CN111327170A - Modeling method for equivalent magnetic circuit of hybrid excitation axial flux switching motor - Google Patents

Abstract

The invention discloses a modeling method for the equivalent magnetic circuit of a hybrid excitation axial magnetic flux switching motor. The motor involved is a new type of axial hybrid excitation motor, which adopts the structure of double stator and single rotor, and mainly consists of a stator, a rotor, a The permanent magnets, armature windings and excitation windings are composed of the permanent magnets, stators, rotors and air gaps of the hybrid excitation axial flux switching motor. The modeling process includes: Step 1: Equivalent permanent magnets is a magnetomotive force source F _pm and an internal resistance R _pm ; Step 2: According to the relative positions of the stator teeth and rotor teeth at the inner and outer diameters, divide the rotor position in a half cycle into n regions, and calculate the inner and outer diameters of each region. The stator and rotor iron core reluctance and the air gap reluctance; step 3, combine the equivalent reluctance of each part to establish the equivalent magnetic circuit model of each region; step 4, the motor modeling process is completed. On the basis of ensuring the calculation accuracy, the invention provides a fast calculation method for the initial design and performance optimization of the hybrid excitation axial magnetic flux switching motor.

Description

A Modeling Method for Equivalent Magnetic Circuit of Hybrid Excitation Axial Flux Switching Motor

technical field

The invention relates to a modeling method of a motor magnetic circuit, in particular to a modeling method of an equivalent magnetic circuit of a hybrid excitation axial magnetic flux switching motor.

Background technique

In 2007, French scholar E. Hoang proposed a hybrid excitation flux-switching (HEFS) motor based on the flux-switching permanent magnet motor. This type of motor has good constant power regulation. The speed capability and torque output capability have aroused extensive international attention. Compared with radial field motors, axial field motors have high rotor core utilization, high torque density, good heat dissipation, short axial length and compact structure, and are more suitable for occasions with high efficiency and low speed.

Hybrid excitation axial flux switching motor has the advantages of both HEFS motor and axial motor, and has a relatively broad development prospect in industrial fields such as constant power, wide-range speed control drive and constant voltage power generation (Xu Da. Hybrid excitation axial magnetic field magnetic field) Research on design, analysis and control of switching motor [D]. Southeast University, 2017). Professor Lin Mingyao proposed a 12/10-pole hybrid excitation axial magnetic flux switching motor. The motor adopts a double stator and single rotor structure. The excitation windings and permanent magnets are placed on the stator. The mathematical model of the motor is derived, based on partition control. The working characteristics of the motor are studied by strategy (Zhao Jilong, Lin Mingyao, Xu Da, Jin Long. Field weakening control of hybrid excitation axial magnetic field flux switching motor [J]. Chinese Journal of Electrical Engineering. 2015,35(19):5059-5468) .

At present, there are two commonly used methods for motor research, including finite element method and equivalent magnetic circuit method.

The finite element method can accurately calculate the static characteristics of the motor, which is more suitable for the motor whose two-dimensional magnetic field and size parameters have been determined. However, in the initial design and optimization of the motor, it is necessary to calculate the static characteristics under different structural parameters, and the finite element method is very inconvenient. Especially for the motor with a three-dimensional magnetic field, the modeling process is complicated, the calculation time is long, and the cost is high. The equivalent magnetic circuit method can achieve an effective balance between calculation time and calculation accuracy. According to the geometric structure and magnetic field distribution of the motor, the magnetic field area is divided into several branches in series or parallel with each other. It is composed of units such as potential sources, and each unit is connected by a magnetic potential node, thereby forming an equivalent magnetic circuit network of the entire motor. Ge Xiao, Zhang Qi, Huang Surong and other scholars from Shanghai University started from the basic topology of the magnetic pole-split hybrid excitation motor, and derived the equivalent magnetic circuit model of this type of motor (Ge Xiao, Zhang Qi, Huang Surong. Magnetic pole split hybrid excitation Analysis of Equivalent Magnetic Circuit Method of Motor[J]. Motor and Control Application, 2006, 31(1):11-15). Based on the principle of the flux tube, Jun Chen studied the three-dimensional magnetic field of a 12-pole hybrid excitation claw-pole motor, and deduced the reluctance of each part. The research shows that the equivalent magnetic circuit method can greatly reduce the calculation cost on the basis of , can meet the requirements of engineering calculation accuracy (Chen Jun. Equivalent magnetic network analysis and calculation of hybrid claw-pole generator with permanent magnet excitation [D]. Anhui: Hefei University of Technology, 2003).

