CN106208555B - A kind of extended method of built-in brshless DC motor pole embrace - Google Patents

A kind of extended method of built-in brshless DC motor pole embrace Download PDF

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Publication number
CN106208555B
CN106208555B CN201610811230.5A CN201610811230A CN106208555B CN 106208555 B CN106208555 B CN 106208555B CN 201610811230 A CN201610811230 A CN 201610811230A CN 106208555 B CN106208555 B CN 106208555B
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China
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permanent magnet
brshless
motor
pole
angle
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CN106208555A (en
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刘景林
公超
王晓梅
于昊正
张二阳
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Northwestern Polytechnical University
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Northwestern Polytechnical University
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K15/00Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K29/00Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
    • H02K29/03Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K2213/00Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
    • H02K2213/03Machines characterised by numerical values, ranges, mathematical expressions or similar information

Abstract

The present invention provides a kind of extended methods of built-in brshless DC motor pole embrace, first, according to the demagnetized field Strength co-mputation permanent magnet minimum edge thickness under every extremely maximum demagnetization magnetic potential when built-in brshless DC motor nominal operation and high temperature at inflection point k;Then, permanent magnetism shape and size are redesigned using AutoCAD according to minimum edge thickness, and measures the angle between permanent magnet edge;Finally, according to the extension pole embrace of angle and the corresponding angle calculation brshless DC motor of pole span between permanent magnet edge.The method of the present invention makes full use of the structure of permanent magnet trough, by extending permanent magnet edge, increases permanent magnet width so that pole embrace is expanded, and has both avoided the generation of wedge angle demagnetization, has also avoided causing permanent magnet to waste in pole embrace expansion process.After carrying out pole embrace extension using the method for the present invention, air gap flux density is more nearly square wave, can reduce motor torque ripple, vibration and noise by square wave control.

