Rotor structure of asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor and reverse design method thereof

Abstract

The application discloses a rotor structure of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor and a reverse design method thereof, and first, air gap permeance design based on a magnetic resistance torque component and air gap flux density design based on a permanent magnet torque component are completed, and then, synthesis optimization design of non-uniform magnetic barriers and permanent magnets is completed based on the air gap permeance and the air gap flux density; based on the design method, the rotor structure is obtained as follows: the permanent magnets are built-in the rotor core, two adjacent permanent magnets are separated by a magnetic barrier, and the span of different magnetic barriers is set so that the magnetic barriers are asymmetrically distributed. Based on the modulation effect of the rotor structure on the air gap magnetic field, the pole pair number of working harmonics in the air gap magnetic field is selected by using the stator winding, and variable-pole variable-speed operation of the motor is realized; and the amount of the permanent magnets is low, and the material cost of the motor is greatly reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the field of electric machines, in particular to a rotor structure of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor and a reverse design method thereof. BACKGROUND

[0002] The water air conditioner is a water-cooled air conditioner, and underground water circulation is used to realize indoor cooling. The air conditioner is welcomed in areas where underground water is abundant and electric energy resources are poor, and in production workshops, shopping malls and other large space occasions.

[0003] The air conditioner can be driven by a fixed frequency and variable frequency motor system, wherein the fixed frequency driving mode has the advantages of low system cost and simple technology implementation, but the system energy efficiency is low due to the inability to change the motor speed. In recent years, due to the advantages of small size, high power and torque density, simple structure, low vibration and noise, and the like, brushless direct current permanent magnet motors based on variable frequency control have been gradually applied to the air conditioner motor field, effectively improving the energy efficiency of the air conditioner, but the variable frequency driver used in this system increases the cost of the motor system, especially in production workshops, shopping malls and other large space occasions, this problem is particularly prominent.

[0004] Considering the special requirements of the common occasions of the water air conditioner, the driving motor of the water air conditioner only needs to work in several fixed speed conditions, therefore, the variable pole motor driving scheme can realize the speed regulation operation of the water air conditioner without using the variable frequency system, and the cost and energy efficiency of the motor system are considered.

[0005] In fact, changing the number of poles is a common speed regulation method in the field of electric machines. For example, by arranging two sets of armature windings with different numbers of poles on the stator, a so-called double-winding induction motor can be formed, and when different windings are used to generate armature magnetic fields with different numbers of poles, the variable-pole variable-speed operation of the motor can be realized. However, induction motors have low efficiency and low power factor, so there are still problems of large motor system size, high energy consumption and the like. SUMMARY

[0006] In view of the deficiencies in the prior art, the application provides a rotor structure of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor and a reverse design method thereof. The rotor only includes a rotor core, permanent magnets and a magnetic barrier structure, and the reverse design is adopted based on the air gap magnetic field requirement required by variable-pole operation to obtain reasonable sizes of the permanent magnets and the magnetic barrier. The rotor scheme is simple in structure, is conducive to mass production, has low permanent magnet consumption, and greatly reduces the material cost of the motor.

[0007] The application achieves the above technical object through the following technical means.

[0008] A reverse design method of a rotor structure of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor

[0009] (1) Based on the reluctance torque component T re of the air gap permeance Λ g Design

[0010] The pole armature magnetic field before and after the pole change p1, p2 is coupled with two components in the air gap permeance, respectively, to produce two pairs of reluctance torque components T re1 and T re2 The ratio of the two reluctance torque components is defined as a variable b:

[0011]

[0012] Transform the above formula, and define the air gap permeance ratio of p1 pole and p2 pole motor as b':

[0013]

[0014] The end voltage of the permanent magnet motor before and after the pole change is consistent, that is, V ph1 = V ph2 Therefore, the total air gap permeability of the motor is:

[0015]

[0016] Where: ω e1 and ω e2 represent the synchronous speed under p1 and p2 pole, V ph1 and V ph2 are the stator armature winding end voltage corresponding to p1 and p2 pole, Λ p1 and Λ p2 represent the air gap permeance of p1 and p2 pole motor, N1 and N2 represent the series turns per phase of p1 pole and p2 pole armature winding, Λ0 represents the direct current component of total air gap permeability, k w1 and k w2 represent the armature winding coefficient of p1 pole and p2 pole, θ represents the rotor position;

[0017] (2) Based on the air gap flux density B design of the permanent magnet torque component T PM

[0018] The pole armature magnetic field before and after the pole change p1 and p2 is coupled with two components in the air gap flux density, respectively, to produce two pairs of permanent magnet torque components T PM1 and T PM2 The ratio of the two permanent magnet torque components is defined as a variable k:

[0019]

[0020] ​Transforming the above formula, the ratio of the permanent magnet air gap flux density of p1 pole pair and p2 pole pair motor is defined as k':

[0021]

[0022] The total air gap flux density of the permanent magnet motor is expressed as:

[0023] B=k' B p1 cos(p2θ)+B p1 cos(p1θ)

[0024] Where f1 and f2 represent the frequency of p1 pole pair and p2 pole pair motor respectively, τ1 and τ2 represent the pole pitch of p1 pole pair and p2 pole pair motor respectively, B p1 and B p2 represent the fundamental amplitude of the air gap flux density of p1 pole pair and p2 pole pair motor respectively, E 01 and E 02 represent the no-load back EMF of p1 pole pair and p2 pole pair motor respectively.

