CN115549405A - Design method for phase group modular structure capable of improving fault-tolerant capability of permanent magnet motor and considering low torque ripple - Google Patents

Design method for phase group modular structure capable of improving fault-tolerant capability of permanent magnet motor and considering low torque ripple Download PDF

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CN115549405A
CN115549405A CN202211281246.1A CN202211281246A CN115549405A CN 115549405 A CN115549405 A CN 115549405A CN 202211281246 A CN202211281246 A CN 202211281246A CN 115549405 A CN115549405 A CN 115549405A
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phase
permanent magnet
tooth
modular structure
winding
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吉敬华
李�杰
赵文祥
孙玉华
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Jiangsu University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
    • H02K15/0006—Disassembling, repairing or modifying dynamo-electric machines
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/02—Details
    • H02K21/021—Means for mechanical adjustment of the excitation flux
    • H02K21/022—Means for mechanical adjustment of the excitation flux by modifying the relative position between field and armature, e.g. between rotor and stator
    • H02K21/023—Means for mechanical adjustment of the excitation flux by modifying the relative position between field and armature, e.g. between rotor and stator by varying the amount of superposition, i.e. the overlap, of field and armature
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
    • H02K29/03—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
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    • Y02T10/64—Electric machine technologies in electromobility

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Abstract

The invention discloses a design method of a phase group modular structure for improving the fault-tolerant capability of a permanent magnet motor and considering low torque ripple, which solves the problem that the improvement of the fault-tolerant capability and the low torque ripple are difficult to be considered simultaneously. Specifically, the method comprises a design principle of phase group modularization, wherein tooth shoes of a module I, a module III and a module V in the phase group modularization are subjected to clockwise deviation, and tooth shoes of a module II, a module IV and a module VI are subjected to anticlockwise deviation. The invention combines the phase group modular structure and the tooth shoe offset, and adopts the method aiming at the 18-slot/16-pole permanent magnet motor. Because the fault-tolerant teeth exist between every two modules, the interphase coupling can be effectively reduced; the configuration of the winding is changed, the self-inductance amplitude is improved, and the short-circuit current is effectively inhibited; and the tooth shoe of each module is shifted, so that the cogging torque amplitude is restrained, and the torque ripple is reduced. The fault-tolerant capability is improved, and meanwhile low torque pulsation is considered.

Description

Design method for phase group modular structure capable of improving fault-tolerant capability of permanent magnet motor and considering low torque ripple
Technical Field
The invention relates to a design method of a phase group modular structure for improving the fault-tolerant capability of a permanent magnet motor and considering low torque ripple, and belongs to the high-reliability application field of aerospace, electric automobiles and the like.
Background
The permanent magnet motor has the characteristics of high efficiency, high power density and the like, and is widely applied to the fields of national defense and military industry, aerospace, electric automobiles and the like. However, the conventional permanent magnet motor has poor fault tolerance and cannot be applied to high-reliability application. Therefore, increasing concerns are being raised about improving the fault tolerance of permanent magnet motors. The fault-tolerant permanent magnet motor should satisfy characteristics such as good phase-to-phase isolation and low short-circuit current. At present, for improving the fault-tolerant performance of a permanent magnet motor, the redundancy of a winding is increased and a novel stator structure is designed. However, increasing winding redundancy results in increased driver size, while increasing switching devices results in increased switching losses. Designing new stator structures, while effective in improving fault tolerance of the motor, is often accompanied by an increase in cogging torque and torque ripple.
As described in a paper of comprehensive study of fault-tolerant switched-flux permanent-magnet machines published in IEEE Transactions on industrial electronics in 2017, C-shaped, E-shaped and modularized stator structures can improve self-inductance and inhibit short-circuit current compared with the traditional stator structure; and mutual inductance is reduced, so that the phase-to-phase isolation capability is improved. However, the average torque of these several configurations is reduced and the torque ripple is also significantly increased compared to the conventional configuration.
The Chinese patent application number 201811432244.1 discloses a permanent magnet fault-tolerant motor based on tooth-separating windings and unequal stator tooth pitches, each phase of windings of the motor are separated by the separating teeth and combined with the unequal stator tooth pitches, the phase-to-phase isolation capability and the self-inductance amplitude are improved, and the fault-tolerant performance and the capacity of inhibiting short-circuit current of the motor are effectively improved. However, this method may result in increased torque ripple, which affects torque performance.
