A vernier permanent magnet fault-tolerant motor with function multiplexing unit

Abstract

The application discloses a vernier permanent magnet fault-tolerant motor with a function multiplexing unit, and belongs to the technical field of fault-tolerant motors. The stator slot of the vernier permanent magnet fault-tolerant motor comprises two types of open slots and closed slots. The number of the open slots and the closed slots is equal, and the open slots and the closed slots are staggered. An auxiliary groove is arranged on the near air gap surface of the closed slot. Each closed slot and two adjacent stator teeth jointly form a basic function multiplexing unit. Under a short-circuit fault condition, the function multiplexing unit changes the magnetic line of force and the magnetic flux interlinked with the winding, so as to form a ring-tooth magnetic circuit, increase the slot leakage inductance, increase the winding inductance, and effectively suppress the short-circuit current. Under a normal condition, the function multiplexing unit realizes mutual counterbalance of the same direction magnetic line of force and integration of the magnetic field modulation capacity, can hinder the formation of the ring-tooth magnetic circuit, compensate for the weakened magnetic field modulation effect, and ensure high torque output of the motor under the normal condition. Therefore, the vernier permanent magnet fault-tolerant motor can simultaneously consider the strong fault-tolerant capacity and the high torque density.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fault-tolerant motors, and more particularly relates to a vernier permanent magnet fault-tolerant motor with a function multiplexing unit. BACKGROUND

[0002] With the continuous development of modern engineering machinery equipment industry towards high efficiency, intelligence, green and other directions, motors have become important components for providing power sources in the industrial field. Permanent magnet motors have a wider and wider application market due to their simple structure, high power density, high operating efficiency and flexible control. Among them, a kind of vernier permanent magnet motor operating based on the "magnetic field modulation principle" gradually attracts attention due to its multiple working magnetic field harmonic characteristics, and realizes low-speed large torque operation without changing the frequency of the power supply and increasing the number of motor poles and slots. In addition, the magnetic guide directional design method based on the working magnetic field harmonic can further improve the upper limit of the output torque of the vernier permanent magnet motor, better meet the requirements of high torque density of the motor in the high-end equipment field, and has a certain research value.

[0003] In particular, in the high-end equipment field such as aerospace, national defense and military industry, traffic electrification, deep sea exploration, etc., due to the harsh working environment, not only the high-quality operation of the motor torque density and efficiency, but also the high reliability of the fault-tolerant performance and driving system are greatly improved. Influenced by unstable factors such as temperature, humidity, pressure and vibration, faults inevitably occur in the operation of the motor, causing economic losses and personal safety threats. The main types of motor electromagnetic faults are: winding open circuit, end short circuit and inter-turn short circuit, permanent magnet demagnetization, etc., among which the inter-turn short circuit fault has a higher probability and is difficult to control. When the inter-turn short circuit occurs, the permanent magnet motor is difficult to realize fault demagnetization due to the existence of the permanent magnet, and a huge demagnetization current is induced in the short-circuit turn, which can be up to tens of times or even hundreds of times of the rated current. If not intervened in time, it will cause the local temperature of the motor to rise too high, burn the winding insulation, and even cause irreversible demagnetization failure of the permanent magnet. Therefore, the fault-tolerant design of the permanent magnet motor has become a research hotspot in many fields.

[0004] At present, the anti-short-circuit design of the motor is mainly from the perspective of winding arrangement, modularization and stator slot design, etc. By adopting fractional slot concentrated winding, reducing the number of parallel windings and setting magnetic slot wedges at the slot opening, the winding impedance is increased, but the 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, as shown in Figure 1As shown, at least one of the stator core and the rotor core in the motor is of a modular structure, and the magnetic flux path can be changed and the degree of inter-phase coupling of the magnetic lines can be reduced through the radial air gap between adjacent modules, so as to improve the short-circuit current suppression capability of the motor. However, the modular structure design is a way of physically isolating the windings of different phases, and has no isolating effect on the windings in the same stator slot, so the short-circuit current suppression capability is limited. At the same time, the radial air gap introduces the magnetic barrier effect, and the placement of the permanent magnet in the slot opening increases the magnetic flux leakage, so that the torque density of the motor under normal working conditions is low. SUMMARY

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

[0006] In order to achieve the above-mentioned purpose, the present application provides a vernier permanent magnet fault-tolerant motor with a function reuse unit, wherein the stator and the rotor are coaxially sleeved, and an air gap is arranged between the rotor and the stator.