Description

A kind of extended method of built-in brshless DC motor pole embrace
Technical field
The invention belongs to technical field of motors more particularly to a kind of extension sides of built-in brshless DC motor pole embrace Method.
Background technology
Rare-earth permanent-magnet electric machine has simple in structure, easy to maintenance, stable, dependable performance, power density high and speed governing The advantages that performance is good achieves extensive use in wind power generation field, electric vehicle field and digit ctrol machine tool field;Together When, the research for magneto body design and optimization is also more and more, and research contents is mainly set including motor new structure Meter and the optimization parameter of electric machine are to reach the target for reducing torque pulsation, improving power factor, obtaining reasonable air gap flux density, wherein Pole embrace is the key parameter of design of electrical motor, directly affects air gap magnetic density waveform, when pole embrace increases, air gap flux density point Cloth can be gradually become square wave by sine wave, and winding back emf square wave feature can be better, and torque pulsation can reduce, and motor operation is also got over Steadily, motor electromagnetic vibration and noise while can also be improved, therefore, in brshless DC motor design, it is desirable to which pole embrace is got over It is big better.Built-in brshless DC motor is a kind of special construction of brshless DC motor, and magnet steel is embedded in internal rotor, has Higher reliability needs to consider motor volume and power density, polar arc system in the design of built-in brshless DC motor Several values can be limited by rotor size, if pursuing big pole embrace simply in the design process, can lead to rotor Magnetic bridge part becomes smaller so that brshless DC motor leakage field increases.
To reduce leakage field, the both ends of built-in brshless DC motor permanent magnet trough can use three-legged structure, i.e. permanent magnet trough Wedge angle, in being typically designed, permanent magnet trough wedge angle position will not be embedded in permanent magnet.When designed high power density is built-in brushless When direct current generator pole embrace is smaller, pole embrace can be extended using permanent magnet trough wedge angle, method is in slot point Angle Position also fills permanent magnet to increase the width of permanent magnet, but a problem is faced in the expansion process:Permanent magnet trough Wedge angle is thinner closer to marginal position, since the permanent magnet filled to slot wedge angle position is consistent with slot angular shape, when permanent magnetism When body is embedded into slot wedge angle position or is fully filled with slot, permanent magnet edge is along magnetizing direction thickness very little, with motor work temperature Degree increases, and permanent magnet demagnetizing curve bending, armature field can cause permanent magnet marginal position to generate irreversible demagnetization, which claims It demagnetizes for wedge angle, wedge angle demagnetization can cause the permanent magnet close to marginal position to fail, the width of increasing permanent magnet simply, especially It is that when filling up slot wedge angle, permanent magnet can be caused to generate waste because of partial failure.Therefore, the extension of pole embrace can be by point The limitation of angle demagnetization.Built-in high power density brshless DC motor is small, and the arrangement space of permanent magnet is restricted, design Pole embrace takes less than ideal value in the process, and point can be occurred to avoid built-in brshless DC motor permanent magnet by needing to seek one kind The pole embrace extended method of angle demagnetization.
Invention content
Technical problems to be solved
For make up design power is big, small brshless DC motor during can not obtain lacking for big pole embrace It falls into, improves the performance of square wave control brshless DC motor, and avoid permanent magnet that wedge angle demagnetization occurs and cause to waste, the present invention carries Go out a kind of extended method for the built-in brshless DC motor pole embrace that the demagnetization of consideration wedge angle influences.
Technical solution
A kind of extended method of built-in brshless DC motor pole embrace, it is characterised in that steps are as follows:
Step 1:According to h1=Fadm/HkCalculate permanent magnet minimum edge thickness h1, wherein FadmFor built-in brushless direct-current Per extremely maximum demagnetization magnetic potential, H when Rated motor workskFor temperature T when permanent magnet material demagnetizing curve on demagnetization magnetic at inflection point k Field intensity, wherein T >=150 DEG C;FadmCalculation formula beWherein, IaFor rated operational current, WΦFor every phase winding turns-in-series, KWFor winding coefficient, p is number of pole-pairs;
Step 2:The permanent magnet edge thickness after extension is enabled to be equal to h1, according to permanent magnet edge keeping parallelism before and after extension Principle draws permanent magnetism shape after extension using AutoCAD, and marks magnet size, at the same measure be expanded after permanent magnetism Angle α between body edge1, the permanent magnet edge angle be every two edges of pole permanent magnet upper end respectively with the intersection point A of slot, The angle of line between A ' and rotor axis O;
Step 3:According to αpmax1The pole embrace maximum value of built-in brshless DC motor after extension is calculated in/β αpmax, then the spreading range of pole embrace is (α/β, αpmax];Wherein, β is the corresponding angle of pole span, and α is permanent magnet side before extension Intermarginal angle.
Advantageous effect
A kind of extended method of built-in brshless DC motor pole embrace proposed by the present invention, makes full use of permanent magnet trough Structure, pass through and extend permanent magnet edge, increase permanent magnet width so that pole embrace is expanded;Utilize Rated motor work Permanent magnet minimum edge thickness is determined per extremely maximum demagnetization magnetic potential and the ratio of the demagnetized field intensity at inflection point k, both kept away when making The generation for having exempted from wedge angle demagnetization, also avoids causing permanent magnet to waste in pole embrace expansion process.Using the method for the present invention into Row pole embrace extension after, air gap flux density is more nearly square wave, by square wave control can reduce motor torque ripple, vibration and Noise.
Description of the drawings
Fig. 1 is a kind of calculation flow chart of built-in brshless DC motor pole embrace extended method of the present invention.
Fig. 2 is neodymium iron boron 35SH demagnetizing curves at 150 DEG C.
Fig. 3 is the front and back rotor schematic diagram of built-in brshless DC motor pole embrace extension.
Specific implementation mode
Present invention will be further explained below with reference to the attached drawings and examples, and the present invention includes but are not limited to following implementations Example.
Since built-in brshless DC motor pole embrace size is related with the spatial distribution of permanent magnet on rotor, permanent magnet Width is wider, and motor pole embrace is bigger.If slot pointed part filling permanent magnet can be extended to the width of permanent magnet, polar arc system Number increases therewith so that brshless DC motor air gap flux density is more nearly square wave, and square wave controls the brshless DC motor torque arteries and veins Dynamic and noise can reduce.However, when motor operating temperature be higher than certain value when, winding generate demagnetized field be more than certain value after, Permanent magnet demagnetizing curve can drastically decline, and new recovery curve is no longer overlapped with demagnetizing curve, irreversible demagnetization be generated, after demagnetization The flux density that is provided out of permanent magnet strongly reduce, repeated work even results in the complete loss of excitation of permanent magnet, thus permanent magnet to Slot wedge angle needs to check minimum thickness when extending, and avoids that wedge angle demagnetization occurs, while can prevent permanent magnet from wasting.
Based on above-mentioned thought, as shown in Figure 1, the magneto pole embrace extension for considering wedge angle demagnetization and influencing of the present invention Method detailed process is as follows:
1) the demagnetized field intensity H at permanent magnet demagnetizing curve inflection point k is determinedk
Wedge angle demagnetization occurs under the high temperature conditions, and the high power density magneto internal temperature to work long hours is 100 DEG C or more, the present embodiment motor operating temperature is about 150 DEG C, selects the magnetic field at 150 DEG C of neodymium iron boron 35SH demagnetizing curve inflection points k Intensity is come the permanent magnet minimum edge thickness that calculates, as shown in Fig. 2, demagnetized field intensity size is H at inflection point kk= 487000A/m;
2) per extremely maximum demagnetization magnetic potential F when determining brshless DC motor nominal operationadm
Temperature increases when motor is in rated operation for a long time, the demagnetized field meeting that machine winding current generates later Cause permanent magnet that irreversible demagnetization occurs, so, to estimate that the minimum thickness of permanent magnet needs to determine that Rated motor works first When per extremely maximum demagnetization magnetic potential, calculation formula beWherein, IaFor rated operational current, WΦIt is every Phase winding turns-in-series, KWFor winding coefficient, p is number of pole-pairs.The built-in brushless DC motor rotor schematic diagram of the present embodiment As shown in figure 3, its rated current Ia=50A, per phase winding turns-in-series WΦ=42, winding coefficient KW=0.96, number of pole-pairs p= 3, then it is F that every extremely maximum demagnetization magnetic potential, which can be calculated,adm=581.9A.
3) permanent magnet minimum edge thickness h is calculatedmin
Permanent magnet minimum edge thickness can be obtained equal to per extremely maximum demagnetization magnetic potential by multiplying magnetic field intensity equal to distance according to magnetic potential FadmDivided by magnetic field intensity Hk, calculation formula hmin=Fadm/Hk, the present embodiment minimum thickness is hmin=1.19mm.
4) permanent magnet is redesigned
The shape of permanent magnet trough is with size by prefetching pole embrace αpIt is determined with magnetic bridge width c, as shown in figure 3, this reality It applies middle permanent magnet edge vertices to overlap with A points, permanent magnetism shape is consistent with permanent magnet trough, and groove edge position forms slot wedge angle, should Position some there is no permanent magnet filling.Wherein, αp=α/β, α are the angles between permanent magnet edge, i.e., per pole permanent magnet two Respectively with intersection point A, A of slot ' angle of line between rotor axis O, β is the corresponding angle of pole span, this reality for a edge upper end It applies and prefetches pole embrace α in examplepIt is 0.83, angle α=50 ° between permanent magnet edge, corresponding angle beta=60 ° of pole span.
To avoid the generation of wedge angle demagnetization, with permanent magnet minimum edge thickness hminFor the boundary condition that permanent magnet is widened, i.e., Enable the edge thickness h of permanent magnet after extending1=hmin, permanent magnet trench structure is relied on, using AutoCAD directly in slot wedge angle Permanent magnet edge is drawn, according to the principle of permanent magnet edge keeping parallelism before and after extension, permanent magnet edge still hangs down with groove edge AB Directly, i.e. h1//h, as shown in figure 3, the new permanent magnet obtained after extension is former permanent magnet and permanent magnet expansion and the mistake The shape of journey permanent magnet is changed, and can directly measure permanent magnet the size of each part using AutoCAD, and be labeled.
After the extension of permanent magnet width, the angle between permanent magnet edge becomes larger, and can be obtained by AutoCAD measurements:New permanent magnetism Body upper end-face edge generates new intersection point C with slot1、C2, make auxiliary line from rotor axis O to this 2 points, pressed from both sides between measurement two lines section Angle, that is, the angle α after extending between permanent magnet edge1=55.8 °.
5) the pole embrace α of built-in brshless DC motor after extending is calculatedpmax
By αpmax1Pole embrace α after/β extensionspmax, the pole embrace after the present embodiment extension is αpmax=0.93, Increase much it can be seen that relatively prefetching pole embrace.It should be noted that:αpmaxIt is the maximum polar arc system for being avoided that wedge angle demagnetization It counts, (α/β, α is taken in optimization processpmax] between any value wedge angle can be avoided to demagnetize phenomenon.

