CN103823926A - Analytical algorithm for optimization design of magnetic conductivity of permanent-magnet-motor sheath - Google Patents

Abstract

The invention discloses an analytical algorithm for optimization design of magnetic conductivity of a permanent-magnet-motor sheath. The analytical algorithm includes creating a permanent-magnet-motor equivalent model and a permanent-magnet-motor equivalent magnetic circuit, determining a magnetic leakage coefficient according to an undetermined coefficient by the iterative convergence method and calculating an induced electromotive force. Through the analytical algorithm and setting of corresponding variables, motors in different sizes can be analyzed rapidly, certain universality is realized during calculation and analysis, and analysis of electromagnetic fields is facilitated. According to the design method, the magnetic conductivity of the magnetic sheath is set as a variable, so that influences of the magnetic sheath on air gap fields and induced electromotive forces of the motors can be analyzed rapidly, and further optimization design of the magnetic conductivity of the sheath is performed.

Description

Analytical algorithm is to magneto sheath magnetic permeability optimal design

Technical field

The present invention relates to a kind of weak analytical algorithm to magneto sheath magnetic permeability optimal design.

Technical background

Compared with electro-magnetic motor, magneto, particularly rare-earth permanent-magnet electric machine have simple in structure, reliable; Volume is little, and quality is light; Loss is little, and efficiency is high; The shape and size of motor can versatile and flexiblely wait remarkable advantage, thereby range of application is very extensive, almost spreads all over the every field of Aero-Space, national defence, industrial and agricultural production and daily life.And the advantage such as surface label magnetic type rotor structure magneto is simple in structure with it, manufacturing cost is lower, moment of inertia is little is widely applied in permagnetic synchronous motor; In addition the permanent magnetism magnetic pole in surface label magnetic type rotor structure is easy to realize optimal design, makes it motor gas-gap magnetic flux density waveforms and levels off to sinusoidal wave pole form, can significantly improve the performance of motor.

In surface label magnetic type rotor structure magneto; the surface of permanent magnet generally adopts the sheath of carbon fiber or alloy material to fix and to protect permanent magnet; especially in high-speed permanent magnet motor, huge centrifugal force generally needs the sheath of adequate thickness to meet its mechanical property.The rare-earth permanent magnet that high-speed electric expreess locomotive is generally selected, its tension that can bear is much smaller than compressive stress, therefore the sheath of high-speed permanent magnet motor will provide certain compressive pre-stress for permanent magnet, makes high-speed permanent magnet motor in the time of high-speed cruising, be unlikely to the tension that permanent magnet bears and is greater than its tolerance range.Adopt alloy sleeve to play certain shielding action to high frequency magnetic field, and can reduce the high frequency added losses in permanent magnet and rotor yoke, heat conductivility is better simultaneously, is conducive to the heat radiation of permanent magnet, and therefore alloy sleeve more has superiority in application aspect.

But in high-speed permanent magnet motor, jacket thickness is generally larger, more than the several times of gas length, cause the magnetic resistance in motor magnetic circuit mainly to concentrate on sheath position, therefore make permanent magnet excitation successful reduce, and adopt ferromagnetism sheath will make permanent magnet magnetic stimulated the menstrual flow sheath and closure, so in high-speed permanent magnet motor designs, the thickness of sheath and the selection of electromagnetic property thereof have great importance.And employing alloy material, by the appropriate design to magnetic permeability, can reduce sheath magnetic resistance by increasing sheath magnetic permeability on the one hand, increase the excitation effect of permanent magnet, to take into account on the other hand the interelectrode magnetic leakage that permanent magnet excitation produces in sheath.

Summary of the invention

The object of patent of the present invention is to provide a kind of analytical algorithm to magneto sheath magnetic permeability optimal design, this rotor sheath has certain magnetic conduction ability, by the optimal design to sheath magnetic permeability, also the magnetic resistance of motor main magnetic circuit be can effectively reduce, the working point of permanent magnet and the utilization factor of permanent magnetic material improved.

Accompanying drawing explanation

Fig. 1 is the general analytical calculation model of surface label magnetic magneto of the present invention.

Fig. 2 is permanent magnet equivalent magnetic circuit of the present invention.

Fig. 3 is the calculated relationship of the unloaded magnetic leakage factor of the present invention and permanent magnet flux density.

Fig. 4 is undetermined coefficient-iteration convergence calculation flow chart of the present invention.

Fig. 5 is the work main flux graph of a relation of sheath magnetic permeability of the present invention and motor.