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

[0008] The stator slot comprises two types of open slot and closed slot; the number of open slots and closed slots is equal, and they are arranged alternately; 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.

[0009] One closed slot and two stator teeth adjacent to the closed slot form a function reuse unit; the function reuse unit is used for guiding the magnetic field to amplify the torque under normal working conditions; and the function reuse unit changes the direction of the magnetic lines and the magnetic flux interlinked with the winding to form a ring-tooth magnetic circuit to reduce the short-circuit current under short-circuit fault working conditions.

[0010] Further preferably, the armature winding is a three-phase alternating winding, comprising double-layer winding coils; the two winding coils in the same closed slot belong to different phases, and the current polarities flowing through them are opposite.

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

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

[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 , the number of rotor permanent magnet pole pairs P r and the number of armature winding pole pairs P a satisfy the following relationship:

[0016]

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

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

[0019] whether each armature winding harmonic of the motor contributes to the motor back electromotive force and the positive or negative contribution is determined by a motor simulation model, and the armature winding harmonic that contributes to the back electromotive force is taken as a working harmonic; wherein the motor simulation model is a simulation model of the above vernier permanent magnet fault-tolerant motor without auxiliary slots;

[0020] Based on the principle of magnetic field modulation, the pole pair number and phase of the magnetic flux guide harmonic corresponding to each working harmonic are calculated, and the phase of the magnetic flux guide harmonic corresponding to the armature winding harmonic with negative contribution to the back electromotive force is reversed by 180° as the phase of the magnetic flux guide harmonic;

[0021] Based on the pole pair number and phase of the magnetic flux guide harmonic corresponding to each working harmonic, a spatial magnetic flux guide waveform having a mapping relationship with the stator tooth structure is constructed;

[0022] Based on the positive and negative information of the spatial magnetic flux guide waveform, and in combination with the stator tooth distribution of the motor simulation model, the starting position and arc of each auxiliary slot in the circumferential direction are determined as the final position distribution design result.

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

[0024]

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

[0026] Further preferably, the slot depth size of each auxiliary slot is determined by the following way:

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

[0028] Adjusting the slot depth size of each auxiliary slot in the motor simulation model, the slot depth size of each auxiliary slot when the magnetic permeability harmonic corresponding to each working harmonic of the motor is maximized is taken as the final slot depth size design result.

[0029] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0030] 1. The vernier permanent magnet fault-tolerant motor provided by the present application has two types of stator slots, i.e., open slots and closed slots; the number of open slots and closed slots is equal, and the open slots and closed slots are staggered; the near air gap surface of the closed slot is provided with an auxiliary slot; each closed slot and two adjacent stator teeth together form a basic function reuse unit. In the short circuit fault condition, since the slot opening of the closed slot is an arc-shaped core structure rather than air, the magnetic permeability of the arc-shaped core is several thousand times that of air, and compared with the long magnetic path closure of the magnetic force line, the function reuse unit is more likely to guide the magnetic force line to the ring tooth magnetic path with relatively lower magnetic resistance, thereby changing the direction of the magnetic force line and the magnetic flux interlinked with the winding, forming a ring tooth magnetic path, increasing the slot leakage inductance to increase the winding inductance, and achieving effective suppression of the short circuit current and improvement of the fault tolerance performance of the motor. In the normal condition, the function reuse unit plays a role in magnetic conduction and modulation of harmonic pole number, and the composition of the magnetic permeability harmonic determines the conversion effect of the magnetic field harmonic pole number, that is, a large number of high-pole-number and short-wavelength harmonics are not generated, which to some extent hinders the magnetic force line from going through the ring tooth magnetic path, and ensures the high torque output advantage of the vernier motor in the normal condition. Based on this, the present application can simultaneously consider the strong fault tolerance and high torque density of the vernier permanent magnet motor.

