A design method for a modular dual three-phase winding structure to improve the fault tolerance of permanent magnet motors

Abstract

The present invention discloses a design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor, determining different modular winding structures, and determining the harmonic order of the armature synthetic magnetomotive force according to the different distribution laws of different modular winding structures on the stator circumference; determining that the harmonic content of the armature winding magnetomotive force is the main factor affecting the self-inductance of the motor according to the winding function theory; determining that the short-circuit current of a certain phase is inversely proportional to the self-inductance of the motor in combination with the equivalent circuit diagram when a certain phase is short-circuited and the vector diagram under the d-q axis reference system; determining that the magnetic isolation capability between modules of different modular winding structures is determined according to the armature synthetic magnetomotive force function of modules I and III in different modular winding structures; determining the optimal modular winding structure by comparing the short-circuit current of a certain phase and the magnetic isolation capability between modules of different modular winding structures. The method of the present invention solves the problem of poor fault tolerance of the dual three-phase motor of the traditional design.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet motors, and in particular relates to a design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor. Background Art

[0002] Dual three-phase permanent magnet motors have the advantages of high torque density, high power density, and low torque pulsation, and have good application prospects in aerospace and electric vehicles. However, traditional dual three-phase permanent magnet motors have disadvantages such as high short-circuit current amplitude and severe phase coupling, which restrict their application in fields with high reliability requirements. Therefore, improving the fault tolerance performance of permanent magnet motors is receiving more and more attention. At present, the main way to improve the fault tolerance performance of permanent magnet motors is to increase winding redundancy and design new stator structures.

[0003] The prior art combines a distributed winding structure with a block-type stator to improve the torque density and fault tolerance of the motor. However, the stator of this modular structure is asymmetric, which leads to problems such as increased cogging torque amplitude, severe magnetic leakage, and unbalanced magnetic pull. The prior art also introduces isolation teeth to construct a modular winding structure, which can play a role in short-circuit current suppression and phase isolation, but this method changes the number of cycles of the cogging torque, which will lead to an increase in the cogging torque amplitude. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a design method for a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A design method for a modular dual three-phase winding structure to improve the fault tolerance of permanent magnet motors:

[0007] Based on the unit motor definition, the number of modules of a given slot-pole matching motor is calculated, and the slot potential star diagram is drawn to determine different modular winding structures;

[0008] According to the different distribution rules of different modular winding structures on the stator circumference, the harmonic orders of the armature synthetic magnetomotive force of different modular winding structures are determined;

[0009] According to the winding function theory, it is determined that the harmonic content of the armature winding magnetomotive force is the main factor affecting the motor's self-inductance;

[0010] Combined with the equivalent circuit diagram when a phase is short-circuited and the vector diagram under the dq axis reference system, it is determined that the short-circuit current of a phase is inversely proportional to the self-inductance of the motor;

[0011] According to the armature synthetic magnetomotive force function of module I and module III in different modular winding structures, the magnetic isolation capability between modules of different modular winding structures is determined;

[0012] The optimal modular winding structure is determined by comparing the short-circuit current of a certain phase and the magnetic isolation capability between modules of different modular winding structures.

[0013] Furthermore, the motor uses 48 slots / 8 poles.

[0014] Furthermore, the number of modules of the motor is 4, which are respectively recorded as module I, module II, module III and module IV.

[0015] Furthermore, by making different combinations of the overlapping vectors in the slot potential star diagram and considering the elimination of the unbalanced magnetic pull, the number of modular winding structures is 4, and the 4 modular winding structures are respectively recorded as W-Ⅰ, W-Ⅱ, W-Ⅲ and W-Ⅳ.