As described in a paper "multiple phase modulated surface-complete permanent-magnetic machine with double-layer structured-slot coupled winding" published in IEEE Transactions on Magnetics in 2019, a novel stator structure is designed, wherein windings in the structure are in a single-layer and double-layer mixed configuration, mutual inductance between phases is almost zero, coupling between phases is effectively reduced, and fault tolerance is improved. However, this configuration reduces the least common multiple of the slot number and pole number, resulting in a significant increase in cogging torque amplitude.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and provides a design method of a phase group modular structure for improving the fault-tolerant capability of a permanent magnet motor and considering low torque ripple.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose: a design method for improving fault-tolerant capability of a permanent magnet motor and considering a phase group modular structure with low torque ripple comprises the following specific steps:
step 1, determining the size parameters of a traditional permanent magnet motor, specifically comprising the slot pole matching of the permanent magnet motor, the size of the inner diameter and the outer diameter of a stator, the pole arc coefficient of a permanent magnet, the length of an air gap between the stator and a rotor and the thickness of a rotor sheath;
step 2, on the basis of the size of the traditional permanent magnet motor, designing a phase group modular structure, wherein each phase winding in the structure exists in an independent module and is isolated by fault-tolerant teeth; the conventional permanent magnet motor has 18 coils, the number of turns of each coil is 40, the total number of turns is 720, the number of the coils of the structure is changed into 12, the total number of turns is unchanged from that of the conventional motor, and then the number of turns of each coil of the structure is changed into 60 turns; in order to ensure the utilization rate of the groove area, the full rate of the structure is consistent with that of the traditional structure; furthermore, the structure contains 6 modules: the mechanical angle corresponding to each module is kept consistent with that of a traditional motor, namely 60 degrees;
step 3, respectively carrying out anticlockwise and clockwise deviation on the tooth shoes of the modules I, III and V and the tooth shoes of the modules II, IV and VI on the designed phase group modular structure by the same angle, and deducing a tooth space torque expression after the tooth shoes deviate;
step 4, the mechanical angles spanned by the stator tooth distribution and the tooth tops of the phase group modular structure combined with the tooth shoe offset are changed, and the pitch coefficient and the distribution coefficient are changed, so that the winding factors are different;
and 5, deducing a short-circuit current expression according to the equivalent circuit diagram of the A-phase short circuit.
Step 6, changing the winding turns and the arrangement mode of the phase group modular structure combined with the tooth shoe offset, deducing a winding function of the phase group modular structure, and carrying out magnetomotive force harmonic analysis and derivation of a self-inductance expression according to the winding function;
and 7, analyzing by comparing finite element software with the traditional stator structure to obtain performance indexes such as magnetomotive force harmonic waves, self-inductance, mutual inductance, short-circuit current, average torque, torque ripple and the like, and verifying the effectiveness of the invention.
Further, in the step 1, the adopted motor is an 18-slot/16-pole permanent magnet synchronous motor, and comprises six parts, namely a stator iron core, an armature winding, an air gap, a rotor sheath, a rotor iron core and a rotor permanent magnet; the stator core comprises 18 stator teeth; the armature winding adopts a double-layer fractional slot concentrated winding; the air gap and the rotor sheath are positioned between the stator and the rotor, wherein the length of the air gap is 0.7mm, and the thickness of the sheath is 0.3mm; the rotor core comprises 16 grooves; the 16 rotor permanent magnets are respectively embedded into the 16 grooves of the rotor core; the stator iron core material is B35-AH230, the rotor iron core material is DT4C, and the permanent magnet material is N42UH.
Further, in step 2, in order to ensure the utilization rate of the slot area, when designing the phase group modularization, the slot fullness ratio should be kept consistent with the conventional structure, and the expression of the slot fullness ratio K is as follows:
Figure BDA0003898407960000031
wherein n represents the number of parallel turns of the wire, S m Denotes the number of turns of each coil, S denotes the cross-sectional area of the wire, A m Showing the stator slot area.