Fig. 6 is the computer interface figure of sheath magnetic permeability analysis software.

Embodiment

Describe the concrete implementation step of patent of the present invention in detail below in conjunction with accompanying drawing:

Step 1 is set up magneto equivalent model

As shown in Figure 1, set up the general general analytical calculation model (magneto equivalent model) of protective metal shell surface label magnetic permagnetic synchronous motor, motor is divided into four regions by this model, is respectively permanent magnet excitation region, rotor jacket, air gap and stator core region.When stator core external radius, air gap external radius, sheath external radius, permanent magnet external radius and permanent magnet inside radius are respectively R _s, R _a, R _r, R _pand R _ztime, permanent magnet magnetic conductance, sheath magnetic permeability, air-gap permeance and stator core magnetic permeability are respectively μ _p, μ _r, μ ₀and μ _s.

Step 2 is set up magneto equivalent magnetic circuit

The derivation of resolving is based on Maxwell equation, described model to be calculated, and in induction electromotive force computation process, permanent magnet is excitation source, is also excitation boundary condition important in analytical derivation procedure simultaneously; But due to this material self, the excitation effect of permanent magnet is that the working point of permanent magnet changes the change along with the main magnetic conductance of motor and leakage permeance, adopts permanent magnet magnetic equivalent circuit method to analyze the magnetic flux of permanent magnet in patent of the present invention; As shown in Figure 2, in permanent magnet equivalent magnetic circuit, permanent magnet is become the parallel connection of magnetic conductance in a permanent sources of magnetic flux and permanent magnet by equivalence.

Step 3 undetermined coefficient-iteration convergence is determined the magnetic leakage factor of magneto

In described permanent sources of magnetic flux and permanent magnet in the permanent magnet equivalent magnetic circuit of magnetic conductance parallel connection, main magnetic conductance and leakage permeance all can be along with the change of sheath magnetic permeability difference.In order to obtain the main flux of motor with the unloaded induction electromotive force of calculating motor, just must obtain the magnetic conductance of permanent magnet equivalent magnetic circuit each several part.Magnetic conductance Λ in permanent magnet ₀can calculate by formula (1), and the main magnetic conductance of motor is under the hypothesis of ignoring magnetic conductance unshakable in one's determination, only has air-gap permeance, sheath magnetic conductance and permanent magnet magnetic conductance to form, and also easily solves.But the leakage permeance of motor (only considering the interelectrode magnetic leakage of motor in two-dimensional electromagnetic field) will be a complicated computation process, and along with the change of sheath magnetic permeability, the interelectrode magnetic leakage of permanent magnet is difficult to determine especially.

${\mathrm{\Λ}}_0=\frac{{\mathrm{\μ}}_p{A}_m}{h_{\mathrm{mp}}}---\left(1\right)$

In formula: A _mrepresent the sectional area of permanent magnet, h _mprepresent permanent magnet magnetization direction length.

In order to determine that the leakage permeance of motor further obtains the main flux of motor, the computing method that proposed permanent magnet convergent iterations are calculated it.According to the defined formula (2) of the unloaded magnetic leakage factor of magneto, by the unloaded magnetic leakage factor σ ' of a motor of original hypothesis ₀the motor flux leakage that just can obtain under supposed premise is led, therefore can determine according to permanent magnet equivalent magnetic circuit the magnetic flux that permanent magnet provides, the magnetic flux providing by permanent magnet can be obtained the close size of magnetic of permanent magnet surfaces, and the boundary condition of permanent magnet excitation is also just provided for the analytical Calculation of electromagnetic field in motor.By the analytical Calculation of further electromagnetic field, can obtain the useful flux that enters into electric machine stator iron, according to unloaded magnetic leakage factor formula (3), can obtain under this assumed condition, the empty load of motor magnetic leakage factor of utilizing Maxwell equation group to obtain, if this magnetic leakage factor is consistent with hypothesis magnetic leakage factor, proves that this magnetic leakage factor is the unloaded interelectrode magnetic leakage coefficient of motor reality, if inconsistent, hypothesis is calculated again.

${\mathrm{\σ}}_0^{\′}=1+\frac{{\mathrm{\Λ}}_{\mathrm{\σ}}}{{\mathrm{\Λ}}_{\mathrm{\δ}}}---\left(2\right)$

In formula: Λ _σrepresent the leakage permeance of motor, Λ _δrepresent the main magnetic conductance of motor.