[0016] Furthermore, when determining the motor self-inductance, the winding factors are based on different modular winding structures, where:

[0017] The winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅰ and the winding factors k of phases B1, B2, C1 and C2 in W-Ⅱ ων for:

[0018]

[0019] The winding factors of phases A1 and A2 in W-Ⅱ are:

[0020]

[0021] The winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅲ and the winding factors of phases B1, B2, C1 and C2 in W-Ⅳ are:

[0022]

[0023] The winding factors of phases A1 and A2 in W-IV are:

[0024]

[0025] Furthermore, the DC component of the self-inductance satisfies the following equation:

[0026]

[0027] Where L0 represents the DC component of self-inductance, μ0 represents the vacuum permeability, R represents the air gap radius, and L efrepresents the axial length of the motor, g represents the air gap function, N represents the number of turns of each phase winding coil, and v represents the harmonic order.

[0028] Furthermore, the steady-state short-circuit current of a phase is inversely proportional to the motor self-inductance, specifically:

[0029]

[0030] Among them, i s_steady (t) represents the steady-state short-circuit current, ψ m(0) represents the initial value of magnetic flux, ω represents the electrical angular velocity, represents the initial phase angle, L A1A1 Indicates the self-inductance of phase A1.

[0031] Furthermore, the magnetic isolation capability between modules is reflected by the mutual inductance value of the modular winding structure.

[0032] Furthermore, the optimal modular winding structure is W-IV.

[0033] Furthermore, the modules I and III of the W-Ⅳ include three-phase windings A1, B1 and C1, and the modules II and IV include three-phase windings A2, B2 and C2; the connection order of the A1 phase winding is S1→S7→S12→S6→S25→S31→S36→S30, the connection order of the B1 phase winding is S4→S10→S5→S11→S28→S34→S29→S35, and the connection order of the C1 phase winding is S9→S 3→S8→S2→S33→S27→S32→S26, the connection order of the A2 phase winding is S13→S19→S24→S18→S37→S43→S48→S42, the connection order of the B2 phase winding is S16→S22→S17→S23→S40→S46→S41→S47, and the connection order of the C2 phase winding is S21→S15→S20→S14→S45→S39→S44→S38.

[0034] The beneficial effects of the present invention are:

[0035] (1) The present invention discloses a design method for a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor. Four modular winding structures are determined. The optimal modular winding structure is determined by comparing the short-circuit current of a certain phase of the four modular winding structures and the magnetic isolation capability between modules. The optimal modular winding structure not only has better short-circuit current suppression capability, but also has better phase-to-phase isolation capability, thereby solving the problem of poor fault tolerance of the dual three-phase motor of the traditional design.

[0036] (2) The four modular winding structures of the present invention are designed by combining the overlapping vectors in the slot potential star diagram in different ways and eliminating the unbalanced magnetic pull. Only the connection method of the armature winding is changed, so the amplitude of the cogging torque will not be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a cross-sectional topological diagram of a 48-slot 8-pole motor of the present invention;

[0038] FIG2( a ) is a star diagram of the slot potential of the W-I structure of the present invention;

[0039] FIG2( b ) is a star diagram of the slot potential of the W-II structure of the present invention;

[0040] FIG2( c ) is a star diagram of the slot potential of the W-III structure of the present invention;

[0041] FIG2( d ) is a star diagram of the slot potential of the W-IV structure of the present invention;

[0042] Fig. 2(e) is a topological diagram of the W-I structure of the present invention;

[0043] FIG2(f) is a topological diagram of the W-II structure of the present invention;

[0044] FIG2( g ) is a topological diagram of the W-III structure of the present invention;

[0045] FIG2(h) is a topological diagram of the W-IV structure of the present invention;

[0046] FIG3( a ) is a winding function diagram of the A1 phase of the four modular winding structures of the present invention;

[0047] FIG3( b ) is a magnetomotive force spectrum diagram of the A1 phase of the four modular winding structures of the present invention;

[0048] FIG3( c ) is a winding function diagram of the B1 phase of the four modular winding structures of the present invention;

[0049] FIG3( d ) is a magnetomotive force spectrum diagram of the B1 phase of the four modular winding structures of the present invention;

[0050] FIG4( a ) is a diagram showing the magnetomotive force distribution of the armature windings when the four modular winding structures of the present invention are operated in single redundancy;

