc of each auxiliary groove along the circumferential direction are determined as the final position distribution design result.

[0023] Further preferably, the spatial magnetic permeability waveform is formed by superimposing the waveforms of each spatial magnetic permeability element; the expression of the waveform of the i-th spatial magnetic permeability element is:

[0024]

[0025] Among them, k wPr and k wv Pr The coefficient of the subharmonic winding and the v subharmonic winding coefficient; P r is the number of rotor permanent magnet pole pairs; v is the order of the harmonic of the working armature winding, v = |P r ±P mj |; j is the harmonic order of magnetic permeability; θ mj is the phase value of the jth permeance harmonic, P mj is the number of pole pairs of the jth permeance harmonic, θ si is the position of the i-th spatial magnetic permeance element.

[0026] Further preferably, the groove depth of each auxiliary groove is determined by:

[0027] In the motor simulation model, each auxiliary groove is set on the near-air-gap surface of each closed slot according to the above-mentioned final position distribution design result;

[0028] The slot depth of each auxiliary groove in the motor simulation model is adjusted, and the slot depth of each auxiliary groove when the amplitude of the magnetic permeance harmonic corresponding to each working harmonic of the motor is maximized is taken as the final slot depth size design result.

[0029] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0030] 1. The present invention provides a vernier permanent magnet fault-tolerant motor, whose stator slots include two types: open slots and closed slots; the number of open slots and closed slots is equal, and they are staggered; the air gap surface of the closed slot is provided with an auxiliary groove; each closed slot and two adjacent stator teeth together constitute a basic functional reuse unit. Under short-circuit fault conditions, since the slot opening of the closed slot is an arc-shaped iron core structure instead of air, the magnetic permeability of the arc-shaped iron core is several thousand times that of air. Compared with the long magnetic circuit closure of the magnetic line of force, the functional reuse unit is more likely to guide it to the ring tooth magnetic circuit with relatively lower magnetic resistance, thereby changing the direction of the magnetic line of force and the magnetic flux interlinked with the winding, forming a ring tooth magnetic circuit, increasing the slot leakage inductance to increase the winding inductance, achieving effective suppression of short-circuit current, and improving the fault tolerance performance of the motor. Under normal working conditions, the function multiplexing unit plays the role of magnetic conduction and modulation harmonic pole number. The composition of magnetic conduction harmonics determines its conversion effect on the magnetic field harmonic pole number, that is, it will not produce a large number of harmonics with high pole number, short wavelength, and easy to form short magnetic circuit, which will hinder the magnetic lines of force from running through the ring gear magnetic circuit to a certain extent, ensuring the high torque output advantage of the vernier motor under normal working conditions. Based on this, the present invention can coordinate the strong fault tolerance and high torque density of the vernier permanent magnet motor.

[0031] 2. Furthermore, the vernier permanent magnet fault-tolerant motor provided by the present invention has an armature winding which is a three-phase AC winding, including a double-layer winding coil; the two winding coils in the same closed slot belong to different phases, and the polarities of the currents passed through them are opposite. Under normal operating conditions, magnetic motive forces of the same magnitude and direction but different phases will be generated. The mutual antagonism of the magnetic lines of force in the same direction prevents most of the magnetic lines of force from taking the circular magnetic circuit, and the difference in phases prevents the magnetic motive forces from being completely offset, thereby reducing the torque density, further ensuring the torque performance of the motor under normal operating conditions.

[0032] 3. Furthermore, the setting of the function reuse unit of the vernier permanent magnet fault-tolerant motor provided by the present invention will cause the number of modulation teeth to be halved, and part of the working permeance harmonics will be converted into non-working permeance harmonics, resulting in the weakening of the magnetic field modulation capability and the decrease in the amplitude of the modulated working magnetic field harmonics. For the vernier permanent magnet motor, the working harmonic content directly determines the torque quality of the motor. Therefore, from the harmonic perspective, the optimal position arrangement of the auxiliary grooves is derived by directional editing of the pole pairs and phase composition of the permeance harmonics. The optimal function reuse unit structure after directional design improves the amplitude of the effective working magnetic field harmonics that contribute to the positive and reverse electromotive force, compensates for the weakened magnetic field modulation effect due to the setting of half of the closed slots, solves the contradiction between the motor's short-circuit resistance and the weakened permeance modulation effect due to the use of closed slots, and better guarantees the high torque output of the motor under normal working conditions.