Further, the stepsIn step 3, cogging torque T cog The expression of (β) is:
Figure BDA0003898407960000032
wherein v represents the harmonic order, T cν Magnitude of cogging torque, N, representing generation of ν -th harmonic 2pz The least common multiple of the number of slots and the number of poles is shown, and beta represents the relative position angle of the stator and the rotor.
Further, in step 3, according to the cogging torque expression, the tooth shoes of the modules i, iii, and v are subjected to counterclockwise shift, the tooth shoes of the modules ii, iv, and vi are subjected to clockwise shift, and the cogging torques after the tooth shoes are subjected to counterclockwise and clockwise shifts may be respectively represented as:
Figure BDA0003898407960000033
Figure BDA0003898407960000034
wherein T is cog_L (. Beta.) and T cog_R (beta) represents the cogging torque after the tooth shoe has been displaced counterclockwise and clockwise, respectively, beta x The mechanical angle representing the offset of the tooth shoe is represented by the joint type (3) and (4), and the final cogging torque table is as follows:
Figure BDA0003898407960000035
further, in step 4, the winding factor is obtained by multiplying the pitch coefficient and the distribution coefficient, and the stator tooth distribution and the mechanical angle spanned by the tooth crest of the phase group modular structure combined with the tooth shoe offset are changed, so that the winding factor is changed accordingly.
Further, in the step 5, according to the equivalent circuit diagram when the a phase is short-circuited, the following expression may be obtained:
Figure BDA0003898407960000036
wherein psi A Represents the magnetic flux linkage of phase A, L AA Denotes the self-inductance of phase A, i s Representing short-circuit current, N representing winding function amplitude, # m Represents the flux linkage amplitude, delta represents the angle between the short-circuit phase and the d-axis, U Δ Represents terminal voltage of phase A, R A The phase resistance of the A phase is shown, and t is time.
Further, in step 6, the number of turns of the winding and the arrangement of the phase group modular structure combined with the offset of the tooth shoe are changed, and the expression of the winding function of the phase a of the structure is as follows:
N A (θ)＝n(θ)-avg[n(θ)] (7)
wherein N is A (theta) represents a winding function of the A phase, n (theta) represents a turn function of the A phase, avg [ n (theta) ]]The average of the a phase turns function is shown and theta represents the angular position of the stator reference frame relative to the phase a axis. N is a radical of A The fourier expansion expression of (θ) is:
Figure BDA0003898407960000041
wherein a is 0 、a ν And b ν Denotes fourier expansion coefficients, and ν denotes harmonic order.
Further, in the step 6, for the three-phase symmetrical winding, the resultant magnetomotive force F is s The expression of (a) is:
F s ＝∑(N A I A +N B I B +N C I C ) (9)
wherein N is A 、N B And N C Fourier expansion expressions, I, representing winding functions of phase A, phase B and phase C, respectively A 、I B And I C Phase currents of phase a, phase B and phase C are shown, respectively.
Further, in step 6, a self-inductance expression is derived according to the winding function theory as follows:
Figure BDA0003898407960000042
wherein L is AA Denotes the self-inductance of phase A,. Mu. 0 Denotes the vacuum permeability, r denotes the outer diameter of the stator of the motor, l denotes the axial length of the stator laminations, and g denotes the air gap length.
Further, on the target motor, a phase group modular structure is designed, and each phase winding in the structure exists in an independent module and is isolated by fault-tolerant teeth; the number of coils is changed into 2/3 of that of the traditional permanent magnet motor, and the total number of turns is kept unchanged; in order to ensure the utilization rate of the groove area, the full rate of the structure is consistent with that of the traditional structure; in addition, the structure comprises 6 modules (module I-module VI), and the mechanical angle corresponding to each module is also consistent with that of the traditional motor, namely 60 degrees;
furthermore, the tooth shoes of each module in the phase group modular structure are offset, wherein the tooth shoes of the module I, the module III and the module V are offset anticlockwise, and the tooth shoes of the module II, the module IV and the module VI are offset clockwise.
Further, according to the expression of the cogging torque, the expressions of the cogging torque after the tooth shoe is deflected anticlockwise and clockwise are obtained respectively, and finally the synthesized expression of the cogging torque is obtained.
Further, according to the phase group modular structure, the stator tooth distribution after the tooth shoe deflection and the mechanical angle spanned by the tooth crest are combined, a slot potential star diagram is obtained, and the winding factor is calculated.