[0051] FIG4( b ) is a diagram showing the harmonic spectrum of the armature winding magnetomotive force when the four modular winding structures of the present invention are operated in single redundancy;

[0052] FIG4( c ) is a distribution diagram of the magnetomotive force of the armature windings when the four modular winding structures of the present invention are in healthy operation;

[0053] FIG4( d ) is a graph showing harmonic spectra of the magnetomotive force of the armature windings when the four modular winding structures of the present invention are operating in a healthy state;

[0054] FIG5( a ) is an equivalent circuit diagram of the present invention when the A1 phase winding is short-circuited;

[0055] FIG5( b ) is a dq axis reference system vector diagram when the A1 phase winding is short-circuited in the present invention;

[0056] FIG6(a) is a magnetomotive force distribution diagram of the armature windings of module I and module III of the two winding structures W-I and W-III of the present invention;

[0057] FIG6( b ) is a magnetomotive force distribution diagram of the armature windings of the modules I and III of the two winding structures W-II and W-IV of the present invention;

[0058] FIG. 7( a ) is a waveform diagram of the self-inductance of phase A1 of four modular winding structures of the present invention;

[0059] FIG. 7( b ) is a waveform diagram of the self-inductance of phase B1 of the four modular winding structures of the present invention;

[0060] FIG8( a ) is a short-circuit current waveform diagram of phase A1 of four modular winding structures of the present invention;

[0061] FIG8( b ) is a short-circuit current waveform diagram of phase B1 of four modular winding structures of the present invention;

[0062] Fig. 9 The braking torque changes with the rotation speed when a short circuit fault occurs in the three-phase winding of the four modular winding structures A1B1C1 of the present invention;

[0063] In the figure: 1- stator core, 2- air gap, 3- permanent magnet, 4- rotor core, 5- armature winding. DETAILED DESCRIPTION

[0064] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0065] A design method for a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor comprises the following steps:

[0066] Step (1), determining the electromagnetic parameters of the motor, specifically including the slot-pole matching, stator part parameters and rotor part parameters of the permanent magnet motor, the stator part parameters include the inner diameter and outer diameter of the stator core, the stator tooth width, the stator yoke thickness, the slot opening width and height and the slot wedge height, the rotor part parameters include the rotor core inner diameter, the rotor yoke thickness, the permanent magnet thickness, and the armature winding part adopts a single-layer winding;

[0067] In this embodiment, the prototype example used is a 48-slot 8-pole permanent magnet motor. Figure 1 As shown, the electromagnetic part specifically includes a stator core 1, a rotor core 4, an armature winding 5, an air gap 2 and a permanent magnet 3; the air gap 2 is located between the stator core 1 and the rotor core 4; the permanent magnet 3 adopts an internal single-layer "V" shape, embedded in the rotor core 4, and the thickness of the permanent magnet 3 is 4.6mm; the armature winding 5 is wound on the stator teeth, adopts a single-layer full-pitch configuration, and the span is 6; the inner diameter and outer diameter of the stator core 1 are 155mm and 100mm respectively, the stator tooth width is 4mm, the stator yoke thickness is 10.5mm, the slot opening width and height are 2mm and 0.8mm respectively, and the slot wedge height is 0.2mm; the inner diameter of the rotor core 4 is 36mm, and the rotor yoke thickness is 20.5mm; the materials of the stator core 1 and the rotor core 4 are both DW310-35, and the material of the permanent magnet 3 is N38SH.

[0068] Step (2), according to the definition of the unit motor, the number of modules of the given slot-pole matching motor is calculated, and the slot potential star diagram is drawn. Based on the distribution law of the slot vectors in each phase band of the slot potential star diagram, different modular winding structures are determined; for different modular winding structures, a winding function is established based on the spatial distribution characteristics of the stator circumferential winding, and the winding factors under different connection modes are derived;

[0069] For a given slot-pole combination, the number of unit motors can be expressed as:

[0070]

[0071] Among them, t represents the number of unit motors, Q represents the number of stator slots of the motor, p represents the number of permanent magnet pole pairs, and GCD[Q,p] represents the greatest common divisor of the number of stator slots and the number of permanent magnet pole pairs.