[0033] 4. Furthermore, the vernier permanent magnet fault-tolerant motor provided by the present invention adopts a double-layer winding across two teeth with a coil span of 2. Compared with the conventional fractional slot concentrated winding, the working harmonic winding coefficient remains unchanged. At the same time, the results show that the winding connection method across two teeth combined with the function multiplexing unit can further reduce the short-circuit current. The difference between the two is that at this time, part of the magnetic lines of force flowing through the stator teeth on both sides of the function multiplexing unit also come from the magnetomotive force generated by the same coil across the two teeth, and the motor's short-circuit resistance and dynamic performance are further improved.

[0034] 5. Furthermore, the vernier permanent magnet fault-tolerant motor provided by the present invention will take the slot depth size of each auxiliary groove when the amplitude of the magnetic permeance harmonic corresponding to each working armature winding harmonic of the motor is maximized as the final slot depth size design result, further improving the magnetic field modulation capability of the vernier permanent magnet motor and ensuring its high torque density advantage under normal working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the hybrid excitation vernier permanent magnet fault-tolerant motor provided in CN114465377A;

[0036] Figure 2 It is a structural schematic diagram of a traditional vernier permanent magnet motor;

[0037] Figure 3 A schematic diagram of the structure of a vernier permanent magnet fault-tolerant motor provided by an embodiment of the present invention

[0038] Figure 4 A schematic diagram of the structure of a function multiplexing unit provided in an embodiment of the present invention;

[0039] Figure 5 It is a schematic diagram of the direction of magnetic lines of force of a traditional vernier permanent magnet motor only when the stator armature winding is excited under a short circuit fault;

[0040] Figure 6 A schematic diagram of the direction of magnetic lines of force of the vernier permanent magnet fault-tolerant motor provided by an embodiment of the present invention only when the stator armature winding is excited under a short-circuit fault;

[0041] Figure 7 The output torque comparison diagram of the vernier permanent magnet fault-tolerant motor and the traditional vernier permanent magnet motor before and after the directional design of this embodiment under normal working conditions;

[0042] Figure 8 The figure is a comparison diagram of the short-circuit current between the turns of the windings of the vernier permanent magnet fault-tolerant motor designed in this embodiment and the traditional vernier permanent magnet motor under a short-circuit fault.

[0043] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0044] I-2 is the rotor core, I-3 is the tangentially magnetized permanent magnet, I-4 is the armature winding, I-5 is the DC excitation winding, I-6 is the air gap, I-7 is the first small stator tooth, I-8 is the second large stator tooth, I-9 is the third small stator tooth, I-10 is the stator module, and I-11 is the stator radial air gap;

[0045] 1 is the stator core, 2 is the armature winding, 3 is the permanent magnet, 4 is the rotor core, 5 is the function multiplexing unit, and 6 is the auxiliary groove. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] In order to achieve the above-mentioned object, the present invention provides a vernier permanent magnet fault-tolerant motor with a function multiplexing unit, which is a vernier permanent magnet motor with strong fault tolerance and high torque density, wherein the stator and the rotor are coaxially mounted, and an air gap is provided between the rotor and the stator;

[0048] The stator comprises: a stator core and an armature winding; the stator core is provided with stator teeth arranged along the circumferential direction; a stator slot is arranged between two adjacent stator teeth; the armature winding is wound in the stator slot;

[0049] The stator slots include two types: open slots and closed slots; the number of open slots and closed slots is equal and they are staggered; an arc-shaped iron core is arranged at the slot opening of each closed slot, and an auxiliary groove is arranged near the air gap surface;

[0050] A closed slot and two stator teeth adjacent to the closed slot constitute a function multiplexing unit; the function multiplexing unit is used to conduct magnetism to amplify torque under normal working conditions; under short-circuit fault conditions, the direction of magnetic lines of force and the magnetic flux linked with the winding are changed to form a ring tooth magnetic circuit to reduce the short-circuit current.