${\mathrm{\σ}}_0=\frac{{\mathrm{\Φ}}_m}{{\mathrm{\Φ}}_{\mathrm{\δ}}}---\left(3\right)$

In formula: Φ _mrepresent permanent magnet excitation magnetic flux, Φ _δrepresent the main flux of motor.

The dual corresponding calculated relationship of the two close with permanent magnet excitation magnetic of the unloaded magnetic leakage factor of magneto, as shown in Figure 3, this iteration convergence computation process is actually and solves the intersection point of dual computation process curve between the two.This iteration convergence calculation process as shown in Figure 4.

Step 4 is calculated induction electromotive force

Maxwell equation group adopts magnetic vector potential to represent in this article, and in induction electromotive force solution procedure, ignore inductive loop and kelvin effect in sheath, magnetic vector potential A should meet Laplace equation.In the derivation of two-dimensional electromagnetic field, within the scope of the effective length of stator and rotor iron core, magnetic vector potential A only contains axial component, and

therefore the only scalar Laplace's equation of Az (formula 4) in demand solution polar coordinates

$\frac{{\&PartialD;}^2{A}_z}{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}+\frac{1}{r}\frac{{\&PartialD;A}_z}{\&PartialD;r}+\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\frac{{\&PartialD;}^2{A}_z}{{\&PartialD;\mathrm{\&theta;}}^2}=0---\left(4\right)$

Can adopt the separation of variable to solve for formula (4), zones of different magnetic vector potential A in motor _zresult of calculation as shown in formula (5)-formula (7).

A. sheath region:

$A_z^1=(f_1^1{r}^p+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_2^1{r}^{-p})(f_3^1\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})+{\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_4^1\sin (\mathrm{\&omega;t}+\mathrm{p\&theta;}))---\left(5\right)$

B. air gap region:

$A_{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">z</figure-callout>}}^2=(f_1^2{r}^p+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_2^2{r}^{-p})(f_3^2\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})+{\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_4^2\sin (\mathrm{\&omega;t}+\mathrm{p\&theta;}))---\left(6\right)$

C. stator core region:

$A_z^3=(f_1^3{r}^p+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_2^3{r}^{-p})(f_3^3\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})+{\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">f</figure-callout>}}_4^3\sin (\mathrm{\&omega;t}+\mathrm{p\&theta;}))---\left(7\right)$

In formula: coefficient can determine by boundary condition, and ω is fundamental wave magnetic field angular frequency, and r is radius, and p is number of pole-pairs, and θ represents mechanical angle.

Owing to only the first-harmonic of electromagnetic field in motor being processed in this section, therefore the excitation field of permanent magnet is also approximate according to Sine distribution processing, is Sine distribution so close at the magnetic of permanent magnet surfaces;

$B_r{|}_{r=R_1}=B_1\sin \mathrm{p\&theta;}---\left(8\right)$

According to formula (8), can determine coefficient

be equal to 0, formula (5)-formula (7) can be simplified the following form of being write as so:

$A_z^1=(g_1^1{r}^p+{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^1{r}^{-p})\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})$

$\left(9\right)$

$A_{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">z</figure-callout>}}^2=(g_1^2{r}^p+{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^2{r}^{-p})\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})---\left(10\right)$

$A_z^3=(g_1^3{r}^p+{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^3{r}^{-p})\cos (\mathrm{\&omega;t}+\mathrm{p\&theta;})---\left(11\right)$

In order to determine the coefficient of formula (9)-formula (11), other 5 boundary conditions will provide at equation (12)-equation (16):

$B_n{|}_{r=R_r}=\frac{\&PartialD;A_1}{\&PartialD;\mathrm{\&theta;}}{|}_{r=R_r}=\frac{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">A</figure-callout>}}_2}{\&PartialD;\mathrm{\&theta;}}{|}_{r=R_r}---\left(12\right)$

$H_t{|}_{r=R_r}=-\frac{1}{{\mathrm{\&mu;}}_r}\frac{\&PartialD;A_1}{\&PartialD;n}{|}_{r=R_r}=-\frac{1}{{\mathrm{\&mu;}}_0}\frac{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">A</figure-callout>}}_2}{\&PartialD;n}{|}_{r=R_r}---\left(13\right)$

$B_n{|}_{r=R_a}=\frac{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">A</figure-callout>}}_2}{\&PartialD;\mathrm{\&theta;}}{|}_{r=R_a}=\frac{{\&PartialD;A}_3}{\&PartialD;\mathrm{\&theta;}}{|}_{r=R_a}---\left(14\right)$