[0072] In the prototype example adopted in this embodiment, Q=48 and p=4, so it is deduced that the number of unit motors of the prototype example is 4, so the prototype example can be divided into 4 completely identical modules, each module containing 12 stator slots.

[0073] The electrical angle between two adjacent stator slots is p*360° / Q. The slot potential star diagram of a module is drawn according to the electrical angle. Since 48 slots and 8 poles contain 4 identical modules, the complete slot potential star diagram is composed of slot potential star diagrams of 4 modules. Then, the overlapping vectors in the slot potential star diagram are combined in different ways, and the elimination of unbalanced magnetic pull is considered. Finally, the slot potential star diagrams of 4 modular winding structures are obtained, see Figure 2 (a), (b), (c), (d), and the corresponding 4 modular winding structures are shown in Figure 2 (e), (f), (g), (h). For the convenience of representation, W-Ⅰ, W-Ⅱ, W-Ⅲ and W-Ⅳ are used to represent different modular winding structures, representing the first modular winding structure, the second modular winding structure, the third modular winding structure and the fourth modular winding structure, respectively.

[0074] The following are four modular winding structures described in detail:

[0075] For W-Ⅰ and W-Ⅱ, each module contains six-phase windings: A1, B1, C1, A2, B2 and C2. In W-Ⅰ, the connection order of the A1 phase winding is S1→S7→S14→S20→S25→S31→S38→S44, the connection order of the B1 phase winding is S5→S11→S18→S24→S29→S35→S42→S48, the connection order of the C1 phase winding is S9→S3→S22→S16→S33→S27→S46→S40, the connection order of the A2 phase winding is S2→S8→S13→S19→S26→S32→S37→S43, the connection order of the B2 phase winding is S6→S12→S17→S23→S30→S36→S41→S47, and the connection order of the C2 phase winding is S10→S4→S21→S15→S34→S28→S45→S39; In W-Ⅱ, the connection order of the A1 phase winding is S1→S7→S24→S18→S25→S31→S48→S42, the connection order of the B1 phase winding is S5→S11→S16→S22→S29→S35→S40→S46, the connection order of the C1 phase winding is S9→S3→S20→S14→S33→S27→S44→S38, the connection order of the A2 phase winding is S12→S6→S13→S19→S36→S30→S37→S43, the connection order of the B2 phase winding is S4→S10→S17→S23→S28→S34→S41→S47, and the connection order of the C2 phase winding is S8→S2→S21→S15→S32→S26→S45→S39.

[0076] For W-Ⅲ and W-Ⅳ, its modules Ⅰ and Ⅲ contain three-phase windings A1, B1 and C1, and modules Ⅱ and Ⅳ contain three-phase windings A2, B2 and C2. In W-Ⅲ, the connection order of the A1 phase winding is S1→S7→S2→S8→S25→S31→S26→S32, the connection order of the B1 phase winding is S5→S11→S6→S12→S29→S35→S30→S36, the connection order of the C1 phase winding is S10→S4→S9→S3→S34→S28→S33→S27, the connection order of the A2 phase winding is S13→S19→S14→S20→S37→S43→S38→S44, the connection order of the B2 phase winding is S17→S23→S18→S24→S41→S47→S42→S48, and the connection order of the C2 phase winding is S22→S16→S21→S15→S46→S40→S45→S39; In W-Ⅳ, the connection order of the A1 phase winding is S1→S7→S12→S6→S25→S31→S36→S30, the connection order of the B1 phase winding is S4→S10→S5→S11→S28→S34→S29→S35, the connection order of the C1 phase winding is S9→S3→S8→S2→S33→S27→S32→S26, the connection order of the A2 phase winding is S13→S19→S24→S18→S37→S43→S48→S42, the connection order of the B2 phase winding is S16→S22→S17→S23→S40→S46→S41→S47, and the connection order of the C2 phase winding is S21→S15→S20→S14→S45→S39→S44→S38.