[0025] (3) Based on the uneven magnetic barrier and the synthesis optimization design of the permanent magnet of air gap permeance Λ g and air gap flux density B

[0026] The air gap flux density Bp2 of p2 pole pair motor is defined as the optimization target;

[0027] The boundary conditions are defined as:

[0028]

[0029]

[0030] The Lagrange function of the span α of all permanent magnets and their two end magnetic barriers, and the span β of all permanent magnets excluding their two end magnetic barriers is expressed as:

[0031]

[0032] The extreme value of the Lagrange function is calculated iteratively to obtain the values of α and β when the is optimal, that is, the size parameters and arrangement of the permanent magnets and uneven magnetic barriers that make the air gap flux density reach the optimal value;

[0033] Where τ p1 and τ p2 represent the average pole arc span of the permanent magnet of p1 pole pair and p2 pole pair motor respectively, α i represents the span of the i-th permanent magnet and its two end magnetic barriers, β i represents the span of the i-th permanent magnet excluding its two end magnetic barriers, and d and e represent the coefficients of the Lagrange function respectively.

[0034] Further, the i-th permanent magnet does not contain the span of the magnetic barrier at both ends thereof

[0035] n c Indicates the number of slots on the rotor in which the self-starting squirrel cage copper bars are embedded.

[0036] The rotor structure of the asynchronous starting uneven magnetic barrier double-speed variable-pole permanent magnet motor is characterized in that: the permanent magnets are arranged in the rotor core; the two adjacent permanent magnets are separated by the magnetic barriers; the spans of the different magnetic barriers are arranged to make the magnetic barriers asymmetrically distributed.

[0037] In the above technical solution, when p1=2 and p2=3, the number of permanent magnets is 6, and the uneven magnetic barriers are 4.

[0038] In the above technical solution, the six permanent magnets are arranged in a V shape and divided into three pairs; three gaps are formed in the rotor core between the three pairs of permanent magnets, and two uneven magnetic barriers are arranged in the two gaps.

[0039] In the above technical solution, the excitation magnetic field of the permanent magnet motor includes a 4-pole magnetic loop and a 6-pole magnetic loop.

[0040] In the above technical solution, the uneven magnetic barriers increase the path of the 4-pole magnetic loop in the excitation magnetic field of the permanent magnet motor, and meanwhile, the magnetic field amplitude is enhanced.

[0041] In the above technical solution, when the permanent magnet motor needs to run at low speed, the p2-pole armature winding is turned on, the armature reaction magnetic field generated by the p2-pole armature winding and the excitation magnetic field of the p2-pole are effectively coupled with each other, and stable electromagnetic torque output is generated at low speed; when the motor needs to run at high speed, the p1-pole armature winding is turned on, the armature reaction magnetic field generated by the p1-pole armature winding and the excitation magnetic field of the p1-pole are effectively coupled with each other, and stable electromagnetic torque output is generated at high speed.

[0042] The beneficial effects of the present application are as follows:

[0043] (1) The motor of the present application is based on the electromagnetic reverse design principle, and the rotor permanent magnet and the permanent magnet magnetic barrier arrangement are designed from the torque generation mechanism. According to the rotor structure designed by the present application, by designing the permanent magnet and the permanent magnet magnetic barrier arrangement, only one set of permanent magnet can generate excitation magnetic fields of different pole pairs, and the double-speed operation of the permanent magnet motor is realized; the structure is simple, the material cost is reduced, and the problem of large motor system size is solved.

[0044] (2) The stator armature winding of the motor in the application adopts two sets of winding of p1 pole pair single-layer winding and p2 pole pair single-layer winding, each coil is connected with a switching component through a lead-out wire, and the pole pair number of the stator armature magnetic field can be conveniently changed. When the motor needs to run at low speed, the p2 (p2 > p1) pole armature winding is turned on, the armature reaction magnetic field generated is effectively coupled with the excitation magnetic field of the p2 pole, and stable electromagnetic torque output is generated at low speed; when the motor needs to run at high speed, the p1 (p1 < p2) pole armature winding is turned on, the armature reaction magnetic field generated is effectively coupled with the excitation magnetic field of the p1 pole, and stable electromagnetic torque output is generated at high speed. Through the reverse design of the electromagnetic torque mechanism, only one set of permanent magnet and permanent magnet magnetic barrier is adopted on the motor rotor, and the excitation magnetic fields of the p1 pole and the p2 pole can be generated at the same time, the stator armature winding of different pole pairs is turned on, and the dual-speed variable-pole operation of the motor is realized. The motor designed by the design method of the application realizes the variable-pole variable-speed operation of the motor based on the modulation effect of the rotor structure on the air gap magnetic field, selects the pole pairs of the working harmonics in the air gap magnetic field through the stator winding, and realizes the variable-pole variable-speed operation of the motor. The designed motor essentially belongs to a variable-pole permanent magnet motor and has the characteristics of variable-pole dual-speed operation. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is an asynchronous starting uneven magnetic barrier dual-speed variable-pole permanent magnet motor structure schematic diagram of the embodiment 2 / 3 of the application;

[0046] Figure 2 It is an air gap magnetic conductance distribution waveform diagram of the p2 / p1 pole synchronous reluctance motor of the embodiment 2 / 3 of the application;

[0047] Figure 3 It is an air gap magnetic conductance distribution waveform diagram of the p2 / p1 pole synchronous reluctance motor in an ideal state;

[0048] Figure 4 It is an initial rotor structure schematic diagram of the p2 / p1 pole synchronous reluctance motor;