[0031] 2、Further, the vernier permanent magnet fault-tolerant motor provided by the application has three-phase alternating current windings, including double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current flowing through them has opposite polarities, and under normal working conditions, the same magnetic force lines are balanced to each other, so that most of the magnetic force lines do not pass through the annular magnetic circuit, and the different phases make the magnetic motive force not completely offset, thereby reducing the torque density and further ensuring the torque performance of the motor under normal working conditions.

[0032] 3、Further, the vernier permanent magnet fault-tolerant motor provided by the application has three-phase alternating current windings, including double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current flowing through them has opposite polarities, and under normal working conditions, the same magnetic force lines are balanced to each other, so that most of the magnetic force lines do not pass through the annular magnetic circuit, and the different phases make the magnetic motive force not completely offset, thereby reducing the torque density and further ensuring the torque performance of the motor under normal working conditions.

[0033] 4、Further, the vernier permanent magnet fault-tolerant motor provided by the application has three-phase alternating current windings, including double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current flowing through them has opposite polarities, and under normal working conditions, the same magnetic force lines are balanced to each other, so that most of the magnetic force lines do not pass through the annular magnetic circuit, and the different phases make the magnetic motive force not completely offset, thereby reducing the torque density and further ensuring the torque performance of the motor under normal working conditions.

[0034] 5、Further, the vernier permanent magnet fault-tolerant motor provided by the application has three-phase alternating current windings, including double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current flowing through them has opposite polarities, and under normal working conditions, the same magnetic force lines are balanced to each other, so that most of the magnetic force lines do not pass through the annular magnetic circuit, and the different phases make the magnetic motive force not completely offset, thereby reducing the torque density and further ensuring the torque performance of the motor under normal working conditions. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0037] Figure 3 Structure diagram of vernier permanent fault-tolerant motor provided by the embodiment of the present application

[0038] Figure 4 Structure diagram of function multiplexing unit provided by the embodiment of the present application

[0039] Figure 5 Magnetic flux line direction diagram of traditional vernier permanent motor under short-circuit fault only when the stator armature winding is excited

[0040] Figure 6 Magnetic flux line direction diagram of vernier permanent fault-tolerant motor provided by the embodiment of the present application under short-circuit fault only when the stator armature winding is excited

[0041] Figure 7 Output torque comparison diagram of vernier permanent fault-tolerant motor before and after directional design of the embodiment and traditional vernier permanent motor under normal working condition

[0042] Figure 8 Winding inter-turn short-circuit current comparison diagram of vernier permanent fault-tolerant motor after directional design of the embodiment and traditional vernier permanent motor under short-circuit fault.

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

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

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

[0046] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application 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 purpose, the present application provides a vernier permanent fault-tolerant motor with a function multiplexing unit, which is a vernier permanent motor with strong fault tolerance and high torque density. The stator and the rotor are coaxially sleeved, and an air gap is arranged 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 in a circumferential direction; two adjacent stator teeth are provided with a stator slot; the armature winding is wound in the stator slot;

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

[0050] One closed slot and two stator teeth adjacent to the closed slot form a functional reuse unit; the functional reuse unit is used for magnetic conduction to amplify torque under normal working conditions; under short-circuit fault working conditions, the magnetic flux line direction and the magnetic flux interlinked 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 alternating current winding, comprising double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current polarity flowing through them is opposite. The coil span of the armature winding can be 1, 2, 3, etc., and is preferably 2.

[0052] It should be noted that the stator teeth can be parallel teeth, helical teeth, split teeth, large teeth, etc. Preferably, in an optional embodiment, the stator teeth are parallel teeth.