[0077] According to the spatial distribution characteristics of stator circumferential windings in different modular winding structures, the winding functions of four modular winding structures are derived using the Fourier series expansion expression of the winding function amplitude.

[0078] In the four modular winding structures in this embodiment, the winding connection methods of the A1A2 phases in W-Ⅱ and the other four phases are different, and the same situation exists in W-Ⅳ. Therefore, the winding factors in W-Ⅱ and W-Ⅳ need to be derived separately, with the A1 phase and B1 as the derivation objects, and the winding functions of each order harmonic need to be derived in combination with formula (6) and Figure 3. The winding functions of these four modular winding structures on (0, 2π) have π as a period, and the winding function of the A1 phase of each structure on (0, π) can be expressed as:

[0079]

[0080] Figure 3 (a) and (c) show the winding function diagrams of phase A1 and phase B1 at (0, 2π) for four modular winding structures;

[0081] Taking W-Ⅰ as an example, according to the definition of Fourier series expansion, the coefficients a0 and a in the Fourier series expansion expression are derived respectively. ν and b ν The specific expression is as follows:

[0082]

[0083] Wherein, N represents the number of turns of each phase winding coil, and v represents the harmonic order;

[0084] Therefore, the Fourier series of the winding function can be expressed as:

[0085]

[0086] Where, θ represents the relative position angle between the stator and the rotor;

[0087] Substituting equation (3) into equation (4), the following expression is derived by converting the sum and difference of trigonometric functions into products:

[0088]

[0089] In addition, the winding function can also be expressed as (i.e. the general form of formula (4)):

[0090]

[0091] Among them, N ν The Fourier series expansion coefficients representing the amplitude of the winding function, represents the phase angle, k ων Indicates the winding factor;

[0092] According to formulas (5) and (6), the winding factor k of phase A1 in W-Ⅰ is ων It is expressed as:

[0093]

[0094] Similarly, the winding factors of each phase of the four modular winding structures can be derived.

[0095] The winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅰ and the winding factors k of phases B1, B2, C1 and C2 in W-Ⅱ ων It is expressed as:

[0096]

[0097] The winding factors of phases A1 and A2 in W-Ⅱ are expressed as:

[0098]

[0099] Similarly, the winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅲ and the winding factors of phases B1, B2, C1 and C2 in W-Ⅳ are expressed as:

[0100]

[0101] The winding factors of phases A1 and A2 in W-IV are expressed as:

[0102]

[0103] It can be seen that even in the same structure, there are cases where the winding factors are not equal. This is caused by the asymmetry of the two-phase windings A1 and A2 in W-Ⅱ and W-Ⅳ. Although the winding factor expressions of these structures are different, their fundamental winding factors are consistent, all of which are 0.966. According to equations (8)-(11), Table 1 lists the winding factors of the corresponding harmonic orders, which is consistent with the trend shown in the spectrum in Figures 3(b) and (d), verifying the rationality and correctness of the theoretical analysis. It can be seen from the table that the armature winding magnetomotive force harmonics of each phase contain 2 nd -, 4 th -, 6 th -, 10 th -、12 th -、14 th - and 18 th -Equal order, i.e. not 8 th - and its multiple harmonics.

[0104] Table 1 Winding factors of different harmonic orders

[0105]

[0106] Step (3), according to the spatial distribution characteristics of the stator circumferential winding under different modular winding structures, the armature synthetic magnetomotive force function under healthy operation and single redundancy operation is constructed respectively, and the harmonic elimination law is analyzed;

[0107] The armature synthetic magnetomotive force F of the dual three-phase winding structure can be written as:

[0108] F=F1+F2 (12)

[0109] Among them, F1 represents the armature composite magnetomotive force generated by the A1, B1 and C1 phase windings, and F2 represents the armature composite magnetomotive force generated by the A2, B2 and C2 phase windings; F1 and F2 can be expressed as:

[0110]

[0111] Among them, N A1 、N B1 and N C1Respectively represent the winding functions of phases A1, B1 and C1, N A2 、N B2 and N C2 Represent the winding functions of phases A2, B2 and C2 respectively, i A1 、i B1 、i C1 、i A2 、i B2 and i C2 Represent the phase currents of phases A1, B1, C1, A2, B2 and C2 respectively.

