CN100354540C - Design method for permanent magnet bias outer rotor radial magnetic bearing - Google Patents

Abstract

The design method of radial magnetic bearing with permanent magnetic bias outer rotor has the displacement rigidity of the magnetic bearing as main consideration, and the maximum bearing capacity, saturation magnetic induction and tankful rate as restraint conditions. Compared with available design method with optimal work point of the permanent magnet as target, the method of the present invention has the advantages of easy control of magnetic bearing, reasonable permanent magnet size, high accuracy, and being simple and practical. The design philosophy of the present invention may be used in design of different kinds of radial magnetic bearing with permanent magnetic bias outer rotor.

Description

A kind of design method of permanent magnet offset external rotor radial magnetic bearing

Technical field

The present invention relates to a kind of design method of non-contact magnetically suspension bearing, particularly a kind of magnetically levitated flywheel, magnetic suspension control torque gyroscope etc. need the design method of the device of magnetic suspension bearing with permanent magnet offset external rotor radial magnetic bearing, and its design philosophy can be used as the design of all kinds of permanent magnet offset external rotor radial magnetic bearings.

Background technique

Magnetic suspension bearing divides pure electromagnetic type and permanent magnet bias to power up the hybrid magnetic suspension bearing of magnetic control system, the former uses, and electric current is big, power consumption is big, permanent magnet bias powers up the hybrid magnetic suspension bearing of magnetic control system, main bearing capacity is born in the magnetic field that permanent magnet produces, electromagnetism magnetic field provides auxiliary adjusting bearing capacity, thereby this bearing can reduce to control electric current greatly, reduces the wastage.What magnetic bearings control mode commonly used adopted is traditional pid control mode, realize that the controller parameter of this kind mode determined by bearing rigidity and damping, through facts have proved in a large number,, should make bearing rigidity and its displacement rigidity on the same order of magnitude for making magnetic bearing have excellent characteristic.Therefore the displacement rigidity of magnetic bearing is most important for the control of magnetic bearing.Existing magnetic bearing design method all utilizes the permanent magnet best operating point to design, purpose is to make permanent magnet volume minimum, but the magnet size that calculates by this method is often not too reasonable, and processing difficulties, owing to do not consider the influence of displacement rigidity, thereby existing design method exists poor accuracy and restive defective to control system.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of design method of permanent magnet offset external rotor radial magnetic bearing is provided.

Technical solution of the present invention is: a kind of design method of permanent magnet offset external rotor radial magnetic bearing needs to determine: stator core radially inner side height D _S2, stator slot radially inner side height H, frame diameter D _S1, stator core width b _s, the stator core axial length L _Sfe, the rotor core inside diameter D _R2, the rotor core outer diameter D _R1(be the permanent magnet inside diameter D _Pm2), the rotor core axial length is L _Rfe, the permanent magnet outer diameter D _Pm1, permanent magnet axial length h _Pm, width of rebate L _cAnd turn number N,

It is characterized in that: this method is based on the displacement rigidity of magnetic bearing, and its concrete steps are as follows:

(1) sets rotor speed n and maximum load capacity F according to the index request of the device of required magnetic suspension bearing _Max, require to set the static suspension current i according to power consumption, according to existing level of processing setting gap length δ and lamination COEFFICIENT K _Fe, set the displacement rigidity K of magnetic bearing according to the requirement of existing magnetic bearing controller _x, set leakage coefficient σ, set saturation magnetic induction B unshakable in one's determination according to magnetic field analysis according to the magnetization characteristic of selected core material _s

(2) intensity and the mode according to stator requires given stator core radially inner side height D _S2

(3) according to maximum load capacity F _Max, saturation magnetic induction B _sAnd lamination COEFFICIENT K _FeDetermine stator core sectional area A;

(4) determine stator core width b according to the actual requirements _sWith the stator core axial length L _SfeProportionate relationship, and then definite stator core width b _sWith the stator core axial length L _SfeAnd rotor core axial length L _Rfe