[0049] Figure 5 It is an air gap synthesized magnetic density waveform diagram of the p2 / p1 pole permanent magnet motor;

[0050] Figure 6 It is an initial rotor structure schematic diagram of the p2 / p1 pole permanent magnet motor;

[0051] Figure 7 It is an asynchronous starting uneven magnetic barrier dual-speed variable-pole permanent magnet motor structure schematic diagram of the embodiment 2 / 3 of the application;

[0052] Figure 8 It is a magnetic force line and magnetic density cloud map distribution diagram of the asynchronous starting uneven magnetic barrier dual-speed variable-pole permanent magnet motor of the embodiment 2 / 3 of the application;

[0053] Fig. 9(a) is a no-load air-gap flux density waveform diagram of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0054] Fig. 9(b) is a Fourier decomposition diagram of the no-load air-gap flux density waveform of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0055] Figure 10 Fig. 10 is a magnetic motive force waveform diagram of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0056] Figure 11 Fig. 11 is a magnetic permeance waveform diagram of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0057] Fig. 12(a) is a 2-pole-pair winding connection diagram of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0058] Fig. 12(b) is a 3-pole-pair winding connection diagram of the embodiment 2 / 3 of the application for pole-pair asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor;

[0059] In the figure: 1 - stator, 2 - rotor, 3 - rotating shaft, 4 - permanent magnet, 5 - magnetic barrier, 6 - stator slot, 7 - armature winding, 8 - stator slot, 9 - stator tooth, 10 - stator yoke, 1-1 - stator core, 2-1 - rotor core. DETAILED DESCRIPTION

[0060] The application will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of protection of the application is not limited thereto.

[0061] The application is an asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor rotor structure and its reverse design method, including the following two parts:

[0062] 1. An asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor, comprising a stator, a rotor and a rotating shaft, the rotor is arranged on the rotating shaft and fixed as a whole, and an air gap is arranged between the stator and the rotor. The stator core adopts a lamination form of 0.5mm or 0.35mm stamping sheet, so as to reduce the eddy current loss of the ferromagnetic material. The stator core is provided with a slot for embedding two sets of armature windings with different pole pairs, one set of winding coils forms a p1-pole armature winding, and the other set of winding coils forms a p2-pole armature winding. Each coil is connected with a switching element through a lead-out wire, and the working magnetic field pole number of the armature reaction magnetic field of the motor armature winding is controlled through different switching states, so as to be coupled with the p1-pole and p2-pole permanent magnet fields, to generate stable torque output, and the motor is operated at dual speed by changing the pole pair number of the magnetic field coupling in the air gap. The rotor mainly comprises a self-starting squirrel cage copper strip, a rotor core, permanent magnets and magnetic barriers, the permanent magnets are built-in the rotor core, adjacent two permanent magnets are separated by a magnetic barrier, and the asymmetric distribution of the magnetic barriers is formed by setting different magnetic barrier spans; the rotor core on the side close to the air gap is provided with a copper strip closed slot for placing the self-starting squirrel cage copper strip; and the rotor core adopts a lamination form of 0.5mm or 0.35mm stamping sheet, so as to reduce the eddy current loss of the ferromagnetic material.

[0063] The excitation magnetic field generated by the permanent magnets enters the air gap through the magnetic bridge between the adjacent magnetic barriers, and forms a closed magnetic loop through the air gap and the stator core. When the circumferential length of the magnetic barrier is inconsistent, the permanent magnet field distribution at both ends of the magnetic barrier will change, on the one hand, the magnetic loop path is widened through the design of the circumferential length of the magnetic barrier, and on the other hand, based on the air gap magnetic field modulation theory, the magnetic barrier modulator will modulate the air gap magnetic field, and then different pole numbers of permanent magnet fields are generated through the design of the permanent magnet arrangement and the magnetic barrier. In combination with different pole numbers of the stator armature reaction magnetic field, the dual-speed operation of the motor at a fixed frequency is realized. Specifically, when the motor needs to run at low speed, the p2 (p2>p1) pole armature winding is turned on, the generated armature reaction magnetic field is effectively coupled with the p2-pole excitation magnetic field, and stable electromagnetic torque output is generated at low speed; when the motor needs to run at high speed, the p1 (p1<p2) pole armature winding is turned on, the generated armature reaction magnetic field is effectively coupled with the p1-pole excitation magnetic field, and stable electromagnetic torque output is generated at high speed.

[0064] 2. A non-uniform magnetic barrier permanent magnet rotor reverse design method

[0065] The asynchronous starting non-uniform magnetic barrier dual-speed variable-pole permanent magnet motor of the present application has p1 and p2 as the pole numbers of the permanent magnet fields before and after the pole change, therefore, the permanent magnet field in the air gap of the motor should contain p1 and p2 pole harmonic components, and can be expressed as:

[0066]

[0067] wherein, B gm represents the resultant air-gap flux density of the motor; θ represents the current position of the rotor, which is the angle between the d-axis of the d-q coordinate system and the center line of the A-phase winding; F gm (θ) represents the permanent magnet motive force of the motor, which is a function of the rotor position θ; Λ g represents the resultant air-gap permeance; B0 represents the direct current component in the air-gap flux density; respectively represent the p1 and p2 pole pair permanent magnet field harmonic flux density amplitudes.

[0068] According to the basic theory of the motor, in addition to the required p1 and p2 pole pair flux density harmonic components, there are other high-order harmonics in the resultant air-gap flux density.