[0053] It should be noted that the rotor can be arranged inside 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 the following method:

[0055] Whether each order armature winding harmonic of the motor contributes to the motor back electromotive force and the positive and negative situation of the contribution are determined through a motor simulation model, and the armature winding harmonic that contributes to the back electromotive force is taken as a working harmonic; wherein the motor simulation model is a simulation model of the above vernier permanent magnet fault-tolerant motor without auxiliary grooves;

[0056] Based on the principle of magnetic field modulation, the pole pair number and phase of the magnetic guide harmonic corresponding to each order working harmonic are calculated, and the phase of the magnetic guide harmonic corresponding to the armature winding harmonic with negative contribution to the back electromotive force is reversed by 180° as the phase of the magnetic guide harmonic;

[0057] Based on the pole pair number and phase information of the magnetic flux guide harmonics corresponding to each working harmonic, a spatial magnetic flux guide waveform having a mapping relationship with the stator tooth structure is constructed; the spatial magnetic flux guide waveform is formed by superimposing the waveforms of each spatial magnetic flux guide element; the waveform K i of the i th spatial magnetic flux guide element is expressed as:

[0058]

[0059] Wherein, k wPr and k wv are the coefficients of the P r th harmonic winding and the v th harmonic winding; P r is the pole pair number of the rotor permanent magnet; v is the order of the working armature winding harmonic, v = |P r ± P mj |; j is the order of the magnetic flux guide harmonic; θ mj is the phase value of the j th magnetic flux guide harmonic, P mj is the pole pair number of the j th magnetic flux guide harmonic, and θ si is the position of the i th spatial magnetic flux guide element.

[0060] Based on the positive and negative information of the spatial magnetic flux guide waveform, and in combination with the stator tooth distribution of the motor simulation model, the starting position and arc of each auxiliary slot in the circumferential direction are determined as the final position distribution design result.

[0061] In an optional embodiment, the slot depth size of each auxiliary slot is determined by the following method:

[0062] The near air gap surface of each closed slot in the motor simulation model is provided with each auxiliary slot according to the final position distribution design result;

[0063] Adjusting the slot depth size of each auxiliary slot in the motor simulation model will maximize the slot depth size of each auxiliary slot when the amplitude of the magnetic flux guide harmonic corresponding to each working harmonic of the motor is maximized, and the slot depth size is taken as the final slot depth size design result.

[0064] It should be noted that the shape of the auxiliary slot in the radial 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 application, a vernier permanent magnet fault-tolerant motor with a stator and a rotor coaxially sleeved from the outside to the inside is taken as an example for detailed description:

[0066] Figure 2This embodiment provides a schematic diagram of a conventional vernier permanent magnet motor, including a stator and a rotor; the stator and rotor are coaxially mounted from the outside to the inside, with an air gap between them; when the motor is working, the rotor rotates relative to the stator around its axis. The stator includes: a stator core 1 and an armature winding 2; the stator core 1 has stator teeth evenly distributed circumferentially. The rotor includes: a permanent magnet 3 and a rotor core 4.

[0067] The stator teeth are parallel teeth; multiple stator slots are evenly distributed circumferentially on the inner wall of the stator, 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 each permanent magnet in it has the same shape, thickness and pole arc coefficient, is magnetized in the radial direction, and adjacent permanent magnets have opposite polarities, and are fixed around the rotor core 4 in the order of NS-NS, and the material is a hard magnetic material such as neodymium iron boron, samarium cobalt or ferrite.

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

[0069] Stator slots are arranged between two adjacent stator teeth, and each stator slot is evenly distributed circumferentially 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. Here, open and closed refer to whether the side facing the rotor is open or closed. An auxiliary groove 6 is arranged on the near air gap surface of the closed slot. Each closed slot and its two adjacent stator teeth together constitute a basic functional multiplexing unit 5. By directionally editing the number of pole pairs and phase composition of the magnetic permeation harmonics, the optimal position arrangement of the auxiliary grooves 6 was derived. The optimal functional multiplexing unit structure after directional design improves the amplitude of the effective working magnetic field harmonics contributing positive and negative electromotive forces, and compensates for the magnetic field modulation effect weakened by the setting of half of the closed slots.