(5) according to the stator core axial length L _SfeCalculate stator slot radially inner side height H;

(6) according to the magnetic air gap length δ between the rotor, determine permanent magnet axial length h _PmAnd width of rebate L _c

(7) according to displacement rigidity K _xAnd rotor gravity G determines current stiffness K _i, determine the diameter d of winding wire by current density, J and static suspension current i _c

(8) require to determine frame diameter D according to copper factor _S1, can determine the rotor core inside diameter D by gap length δ again _R2

(9) calculate the rotor core outer diameter D according to the close basic equal principle of stator and rotor yoke portion magnetic by stator core yoke portion area _R1, also be the permanent magnet inside diameter D _Pm2

(10) according to displacement rigidity K _xDetermine the permanent magnet outer diameter D _Pm1, according to current stiffness K _iDetermine turn number N.

Described displacement rigidity span determines by controller, for-0.5N/um～-3N/um; Described gap length δ is 0.15～0.35mm; Described leakage coefficient σ is 1.1～3; Described lamination COEFFICIENT K _FeBeing that ratio by actual stator or rotor core weight and its calculated value obtains, is 0.75～0.95; Described stator core width b _sWith the stator core axial length L _SfeProportionate relationship require to determine that by reality if magnetic bearing requires axial length short, then this ratio value is taken as 4～6, otherwise this ratio value is taken as 1～3; Described copper factor generally is taken as 40%～60%.

Principle of the present invention is: the present invention starts with the displacement rigidity of radial direction magnetic bearing and designs, and sets each parameter as requested, by the magnetic circuit analysis and the calculating of this kind magnetic bearing, can obtain other physical dimension of magnetic bearing.Intensity and mode according to stator require to provide stator core radially inner side height D _S2, according to maximum load capacity F _Max, saturation magnetic induction B _sAnd lamination COEFFICIENT K _FeDetermine stator core sectional area A by following formula.

$A=\frac{F_{\max }\·{\mathrm{\μ}}_0}{B_s^2\·K_{\mathrm{fe}}}---\left(1\right)$

μ in the formula ₀=4 π * 10 ^-7H/m is the permeability of air.

Set sub width b unshakable in one's determination _sWith the stator core axial length L _SfeRatio be C, stator core width b then _sWith the stator core axial length L _SfeFor:

$L_{\mathrm{sfe}}=\sqrt{\frac{A}{C}}---\left(2\right)$

b _s＝C·L _sfe (3)

For fear of because stator and rotor axis unshakable in one's determination misaligns the magnetic pull that causes, desirable rotor core axial length is:

L _rfe＝1.15·L _sfe (4)

And then can get stator slot radially inner side height H and be:

H＝D _s2+2*L _sfe (5)

Magnetic air gap length δ according between the rotor of setting can obtain permanent magnet axial length h _PmAnd width of rebate L _cFor:

h _pm＝K ₁·δ (6)

L _c＝K ₂·h _pm (7)

K in the formula ₁, K ₂Be constant, rule of thumb value.

According to displacement rigidity K _xAnd rotor gravity G can get current stiffness K _i:

$K_i=\frac{G/2-K_x\·x}{i}---\left(8\right)$

Rotor center was apart from the side-play amount of magnetic center when x was static suspension in the formula.

Determine the diameter d of winding wire by current density, J and static suspension current i _cFor:

$d_c=\sqrt{\frac{4\·i}{\mathrm{\π}\·J}}---\left(9\right)$

Then according to the NBS value.