Furthermore, a short-circuit current expression is deduced according to an equivalent circuit diagram of the A-phase short circuit.
Further, in the phase group modular structure combining the tooth shoe offset, the number of turns and the arrangement mode of the armature windings are changed, and the winding function of the structure is deduced according to the change.
Further, magnetomotive force harmonic analysis is carried out through the winding function, and a self-inductance expression is deduced according to the winding function.
Further, the effectiveness of the invention is verified by comparing the magnetomotive force, the inductance, the short-circuit current, the cogging torque and the torque of the traditional structure and the structure of the invention through finite element simulation.
The invention has the following benefits and effects:
1. the invention designs a phase group modular structure which can effectively inhibit short-circuit current and reduce the inter-phase coupling degree, thereby improving the fault-tolerant capability of the motor.
2. The invention combines tooth shoe offset on the basis of a phase group modular structure, improves the fault-tolerant capability of the motor and ensures low torque pulsation at the same time.
3. The invention improves the fundamental wave winding factor, thereby improving the average torque.
In conclusion, the design method for improving the fault-tolerant capability of the permanent magnet motor and considering the phase group modular structure of the low torque ripple overcomes the limitation that the prior art is difficult to combine the improvement of the fault-tolerant capability and the low torque ripple.
Drawings
Fig. 1 is a schematic view of a conventional motor structure;
FIG. 2 is a schematic view of the motor structure of the present invention; a schematic diagram of a phase group modular structure; (b) is a schematic diagram of an embodiment of the invention;
FIG. 3 is a schematic diagram of the present invention; a schematic diagram of phase group modularization; (b) is a schematic diagram of an embodiment of the invention;
FIG. 4 is a graph of the cell potential star; (a) is a conventional structure tank potential star diagram; (b) is a star plot of cell potentials according to embodiments of the present invention;
FIG. 5 is an equivalent circuit diagram of the phase A short circuit;
FIG. 6 is a graph comparing winding functions of a conventional motor structure and an embodiment of the present invention;
FIG. 7 is a magnetomotive force harmonic contrast plot for a conventional motor configuration and an embodiment of the present invention;
FIG. 8 is a graph comparing conventional motor construction and inductance of an embodiment of the present invention; (a) is a self-inductance contrast graph; (b) is mutual inductance comparison graph;
FIG. 9 is a diagram of a comparison of magnetic lines of force between a conventional motor structure and an embodiment of the present invention; (a) is a magnetic force line distribution diagram of the traditional motor structure; (b) is the magnetic force line distribution diagram of the embodiment of the invention;
FIG. 10 is a comparison of short circuit current for a conventional motor configuration and a motor in accordance with an embodiment of the present invention;
FIG. 11 is a schematic diagram of the cogging torque suppression of the motor according to the embodiment of the present invention;
FIG. 12 is a comparison of cogging torque for a phase bank modular configuration versus an embodiment of the present invention;
FIG. 13 is a torque comparison graph of a conventional, phase group modular structure with an embodiment of the present invention;
Detailed Description
To explain the design principles, technical solutions and profitable effects of the present invention in more detail, the present invention will be explained with reference to the embodiments and the accompanying drawings.
Fig. 1 is a schematic view of a conventional permanent magnet motor structure incorporating the present invention, the slot pole of the motor being a 18 slot/16 pole fit, wherein 1 denotes a stator core, 2 denotes a rotor core, 3 denotes armature teeth, 4 denotes an armature winding, 5 denotes permanent magnets, and 6 denotes a rotor sheath. The armature winding of the motor adopts a double-layer fractional slot concentrated winding, the permanent magnet adopts a surface-mounted structure, the material of a stator iron core is B35-AH230, the material of a rotor iron core is DT4C, and the material of the permanent magnet is N42UH;
fig. 2 (a) and (b) show a phase group modular structure and a structure view of an embodiment of the present invention, respectively, in which 7 denotes an auxiliary tooth, 8 denotes an undeflected tooth shoe, and 9 denotes a deflected tooth shoe. Fig. 3 (a) and (b) show the principle of designing the phase group modularity and the tooth shoe offset, respectively. When the phase group modularization is designed, the number of winding wire turns is changed into 2/3 of the number of winding wire turns of the traditional structure, the total number of turns of the coil is kept unchanged, the number of the winding wire turns of the phase group modularization structure is changed into 3/2 of the number of winding wire turns of the traditional structure, and the slot filling factor is kept consistent with the traditional structure in order to ensure the slot area utilization rate. From the expression (1) for the bin-full ratio, it can be deduced that A 2 ＝1.5A 1 ，A 3 ＝0.75A 1 . Wherein A is 1 Denotes the groove area of the conventional structure, A 2 Large slot area, A, representing phase group modular structure 3 Modular junction of representative phase groupsSmall groove area of the structure. The expression (5) of the cogging torque after the tooth shoe is offset is combined, and the time beta can be deduced x If the angle is 1.875 °, the cogging torque is suppressed well.