[0051] In an optional embodiment, the armature winding is a three-phase AC winding, including a double-layer winding coil; the two winding coils in the same closed slot belong to different phases, and the current polarities passing through them are opposite. The coil span of the armature winding can be 1, 2, 3, etc., preferably 2.

[0052] It should be noted that the stator teeth may be parallel teeth, helical teeth, split teeth, large and small teeth, etc. Preferably, in an optional implementation, the stator teeth are parallel teeth.

[0053] It should be noted that the rotor can be arranged inside the stator or outside the stator, which is not limited here. In an optional embodiment, the rotor is arranged inside the stator, and the stator teeth are arranged on the inner side of the stator core to form an outer stator structure. In another optional embodiment, the rotor is arranged outside the stator, and the stator teeth are arranged on the outer side of the stator core to form an inner stator structure.

[0054] In an optional embodiment, the position distribution of each auxiliary groove is determined by:

[0055] Determine whether each harmonic of the motor's armature winding contributes to the motor's back electromotive force and whether the contribution is positive or negative through a motor simulation model, and use the armature winding harmonic that contributes to the back electromotive force as a working harmonic; wherein the motor simulation model is a simulation model of the above-mentioned vernier permanent magnet fault-tolerant motor without auxiliary grooves;

[0056] Based on the magnetic field modulation principle, the pole pairs and phases of the permeance harmonics corresponding to each operating harmonic are calculated respectively, and the phase of the permeance harmonic corresponding to the armature winding harmonic with a negative contribution to the back electromotive force is reversed by 180° as the phase of the permeance harmonic;

[0057] Based on the pole pair number and phase information of the permeance harmonic corresponding to each working harmonic, a spatial permeance waveform with a mapping relationship with the stator tooth structure is constructed; wherein the spatial permeance waveform is formed by superimposing the waveforms of each spatial permeance element; the waveform K of the i-th spatial permeance element i The expression is:

[0058]

[0059] Among them, k wPr and k wv P r The coefficient of the subharmonic winding and the v subharmonic winding coefficient; P r is the number of rotor permanent magnet pole pairs; v is the order of the harmonic of the working armature winding, v = |P r ±P mj |; j is the harmonic order of magnetic permeability; θ mj is the phase value of the jth permeance harmonic, P mj is the number of pole pairs of the jth permeance harmonic, θ si is the position of the i-th spatial magnetic permeance element.

[0060] Based on the positive and negative information of the spatial magnetic permeability waveform and the stator tooth distribution of the motor simulation model, the starting position and arc of each auxiliary groove along the circumferential direction are determined as the final position distribution design result.

[0061] In an optional embodiment, the groove depth of each auxiliary groove is determined by:

[0062] In the motor simulation model, each auxiliary groove is set on the near-air-gap surface of each closed slot according to the above-mentioned final position distribution design result;

[0063] The slot depth of each auxiliary groove in the motor simulation model is adjusted, and the slot depth of each auxiliary groove when the amplitude of the magnetic permeance harmonic corresponding to each working harmonic of the motor is maximized is taken as the final slot depth size design result.

[0064] It should be noted that the shape of the auxiliary groove in the radial cross section can be rectangular, arc-shaped, triangular, trapezoidal, etc., which is not limited here.

[0065] In order to further illustrate the vernier permanent magnet fault-tolerant motor provided by the present invention, a vernier permanent magnet fault-tolerant motor in which the stator and the rotor are coaxially mounted from the outside to the inside is taken as an example for detailed description:

[0066] Figure 2The structural schematic diagram of a traditional vernier permanent magnet motor provided in this embodiment includes a stator and a rotor; the stator and the rotor are coaxially mounted from the outside to the inside, and an air gap is provided between the rotor and the stator; when the motor is working, the rotor rotates around the rotating axis relative to the stator. The stator includes: a stator core 1, an armature winding 2; the stator core 1 is provided with stator teeth evenly distributed along the circumferential direction. The rotor includes: a permanent magnet 3 and a rotor core 4.