The magnetic field of the hybrid excitation axial flux switching motor is three-dimensionally distributed, and there are both circumferential and axial magnetic fields, which makes the design and analysis process more complicated. Using the equivalent magnetic circuit method to analyze, design and optimize this type of motor can effectively reduce the calculation time of magnetic field analysis and save the calculation cost under the premise of satisfying a certain calculation accuracy.

At present, the finite element method is used for the design and optimization of the hybrid excitation axial flux switching motor, which consumes the calculation time and increases the calculation cost. The above-mentioned equivalent magnetic circuit method lacks consideration of local magnetic field saturation and magnetic flux leakage at the end of the motor. In addition, in the cutting process of the air-gap flux tube, the influence of the shape and size of the stator and rotor teeth is not considered, which seriously affects the accuracy of the equivalent magnetic circuit model.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a modeling method for the equivalent magnetic circuit of the hybrid excitation axial flux switching motor, and to provide a simple and effective calculation method for the initial design and optimal design of the hybrid excitation axial flux switching motor.

The technical solution that realizes the object of the present invention is:

1) A modeling method for the equivalent magnetic circuit of a hybrid excitation axial flux switching motor. The motor involved is a new type of axial hybrid excitation motor, which adopts the structure of double stator and single rotor, mainly composed of stator, rotor and permanent magnet. , the armature winding and the field winding are composed, and the size of the permanent magnet, stator, rotor and air gap of the hybrid excitation axial flux switching motor is determined. It is characterized in that the modeling process includes the following steps:

Step 1: The permanent magnet is equivalent to a magnetomotive force source F _pm and an internal resistance R _pm ;

Step 2: According to the relative positions of stator teeth and rotor teeth at the inner and outer diameters, divide the rotor position in a half cycle into n regions; calculate the stator and rotor core reluctance and air gap reluctance in each region;

Step 3, combine the equivalent magnetic resistance of each part to establish the equivalent magnetic circuit model of each region;

Step 4, the motor modeling process is completed.

2) The modeling method according to claim 1, wherein in the step 2, the magnetic resistance of the stator and rotor iron core is composed of four parts, including the magnetic resistance R _sty and R _sy of the stator yoke, the stator teeth The reluctance R _stt1 , R _stt2 , the reluctance R _smt of the intermediate teeth of the stator and the reluctance R _r of the rotor teeth; R _sty , R _stt1 and R _stt2 are all linear reluctances, and R _sy , R _smt and R _r are non-linear Linear magnetoresistance, the expression of each magnetoresistance is shown below.

3) modeling method according to claim 1, is characterized in that, in described step 2, utilizes magnetic flux tube segmentation method to study air gap magnetic resistance, adopts elliptical arc to replace traditional arc to cut air gap; The distribution of the air-gap magnetic field at different positions is summarized, and six typical types of air-gap flux tubes are obtained. The proportional coefficients k ₁ and k ₂ are introduced, and the reluctance expressions of each flux tube are shown below.

4) The modeling method according to claim 1, characterized in that, in the step 3, the parameters such as magnetoresistance and magnetomotive force obtained by calculation are connected through the magnetomotive force node, and the etc. parameters of each rotor position area are obtained. The effective magnetic circuit is integrated, and n regions are integrated to obtain the equivalent magnetic circuit model of the hybrid excitation axial flux switching motor.

5) The modeling method according to claim 1, characterized in that, in the step 1, the permanent magnet is equivalent to a magnetomotive force source F _pm and an internal magnetoresistance R _pm , the calculation of the magnetomotive force source The formula is F _pm =H _c h _m , and the calculation formula of the internal reluctance is R _pm =h _m /(μ ₀ l _pm l _s ); the magnetic leakage of the motor mainly exists at the end of the permanent magnet, and the leakage magnetic resistance The calculation formula is R _leak =1/(0.26μ ₀ l _i ).