$H_t{|}_{r=R_a}=-\frac{1}{{\mathrm{\&mu;}}_0}\frac{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">A</figure-callout>}}_2}{\&PartialD;n}{|}_{r=R_a}=-\frac{1}{{\mathrm{\&mu;}}_s}\frac{{\&PartialD;A}_3}{\&PartialD;n}{|}_{r=R_a}---\left(15\right)$

$B_n{|}_{r=R_s}=0---\left(16\right)$

The boundary values system of equations of trying to achieve motor according to above-mentioned boundary condition is:

$\begin{array}{c}{R}_1^p{g}_1^1+R_1^{-\mathrm{<figure-callout\; id="2"\; label="p\; g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}{g}_{}^{}{}_2^1=-B_1{R}_1\\ R_2^p{g}_1^1+R_2^{-\mathrm{<figure-callout\; id="2"\; label="p\; g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}{g}_{}^{}{}_2^1-R_2^p{g}_1^2-R_2^{-\mathrm{<figure-callout\; id="2"\; label="p\; g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}{g}_{}^{}{}_2^2=0\\ {\mathrm{\&mu;}}_2{R}_2^{p-1}{g}_1^1-{\mathrm{\&mu;}}_2{R}_2^{-p-1}{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^1-{\mathrm{\&mu;}}_1{R}_2^{p-1}{g}_1^2+{\mathrm{\&mu;}}_1{R}_2^{-p-1}{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^2=0\\ R_3^p{g}_1^2+R_3^{-\mathrm{<figure-callout\; id="2"\; label="p\; g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}{g}_{}^{}{}_2^2-R_3^p{g}_1^3-R_3^{-\mathrm{<figure-callout\; id="2"\; label="p\; g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}{g}_{}^{}{}_2^3=0\\ {\mathrm{\&mu;}}_3{R}_3^{p-1}{g}_1^2-{\mathrm{\&mu;}}_3{R}_3^{-p-1}{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^2-{\mathrm{\&mu;}}_2{R}_3^{p-1}{g}_1^3+{\mathrm{\&mu;}}_2{R}_3^{-p-1}{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^3=0\\ R_4^{p-1}{g}_1^3-R_4^{-p-1}{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="HDA0000464785200000032.png"\; state="\{\{state\}\}">g</figure-callout>}}_2^3=0\end{array}---\left(17\right)$

Above-mentioned equation can represent as follows according to the mode of Matrix Solving:

A·x＝B （18）

Wherein:

$A=\left[\begin{array}{cccccc}{R}_1^p& R_1^{-\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="HDA0000464785200000031.png,HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}& 0& 0& 0& 0\\ R_2^p& R_2^{-p}& -R_2^p& -R_2^{-\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="HDA0000464785200000031.png,HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}& 0& 0\\ {\mathrm{\&mu;}}_2{R}_2^{p-1}& -{\mathrm{\&mu;}}_2{R}_2^{-p-1}& -{\mathrm{\&mu;}}_1{R}_2^{p-1}& {\mathrm{\&mu;}}_1{R}_2^{-p-1}& 0& 0\\ 0& 0& R_3^p& R_3^{-p}& -R_3^p& -R_3^{-\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="HDA0000464785200000031.png,HDA0000464785200000032.png"\; state="\{\{state\}\}">p</figure-callout>}}\\ 0& 0& {\mathrm{\&mu;}}_3{R}_3^{p-1}& -{\mathrm{\&mu;}}_3{R}_3^{-p-1}& -{\mathrm{\&mu;}}_2{R}_3^{p-1}& {\mathrm{\&mu;}}_2{R}_3^{-p-1}\\ 0& 0& 0& 0& R_4^{p-1}& -R_4^{-p-1}\end{array}\right]$

Ultimate principle:

Motor jacket thickness is generally larger, if adopt nonmagnetic sheath, the magnetic resistance of motor main magnetic circuit mainly concentrates in air gap and sheath, cause motor main magnetic circuit magnetic resistance very large, the working point of permanent magnet is not high, and the excitation successful of permanent magnet reduces, and its output magnetic flux reduces.The sheath if adopted with certain magnetic conduction ability, can effectively reduce the magnetic resistance that sheath produces in main magnetic circuit, and Operating Point of Permanent Magnet is improved, and its output magnetic flux is increased, and has higher advantage for improving Operating Point of Permanent Magnet aspect.