[0112] Single redundancy operation means that only phases A1, B1 and C1 are in operation, while healthy operation means that phases A1, B1, C1, A2, B2 and C2 are all in operation. Figure 4(a) and (c) are the distribution diagrams of the armature winding composite magnetomotive force under single redundancy operation and healthy operation of the four modular winding structures, respectively. Figure 4(b) and (d) are the harmonic spectrum diagrams of the armature winding composite magnetomotive force under single redundancy operation and healthy operation of the four modular winding structures, respectively. It can be seen that under single redundancy operation, compared with W-Ⅲ and W-Ⅳ, the winding connection methods of W-Ⅰ and W-Ⅱ are more evenly distributed on the circumference of the stator air gap. Therefore, even if these four modular winding structures contain 2 under single redundancy operation, nd -, 4 th -, 6 th -, 10 th -、12 th -、14 th - and 18 th -Equal order harmonics, but the subharmonic amplitudes of W-Ⅰ and W-Ⅱ are smaller; in healthy operation, the armature windings of the four modular winding structures have the same magnetomotive force harmonic content, all containing 4 (6ν±1) th -harmonics, and the harmonic amplitudes are the same, thanks to the fact that they are all based on the same 0° phase shift structure.

[0113] Step (4), according to the winding function theory, derive the self-inductance expression to reveal the relationship between the DC component of the self-inductance and the harmonic content of the armature winding magnetomotive force;

[0114] Taking phase A1 as an example, according to the winding function theory, the self-inductance expression is derived as shown in formula (14):

[0115]

[0116] Among them, L A1A1 represents the self-inductance of phase A1, μ0 represents the vacuum magnetic permeability, R represents the air gap radius, L ef represents the axial length of the motor, g represents the air gap function, N A1 (θ) represents the A1 phase winding function.

[0117] Substituting the winding function (formula (5)) from step (2) into formula (14), the final expression for self-inductance is:

[0118]

[0119] Among them, β ν1 and β ν2 They represent the initial phase angles of the first and second sets of windings corresponding to the harmonic orders (v1, v2), respectively. np and φ np are the amplitude and phase of the npth inductance harmonic, k ωv1 , k ωv2 The winding factors of ν1 and ν2 harmonics and L0 represent the DC component of self-inductance, which can be expressed as:

[0120]

[0121] From equation (16), it can be seen that the harmonic content of the armature winding magnetomotive force is the main factor affecting the motor self-inductance. Therefore, the motor self-inductance can be improved by introducing harmonics.

[0122] Step (5), based on the equivalent circuit diagram of the A1 phase short circuit and the vector diagram under the dq axis reference system, derive the short-circuit current expression to reveal the factors that affect the short-circuit current amplitude;

[0123] According to the equivalent circuit diagram when phase A1 is short-circuited and the vector diagram under the dq axis reference system, see Figure 5(a) and Figure 5(b) respectively, the following expression is obtained:

[0124]

[0125] Among them, ψ A1 represents the flux linkage of phase A1, N represents the number of turns of each phase winding, ψ m represents the flux amplitude, δ represents the angle between the short-circuit phase and the d-axis, U Δ represents the terminal voltage of phase A1, t represents time, R A1 represents the phase resistance of A1, i s Indicates short-circuit current:

[0126]

[0127] Where: I N Indicates rated current, ψ m(0) represents the initial amplitude of the magnetic flux, ω represents the electrical angular velocity;

[0128] It can be seen from formula (18) that the short-circuit current is divided into two parts: steady-state and transient. The steady-state part can be simplified as:

[0129]

[0130] in, When the phase reactance (ωL A1A1 ) is much larger than the phase resistance (R A1 ), formula (19) can be finally simplified to formula (20):

[0131]

[0132] Among them, i s_steady (t) represents the steady-state short-circuit current, ψ m(0) represents the initial value of the magnetic flux, ω represents the electrical angular velocity, and the initial phase angle

[0133] It can be seen from formula (20) that the amplitude of the short-circuit current is inversely proportional to the self-inductance, that is, increasing the self-inductance will be beneficial to suppressing the short-circuit current.