[0070] The armature winding 2 in the embodiment adopts a double-layer winding form with a coil span of 2, in order to ensure high torque density of the vernier permanent magnet fault-tolerant motor under normal working conditions, the polarity of the winding coils belonging to different phases in the same closed slot is kept opposite, and under the slot-pole matching in the embodiment, the working harmonic winding coefficient is 0.866 whether the conventional fractional-slot concentrated winding form or the double-tooth winding form is adopted. In comparison, the double-tooth winding form cooperates with the function reuse unit 5 to better ensure high torque density of the vernier permanent magnet fault-tolerant motor under normal working conditions, and further improve the short-circuit resistance of the motor. The difference between the two lies in that when the conventional fractional-slot concentrated winding form is adopted, the magnetic flux lines flowing through the two sides of the stator tooth of the function reuse unit 5 are mostly derived from the magnetic motive force generated by the two winding coils belonging to different phases in the same closed slot, and the size and direction are the same but the phase is different; when the double-tooth winding form is adopted, the magnetic flux lines flowing through the two sides of the stator tooth of the function reuse unit 5 are not only derived from the magnetic motive force generated by the two coil windings belonging to different phases in the same closed slot, but also partly derived from the magnetic motive force generated by the same coil across the two teeth, and the size, direction and phase are all the same; the latter part of the magnetic flux lines is more likely to flow through the ring tooth magnetic circuit under healthy conditions due to the mutual cancellation of the completely same magnetic motive force; under fault conditions, the magnetic motive force whose phase is different at first is now unbalanced in size, and the weakening of the counteraction between the same magnetic flux lines tends to guide the magnetic flux lines to flow through the ring tooth magnetic circuit, further increasing the slot leakage inductance and phase winding self-inductance, and playing a role in inhibiting short-circuit current under short-circuit fault (including single-phase short-circuit and turn-to-turn short-circuit), and further improving the short-circuit resistance and dynamic performance of the motor. The stator core 1 and the rotor core 4 can be made of soft magnetic materials such as silicon steel sheets.

[0071] In the embodiment, the permanent magnet 3 is provided with 16 pieces, the stator slot is provided with 12 pieces, the function reuse unit 5 is provided with 6 pieces, and the number of the function reuse unit 5 is half of the number of the stator slot. The number of the stator slot Z s , the number of the permanent magnet pole pair P r and the number of the stator armature winding pole pair P a have multiple possibilities, and satisfy the following relationship:

[0072]

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

[0074] A magnetic guide directional design method is provided in the embodiment, and the optimal position distribution of the auxiliary grooves is derived by directionally editing the pole pair number and phase composition of the magnetic guide harmonics. Specifically, in the embodiment, the position distribution of each auxiliary groove is designed in the following manner:

[0075] S1, determine whether each armature winding harmonic of the motor contributes to the back electromotive force of the motor and the positive and negative contribution through a motor simulation model, and take 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 vernier permanent magnet fault-tolerant motor without auxiliary grooves;

[0076] Specifically, in the embodiment, the axis of the A-phase winding is the initial position 0°, and the related parameters of each harmonic of the cross-tooth double-layer winding, such as the harmonic winding coefficient k wv , the slot opening coefficient k sv , the harmonic phase θ sν and other information are shown in Table 1.