Fig. 4 is a star diagram of slot potentials of the conventional structure and the embodiment of the present invention, from which distribution coefficients of two structures can be obtained, respectively, according to the expression of the winding factor:
k ων ＝k pν ·k dν (10)
wherein k is ων Representing the winding factor, k pν Denotes the pitch coefficient, k dν Representing the distribution coefficient. Through calculation, the fundamental wave winding factor of the conventional structure is 0.945, and the fundamental wave winding factor of the embodiment of the invention is 0.966.
Fig. 5 is an equivalent circuit diagram of a phase a short circuit, and equation (6) can be further expressed as:
Figure BDA0003898407960000061
wherein i s (t) represents a short-circuit current, I N Indicating rated current, # m(0) Denotes the initial amplitude of the flux linkage, ω denotes the electrical angular frequency, δ 0 Representing the initial angle of δ. As can be seen from equation (11), the short-circuit current is divided into two parts, a steady-state part and a transient part, wherein the steady-state part i s_steady (t) can be reduced to
Figure BDA0003898407960000062
Wherein
Figure BDA0003898407960000063
Phase-current reactance (omega L) AA ) Much greater than the phase resistance (R) A ) While, formula (12) can be simplified to
Figure BDA0003898407960000064
As can be seen from equation (13), the magnitude of the short-circuit current is inversely proportional to the self-inductance, i.e., increasing the self-inductance will favor suppression of the short-circuit current.
Fig. 6 is a diagram comparing the winding function of the conventional motor structure and the winding function of the embodiment of the present invention, and it can be seen that the function of the embodiment of the present invention has a larger amplitude, and it can be seen that the coupling region exists in the conventional motor structure, but does not exist in the embodiment of the present invention. Fourier expansion expressions of winding functions of the conventional structure and the embodiment of the present invention are derived in conjunction with fig. 6 and equation (8), respectively:
Figure BDA0003898407960000065
wherein N is Ac (theta) represents the winding function of the conventional structure, N c The magnitude of the winding function is expressed as:
Figure BDA0003898407960000071
wherein N is coil The number of turns of each coil is indicated.
Figure BDA0003898407960000072
Wherein N is AP Winding function, N, representing an embodiment of the invention P1 And N P2 The amplitudes of the winding function when v is odd and even are respectively expressed as:
Figure BDA0003898407960000073
FIG. 7 is a comparison graph of magnetomotive force harmonic spectra of a motor of a conventional configuration and an embodiment of the present invention. For a three-phase symmetric composite magnetomotive force, it can be derived from the winding function derived above and equation (9). The magnetomotive force expression of the traditional structure is as follows:
Figure BDA0003898407960000074
wherein f represents forward rotation, b represents reverse rotation, c represents conventional structure, I represents amplitude of phase current, p represents pole pair number of permanent magnet, and ω is r Representing angular speed of the rotor, gamma d Representing the phase angle between the current vector and the d-axis of the rotor.
The magnetomotive force expression of the embodiment of the invention is as follows:
Figure BDA0003898407960000075
wherein P represents an embodiment of the present invention, N P ，N t1 And N t2 Respectively expressed as:
Figure BDA0003898407960000076
according to the derivation results, the embodiment of the invention has two parts due to the offset of the tooth shoes, so that the composite magnetomotive force has two parts. When v is an even number, the magnetomotive force harmonic order of the embodiment of the invention is the same as that of the traditional structure; when ν is an odd number, the 1, 5, 7, 11, 13, 17, and 19-order harmonics in the embodiment of the present invention are not present in the conventional structure. According to the spectrogram, the harmonic content of the traditional structure and the harmonic content of the embodiment of the invention are consistent with the derivation result, and the accuracy of theoretical derivation is verified. In addition, the fundamental wave amplitude of the motor in the embodiment of the invention is larger than that of the traditional structure, which is the same as the trend of the winding factor, and the accuracy of the winding factor calculation is verified. In addition, the fundamental wave winding factor is increased, which is beneficial to improving the torque.