[0067] The stator teeth are parallel tooth type; the inner wall of the stator is evenly distributed with multiple stator slots along the circumferential direction, all of which are open slots; the armature winding 2 is wound in the stator slots; the rotor includes a permanent magnet array 3 and a rotor core 4; the permanent magnet array 3 is fixed around the rotor near the air gap surface, and the shape, thickness and pole arc coefficient of each permanent magnet are equal, and they are magnetized along the radial direction. Adjacent permanent magnets have opposite polarities and are fixed around the rotor core 4 in the order of NS-NS. The material is hard magnetic materials such as neodymium iron boron, samarium cobalt or ferrite.

[0068] like Figure 3 The structure diagram of a vernier permanent magnet fault-tolerant motor provided in this embodiment is shown, which includes a stator and a rotor; the stator and the rotor are coaxially mounted from the outside to the inside, an air gap is provided between the rotor and the stator, and the rotor rotates around the rotating axis relative to the stator. The stator includes: a stator core 1, an armature winding 2; the stator core 1 is provided with stator teeth evenly distributed along the circumferential direction; the rotor includes: a permanent magnet 3 and a rotor core 4.

[0069] Stator slots are arranged between two adjacent stator teeth. Each stator slot is evenly distributed along the circumferential direction on the inner wall of the stator core 1. There are two types of stator slots: open slots and closed slots. The number of open slots and closed slots is equal and they are staggered. Among them, open and closed indicate whether the side facing the rotor is open or closed. Auxiliary slots 6 are arranged near the air gap surface of the closed slot. Each closed slot and its two adjacent stator teeth together constitute a basic functional multiplexing unit 5. The optimal position arrangement of the auxiliary slots 6 is derived by directional editing of the pole pair number and phase composition of the permeance harmonics. The optimal functional multiplexing unit structure after directional design improves the amplitude of the effective working magnetic field harmonics that contribute to the positive and reverse electromotive force, and compensates for the magnetic field modulation effect weakened by the setting of half of the closed slots.

[0070] The armature winding 2 in this embodiment adopts a double-layer winding form across two teeth with a coil span of 2. In order to ensure the high torque density of the vernier permanent magnet fault-tolerant motor under normal working conditions, the polarities of the currents passed through the winding coils belonging to different phases in the same closed slot remain opposite. Under the slot-pole coordination of this embodiment, whether the conventional fractional slot concentrated winding form or the winding form across two teeth is adopted, the working harmonic winding coefficient is 0.866. In contrast, the winding form across two teeth in combination with the function multiplexing unit 5 can better ensure the high torque density of the vernier permanent magnet fault-tolerant motor under normal working conditions, and further improve the motor's anti-short circuit capability. The difference between the two is that when the conventional fractional slot concentrated winding form is adopted, most of the magnetic lines of force of the function multiplexing unit 5 flowing through the stator teeth on both sides are derived from the magnetomotive force generated by the two winding coils belonging to different phases in the same closed slot, and their magnitude and direction are the same, but the phase is different; while when the winding form across two teeth is adopted, the magnetic lines of force of the function multiplexing unit 5 flowing through the stator teeth on both sides are not only derived from the two coil windings belonging to different phases in the same closed slot, but also some of the magnetic lines of force are derived from the magnetomotive force generated by the same coil across the two teeth, and their magnitude is , direction and phase are the same; the latter part of the magnetic force lines is more likely to not go through the ring tooth magnetic circuit under healthy conditions due to the mutual cancellation of the completely identical magnetic motive forces; under fault conditions, the magnitude of the magnetic motive forces that were originally different in phase also becomes unbalanced, and the weakening of the counteraction between the magnetic force lines in the same direction is more inclined to guide the magnetic force lines to go through the ring tooth magnetic circuit, further increasing the slot leakage inductance and the phase winding self-inductance, playing a role in suppressing the short-circuit current under short-circuit faults (including single-phase short circuits and turn-to-turn short circuits), and further improving the short-circuit resistance and dynamic performance of the motor. Both the stator core 1 and the rotor core 4 can be laminated with soft magnetic materials such as silicon steel sheets.