Claims (1)

1. a kind of extended method of built-in brshless DC motor pole embrace, it is characterised in that steps are as follows:
Step 1:According to h1=Fadm/HkCalculate permanent magnet minimum edge thickness h1, wherein FadmFor built-in brshless DC motor Per extremely maximum demagnetization magnetic potential, H when nominal operationkFor temperature T when permanent magnet material demagnetizing curve on demagnetized field at inflection point k it is strong Degree, wherein T >=150 DEG C;FadmCalculation formula beWherein, IaFor rated operational current, WΦFor Per phase winding turns-in-series, KWFor winding coefficient, p is number of pole-pairs;
Step 2:The permanent magnet edge thickness after extension is enabled to be equal to h1, according to the principle of permanent magnet edge keeping parallelism before and after extension, Draw permanent magnetism shape after extension using AutoCAD, and mark magnet size, at the same measure be expanded after permanent magnet edge Between angle α1, the permanent magnet edge angle be every two edges of pole permanent magnet upper end respectively with intersection point A, A of slot ' with turn The angle of line between sub- axle center O;
Step 3:According to αpmax1The pole embrace maximum value α of built-in brshless DC motor after extension is calculated in/βpmax, Then the spreading range of pole embrace is (α/β, αpmax];Wherein, β is the corresponding angle of pole span, and α is between extending preceding permanent magnet edge Angle.
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