Fig. 8 is a graph comparing inductances of the conventional structure and the embodiment of the present invention. The self-inductance can be obtained by respectively substituting Fourier expansion of winding functions of two structures into an equation (10) and deriving self-inductance expressions of different structures. Wherein, the A phase of the traditional structure has self-inductance L AAc The expression of (a) is:
Figure BDA0003898407960000081
phase A self-inductance L of the embodiment of the invention AAP The expression of (a) is:
Figure BDA0003898407960000082
by comparison, the self-inductance amplitude of the embodiment of the invention is larger than that of the traditional structure. And the result shown in the graph (a) is consistent with the derivation result, so that the accuracy of theoretical derivation is verified, and the embodiment of the invention has better capability of inhibiting the short-circuit current. As can be seen from the graph (b), the mutual inductance of the embodiment of the present invention is almost 0, which illustrates that the embodiment of the present invention has better fault tolerance.
Fig. 9 is a comparison of magnetic lines of a phase a in the conventional structure and the embodiment of the present invention. The phase-to-phase isolation can be reflected from mutual inductance and can be represented by magnetic lines of force. Fig. (a) is a distribution diagram of a phase a magnetic force lines in a conventional structure, from which it can be seen that the magnetic force lines are distributed not only in phase a but also in other phases, which may cause severe inter-phase coupling; however, the magnetic field lines in the diagram (b) are distributed only in the phase a, and are not distributed in other phases, which shows that the embodiment of the present invention has better phase-to-phase isolation capability.
Fig. 10 is a graph comparing short circuit current of a conventional structure and an embodiment of the present invention. It can be seen from the figure that the amplitude of the short-circuit current is reduced from 18.4A to 12.8A, which is reduced by 30.4%, which shows that the embodiment of the invention has better capability of inhibiting the short-circuit current.
Fig. 11 is a schematic diagram of cogging torque suppression according to an embodiment of the present invention. As can be seen from the figure, as the shoe is shifted in different directions, the phase of the cogging torque waveform is shifted accordingly. According to the above derivation, when the offset angle is 1.875 °, two cogging torque waveforms having opposite waveforms are obtained, in which case the suppression effect on the cogging torque is the best.
Fig. 12 is a comparison of cogging torque for a phase group modular configuration versus an embodiment of the present invention. It can be seen from the figure that when the shoe is offset by 1.875 °, the magnitude of cogging torque is reduced from 290 Nm to 115 Nm, which is reduced by more than 60%. It is demonstrated that cogging torque can be effectively suppressed using shoe deflection.
Fig. 13 is a torque comparison graph of a conventional structure, a phase group modular structure, and an embodiment of the present invention. As can be seen from the figure, the phase group modular structure has the maximum average torque, but the torque ripple thereof reaches 9.02%, which is unacceptable. The embodiment of the invention not only has the torque larger than that of the traditional structure, but also has the torque ripple at a lower level. In general, the torque performance of the embodiment of the invention is better.
In conclusion, the invention provides a design method of a phase group modular structure for improving the fault tolerance performance of a permanent magnet motor and considering low torque ripple. Firstly, determining relevant parameters of a motor; then, a design method of a phase group modular structure and relevant characteristics of the structure are pointed out, and an offset angle of a tooth shoe is deduced according to a tooth socket torque expression; secondly, deriving respective winding function expressions according to the traditional structure and the winding distribution characteristics of the embodiment of the invention; then, analyzing magnetomotive force harmonic waves and deducing an inductance expression according to a winding function; finally, the accuracy of theoretical derivation is verified through finite element simulation, and meanwhile, the embodiment of the invention has better short-circuit current inhibiting capability and interphase isolation capability, and the fault tolerance capability is improved; in addition, the embodiment of the invention not only improves the average torque, but also has lower torque ripple, and realizes the combination of improving the fault-tolerant capability and low torque ripple. The invention can provide reference and theoretical guidance for improving the fault-tolerant performance of the motor and inhibiting the torque pulsation.