[0069] According to equation (1), the resultant air-gap flux density of the motor is related to the permanent magnet motive force F gm (θ) and the air-gap permeance Λ g , that is, the resultant air-gap flux density of the motor is related to the size parameters and arrangement of the rotor permanent magnets and the magnetic barriers. Therefore, by designing the size parameters and arrangement of the permanent magnets and the magnetic barriers, the specific air-gap flux density waveform required by the present application can be obtained.

[0070] The synchronous electromagnetic torque T s of the permanent magnet motor can be represented as the sum of the synchronous permanent magnet torque component and the synchronous reluctance torque component, that is:

[0071]

[0072] In the equation, T PM and T re respectively represent the synchronous permanent magnet torque component generated by the permanent magnet field and the synchronous reluctance torque component generated by the reluctance, m, p, ω e , E0, V ph , X d , X q and δ respectively represent the number of phases, the number of pole pairs, the synchronous speed, the effective value of the induced electromotive force, the phase voltage, the d-axis reactance, the q-axis reactance and the load angle of the motor.

[0073] Therefore, the rotor structure of the uneven magnetic barrier double-speed variable pole permanent magnet motor and the reverse design method thereof of the present application analyze the reluctance torque component and the permanent magnet torque component of the p1 and p2 pole pair motor, and use the Lagrange function to optimize the arrangement positions of the magnetic barriers and the permanent magnets to obtain the final design scheme of the size parameters and arrangement of the rotor permanent magnets and the magnetic barriers.

[0074] (1) Based on the reluctance torque component T re , the air-gap permeance Λ g is designed

[0075] Firstly, the reluctance torque component T re of the motor can be expressed as:

[0076]

[0077] where m, p, ω e , V ph , X dp , X qp and δ represent the number of phases, the number of pole pairs, the synchronous speed, the effective value of induced electromotive force, the phase voltage, the d-axis reactance corresponding to the pth pole pair, the q-axis reactance corresponding to the pth pole pair and the load angle of the motor, respectively.

[0078] Therefore, the p1 and p2 pole armature magnetic fields generated by the motor before and after the pole change are coupled with two components in the air gap permeance, respectively, to generate respective reluctance torque components T re1 and T re2 , and the ratio of the two reluctance torque components is defined as a variable b:

[0079]

[0080] where V ph1 and V ph2 are the stator armature winding terminal voltages corresponding to the p1 and p2 pole pairs, respectively, and in the present design, the terminal voltages of the two sets of stator armature windings are the same, i.e. V ph1 = V ph2 ; ω e1 and ω e2 represent the synchronous speeds under the p1 and p2 pole pairs, respectively; X d1 and X q1 represent the d-axis and q-axis reactances under the p1 pole pair, respectively; X d2 and X q2 represent the d-axis and q-axis reactances under the p2 pole pair, respectively; and the ratio of the reluctance torque components under the p1 and p2 pole pairs is equal to b, which is determined by the design requirements.

[0081] Secondly, the air gap permeances Λ p1 and Λ p2 of the p1 and p2 pole motor can be expressed in the form of Fourier series:

[0082]

[0083] where Λ 01 and Λ 02 represent the direct current components of the air gap permeances of the p1 pole and p2 pole motor, respectively; Λ p1 and Λ p2 represent the fundamental component amplitudes of the air gap permeances of the p1 pole and p2 pole motor, respectively; and θ represents the rotor position.

[0084] According to the basic principle of the motor, the reactance of d-q axis can be expressed as the sum of mutual reactance and leakage reactance, which can be ignored due to the leakage reactance is much smaller than the mutual reactance. Therefore, for p1 and p2 pole motor, the d-axis reactance can be expressed as shown in formula (7) and formula (8):

[0085]

[0086] Wherein, X d1 and X d2 respectively represent the d-axis reactance of p1 and p2 pole motor; X md1 and X md2 respectively represent the d-axis mutual reactance of p1 and p2 pole motor; N1 and N2 respectively represent the series turns per phase of p1 and p2 pole armature winding; c0 represents a constant; k w1 and k w2 respectively represent the armature winding coefficient of p1 and p2 pole.

[0087] Similarly, for p1 and p2 pole motor, the q-axis reactance can be expressed as shown in formula (9) and formula (10):

[0088]

[0089] Wherein, X q1 and X q2 respectively represent the q-axis reactance of p1 and p2 pole motor; X mq1 and X mq2 respectively represent the q-axis mutual reactance of p1 and p2 pole motor; N1 and N2 respectively represent the series turns per phase of p1 and p2 pole armature winding; c0 represents a constant; k w1 and k w2 respectively represent the armature winding coefficient of p1 and p2 pole.

[0090] According to formula (7)-(10) and ignoring high-order harmonics, the reactance ratio of d-q axis of p1 and p2 pole motor can be expressed as:

[0091]

[0092] Substituting formula (8)-(12) into formula (4), the reluctance torque ratio of p1 and p2 pole motor can be expressed as a function of air gap permeance:

[0093]

[0094] Wherein, T re1 and T re2 respectively represent the synchronous reluctance torque of p1 and p2 pole synchronous reluctance motor.

[0095] Generally, the AC component of the magnetic flux linkage is much smaller than the DC component, and equation (13) can be simplified as:

[0096]

[0097] By transforming equation (14), the ratio of the air-gap permeance of the p1-pole motor to the p2-pole motor is expressed as a function of the ratio of the reluctance torque components b, and the ratio of the air-gap permeance of the p1-pole motor to the p2-pole motor is defined as b':

[0098]

[0099] The terminal voltage of the motor before and after the pole change is consistent, i.e., V ph1 = V ph2 Therefore, the total air-gap permeability of the motor is:

[0100]

[0101] where Λ0represents the DC component of the total air-gap permeability.