Require to determine frame diameter D according to copper factor _S1, can determine the rotor core inside diameter D by gap length again _R2For:

D _r2＝D _s1+2·δ (10)

Calculate the rotor core outer diameter D according to the close basic equal principle of stator and rotor yoke portion magnetic by stator core yoke portion area _R1(be the permanent magnet inside diameter D _Pm2) be:

$D_{r1}=\frac{b_s\·L_{\mathrm{sfe}}}{2\·L_{\mathrm{rfe}}}+D_{r2}---\left(11\right)$

After this again according to displacement rigidity K _xDetermine the permanent magnet outer diameter D _Pm1For:

$D_{\mathrm{pm}1}=\sqrt{\frac{2\·{\mathrm{\μ}}_0\·A\·h_{\mathrm{pm}}}{(\frac{1}{\sqrt{C1}}-\mathrm{\δ})\·{\mathrm{\μ}}_0\·{\mathrm{\μ}}_{\mathrm{pm}}}\·\frac{4}{\mathrm{\π}}+D_{\mathrm{pm}2}^2}---\left(12\right)$

In the formula: $C1=\frac{-K_x\·{\mathrm{\σ}}^2\·\mathrm{\δ}}{{\mathrm{\μ}}_0\·A\·F_{\mathrm{pm}}^2}---\left(13\right)$

F wherein _Pm=H _PmH _PmBe the magnetomotive force of permanent magnet, H _PmBe the coercivity of permanent magnet, generally be taken as 760kA/m～790kA/m; μ _PmBe the relative permeability of permanent magnet, generally be taken as 1.03～1.05.

According to current stiffness K _iCan be in the hope of turn number N:

$N=\frac{K_k\·R_{\mathrm{pmsum}}\·\mathrm{\σ}\·{\mathrm{\δ}}^2}{2\·F_{\mathrm{pm}}\·(R_{\mathrm{pmsum}}-R_{\mathrm{pm}})\·{\mathrm{\μ}}_0\·A}---\left(14\right)$

In the formula: R _PmBe permanent magnet magnetic resistance, R _PmsumBe the total magnetic resistance of permanent magnetic circuit.

So far, whole magnetic bearing design finishes.

The present invention's advantage compared with prior art is: the present invention is because employing is the design method of starting point with the radial direction magnetic bearing displacement rigidity, is that the design method of starting point is compared with the design of existing external rotor radial magnetic bearing with the permanent magnet best operating point, be beneficial to control more, the parameter that obtains is more reasonable.

Description of drawings

Fig. 1 is the structural drawing of the permanent magnet offset external rotor radial magnetic bearing that the present invention is directed to;

Fig. 2 is a design flow diagram of the present invention;

The permanent magnet offset external rotor radial magnetic bearing pictorial diagram of Fig. 3 for designing according to the present invention, wherein (a) is the stator module of external rotor radial magnetic bearing, (b) is the rotor assembly of external rotor radial magnetic bearing.

Embodiment

As shown in Figure 1, design object of the present invention is a kind of magnetically levitated flywheel permanent magnet offset external rotor radial magnetic bearing, and 1 is stator core among the figure, and 2 is coil, and 3 is the magnetic air gap between the rotor, and 4 is permanent magnet, and 5 is magnetic guiding loop, and 6 are rotor core.Set the displacement rigidity K of magnetic bearing according to the requirement of existing magnetic bearing controller _xFor-1N/um, according to the given stator core radially inner side height D that requires of stator intensity and mode _S2Be 42mm, set gap length δ according to existing level of processing and be taken as 0.2mm, the lamination COEFFICIENT K _FeBe 0.85, setting leakage coefficient σ according to the magnetic field analysis of this magnetic bearing is 1.3, sets maximum load capacity F according to the index request of magnetically levitated flywheel _MaxBe 178N, setting the static suspension current i according to the power consumption requirement of magnetically levitated flywheel is 0.2A, and the static suspension current density, J is 3A/mm ², the stator and rotor iron core of magnetic bearing is selected the thick 1J50 of iron nickel magnetically soft alloy 0.1mm for use among this embodiment, sets saturation magnetic induction B according to the magnetization curve of 1J50 _sBeing 1.2T, is 40% according to the level set stator copper factor that rolls off the production line that has coil now.