[0071] In this embodiment, there are 16 permanent magnets 3, 12 stator slots, and 6 function multiplexing units 5, and the number of function multiplexing units 5 is half of the number of stator slots. s , permanent magnet pole pair number P r and the number of stator armature winding pole pairs P a There are multiple possibilities that satisfy the following relationship:

[0072]

[0073] Among them, P a =min{iZ s ±P r |, i∈ positive integer set}, min represents the minimum value among all possible values; GCD(Z s ,P a ) is Z s and P a The greatest common divisor of .

[0074] This embodiment provides a method for designing a magnetic permeance orientation, and derives the optimal position arrangement of the auxiliary grooves by directional editing of the pole pairs and phase composition of the magnetic permeance harmonics. Specifically, in this embodiment, the position distribution of each auxiliary groove is designed in the following manner:

[0075] S1. Determine whether each harmonic of the motor's armature winding contributes to the motor's back electromotive force and whether the contribution is positive or negative through a motor simulation model, and use the armature winding harmonic that contributes to the back electromotive force as a working harmonic; wherein the motor simulation model is a simulation model of the above-mentioned vernier permanent magnet fault-tolerant motor without auxiliary grooves;

[0076] Specifically, in this embodiment, the center axis of the A-phase winding is at the initial position of 0°, and the relevant parameters of each harmonic of the two-tooth double-layer winding, such as the harmonic winding coefficient k wv , notch coefficient k sv 、Harmonic phase θ sν The information is shown in Table 1 below.

[0077] Table 1 Winding harmonics

[0078]

[0079] S2. Based on the magnetic field modulation principle, the pole pairs and phases of the permeance harmonics corresponding to each working harmonic are calculated respectively, and the phase of the permeance harmonic corresponding to the armature winding harmonic with a negative contribution to the back electromotive force is reversed by 180° as the phase of the permeance harmonic;

[0080] In this embodiment, the number of pole pairs of the effective working magnetic field harmonics is determined to be 4, 8, 16, 28, and 32, and the number of pole pairs and phase information of the target magnetic permeability harmonics are further derived as shown in Table 2 below.

[0081] Table 2 Design permeance harmonic phase

[0082] Permeability harmonic pole pairs Permeability Harmonic Phase 12 180° 24 180° 36 0°

[0083] S3, based on the pole pairs and phases of the permeance harmonics corresponding to each working harmonic, construct a spatial permeance waveform having a mapping relationship with the stator tooth structure;

[0084] Specifically, a spatial permeance waveform is constructed based on the target permeance harmonic information in Table 2.

[0085] S4. Based on the positive and negative information of the spatial permeance waveform and the stator tooth distribution of the motor simulation model, determine the position distribution of each auxiliary groove;

[0086] There is a certain mapping relationship between the spatial permeability waveform and the modulation tooth structure, that is, the positive value of the permeability corresponds to the teeth of the modulation unit (that is, the tooth slot distribution structure corresponding to the harmonic modulation effect), and the negative value of the permeability corresponds to the slot of the modulation unit, thereby obtaining the position distribution of each auxiliary groove; wherein, the position distribution includes parameters such as the starting position of each auxiliary groove, the angle range (the arc of the auxiliary groove along the circumferential direction), etc.

[0087] After obtaining the position distribution of the auxiliary grooves, the depth of each auxiliary groove is further optimized, specifically including:

[0088] In the motor simulation model, each auxiliary groove is arranged on the near-air-gap surface of each closed slot according to the obtained position distribution;

[0089] The slot depth of each auxiliary groove in the motor simulation model is adjusted, and the slot depth of each auxiliary groove when the amplitude of the magnetic permeance harmonic corresponding to each working harmonic of the motor is maximized is taken as the final slot depth design result, and finally the following is obtained: Figure 4 The structure of the function multiplexing unit 5 is shown. In this embodiment, the curvature and depth of each auxiliary groove are the same.