[0102] (2) Design based on the air-gap flux density B of the permanent magnet torque component T PM

[0103] First, according to equation (2), the permanent magnet torque component T PM of the motor can be expressed as:

[0104]

[0105] where m, p, ω e , E0, V ph , X d , and δ respectively represent the number of phases, the number of pole pairs, the synchronous speed, the effective value of the induced electromotive force, the phase voltage, the d-axis reactance, and the load angle.

[0106] Therefore, the p1 and p2 armature magnetic fields generated by the motor before and after the pole change are respectively coupled with two components in the air-gap flux density of the permanent magnet, generating respective permanent magnet torque components T PM1 and T PM2 , and the ratio of the two permanent magnet torque components is defined as a variable k:

[0107]

[0108] where m represents the number of phases of the motor; V ph1 and V ph2 are the terminal voltages of the stator armature windings corresponding to the p1 and p2 poles, respectively, and in this design, the terminal voltages of the two sets of stator armature windings are the same, i.e., V ph1 = V ph2 ​; ω e1 and ω e2 represent the synchronous speed under p1 and p2 pole pairs, respectively, and ω e1 = 2πf1, ω e2 = 2πf2, f1 and f2 represent the frequency of p1 pole pair and p2 pole pair motor, respectively; X d1 and X d2 represent the d-axis reactance under p1 pole pair; E 01 and E 02 represent the back EMF of p1 pole pair and p2 pole pair motor, respectively; let the ratio of permanent magnet torque component under p1 and p2 pole pairs equal to k, which is determined by design requirements.

[0109] Secondly, according to the basic principle of motor, for p1 pole pair and p2 pole pair permanent magnet motor, the d-axis reactance can be expressed as formula (19) and formula (20) shown:

[0110]

[0111] wherein, N1 and N2 represent the series turns per phase of p1 pole pair and p2 pole pair motor armature winding, respectively; k w1 and k w2 represent the armature winding coefficient of p1 pole pair and p2 pole pair motor, respectively; τ1 and τ2 represent the pole pitch of p1 pole pair and p2 pole pair motor, respectively; m, μ0, L stk , g d represent the phase number of motor, vacuum permeability, equivalent length and d-axis equivalent air gap length, respectively; B p1 and B p2 represent the fundamental amplitude of air gap flux density of p1 pole pair and p2 pole pair motor; B ad represents the armature reaction flux density.

[0112] Substitute formula (19)-(20) into formula (18), the permanent magnet torque ratio of p1 pole pair and p2 pole pair motor can be expressed as a function of air gap flux density:

[0113]

[0114] wherein, T PM1 and T PM2 represent the permanent magnet torque component of p1 pole pair and p2 pole pair motor, respectively; E 01 and E 02 represent the induced EMF of p1 pole pair and p2 pole pair motor, respectively.

[0115] Transform formula (21), the permanent magnet air gap flux density ratio of p1 pole pair and p2 pole pair motor is expressed as a function of permanent magnet torque component ratio k, and the permanent magnet air gap flux density ratio of p1 pole pair and p2 pole pair motor is defined as k'.

[0116]

[0117] Therefore, the total air-gap flux density of the motor is:

[0118] B=k'B p1 cos(p2θ)+B p1 cos(p1θ)+…(23)

[0119] (3) Based on the air-gap permeance Λ g and the uneven magnetic barrier and the synthesis optimization design of the permanent magnet corresponding to the air-gap flux density B

[0120] According to the above method, the total air-gap permeance Λ g corresponding to the ratio b of the reluctance torque component of the p1 and p2 pole motor and the ratio k of the permanent magnet torque component can be obtained. The synthesis and structure optimization analysis of the two torque components are as follows.

[0121] In the rotor structure and the reverse design method mentioned in the application, the Lagrange function method is used to synthesize and optimize the uneven magnetic barrier and the permanent magnet structure parameters and arrangement mode corresponding to the two torque components.

[0122] The air-gap flux density Bp2 of the p2 pole motor is defined as the optimization target.

[0123] According to the motor design theory, the boundary condition is defined as:

[0124]

[0125] Where, α i represents the span of the i-th permanent magnet and the magnetic barrier at both ends thereof, i=1, 2, …, 2p1 for the p1 pole, and i=1, 2, …, 2p1, …, 2p2 for the p2 pole; τ p1 and τ p2 respectively represent the average pole arc span of the permanent magnet of the p1 pole motor and the p2 pole motor, and are defined as:

[0126]

[0127] Where, β i represents the span of the i-th permanent magnet without the magnetic barrier at both ends thereof, i=1, 2, …, 2p1 for the p1 pole, and i=1, 2, …, 2p2 for the p2 pole, and is defined as:

[0128]

[0129] Where, n c represents the number of slots in which the self-starting squirrel-cage copper bars are embedded on the rotor.

[0130] From formulas (24)-(27), the Lagrangian functions of the span α of the permanent magnet and its two ends magnetic barriers, and the span β of the permanent magnet excluding the magnetic barriers at its two ends, can be obtained as follows:

[0131]

[0132] Where d and e represent the coefficients of the Lagrange function, which are unknown constant coefficients that need to be solved.