Compared with the prior art, the present invention has significant advantages:

1. At present, the research on hybrid excitation axial flux switching motors is still in its infancy, and finite element analysis is used for the design and optimization of such motors, which is time-consuming and costly. The invention provides a fast and effective magnetic circuit calculation method for the initial design and optimal design of this type of motor.

2. When establishing the equivalent magnetic circuit model of the hybrid excitation axial flux switching motor, the present invention considers the problems of local magnetic field saturation of the iron core and magnetic leakage at the end of the permanent magnet, and improves the calculation accuracy of the equivalent magnetic circuit model .

3. The invention fully considers the influence of the shape and size of the tooth surface of the stator and rotor of the motor, and refines the division of the rotor position area; introduces a proportional coefficient, optimizes the calculation formula of the air gap reluctance, and further improves the calculation of the equivalent magnetic circuit model accuracy.

Description of drawings

Fig. 1 is the flow chart of the equivalent magnetic circuit modeling method of the hybrid excitation axial flux switching motor of the present invention;

2 is a schematic structural diagram of a 6/10-pole hybrid excitation axial flux switching motor of the present invention;

3 is a schematic diagram of the path of the rotor teeth of the present invention at the inner and outer diameters;

4 is a schematic diagram of the rotor position area of the 6/10-pole hybrid excitation axial flux switching motor according to the present invention;

Fig. 5 is the equivalent schematic diagram of stator and rotor iron core and permanent magnet of the present invention;

Fig. 6 is the schematic diagram of nonlinear reluctance in the iron core of the present invention;

Figure 7 is a schematic diagram of a typical air gap flux tube type of the present invention;

Fig. 8 is the schematic diagram of magnetic flux leakage at the end of the permanent magnet of the present invention;

FIG. 9 is a structural diagram of an equivalent magnetic circuit model of the present invention.

In the figure: 1 is the stator, 2 is the rotor, 3 is the permanent magnet (PM), 4 is the armature winding, and 5 is the excitation winding.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention provides a method for modeling an equivalent magnetic circuit of a hybrid excitation axial flux switching motor. The motor involved is a new type of axial hybrid excitation motor, which adopts the structure of double stator and single rotor, and mainly consists of a stator, a rotor, a permanent magnet and a permanent magnet. Magnets, armature windings and excitation windings, determine the size of the permanent magnet, stator, rotor and air gap of the hybrid excitation axial flux switching motor. The modeling process includes: Step 1: The permanent magnet is equivalent to A magnetomotive force source F _pm and internal resistance R _pm ; Step 2: According to the relative positions of stator teeth and rotor teeth at the inner and outer diameters, divide the rotor position in half a cycle into n regions, and calculate the Stator and rotor iron core reluctance and air gap reluctance; Step 3, combine the equivalent reluctance of each part to establish the equivalent magnetic circuit model of each region; Step 4, the motor modeling process is completed. On the basis of ensuring the calculation accuracy, the invention provides a fast calculation method for the initial design and performance optimization of the hybrid excitation axial magnetic flux switching motor.

1 Motor structure

Figure 2 shows a schematic diagram of the structure of a 6/10-pole hybrid excitation axial flux switching motor. The motor adopts the structure of double stator and single rotor, which is mainly composed of stator 1, rotor 2, permanent magnet 3, armature winding 4 and excitation winding. 5 compositions. Each stator 1 is composed of six E-type iron cores and six permanent magnets 3 alternately. The E-type iron cores use parallel slots, and the permanent magnets 3 use parallel magnetization. The magnetization directions of the adjacent permanent magnets 3 are opposite. The magnetization direction of the upper corresponding permanent magnet 3 is also opposite. The armature winding 4 is wound on two adjacent stator teeth, and the field winding 5 is wound on the middle tooth of the E-shaped iron core. The six groups of coils on each stator are connected in series to form three-phase armature windings, and the opposite same-phase armature coils on both sides of the stator are also connected in series. Both the armature winding 4 and the excitation winding 5 adopt concentrated windings, which shortens the length of the ends of the windings, thereby reducing the copper consumption and copper consumption of the motor. The structure of the rotor 2 is very simple. It has neither permanent magnets nor windings. It consists of 10 rotor teeth evenly distributed along the circumference. The rotor teeth are connected by a non-magnetically conductive ring.