[0090] The vernier permanent magnet fault-tolerant motor provided in this embodiment, under normal working conditions, on the one hand, due to the winding design, the polarity of the current passed through the winding coils belonging to different phases in the same closed slot is opposite, and the winding coils on both sides will generate magnetic motive forces of the same magnitude and direction but different phases. The difference in phase will prevent the magnetic motive forces from being completely offset, thereby reducing the torque density. In addition, part of the magnetic lines of force in the two stator teeth of the functional multiplexing unit also come from the magnetic motive force generated by the same coil across the two teeth, and their magnitude, direction and phase are exactly the same, and the counteraction between the same magnetic lines of force is stronger. On the other hand, the functional multiplexing unit plays the role of magnetic conduction and modulation of the harmonic pole number. The composition of the magnetic conduction harmonic determines its conversion effect on the harmonic pole number of the magnetic field, that is, it will not generate a large number of harmonics with high pole number, short wavelength, and easy to form a short magnetic circuit, which will hinder the magnetic lines of force from taking the ring tooth magnetic circuit to a certain extent. In general, the mutual counteraction of the same-direction magnetic lines of force and the integration of the magnetic field modulation capability can prevent the magnetic lines of force from not taking the ring tooth magnetic circuit, ensuring the high torque performance of the motor under normal working conditions. Under short-circuit fault conditions, since the slot of the closed slot is an arc-shaped iron core structure instead of air, the magnetic permeability of the arc-shaped iron core is thousands of times that of air. Compared with the long magnetic circuit closed by the magnetic line of force, the functional multiplexing unit can more easily guide it to take the ring tooth magnetic circuit with relatively lower magnetic resistance. At the same time, the magnetomotive force, which was originally only different in phase, also becomes unbalanced in size. The weakening of the balancing effect between the magnetic lines of force in the same direction will also cause most of the magnetic lines of force to take the ring tooth magnetic circuit. The degree of magnetic coupling between the faulty winding and the normal winding is reduced, and the ring tooth magnetic circuit excites a larger slot leakage inductance to increase the winding inductance, so that the motor has the ability to autonomously suppress turn-to-turn short circuit or single-phase short circuit current.

[0091] The slot-pole combination adopts a double-layer winding across two teeth with a coil span of 2. Compared with the conventional fractional-slot concentrated winding, the working harmonic winding coefficient remains unchanged. The results show that the winding connection method across two teeth combined with the functional multiplexing unit can further reduce the short-circuit current, and the short-circuit resistance and dynamic performance of the motor are further improved.

[0092] In addition, by directional editing of the pole pair number and phase composition of the permeance harmonic, the optimal position arrangement of the auxiliary groove 6 is derived. The optimal functional reuse unit structure after directional design improves the amplitude of the effective working magnetic field harmonics that contribute to the positive and negative electromotive force, and solves the contradiction between the short-circuit resistance improved by the use of closed slots and the weakened magnetic field modulation ability, ensuring the high torque density advantage of the vernier permanent magnet motor under normal working conditions, and taking into account the strong fault tolerance performance and high torque output of the vernier permanent magnet motor. Moreover, the technical solution of the present invention is applicable to vernier permanent magnet motors with any slot poles.

[0093] Next, in order to verify the performance difference between the vernier permanent magnet fault-tolerant motor proposed in this embodiment and the traditional vernier permanent magnet motor, the electromagnetic finite element simulation software JMAG-Designer 21.0 is used to compare the torque performance of the motor under healthy working conditions and the short-circuit current of the motor under short-circuit fault under the condition that the inner and outer diameters of the motor rotor and stator and the shaft length are the same:

[0094] The permanent magnet 3 is set as air. After the armature winding 2 is energized with current, the magnetic field line distribution of the traditional vernier permanent magnet motor in the case of a short circuit fault is as follows: Figure 5 As shown, the distribution of magnetic lines of force of the motor in this embodiment is as follows Figure 6 After the function multiplexing unit 5 is adopted, the magnetic flux generated by the armature winding 2 mainly forms a closed annular magnetic circuit in the two adjacent stator teeth corresponding to the function multiplexing unit 5, and only a small amount of magnetic lines of force take the long magnetic circuit to intersect with other phase windings, which reduces the coupling degree between the faulty phase winding and other phase windings, which is reflected in the low phase-to-phase mutual inductance. At the same time, the annular tooth magnetic flux increases the slot leakage inductance, improves the self-inductance of the phase winding under fault conditions, and improves the magnetic isolation capability and fault tolerance performance of the motor.

[0095] Figure 7 The output torque comparison diagram of the vernier permanent magnet fault-tolerant motor and the traditional vernier permanent magnet motor before and after the directional design of this embodiment under normal working conditions is shown in FIG. Figure 7It can be seen that the average torque of the traditional vernier permanent magnet motor is 16.91Nm, the average torque of the vernier permanent magnet fault-tolerant motor before directional design is 12.56Nm, and the average torque of the vernier permanent magnet fault-tolerant motor after directional design is 15.51Nm; under the same current density, the average torque of the motor with the auxiliary slot 6 set according to the magnetic permeance directional design method is increased by 23.49% compared with the case where the auxiliary slot 6 is not set, that is, the magnetic permeance directional design method ensures the high torque density advantage of the vernier permanent magnet motor under normal working conditions, while reducing the torque pulsation, compensating for the magnetic field modulation effect weakened by the halving of the number of modulation teeth caused by the setting of the function multiplexing unit 5, and significantly improving the short-circuit resistance of the vernier permanent magnet motor with only a slight sacrifice of the average torque (the average torque is reduced by 8.28%).

[0096] Figure 8 FIG. 1 is a comparison diagram of the short-circuit current of the armature winding 2 in the vernier permanent magnet fault-tolerant motor after the directional design of this embodiment and the conventional vernier permanent magnet motor under a short-circuit fault. Figure 8 It can be seen that the short-circuit current peak value of the traditional vernier permanent magnet motor is 153.12A, and the short-circuit current peak value of the vernier permanent magnet fault-tolerant motor after directional design is 74.85A. The short-circuit current peak value of the vernier permanent magnet fault-tolerant motor of this embodiment is much smaller than that of the traditional vernier permanent magnet motor, and the short-circuit current is reduced by about 51.12%. Therefore, the vernier permanent magnet motor provided in this embodiment can effectively suppress the inter-turn short-circuit current and has strong fault tolerance.

[0097] It should be noted that the vernier permanent magnet fault-tolerant motor in which the rotor and stator are coaxially assembled from the outside to the inside is similar to the vernier permanent magnet fault-tolerant motor in which the stator and rotor are coaxially assembled from the outside to the inside, and only the positional relationship between the rotor and the stator is different. Specifically, for the vernier permanent magnet fault-tolerant motor in which the stator and the rotor are coaxially assembled from the outside to the inside, the rotor is arranged inside the stator, and the stator teeth are arranged on the inner side of the stator iron core to form an external stator structure; for the vernier permanent magnet fault-tolerant motor in which the rotor and the stator are coaxially assembled from the outside to the inside, the rotor is arranged outside the stator, and the stator teeth are arranged on the outer side of the stator iron core to form an internal stator structure; no further details will be given here.

[0098] It will be easily understood by those skilled in the art that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A vernier permanent magnet fault-tolerant motor with a function multiplexing unit, characterized in that: The stator and the rotor are coaxially mounted, and an air gap is provided between the rotor and the stator; The stator comprises: a stator core and an armature winding; the stator core is provided with stator teeth arranged along the circumferential direction; a stator slot is arranged between two adjacent stator teeth; the armature winding is wound in the stator slot; The stator slots include two types: open slots and closed slots; the number of the open slots and the closed slots is equal and they are staggered; an arc-shaped core is arranged at the slot opening of each closed slot, and an auxiliary groove is arranged near the air gap surface; A closed slot and two stator teeth adjacent to the closed slot constitute a function multiplexing unit; the function multiplexing unit is used to conduct magnetism to amplify torque under normal working conditions; under short-circuit fault conditions, the direction of magnetic lines of force and the magnetic flux linked with the winding are changed to form a ring tooth magnetic circuit to reduce the short-circuit current.