[0133] According to equation (29), the system of linear equations for iterative calculation can be obtained as follows:

[0134]

[0135] The Lagrangian function F in the iterative calculation formula (30) is used to calculate the pair of functions. The partial derivatives can be used to obtain the permanent magnet and the structural parameters and arrangement (α and β) of the non-uniform magnetic barrier structure that achieve the optimal value of air gap magnetic flux density.

[0136] Example

[0137] I. As attached Figure 1 As shown, the 2 / 3 pole asynchronous starting non-uniform magnetic barrier dual-speed variable pole permanent magnet motor in this embodiment adopts a built-in permanent magnet rotor structure. The permanent magnets are arranged in a "V" shape in the rotor core. The motor includes a stator 1, a rotor 2, a shaft 3, permanent magnets 4, armature windings 7, etc. The rotor 2 is mounted on the shaft 3. An air gap is provided between the stator 1 and the rotor 2. The thickness of the air gap is related to the power rating, speed, selected permanent magnet material, and motor processing technology of the motor.

[0138] The stator 1 includes a stator core 1-1 and an armature winding 7. The stator core 1-1 is formed by stacking multiple layers of silicon steel sheets and includes a stator yoke 10 and 36 stator teeth 9. 36 stator slots 8 are formed between adjacent stator teeth 9. Two layers of winding coils are placed in each stator slot 8 from the bottom of the slot to the slot opening 6. The layer of winding coils near the bottom of the slot forms a 2-pole armature winding 7, and the other layer of winding coils near the slot opening forms a 3-pole armature winding 7.

[0139] The rotor 2 comprises a rotor core 2-1 and permanent magnets 4. The rotor core 2-1 is formed by stacking multiple layers of silicon steel sheets, and non-uniform magnetic barriers 5 and slots for inserting permanent magnets 4 are stamped on each rotor lamination. Six permanent magnets 4 of uniform thickness and quantity are inserted into the rotor core 2-1 to generate the excitation magnetic field. A closed slot is opened near the air gap side of the rotor core 2-1 for placing self-starting squirrel-cage copper bars.

[0140] According to the arrangement of 6 permanent magnets and 4 uneven magnetic barriers in the rotor core 2-1, 4-pole and 6-pole magnetic circuits exist in the excitation magnetic field, and due to the modulation of the uneven magnetic barrier permeance, the path of the 4-pole magnetic circuit is larger and the magnetic field amplitude is larger. Therefore, the stator winding should be arranged with two sets of windings according to the 4-pole and 6-pole magnetic fields, and by controlling the switching state of the switching element, the 4-pole winding or the 6-pole winding can be simply and effectively controlled to work.

[0141] II. Specific embodiment of the rotor structure of the 4-pole and 6-pole (2-pole pair and 3-pole pair) motor

[0142] According to the above design method and analysis, the rotor structure topology design of the asynchronous starting uneven magnetic barrier double-speed variable-pole permanent magnet motor of the present application can be divided into the following three parts: (1) air gap permeance Λ g is realized; (2) air gap flux density B g is realized; (3) synthesis optimization design of the uneven magnetic barrier and the permanent magnet of the 2-pole pair and 3-pole pair motor.

[0143] In a specific embodiment, the rotor structure of the asynchronous starting uneven magnetic barrier double-speed variable-pole permanent magnet motor with p1=2 and p2=3 pole pairs is selected for design.

[0144] (1) Air gap permeance Λ g of the 2-pole pair and 3-pole pair motor is realized

[0145] Based on the air gap permeance Λ re of the reluctance torque component T g , i.e. formula (16), the air gap permeance of the 2-pole pair and 3-pole pair motor can be obtained, which is expressed as a function of the ratio b' of the air gap permeance components corresponding to the two pole pairs:

[0146] Λ g = Λ0+b'Λ3cos(4θ)+Λ3cos(6θ) (31)

[0147] Wherein, Λ0 represents the direct current component of the air gap permeance; b' represents the ratio of the synchronous reluctance torque components corresponding to the two pole pairs, according to formula (15), when p1=2 and p3=3:

[0148]

[0149] Wherein, T re1 and T re2 respectively represent the synchronous reluctance torque components corresponding to p1=2 and p2=3; ω e1 and ω e2 respectively represent the synchronous speed corresponding to p1=2 and p2=3; N1 and N2 respectively represent the number of turns per phase of the stator armature winding corresponding to p1=2 and p2=3; k w1and k w2 respectively represent the corresponding stator armature winding winding coefficients when p1=2 and p2=3.

[0150] According to the air gap permeance Fourier decomposition results, under p1=2, p3=3 pole pairs, the air gap permeance should mainly include the direct current component (Λ0), the 4th harmonic component amplitude and the 6th harmonic component That is, the air gap permeance distribution waveform of the 2-pole and 3-pole motor is as shown in the attached Figure 2

[0151] According to the attached Figure 2 and formula (31), the air gap permeance distribution waveform of the 2-pole and 3-pole motor under ideal conditions can be obtained, as shown in the attached Figure 3 . Among them, α represents half of the embedded permanent magnet and the magnetic barrier span at both ends of the permanent magnet, β represents the span of the embedded permanent magnet slot, and γ represents the axial length of the magnetic bridge between adjacent permanent magnets, as shown in the attached Figure 4

[0152] (2) The air gap flux density B of the 2-pole and 3-pole motor is realized

[0153] Based on the air gap flux density B design of the permanent magnet torque component T PM , that is, formula (23), the air gap flux density of the 2-pole and 3-pole motor can be obtained, which is expressed as a function of the ratio k' of the corresponding permanent magnet torque components of the two pole pairs:

[0154] B=k' B2 cos(3θ)+B2 cos(2θ)(33)

[0155] Among them, B2 represents the air gap flux density amplitude generated by the 2-pole permanent magnet; k' represents the ratio of the permanent magnet air gap flux density components of the 2-pole and 3-pole motor, according to formula (22), when p1=2, p3=3:

[0156]

[0157] Among them, T PM1 and T PM2 respectively represent the corresponding permanent magnet torque components when p1=2 and p2=3; E 01 and E 02 respectively represent the corresponding induced electromotive force when p1=2 and p2=3; τ1 and τ2 respectively represent the corresponding stator armature winding span when p1=2 and p2=3; f1 and f2 respectively represent the corresponding motor frequency when p1=2 and p2=3; N1 and N2 respectively represent the corresponding number of turns per phase of the stator armature in series when p1=2 and p2=3; k w1 and k w2 ​​respectively represent the stator armature winding winding coefficient corresponding to p1=2 and p2=3.

[0158] According to the air-gap flux density Fourier decomposition results, under 2-pole and 3-pole (p1=2, p3=3), the air-gap flux density (formula (23)) generated by the permanent magnet mainly includes the 2nd harmonic component amplitude (B p1 = B2) and the 3rd harmonic component (k' B p1 = k' B2). That is, the air-gap flux density waveform is as shown in the accompanying Figure 5 , wherein α1, α2, …, α6 respectively represent the axial lengths of the 1st, 2nd, …, 6th blocks of permanent magnets and the magnetic barriers on both sides thereof.

[0159] According to the air-gap flux density waveform function in the accompanying Figure 5 , the initial rotor structures of the 2-pole and 3-pole motors are as shown in the accompanying Figure 6 , wherein α i (i=1, 2, …, 6) represents the span of the i-th block of permanent magnet and the magnetic barriers on both sides thereof; β i (i=1, 2, …, 6) represents the circumferential length of the i-th block of permanent magnet.

[0160] (3) Synthesis optimization design of uneven magnetic barriers and permanent magnets of 2-pole and 3-pole motors

[0161] Taking B3 as the optimization target, the permanent magnet and uneven magnetic barrier structure parameters and arrangement mode (α and β) that make the air-gap flux density reach the optimal value are solved. The Lagrange function established is:

[0162]

[0163] , wherein α i (i=1, 2, …, 6) represents the circumferential length of the i-th block of permanent magnet and the magnetic barriers on both sides thereof; β i (i=1, 2, …, 6) represents the circumferential length of the i-th block of permanent magnet; B2 and B3 respectively represent the 2nd and 3rd harmonic component amplitudes of the air-gap flux density; b represents the ratio of the 2-pole and 3-pole reluctance torque components; d and e respectively represent the coefficients of the Lagrange function, which are unknown constant coefficients to be solved.

[0164] According to formula (35), the partial derivatives of the Lagrange function F with respect to α i (i=1, 2, …, 6) and β i (i=1, 2, …, 6) are set to zero, and the extreme value of the Lagrange function is solved, so that under the distribution of the permanent magnet and the magnetic barriers (α i (i=1, 2, …, 6) and β i (i=1, 2, …, 6)), the air-gap flux density can reach the optimal value.

[0165]

[0166] Using computer iterative solutions to equation (36), the final non-uniform magnetic barriers and permanent magnet arrangements for 2-pole and 3-pole motors are shown in the appendix. Figure 7 As shown.

[0167] See appendix Figure 8 The figure shows the magnetic loops formed by the two-pole and three-pole magnetic fields generated by the permanent magnet. From the four larger magnetic loops in the figure, it can be seen that the non-uniform magnetic barrier modulator modulates the magnetic permeation waveform of the rotor core, widening the path in the magnetic loop. Based on the magnetic field line distribution in the figure, it can be seen that the non-uniform magnetic barrier, while widening the magnetic loop path, also enhances the magnetic field amplitude of the two-pole magnetic loop. For the motor operating with a two-pole magnetic field (high-speed operation), this results in a larger output torque. For the motor operating with a three-pole magnetic field (low-speed operation), because the magnetic loop is widened, the excitation magnetic field of the permanent magnet can link more turns of the stator winding.

[0168] From the appendix Figure 8 As can be seen from the distribution of the magnetic field lines, the motor described in this invention can operate stably under a 2-pole or 3-pole magnetic field. By setting a non-uniform magnetic barrier rotor structure, the 2-pole excitation magnetic field and the 3-pole excitation magnetic field exist simultaneously in the air gap, thus achieving the goal of stable dual-speed operation of the motor at a fixed electrical frequency.

[0169] From the appendix Figure 9(a) , 9(b) As shown, according to the FFT plot of the air gap flux density, the values ​​of the second and third harmonics are the highest, which verifies that the design of the motor with 2 pole pairs and 3 pole pairs is reasonable.

[0170] Appendix Figure 10 and attached Figure 11 The air gap excitation magnetomotive force waveform and air gap magnetic permeability waveform were plotted based on the rotor structure of the motor, verifying that the final design result of this embodiment conforms to the initial idea.

[0171] Appendix Figure 12(a) , 12(b) This is a schematic diagram showing the connection of the two sets of windings of the motor.