2 The modeling process of the magnetic circuit

The equivalent magnetic circuit method divides the magnetic field area of the motor into several series or parallel magnetic circuits on the basis of the motor structure and magnetic field distribution, and calculates parameters such as reluctance R and magnetomotive force F on each magnetic circuit. Through the connection of the magnetic potential nodes, and then according to the relational formula F=ΦR, the magnetic flux Φ on each branch can be obtained, and then the static characteristics such as the flux linkage and the back electromotive force of the motor can be obtained. Compared with the traditional radial motor, the hybrid excitation axial flux switching motor of the present invention not only has circumferential magnetic flux, but also has axial magnetic flux, so the magnetic circuit is more complicated.

The equivalent magnetic circuit of the hybrid excitation axial flux switching motor is divided into four parts to be solved separately, including the permanent magnet, the stator, the rotor core and the air gap. The accuracy of the equivalent magnetic circuit mainly depends on the accuracy of the magnetoresistance calculation of each part. Considering the complexity of the magnetic circuit of the motor, the calculation formula of the reluctance of the above-mentioned parts in the equivalent magnetic circuit is deduced.

2.1 Division of rotor position area

As the rotor position changes, the magnetic field in the motor is constantly changing, and the saturation degree of the iron core reluctance and the air gap reluctance also change. The rotor position is divided into regions, so that the distribution of the air-gap magnetic field in each region is basically the same, that is, the core reluctance and the air-gap reluctance in each region can be calculated using the same formula. According to the symmetry of the hybrid excitation axial flux switching motor structure, in order to simplify the calculation, the rotor position of the half cycle is analyzed.

表示定子和转子在内径处的位置关系，实心矩形

表示定子和转子在外径处的位置关系。The stator tooth surface of the hybrid excitation axial flux switching motor is a trapezoidal structure, while the rotor tooth surface is a parallel structure. During the rotor rotation process, the rotor teeth have different paths at the inner diameter and outer diameter. As shown in Figure 3, when the rotor rotates to θ _r , L ₁ is the path at the inner diameter of the rotor teeth, and L ₂ is the path at the outer diameter of the rotor. It can be seen from the figure that the two paths L ₁ and L ₂ are inconsistent. When modeling and dividing the rotor position area, the relative position of the stator and rotor teeth at the inner diameter is comprehensively considered, and the rotor position is divided into n areas. Taking the 6/10-pole hybrid excitation axial flux switching motor as an example, Figure 4 shows a schematic diagram of the division of the rotor position area, which is divided into 20 areas. In the figure, the hollow rectangle

Indicates the positional relationship between the stator and rotor at the inner diameter, solid rectangle

Indicates the positional relationship between the stator and the rotor at the outer diameter.

2.2 Calculation of reluctance of stator and rotor core

As shown in Figure 5, the reluctance of the stator and rotor iron core is mainly composed of four parts, which are the reluctance of the yoke of the stator (divided into two sections: R _sty , R _sy ), the magnetic resistance of the teeth of the stator (divided into two sections: R _stt1 , R _stt2 ), the intermediate tooth reluctance R _smt of the stator and the rotor tooth reluctance R _r .

When the magnetic field is not saturated, the magnetic permeability of the iron core is approximately a constant value, that is, the magnetic resistance of the iron core is linear magnetic resistance. R _sty , R _stt1 and R _stt2 are all linear reluctance, the expressions are shown in equations (2.1) to (2.2), R _si and R _so are the inner and outer diameters of the motor μ _Fe are the magnetic field of the iron core when the magnetic field is not saturated Magnetic permeability, l _s is the axial length of the stator, l _sy is the thickness of the stator yoke, β _s , β _st and β _pm are the stator slot width, stator tooth width and permanent magnet thickness at the inner diameter, S _st is the stator tooth The area of the radial plane, C ₁ is a constant with respect to the size, and its expression is shown in (2.3).