According to above condition, can calculate stator core sectional area A=182.2mm by (1) formula ², set sub width b unshakable in one's determination _sWith the stator core axial length L _SfeRatio C=5, then can draw stator core width b by formula (2) and (3) _s=30mm, the stator core axial length L _Sfe=6mm, for fear of because stator and rotor axis unshakable in one's determination misaligns the magnetic pull that causes, can get the rotor core axial length by formula (4) is L _Rfe=7mm can get stator slot radially inner side height H=54mm by formula (5), makes K by formula (6) and (7) ₁=16, K ₂=3, can obtain permanent magnet axial length h _Pm=3.2mm, width of rebate L _c=9.6mm, desirable L in the reality _c=10mm considers the rotor displacement amount x=0.1mm behind the general magnetic bearing static suspension, can get current stiffness K by (8) _i=357.3N/A can be got the diameter d of winding wire by formula (9) _c=0.356mm is taken as 0.35mm, can get frame diameter D according to the copper factor of setting after by program cycle _S1=80mm can get the rotor core inside diameter D by formula (10) _R2=80.4mm can get the rotor core outer diameter D by formula (11) _R1=86.2mm can get the permanent magnet outer diameter D by formula (12) _Pm1=90.2mm can get turn number N=98.9 circles by formula (14), is taken as 100 circles.So far, this permanent magnet offset external rotor radial magnetic bearing design finishes.

The content that is not described in detail in the specification of the present invention belongs to related domain professional and technical personnel's known prior art.

Claims (7)

1, a kind of design method of permanent magnet offset external rotor radial magnetic bearing is characterized in that: this method is based on the displacement rigidity of magnetic bearing, and its concrete steps are as follows:

(1) the displacement rigidity K of setting magnetic bearing _x, gap length δ, leakage coefficient σ, lamination COEFFICIENT K _Fe, maximum load capacity F _Max, static suspension current i and saturation magnetic induction B unshakable in one's determination _s

(2) intensity and the mode according to stator requires given stator core radially inner side height D _S2

(3) according to maximum load capacity F _Max, saturation magnetic induction B _sAnd lamination COEFFICIENT K _FeDetermine stator core sectional area A;

(4) determine stator core width b according to the actual requirements _sWith the stator core axial length L _SfeProportionate relationship, and then definite stator core width b _sWith the stator core axial length L _SfeAnd rotor core axial length L _Rfe

(5) according to the stator core axial length L _SfeCalculate stator slot radially inner side height H;

(6) according to the magnetic air gap length δ between the rotor, determine permanent magnet axial length h _PmAnd width of rebate L _c

(7) according to displacement rigidity K _xAnd rotor gravity G determines current stiffness K _i, determine the diameter d of winding wire by current density, J and static suspension current i _c

(8) require to determine frame diameter D according to copper factor _S1, can determine the rotor core inside diameter D by gap length δ again _R2

(9) calculate the rotor core outer diameter D according to the close basic equal principle of stator and rotor yoke portion magnetic by stator core yoke portion area _R1It also is the permanent magnet inside diameter D _Pm2

(10) according to displacement rigidity K _xDetermine the permanent magnet outer diameter D _Pm1, according to current stiffness K _iDetermine turn number N.

2, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described displacement rigidity span determines by controller, for-0.5N/um～-3N/um.

3, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described gap length δ is 0.15～0.35mm.

4, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described leakage coefficient σ is 1.1～3.

5, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described lamination COEFFICIENT K _FeBeing that ratio by actual stator or rotor core weight and its calculated value obtains, is 0.75～0.95.

6, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described stator core width b _sWith the stator core axial length L _SfeProportionate relationship require to determine that by reality if magnetic bearing requires axial length short, then this ratio value is taken as 4～6, otherwise this ratio value is taken as 1～3.

7, the design method of a kind of permanent magnet offset external rotor radial magnetic bearing according to claim 1 is characterized in that: described copper factor generally is taken as 40%～60%.

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