[0172] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A rotor structure reverse design method of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor, characterized in that: (1) based on the magnetic reluctance torque component T re of the air gap permeance Λ g design The p1 and p2 before and after the pole change are coupled with two components in the air gap permeance, respectively, to generate two kinds of pole-changing reluctance torque components T re1 and T re2 The ratio relationship of the two reluctance torque components is defined as a variable b: The above formula is transformed, and the ratio of the air gap permeance of the p1-pole motor to the p2-pole motor is defined as b': The end voltage of the permanent magnet motor before and after the pole change is consistent, that is, V ph1 = V ph2 Therefore, the total air gap permeability of the motor is obtained as: where ω e1 and ω e2 represent the synchronous speed at p1 and p2 pole pairs, V ph1 and V ph2 are the stator armature winding terminal voltage corresponding to p1 and p2 pole pairs, Λ p1 and Λ p2 represent the air gap permeance of p1 and p2 pole pair machines, N1 and N2 represent the number of turns per phase of p1 pole pair and p2 pole pair armature winding in series, Λ0 represents the direct current component of total air gap permeability, k w1 and k w2 represent the armature winding coefficient of p1 pole pair and p2 pole pair, and θ represents the rotor position. (2) Based on the permanent magnet torque component T PM of the air gap flux density B design The p1 and p2 before and after the pole change are coupled with two components in the magnetic flux density of the permanent magnet, respectively, to generate two permanent magnetic torque components T PM1 and T PM2 The ratio relationship between the two permanent magnetic torque components is defined as a variable k: The above formula is transformed, and the ratio of the permanent magnet air gap flux density of the p1-pole motor to the p2-pole motor is defined as k': The total air gap flux density of the permanent magnet motor is expressed as: B = k' B p1 cos(p2θ) + B p1 cos(p1θ) wherein: f1 and f2 represent the frequencies of the p1 and p2 pole machines, respectively, τ1 and τ2 represent the pole pitches of the p1 and p2 pole machines, respectively, B p1 and B p2 represent the fundamental amplitudes of the air-gap flux densities of the p1 and p2 pole machines, respectively, E 01 and E 02 represent the back-EMFs of the p1 and p2 pole machines at no load, respectively. (3) Based on air-gap permeance Λ g and the synthesis optimization design of the non-uniform magnetic barrier and the permanent magnet of air-gap flux density B Air gap flux density of a p2 pole motor defined as an optimization objective; The boundary conditions are defined: The Lagrange function of the span of the permanent magnet and the magnetic barriers at both ends thereof, and the span of the permanent magnet not containing the magnetic barriers at both ends thereof is expressed as: iteratively calculating the extreme value of the Lagrange function to obtain the values of α and β, i.e. the size parameters and arrangement of the permanent magnet and the uneven magnetic barrier which make the air-gap magnetic flux density reach the optimal value iteratively calculating the extreme value of the Lagrange function to obtain the values of α and β, i.e. the size parameters and arrangement of the permanent magnet and the uneven magnetic barrier which make the air-gap magnetic flux density reach the optimal value where: τ p1 and τ p2 denote the average pole arc span of the p1 and p2 pole pair permanent magnets, respectively, α i denotes the span of the i-th permanent magnet and its end barriers, β i denotes the span of the i-th permanent magnet excluding its end barriers, d and e denote Lagrange function coefficients, respectively.

2. The inverse design method of claim 1, wherein, The span of the i-th permanent magnet does not include the magnetic barrier at its two ends n c denotes the number of slots in which the self-starting squirrel cage copper bars are embedded on the rotor.

3. A rotor structure of an asynchronous starting non-uniform magnetic barrier double-speed variable-pole permanent magnet motor designed according to the inverse design method of any one of claims 1-2, characterized in that: The permanent magnets are built into the rotor core, the adjacent two permanent magnets are separated by a magnetic barrier, and the span of the different magnetic barriers is set to make the magnetic barriers asymmetrically distributed.

4. The rotor structure of the asynchronous starting non-uniform magnetic barrier double-speed variable pole permanent magnet motor of claim 3, characterized in that, When p1=2 and p2=3, the number of permanent magnets is 6, and the non-uniform magnetic barriers are 4.

5. The rotor structure of the asynchronous starting non-uniform magnetic barrier double-speed variable pole permanent magnet motor of claim 4, characterized in that, The 6 permanent magnets are arranged in a "V" shape and divided into 3 pairs, and 3 gaps are formed in the rotor core between the 3 pairs of permanent magnets, and 2 non-uniform magnetic barriers are arranged in the 2 gaps, respectively.

6. The rotor structure of the asynchronous starting non-uniform magnetic barrier double-speed variable pole permanent magnet motor of claim 5, characterized in that, There are 4-pole magnetic circuits and 6-pole magnetic circuits in the excitation magnetic field of the permanent magnet motor.

7. The rotor structure of the asynchronous starting non-uniform magnetic barrier double-speed variable pole permanent magnet motor of claim 6, characterized in that, The non-uniform magnetic barriers increase the path of the 4-pole magnetic circuit in the excitation magnetic field of the permanent magnet motor, and at the same time, enhance the magnetic field amplitude.

8. The rotor structure of the asynchronous starting non-uniform magnetic barrier double-speed variable pole permanent magnet motor of claim 3, characterized in that, When the permanent magnet motor needs to run at low speed, the p2-pole armature winding is turned on, the armature reaction magnetic field generated by the p2-pole armature winding and the excitation magnetic field of the p2-pole are effectively coupled with each other, and stable electromagnetic torque output is generated at low speed; when the motor needs to run at high speed, the p1-pole armature winding is turned on, the armature reaction magnetic field generated by the p1-pole armature winding and the excitation magnetic field of the p1-pole are effectively coupled with each other, and stable electromagnetic torque output is generated at high speed.

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