But due to the increase of sheath magnetic conduction ability, will inevitably be increased in the ratio that the interior closed magnetic flux of rotor jacket accounts for permanent magnet excitation magnetic flux, increase the interelectrode magnetic leakage of permanent magnet, reduced the useful flux that participates in motor power conversion, reduced on the contrary the work main flux of motor.As shown in Figure 5, in figure, quadrilateral DEHG is the useful flux that motor participates in energy conversion to the relation curve schematic diagram of the two.In Fig. 5, show that in addition motor sheath changes to Magnetic protection sleeve by non magnetic sheath, the situation of change of motor main flux, leakage flux and useful flux.Therefore in the time analyzing employing Magnetic protection sleeve high-speed permanent magnet motor, must consider aspect above two.Because the two is not linear relationship on the impact of motor, thus can be by selecting suitable motor sheath magnetic property, make excitation magnetic flux that permanent magnet provides be greater than the recruitment of interelectrode magnetic leakage, the main flux that makes motor participate in energy increases.

Software for Design:

For the magnetic permeability of Magnetic protection sleeve a little less than definite magneto, realize permanent magnet excitation effect optimum, at utmost improve the stock utilization of permanent magnet, on the basis of analytical algorithm, design sheath magnetic permeability analysis software.The computer interface of analysis software as shown in Figure 6.Utilize electromagnetic field to resolve algorithm the high-speed permanent magnet motor electromagnetic field that adopts different magnetic permeability sheaths is calculated, by sheath magnetic permeability variable is set, derive and calculated the variation of high-speed permanent magnetic generator induction electromotive force when sheath magnetic permeability is different.

Claims (5)

1. analytical algorithm is optimized a method for designing to magneto sheath magnetic permeability, is the optimal design of permanent-magnet servo motor, high speed permanent motor, the magneto of general permanent magnet surface subsides magnetic structure being carried out to sheath material, the steps include:

Step 1, set up magneto equivalent model;

Step 2, set up magneto equivalent magnetic circuit, based on Maxwell equation, described model is calculated;

Step 3, undetermined coefficient-iteration convergence are determined the magnetic leakage factor of magneto;

Step 4, calculating induction electromotive force;

By the computational analysis of above step, can carry out fast the calculating of air-gap field and induction electromotive force to the magneto of different size same structure, provide the impact of sheath magnetic permeability on motor gas-gap magnetic field and induction electromotive force, further sheath magnetic permeability is optimized to design.

2. Optimization Design according to claim 1, is characterized in that: the magneto equivalent model of setting up in step 1 is that motor is divided into four regions, is respectively permanent magnet excitation region, rotor jacket, air gap and stator core region.

3. Optimization Design according to claim 1, it is characterized in that: in the calculating that step 2 is carried out described model, in induction electromotive force computation process, permanent magnet is excitation source, also be excitation boundary condition important in analytical derivation procedure simultaneously, adopt permanent magnet magnetic equivalent circuit method to analyze the magnetic flux of permanent magnet; In permanent magnet equivalent magnetic circuit, permanent magnet is become the parallel connection of magnetic conductance in a permanent sources of magnetic flux and permanent magnet by equivalence.

4. Optimization Design according to claim 1, it is characterized in that: the undetermined coefficient-iteration convergence of step 3 is determined the magnetic leakage factor of magneto, by the unloaded magnetic leakage factor of a motor of original hypothesis, the motor flux leakage that can obtain under supposed premise is led, can determine according to permanent magnet equivalent magnetic circuit the magnetic flux that permanent magnet provides, the magnetic flux providing by permanent magnet can be obtained the close size of magnetic of permanent magnet surfaces, and the boundary condition of permanent magnet excitation is also just provided for the analytical Calculation of electromagnetic field in motor; By the analytical Calculation of further electromagnetic field, can obtain the useful flux that enters into electric machine stator iron; According to unloaded magnetic leakage factor formula, can obtain under this assumed condition the empty load of motor magnetic leakage factor of utilizing Maxwell equation group to obtain; If this magnetic leakage factor is consistent with hypothesis magnetic leakage factor, prove that this magnetic leakage factor is the unloaded interelectrode magnetic leakage coefficient of motor reality, if inconsistent, hypothesis is calculated again.

5. Optimization Design according to claim 1, it is characterized in that: the calculating of the induction electromotive force of step 4, it is the distribution that solves motor each several part vector magnetic potential by said method, obtain the magnetic field expression formula in motor gas-gap, further draw the induction electromotive force of motor, by air-gap field and induction electromotive force, motor sheath magnetic permeability is optimized to design.

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