[0077] Table 1 winding harmonic

[0078]

[0079] S2, based on the magnetic field modulation principle, calculate the pole pair number and phase of the magnetic guide harmonic corresponding to each working harmonic, and reverse the phase of the magnetic guide harmonic corresponding to the armature winding harmonic with negative contribution to the back electromotive force by 180° as the phase of the magnetic guide harmonic;

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

[0081] Table 2 design magnetic guide harmonic phase

[0082] Magnetic Conductivity Harmonic Pole Pair Number Magnetic Conductivity Harmonic Phase 12 180° 24 180° 36 0°

[0083] S3, based on the pole pair number and phase of the magnetic guide harmonic corresponding to each working harmonic, construct a spatial magnetic guide waveform having a mapping relationship with the stator tooth structure;

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

[0085] S4, based on the positive and negative information of the spatial magnetic guide waveform, and in combination with the stator tooth distribution of the motor simulation model, determine the position distribution of each auxiliary groove;

[0086] The spatial magnetic flux guide wave form has a certain mapping relationship with the modulation tooth structure, that is, the positive value of the magnetic flux guide corresponds to the tooth of the modulation unit (that is, the tooth slot distribution structure corresponding to the harmonic modulation function), and the negative value of the magnetic flux guide corresponds to the slot of the modulation unit, so as to obtain the position distribution of each auxiliary groove; wherein the position distribution includes the starting position, the angle range (the radian of the auxiliary groove in the circumferential direction) and other parameters of each auxiliary groove.

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

[0088] The near air gap surface of each closed slot in the motor simulation model is provided with the auxiliary groove according to the obtained position distribution;

[0089] Adjusting the groove depth size of each auxiliary groove in the motor simulation model, the groove depth size of each auxiliary groove when the magnetic flux guide harmonic amplitude corresponding to each working harmonic of the motor is maximized is taken as the final groove depth size design result, and finally the structure of the function reuse unit 5 as shown in Figure 4 is obtained. In this embodiment, the radian and groove depth size 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 flowing through the winding coils belonging to different phases in the same closed slot is opposite, the magnetic motive forces generated by the winding coils on both sides are the same in size and direction but different in phase, and the difference in phase makes the magnetic motive forces not completely cancel out, thereby reducing the torque density, in addition, part of the magnetic lines of force in the two stator teeth of the function reuse unit also come from the magnetic motive force generated by the same coil across the two teeth, and the size, direction and phase of the magnetic motive force are completely the same, and the counteraction between the same magnetic lines of force is stronger. On the other hand, the function reuse unit plays the role of magnetic flux guide and modulation of harmonic pole number, and the composition of the magnetic flux guide harmonic determines its conversion effect on the magnetic field harmonic pole number, that is, a large number of harmonics with high pole number and short wavelength, which are easy to form short magnetic circuits, will not be generated, which will hinder the magnetic lines of force from going through the ring tooth magnetic circuit to a certain extent. In general, the mutual counteraction of the same magnetic lines of force and the integration of the magnetic field modulation capability can hinder the magnetic lines of force from not going through the ring tooth magnetic circuit, thereby ensuring the high torque performance of the motor under normal working conditions. Under the short-circuit fault working condition, since the slot opening of the closed slot is an arc-shaped core structure rather than air, the magnetic permeability of the arc-shaped core is several thousand times that of air, compared with the long magnetic circuit closure, the function reuse unit is more likely to guide the magnetic lines of force to go through the ring tooth magnetic circuit with relatively lower magnetic resistance, and the size of the magnetic motive force, which was originally only different in phase, also becomes unbalanced, and the weakening of the counteraction between the same magnetic lines of force will also promote most of the magnetic lines of force to go through the ring tooth magnetic circuit, thereby reducing the magnetic coupling degree between the fault winding and the normal winding, and the ring tooth magnetic circuit excites greater slot leakage inductance to increase the winding inductance, so that the motor has the ability to self-restrict the inter-turn short-circuit or single-phase short-circuit current.