2. The vernier permanent magnet fault-tolerant motor according to claim 1, characterized in that: The armature winding is a three-phase AC winding, including a double-layer winding coil; the two winding coils in the same closed slot belong to different phases, and the currents passing through them have opposite polarities.

3. The vernier permanent magnet fault-tolerant motor according to claim 2, characterized in that: The coil span of the armature winding is 2.

4. The vernier permanent magnet fault-tolerant motor according to claim 1, characterized in that: The stator teeth are of parallel tooth type.

5. The vernier permanent magnet fault-tolerant motor according to claim 1, characterized in that: The material of the stator core is soft magnetic material.

6. The vernier permanent magnet fault-tolerant motor according to claim 1, characterized in that: The rotor is arranged inside the stator, and the stator teeth are arranged inside the stator core to form an outer stator structure; or, the rotor is arranged outside the stator, and the stator teeth are arranged outside the stator core to form an inner stator structure.

7. The vernier permanent magnet fault-tolerant motor according to claim 1, characterized in that: Number of stator slots Z s , rotor permanent magnet pole pair number P r and armature winding pole pair number P a The following relations are satisfied: Among them, P a =min{iZ s ±P r| ,i∈positive integer set}, GCD(Z s ,P a ) is Z s and P a The greatest common divisor of .

8. The vernier permanent magnet fault-tolerant motor according to any one of claims 1 to 7, characterized in that: The position distribution of each auxiliary groove is determined by the following method: Determine whether each harmonic of the motor's armature winding contributes to the motor's back electromotive force and whether the contribution is positive or negative through a motor simulation model, and use the armature winding harmonic that contributes to the back electromotive force as a working harmonic; wherein the motor simulation model is a simulation model of the vernier permanent magnet fault-tolerant motor without auxiliary grooves; Based on the magnetic field modulation principle, the pole pairs and phases of the permeance harmonics corresponding to each operating harmonic are calculated respectively, and the phase of the permeance harmonic corresponding to the armature winding harmonic with a negative contribution to the back electromotive force is reversed by 180° as the phase of the permeance harmonic; Based on the pole pairs and phases of the permeance harmonics corresponding to each operating harmonic, a spatial permeance waveform having a mapping relationship with the stator tooth structure is constructed; Based on the positive and negative information of the spatial permeance waveform and the stator tooth distribution of the motor simulation model, the starting position and arc of each auxiliary groove along the circumferential direction are determined as the final position distribution design result.

9. The vernier permanent magnet fault-tolerant motor according to claim 8, characterized in that: The spatial permeability waveform is formed by superimposing the waveforms of each spatial permeability element; the expression of the waveform of the i-th spatial permeability element is: Among them, k wPr and k wv P r The coefficient of the subharmonic winding and the v subharmonic winding coefficient; P r is the number of rotor permanent magnet pole pairs; v is the order of the harmonic of the working armature winding, v= | P r ±P mj| ; j is the harmonic order of magnetic permeability; θ mj is the phase value of the jth permeance harmonic, P mj is the number of pole pairs of the jth permeance harmonic, θ si is the position of the i-th spatial magnetic permeance element.

10. The vernier permanent magnet fault-tolerant motor according to claim 8, characterized in that: The depth of each auxiliary groove is determined by: In the motor simulation model, each auxiliary groove is arranged on the near-air-gap surface of each closed slot according to the final position distribution design result; The slot depth dimensions of each auxiliary groove in the motor simulation model are adjusted, and the slot depth dimensions of each auxiliary groove when the amplitude of the magnetic permeance harmonic corresponding to each working harmonic of the motor is maximized are taken as the final slot depth dimension design result.

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