When the magnetic field reaches saturation, the magnetic permeability of the iron core is no longer a constant value, and changes with the change of the magnetic field, and its magnetic resistance is nonlinear magnetic resistance. For the magnetic permeability μ′ of nonlinear magnetoresistance, iterative calculation is carried out by means of linear interpolation. The specific solution process: According to the magnetization curve of the iron core material, the slope of the straight line part is set as the initial value of μ ₁ , and the magnetic circuit is obtained by calculation. The magnetic flux of each part and the cross-sectional area of the magnetic circuit can obtain the magnetic density B ₁ of the magnetic circuit of the corresponding core segment; according to B ₁ , the new permeability μ ₂ can be obtained by comparing the magnetization curve of the core. Repeat the above process, when the result error of two iterations is less than a given value, the permeability corresponding to the new magnetic density value is set as the final value of μ′.

R _sy , R _smt and R _r are all nonlinear reluctances, and the expressions are shown in equations (2.4) to (2.6), where l _r is the axial length of the rotor, β _sm is the middle tooth width of the stator at the inner diameter, and S _sm is The area of the stator intermediate teeth in the radial plane, C ₂ is a constant with respect to the size, and its expression is shown in (2.7).

As shown in Fig. 6, R _sy-sat , R _smt-sat and R _r-sat are the nonlinear part of R _sy , R _smt and R _r magnetoresistance, respectively, and the expression of R _sy-sat is shown in (2.8) As shown, R _smt-sat and R _r-sat are functions of _{k sat} and the overlapping area Sa of the stator and rotor teeth, as shown in equations (2.9) to (2.10). k _sat is the introduced saturation depth coefficient, expressed as k _sat =h _sat /h, h _sat is the saturated depth, and h is the calculated height of the tooth. k _sat is a function of the magnetic density of the branch where it is located, and it increases with the increase of saturation.

2.3 Air-gap reluctance calculation

Considering the tooth width of the intermediate teeth of the stator and the axial length of the rotor teeth of the hybrid excitation axial flux switching motor, when dividing the air-gap flux tube, it is not possible to simply use a circular arc, so the present invention uses an elliptical arc for cutting , the specific measures are: introducing proportional coefficients k ₁ and k ₂ into the calculation formula. By analyzing the distribution of the air-gap magnetic field at different positions, six typical types of flux tubes are summarized as shown in Figure 7(a)-(f). A combination of typical air-gap magnetoresistance, the magnetoresistance of each flux tube can be obtained according to equations (2.11) to (2.16).

Among them, x ₁ is the width of the magnetic flux tube at the average radius, _la is the effective radial length, g is the air gap length, k ₁ =L ₁ /(x ₁ +r ₁ ), k ₂ =L ₁ /x ₁ .

Under different rotor positions, the air-gap reluctance in the hybrid excitation axial flux switching motor is the combination of the above six typical air-gap reluctance.

2.4 Equivalent of permanent magnets

The permanent magnet is equivalent to a magnetomotive force source F _pm and an internal magnetoresistance R _pm , as shown in Figure 5, and the calculation formulas are shown in equations (2.17) and (2.18):

Among them, H _c and B _r are the coercive force and residual magnetic flux density of the permanent magnet, h _m is the length of the magnetization direction of the permanent magnet, and l _pm is the radial length of the permanent magnet.

As shown in Figure 8, a schematic diagram of the magnetic flux leakage at the end of the permanent magnet of the present invention; the magnetic flux leakage of the hybrid excitation axial flux switching motor mainly exists at the end of the permanent magnet, and there are four magnetic flux leakage at the end of each permanent magnet. Through the tube, its reluctance can be classified into two categories, including R _leak1 and R _leak2 , the specific formula is as follows:

3 Equivalent Magnetic Circuit Model

Combined with the calculation formulas (2.1)~(2.20) of the equivalent reluctance and magnetomotive force of the above parts, the parameters such as the calculated magnetoresistance and magnetomotive force are connected through the magnetomotive force node, and the obtained value of each rotor position area is The equivalent magnetic network is shown in Figure 9. In the figure, F _dc1 and F _dc2 represent the excitation magnetomotive force generated by the DC current on both sides, and its value is the product of the number of turns of the excitation winding and the DC current; R _GI represents the air-gap magnetic force between the stator intermediate tooth I and the rotor tooth I. R _GII represents the air gap reluctance between stator tooth I and rotor tooth II, R _GIII represents the air gap reluctance between stator tooth II and rotor tooth II, and R _GIV represents the air gap between stator intermediate tooth II and rotor tooth III Gap reluctance; R _GⅤ represents the air-gap reluctance between stator intermediate teeth I and rotor teeth II, R _GVI represents the air-gap reluctance between stator teeth II and rotor teeth III; R _r1 , R _r2 and R _r3 are three Reluctance of rotor teeth; Φ _Ⅰ , Φ _Ⅱ , Φ _Ⅲ and Φ _Ⅳ represent the magnetic flux flowing through stator middle teeth I, stator teeth Ⅰ, stator teeth Ⅱ and stator middle teeth Ⅱ respectively, Φ _Ⅴ is stator middle teeth Ⅰ and the air-gap magnetic flux between the rotor tooth II, Φ _VI is the air-gap magnetic flux between the stator tooth II and the rotor tooth III.

By integrating the n regions, the equivalent magnetic circuit model of the hybrid excitation axial flux switching motor can be obtained.

Claims (5)

1. A modeling method for the equivalent magnetic circuit of a hybrid excitation axial flux switching motor, the motor involved is a new type of axial hybrid excitation motor, which adopts the structure of double stator and single rotor, mainly composed of stator, rotor, permanent magnet , the armature winding and the field winding are composed, and the size of the permanent magnet, stator, rotor and air gap of the hybrid excitation axial flux switching motor is determined. It is characterized in that the modeling process includes the following steps: Step 1: The permanent magnet is equivalent to a magnetomotive force source F _pm and an internal resistance R _pm ; Step 2: According to the relative positions of the stator teeth and rotor teeth at the inner and outer diameters, divide the rotor position in a half cycle into n regions, and calculate the stator and rotor core magnetic resistance and air gap magnetic resistance in each region; Step 3, combine the equivalent magnetic resistance of each part to establish the equivalent magnetic circuit model of each region; Step 4, the motor modeling process is completed. 2 . The modeling method according to claim 1 , wherein in the step 2, the magnetic resistance of the stator and rotor core consists of four parts, including the magnetic resistances R _sty and R _sy of the stator yoke, the stator teeth The reluctance R _stt1 , R _stt2 , the reluctance R _smt of the intermediate teeth of the stator and the reluctance R _r of the rotor teeth; R _sty , R _stt1 and R _stt2 are all linear reluctances, and R _sy , R _smt and R _r are non-linear Linear magnetoresistance, the expressions for each magnetoresistance are as follows:

3. The modeling method according to claim 1 is characterized in that, in the described step 2, the magnetic flux tube segmentation method is used to study the air gap reluctance, and an elliptical arc is used to replace the traditional arc to cut the air gap; The distribution of the air-gap magnetic field at different positions is summarized, and six typical types of air-gap flux tubes are obtained. The proportional coefficients k ₁ and k ₂ are introduced, and the reluctance expression of each flux tube is as follows:

4. The modeling method according to claim 1, characterized in that, in the step 3, parameters such as magnetoresistance and magnetomotive force obtained by calculation are connected through the magnetomotive force node, and the etc. parameters of each rotor position region are obtained. The effective magnetic circuit is integrated, and n regions are integrated to obtain the equivalent magnetic circuit model of the hybrid excitation axial flux switching motor. 5. The modeling method according to claim 1, wherein in the step 1, the permanent magnet is equivalent to a magnetomotive force source F _pm and an internal magneto-resistance R _pm , and the calculation of the magnetomotive force source The formula is F _pm =H _c h _m , and the calculation formula of the internal reluctance is R _pm =h _m /(μ ₀ l _pm l _s ); the magnetic leakage of the motor mainly exists at the end of the permanent magnet, and the leakage magnetic resistance The calculation formula is R _leak =1/(0.26μ ₀ l _i ).

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