[0091] The double-layer winding with a coil span of 2 is adopted under the slot pole matching, compared with the conventional fractional-slot concentrated winding, the working harmonic winding coefficient is unchanged, and the results show that the winding connection mode of the function reuse unit matched with the function reuse 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 orienting the pole pair number and phase composition of the magnetic guide harmonic, the optimal position arrangement of the auxiliary slot 6 is derived, and the optimal function reuse unit structure after directional design improves the amplitude of the effective working magnetic field harmonic contributing to the positive and negative electromotive force, solves the contradiction between the improved short-circuit resistance due to the adoption of the closed slot and the weakened magnetic field modulation ability, guarantees the high torque density advantage of the vernier permanent magnet motor under normal working conditions, and takes into account the strong fault tolerance performance and high torque output of the vernier permanent magnet motor. Moreover, the technical scheme is applicable to the vernier permanent magnet motor of any slot pole.

[0093] Next, to verify the performance difference between the vernier permanent magnet fault-tolerant motor proposed in this embodiment and the conventional 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 conditions and the short-circuit current of the motor under short-circuit fault under the condition that the rotor, stator inner and outer diameters and shaft length of the motor are the same:

[0094] The permanent magnet 3 is air, and the armature winding 2 is connected with current, under the condition of short-circuit fault, the magnetic line distribution of the conventional vernier permanent magnet motor is as shown in Figure 5 The magnetic line distribution of the motor in this embodiment is as shown in Figure 6 After adopting the function reuse unit 5, the magnetic flux generated by the armature winding 2 mainly forms a closed ring magnetic circuit in the adjacent two stator teeth corresponding to the function reuse unit 5, only a small amount of magnetic lines go along the long magnetic circuit and link with other phase windings, which reduces the coupling degree between the fault phase winding and other phase windings, which is reflected as low mutual inductance between phases, and the slot leakage inductance is increased, which improves the self-inductance of the phase winding under fault condition, and the magnetic isolation ability and fault tolerance performance of the motor are improved.

[0095] Figure 7 The output torque comparison chart of the vernier permanent magnet fault-tolerant motor before and after directional design in this embodiment and the conventional vernier permanent magnet motor under normal working conditions is shown in Figure 7As can be seen from the figure, the average torque of the conventional Vernier permanent magnet motor is 16.91 N.m, the average torque of the Vernier permanent magnet fault-tolerant motor before the directional design is 12.56 N.m, and the average torque of the Vernier permanent magnet fault-tolerant motor after the directional design is 15.51 N.m; under the condition of the same current density, the average torque of the motor provided with the auxiliary slot 6 according to the flux guide directional design method is improved by 23.49% compared with the torque without the auxiliary slot 6, that is, the flux guide directional design method ensures the high torque density advantage of the Vernier permanent magnet motor under normal working conditions, reduces the torque ripple, compensates for the weakened magnetic field modulation effect caused by the halving of the number of modulation teeth due to the setting of the function reuse unit 5, and significantly improves 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 For the short-circuit current comparison chart of the armature winding 2 in the Vernier permanent magnet fault-tolerant motor of the embodiment after the directional design and the conventional Vernier permanent magnet motor under short-circuit fault, Figure 8 As can be seen from the figure, the peak short-circuit current of the conventional Vernier permanent magnet motor is 153.12 A, the peak short-circuit current of the Vernier permanent magnet fault-tolerant motor after the directional design is 74.85 A, and the peak short-circuit current of the Vernier permanent magnet fault-tolerant motor of the embodiment is much smaller than that of the conventional Vernier permanent magnet motor, which is reduced by about 51.12%, so the Vernier permanent magnet motor provided in the 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 with the rotor and the stator coaxially sleeved from the outside to the inside is similar to the Vernier permanent magnet fault-tolerant motor with the stator and the rotor coaxially sleeved 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 with the stator and the rotor coaxially sleeved from the outside to the inside, the rotor is arranged inside the stator, the stator teeth are arranged inside the stator core, and an outer stator structure is formed; for the Vernier permanent magnet fault-tolerant motor with the rotor and the stator coaxially sleeved from the outside to the inside, the rotor is arranged outside the stator, the stator teeth are arranged outside the stator core, and an inner stator structure is formed; here, no further description is given.