Claims (10)

1. A design method for improving fault-tolerant capability of a permanent magnet motor and considering a phase group modular structure with low torque ripple is characterized by comprising the following specific steps:
step 1, determining the size parameters of a traditional permanent magnet motor, specifically comprising the slot pole matching of the permanent magnet motor, the size of the inner diameter and the outer diameter of a stator, the pole arc coefficient of a permanent magnet, the length of an air gap between a stator and a rotor and the thickness of a rotor sheath;
step 2, on the basis of the size of the traditional permanent magnet motor, designing a phase group modular structure, wherein each phase winding in the structure exists in an independent module and is isolated by fault-tolerant teeth; the traditional permanent magnet motor is provided with 18 coils, the number of turns of each coil is 40, the total number of turns is 720, the number of the coils in the structure is changed into 12, the total number of turns is unchanged from that of the traditional motor, and then the number of turns of each coil in the structure is changed into 60 turns; in order to ensure the utilization rate of the groove area, the full rate of the structure is consistent with that of the traditional structure; furthermore, the structure contains 6 modules: the mechanical angle corresponding to each module is also consistent with that of a traditional motor, namely 60 degrees;
step 3, respectively carrying out anticlockwise and clockwise offset on the tooth shoes of the modules I, III and V and the tooth shoes of the modules II, IV and VI by the same angle on the designed phase group modular structure, and deducing a tooth space torque expression after the tooth shoes are offset;
step 4, the mechanical angles spanned by the stator tooth distribution and the tooth tops of the phase group modular structure combined with the tooth shoe offset are changed, and the pitch coefficient and the distribution coefficient are changed, so that the winding factors are different;
and 5, deducing a short-circuit current expression according to the equivalent circuit diagram of the A-phase short circuit.
Step 6, changing the winding turns and the arrangement mode of the phase group modular structure combined with the tooth shoe offset, deducing a winding function of the phase group modular structure, and carrying out magnetomotive force harmonic analysis and derivation of a self-inductance expression according to the winding function;
and 7, analyzing by comparing finite element software with the traditional stator structure to obtain performance indexes such as magnetomotive force harmonic waves, self-inductance, mutual inductance, short-circuit current, average torque, torque ripple and the like, and verifying the effectiveness of the invention.
2. The method for designing the phase group modular structure for improving the fault-tolerant capability of the permanent magnet motor and considering the low torque ripple according to claim 1, wherein in the step 1, the adopted motor is an 18-slot/16-pole permanent magnet synchronous motor and comprises six parts, namely a stator core, an armature winding, an air gap, a rotor sheath, a rotor core and a rotor permanent magnet; the stator core comprises 18 stator teeth; the armature winding adopts a double-layer fractional slot concentrated winding; the air gap and the rotor sheath are positioned between the stator and the rotor, wherein the length of the air gap is 0.7mm, and the thickness of the sheath is 0.3mm; the rotor core comprises 16 grooves; the 16 rotor permanent magnets are respectively embedded into the 16 grooves of the rotor core; the stator core material is B35-AH230, the rotor core material is DT4C, and the permanent magnet material is N42UH.
3. The method for designing a phase group modular structure for improving fault-tolerant capability of a permanent magnet motor and considering low torque ripple according to claim 1, wherein in the step 2, in order to ensure the slot area utilization rate, the slot fullness rate is consistent with the conventional structure when designing the phase group modular structure, and the expression of the slot fullness rate K is as follows:
Figure FDA0003898407950000021
wherein n represents the number of parallel turns of the wire, S m Denotes the number of turns of each coil, S denotes the cross-sectional area of the wire, A m Showing the stator slot area.
4. The method for designing the phase group modular structure for improving the fault-tolerant capability of the permanent magnet motor and considering the low torque ripple as claimed in claim 1, wherein in the step 3, the cogging torque T is adopted cog The expression of (β) is:
Figure FDA0003898407950000022
wherein v denotes the harmonic order, T cν Magnitude of cogging torque, N, representing generation of ν harmonics 2pz The least common multiple of the number of slots and the number of poles is shown, and beta represents the relative position angle of the stator and the rotor.