[0134] Step (6), according to the winding distribution characteristics in each module in the modular winding structure, the armature winding synthetic magnetomotive force of module I and module III is established to reveal the magnetic isolation characteristics between modules of different modular winding structures;

[0135] Figure 6 (a) and (b) reflect the interphase coupling degree of the four modular winding structures through the offset component of the synthetic magnetomotive force of the armature of modules I and III. Among them, the offset component can be characterized by the average value of the synthetic magnetomotive force. It can be seen from the figure that the offset component of W-I and W-III is 0.5, while the offset component of W-II and W-IV is 0. This shows that the interphase coupling degree of W-II and W-IV is low, and the magnetic isolation degree between modules is better.

[0136] Step (7), using finite element software, compare the inter-module magnetic isolation capability (mutual inductance) and short-circuit current of the four proposed modular winding structures to determine the optimal modular winding structure design scheme.

[0137] Figure 7(a) and (b) are the self-inductance comparisons of different modular winding structures, and Table 2 lists the specific self-inductance and mutual inductance values ​​of each structure. It can be seen that compared with W-Ⅰ and W-Ⅱ, the self-inductance values ​​of W-Ⅲ and W-Ⅳ are larger, which is due to the rich harmonic content of magnetomotive force in the latter two, which is conducive to the suppression of short-circuit current, as shown in Figure 8(a) and (b); compared with W-Ⅰ and W-Ⅲ, the mutual inductance of W-Ⅱ and W-Ⅳ is smaller, which is because the isolation between modules of W-Ⅱ and W-Ⅳ is better.

[0138] Table 2 Specific self-inductance and mutual inductance values ​​of each structure

[0139]

[0140] Fig. 9The curves of braking torque changing with speed when a short circuit occurs in the three-phase windings of four modular winding structures A1B1C1 are shown in Figure 1. It can be seen that the braking torque of W-Ⅲ and W-Ⅳ is smaller, which is due to their lower short-circuit current.

[0141] In summary, W-Ⅳ not only has better short-circuit current suppression capability, but also has better magnetic isolation capability between modules, and the cogging torque will not increase. Considering the short-circuit current suppression capability, module magnetic isolation capability and cogging torque amplitude, W-Ⅳ is the optimal structural design scheme.

[0142] The present invention proposes a design method for a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor. First, the relevant electromagnetic parameters of the motor are determined; then, according to the definition of the unit motor, the number of modules of the target motor is determined, and according to the slot potential star diagram, four modular winding structures are determined, and the winding function is established according to the spatial distribution characteristics of the stator circumferential winding, and the winding factor under different connection modes is derived; secondly, according to the spatial distribution characteristics of the stator circumferential winding, the synthetic magnetomotive force function under healthy operation and single redundancy operation is constructed respectively, and the distribution law of the harmonics of the armature synthetic magnetomotive force is analyzed; then, the self-inductance expression is derived according to the winding function theory, and the relationship between it and the harmonics of the armature synthetic magnetomotive force is analyzed; in addition, an equivalent circuit diagram is established when one phase is short-circuited, and the short-circuit current expression is derived to explore the factors affecting its amplitude; according to the winding distribution characteristics in each module in the modular winding structure, the armature winding synthetic magnetomotive force of module I and module III is established, and the magnetic isolation characteristics between modules of different modular winding structures are revealed; finally, the accuracy and rationality of the theoretical analysis are verified through finite element simulation. The present invention explores the fault tolerance performance of different modular winding structures, among which W-IV has better short-circuit current suppression capability and better magnetic isolation capability, and does not cause an increase in the amplitude of the cogging torque. The present invention provides a design idea for solving the bottleneck problem of low reliability of traditional dual three-phase motors.