[0098] Those skilled in the art will readily understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A vernier permanent magnet fault-tolerant motor having a function multiplexing unit, characterized by, The stator and the rotor are coaxially sleeved, and an air gap is arranged between the rotor and the stator; The stator comprises a stator core and an armature winding; the stator core is provided with stator teeth in the circumferential direction; two adjacent stator teeth are provided with a stator slot; and the armature winding is wound in the stator slot; The stator slot comprises two types of open slots and closed slots; the number of the open slots and the closed slots is equal, and the open slots and the closed slots are staggered; each closed slot is provided with an arc-shaped core at the slot opening, and an auxiliary groove is arranged near the air gap surface; One closed slot and two stator teeth adjacent to the closed slot form a functional reuse unit; the functional reuse unit is used to simultaneously consider the strong fault tolerance and high torque density of the motor: under normal working conditions, the magnetic flux is guided to amplify the torque; under short-circuit fault working conditions, the magnetic flux is changed to change the magnetic flux linkage with the winding, and a ring tooth magnetic circuit is formed to reduce the short-circuit current.

2. The Vernier permanent magnet fault-tolerant motor of claim 1, wherein, The armature winding is a three-phase alternating current winding, comprising double-layer winding coils; two winding coils in the same closed slot belong to different phases, and the current polarity flowing through them is opposite.

3. The Vernier permanent magnet fault-tolerant motor of claim 2, wherein, The coil span of the armature winding is 2.

4. The Vernier permanent magnet fault-tolerant motor of claim 1, wherein, The stator teeth are parallel teeth.

5. The Vernier permanent magnet fault-tolerant motor of claim 1, wherein, The material of the stator core is a soft magnetic material.

6. The Vernier permanent magnet fault-tolerant motor of claim 1, wherein, The rotor is arranged in 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.

7. The Vernier permanent magnet fault-tolerant motor of claim 1, wherein, number of stator slots Z s number of rotor permanent magnet pole pairs P r and number of armature winding pole pairs P a satisfying the following relationship: wherein , 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 1-7, characterized in that, The position distribution of each auxiliary groove is determined by the following method: Whether each order armature winding harmonic of the motor contributes to the motor back electromotive force and the positive and negative situation of the contribution are determined through a motor simulation model; the armature winding harmonic that contributes to the back electromotive force is used as a working harmonic; 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 pair number and phase of the magnetic guide harmonic corresponding to each order working harmonic are calculated, and the phase of the magnetic guide harmonic corresponding to the armature winding harmonic with negative contribution to the back electromotive force is reversed by 180° as the phase of the magnetic guide harmonic; Based on the pole pair number and phase of the magnetic guide harmonic corresponding to each order working harmonic, a spatial magnetic guide waveform having a mapping relationship with the stator tooth structure is constructed; Based on the positive and negative information of the spatial magnetic guide waveform, the starting position and arc of each auxiliary groove in the circumferential direction are determined in combination with the stator tooth distribution of the motor simulation model, as the final position distribution design result.

9. The Vernier permanent magnet fault-tolerant motor of claim 8, wherein, The spatial magnetic permeability waveform is formed by superimposing the waveforms of each spatial magnetic permeability element; the first i The waveform expression for a spatial magnetic permeability element is: wherein, and are respectively the coefficient and the coefficient of the second harmonic winding; is the number of rotor permanent magnet pole pairs; is the order of the working armature winding harmonics, ; is the permeance harmonic order; is the phase value of the second permeance harmonic, is the pole pair number of the second permeance harmonic, is the position of the th spatial permeance element.

10. The Vernier permanent magnet fault-tolerant motor of claim 8, wherein, The slot depth size of each auxiliary groove is determined by the following method: The near-air-gap surface of each closed slot in the motor simulation model is provided with each auxiliary groove according to the final position distribution design result; The slot depth size of each auxiliary groove in the motor simulation model is adjusted, and the slot depth size of each auxiliary groove when the amplitude of each order working harmonic of the motor corresponding to the magnetic guide harmonic is maximized is used as the final slot depth size design result.

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