5. The method for designing a phase group modular structure for improving fault-tolerant capability of a permanent magnet motor and considering low torque ripple according to claim 1, wherein in the step 3, according to a cogging torque expression, the tooth shoes of the modules i, iii, and v are offset counterclockwise, the tooth shoes of the modules ii, iv, and vi are offset clockwise, and the cogging torques after the tooth shoes are offset counterclockwise and clockwise can be respectively expressed as:
Figure FDA0003898407950000023
Figure FDA0003898407950000024
wherein T is cog_L (. Beta.) and T cog_R (beta) represents the cogging torque after the tooth shoe has been displaced counterclockwise and clockwise, respectively, beta x The mechanical angle of the tooth shoe offset is represented, and the final tooth socket torque table is represented by the joint type (3) and (4):
Figure FDA0003898407950000025
6. the method as claimed in claim 1, wherein in step 4, the winding factor is obtained by multiplying a pitch coefficient and a distribution coefficient, and the mechanical angle spanned by the stator tooth distribution and the tooth crest of the phase group modular structure combined with the tooth shoe offset is changed, resulting in a change of the winding factor.
7. The method for designing a phase group modular structure for improving fault-tolerant capability of a permanent magnet motor and considering low torque ripple according to claim 1, wherein in the step 5, according to an equivalent circuit diagram of a phase short circuit, the following expression can be obtained:
Figure FDA0003898407950000031
wherein psi A Represents the A-phase flux linkage, L AA Denotes the self-inductance of phase A, i s Representing short-circuit current, N representing winding function amplitude, # m Represents the flux linkage amplitude, delta represents the angle between the short-circuit phase and the d-axis, U Δ Terminal voltage of A phase, R A The phase resistance of the A phase is represented, and t represents time.
8. The method for designing a phase group modular structure for improving fault-tolerant capability of a permanent magnet motor and considering low torque ripple according to claim 1, wherein in the step 6, the number of winding turns and the arrangement of the phase group modular structure combined with the tooth shoe offset are changed, and the winding function expression of the phase a of the structure is as follows:
N A (θ)＝n(θ)-avg[n(θ)] (7)
wherein N is A (theta) represents a winding function of the A phase, n (theta) represents a turn function of the A phase, avg [ n (theta) ]]Represents the average of the a-phase turns function and θ represents the angular position of the stator reference frame relative to the phase a axis. N is a radical of A The fourier expansion expression of (θ) is:
Figure FDA0003898407950000032
wherein a is 0 、a ν And b ν Denotes fourier expansion coefficients, and ν denotes harmonic order.
9. The design method for improving fault-tolerant capability of permanent magnet motors and considering phase group modular structure of low torque ripple as claimed in claim 1, wherein in the step 6, for three-phase symmetrical windings, the resultant magnetomotive force F is s The expression of (a) is:
F s ＝∑(N A I A +N B I B +N C I C ) (9)
wherein N is A 、N B And N C Fourier expansion expressions, I, representing winding functions of phase A, phase B and phase C, respectively A 、I B And I C Phase currents of phase a, phase B and phase C are shown, respectively.
10. The method for designing the phase group modular structure for improving the fault-tolerant capability of the permanent magnet motor and considering the low torque ripple as claimed in claim 1, wherein in the step 6, the self-inductance expression is derived according to the winding function theory as follows:
Figure FDA0003898407950000033
wherein L is AA Denotes the self-inductance of phase A,. Mu. 0 Denotes the vacuum permeability, r denotes the motor stator outer diameter, l denotes the axial length of the stator lamination, and g denotes the air gap length.
CN202211281246.1A 2022-10-19 2022-10-19 Design method for phase group modular structure capable of improving fault-tolerant capability of permanent magnet motor and considering low torque ripple Pending CN115549405A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117833575A (en) * 2024-03-06 2024-04-05 山西电机制造有限公司 Single-double layer winding automatic wire embedding method based on large and small slot punching sheets

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117833575A (en) * 2024-03-06 2024-04-05 山西电机制造有限公司 Single-double layer winding automatic wire embedding method based on large and small slot punching sheets
CN117833575B (en) * 2024-03-06 2024-06-07 山西电机制造有限公司 Single-double layer winding automatic wire embedding method based on large and small slot punching sheets

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