[0143] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A design method for a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor, characterized in that: Based on the unit motor definition, the number of modules of a given slot-pole matching motor is calculated, and the slot potential star diagram is drawn to determine different modular winding structures; According to the different distribution rules of different modular winding structures on the stator circumference, the harmonic order of magnetomotive force synthesized by the armature windings of different modular winding structures is determined; According to the winding function theory, it is determined that the harmonic content of the armature winding magnetomotive force is the main factor affecting the motor's self-inductance; Combined with the equivalent circuit diagram when a phase is short-circuited and the vector diagram under the dq axis reference system, it is determined that the short-circuit current of a phase is inversely proportional to the self-inductance of the motor; According to the magnetomotive force function of the armature windings of modules I and III in different modular winding structures, the magnetic isolation capability between modules of different modular winding structures is determined; By comparing the short-circuit current of a certain phase and the magnetic isolation capability between modules of different modular winding structures, the optimal modular winding structure is determined; The number of modules of the motor is 4, which are respectively recorded as module I, module II, module III and module IV; The overlapping vectors in the slot potential star diagram are combined in different ways, and considering the elimination of unbalanced magnetic pull, the number of modular winding structures is 4, and the 4 modular winding structures are respectively recorded as W-Ⅰ, W-Ⅱ, W-Ⅲ and W-Ⅳ; When determining the motor self-inductance, the winding factors are based on different modular winding structures, where: The winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅰ and the winding factors k of phases B1, B2, C1 and C2 in W-Ⅱ ων for: The winding factors of phases A1 and A2 in W-Ⅱ are: The winding factors of phases A1, A2, B1, B2, C1 and C2 in W-Ⅲ and the winding factors of phases B1, B2, C1 and C2 in W-Ⅳ are: The winding factors of phases A1 and A2 in W-IV are: The DC component of self-inductance satisfies the following equation: Where L0 represents the DC component of self-inductance, μ0 represents the vacuum permeability, R represents the air gap radius, and L ef represents the axial length of the motor, g represents the air gap function, N represents the number of turns of each phase winding coil, v represents the harmonic order, and Q represents the number of stator slots of the motor.

2. The design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor according to claim 1 is characterized in that: The motor uses 48 slots / 8 poles.

3. The design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor according to claim 2 is characterized in that: The steady-state short-circuit current of a phase is inversely proportional to the motor's self-inductance, specifically: Among them, i s_steady (t) represents the steady-state short-circuit current, ψ m(0) represents the initial value of magnetic flux, ω represents the electrical angular velocity, represents the initial phase angle, L A1A1 Indicates the self-inductance of phase A1.

4. The design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor according to claim 3 is characterized in that: The magnetic isolation capability between modules is reflected by the mutual inductance value of the modular winding structure.

5. The design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor according to claim 4 is characterized in that: The optimal modular winding structure is W-Ⅳ.

6. The design method of a modular dual three-phase winding structure for improving the fault tolerance of a permanent magnet motor according to claim 5 is characterized in that: Modules I and III of the W-Ⅳ include three-phase windings A1, B1 and C1, and modules II and IV include three-phase windings A2, B2 and C2; the connection order of the A1 phase winding is S1→S7→S12→S6→S25→S31→S36→S30, the connection order of the B1 phase winding is S4→S10→S5→S11→S28→S34→S29→S35, and the connection order of the C1 phase winding is S9→S3→S8→S2→S33→S27→S32→S26, The connection order of the A2 phase winding is S13→S19→S24→S18→S37→S43→S48→S42, the connection order of the B2 phase winding is S16→S22→S17→S23→S40→S46→S41→S47, and the connection order of the C2 phase winding is S21→S15→S20→S14→S45→S39→S44→S38; among them, S1, S2...S48 represent 48 slots of the motor, and the 48 slots of the motor are arranged in sequence counterclockwise.

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