CN101923119A - Method for acquiring limit inductance characteristic of saturable reactor for converter valve - Google Patents

Abstract

The invention provides a method for acquiring limit inductance characteristic of a saturable reactor for a converter valve. When a coil and iron core combined structure is selected, the inductance drop speed has a limitation in the process of dropping from large inductance corresponding to a linear segment iron core to small inductance corresponding to a saturation segment. The method discloses that the characteristic has important guiding function on structural design and electrical design of the saturable reactor, and the feasibility and reasonability of an inductance curve of the reactor can be judged on the premise of not selecting a BH curve of an iron core in a specific specification, so that much work of discussing the influence of the BH characteristic of the iron core on the inductance is avoided.

Description

A kind of method that obtains the limit inductance characteristic of saturable reactor for converter valve

Technical field

The present invention relates to electric system device property field, relate in particular to a kind of method that obtains the limit inductance characteristic of saturable reactor for converter valve.

Background technology

The direct-current transmission converter valve saturable reactor is one of vitals of protection thyristor in the converter valve.It is made up of iron core and winding, utilizes the saturation characteristic of the saturation characteristic acquisition electric parameter of iron core material.About having the telefault of non-linear iron core, the work of the analysis of its inductance and iron loss resistance was carried out.Make us obscuring even wrong idea but wherein comprised.

The document that has lumps nonlinear characteristic unshakable in one's determination and reactor inductance characteristic together.What have also distinguishes these two characteristics, article (Yin Youjun etc., the modeling and simulation of single magnetic core saturable reactor,＜Power System and its Automation journal 〉, 2006,18 (4): 9-13) provided of the influence of core material nonlinear characteristic to the nonlinear device inductance characteristic, and the qualitative relationships of nonlinear device inductance characteristic and structural parameters and core material characteristic.Based on this,, select the trade mark unshakable in one's determination of proper characteristics can satisfy required inductance characteristic when structural parameters one timing.Even but these two characteristics differentiations are clear, be hidden in an important rule in the reactor inductance characteristic, promptly regularly at structural parameters one, even desirable nonlinear characteristic unshakable in one's determination also might can't satisfy required inductance characteristic.When promptly ignoring the transient process of non-linear BH curve unshakable in one's determination, there is the limit in the inductance characteristic of reactor, and this limit inductance characteristic does not disclose.

The present invention will disclose this nonlinear device, especially obtain the method for the limit inductance characteristic of saturable reactor for converter valve, provide the method that obtains this limit inductance characteristic simultaneously.This limit inductance characteristic has important directive significance to the design of nonlinear inductance device, can be under setting structure parameter situation, need not to select the iron core of the concrete trade mark can judge the rationality of structural parameters, avoid waste and do not know but that in the selection of the trade mark unshakable in one's determination structural parameters have determined the ultimate value of inductance characteristic.

Summary of the invention

The objective of the invention is to, disclose a kind of method that obtains the limit inductance characteristic of saturable reactor for converter valve, promptly be when having selected the unitized construction of a kind of coil and iron core, its inductance by the unshakable in one's determination corresponding big inductance of linearity range in the decline process of the small inductor of saturated section correspondence, there is the limit in its decline rate.Disclosed this characteristic and will have very important directive function the structural design and the electrical design of saturable reactor, can not select under the BH curve prerequisite unshakable in one's determination of concrete model, judge the feasibility and the rationality of reactor inductance curve, the influence pass of inductance is fastened thereby avoid a lot of work all to tangle in discussion BH characteristic unshakable in one's determination.

A kind of method that obtains the limit inductance characteristic of saturable reactor for converter valve of the present invention is characterized in that comprising selected structure, sets desirable BH family curve unshakable in one's determination, sets actual BH family curve and limit inductance characteristic unshakable in one's determination; Provide analysis and checking to the saturable reactor limit inductance characteristic, and the limit inductance characteristic that obtains saturable reactor for converter valve and even general nonlinear inductance device, specifically may further comprise the steps:

(1) selected structure, the structural parameters of setting saturable reactor;

Only relevant at the limit inductance characteristic of saturable reactor with the reactor structure, and with irrelevant this rule of magnetic characteristic unshakable in one's determination, the structural parameters of at first selected saturable reactor;

(2) set desirable BH family curve unshakable in one's determination;

There is the limit in the decline rate of the inductance that limit inductance characteristic and magnetic characteristic unshakable in one's determination be irrelevant to be meant saturable reactor from the big inductance of linearity range unshakable in one's determination to saturated section small inductor; This limit corresponds to desirable magnetic characteristic unshakable in one's determination, i.e. Tie Xin desirable BH family curve;

Desirable BH curvilinear characteristic unshakable in one's determination is that unshakable in one's determination have high permeance at linearity range, do not have transitional region directly to enter saturated section; Being converted to the dB/dH description then is, at linearity range, iron core has constant high permeance, enters saturated section in case leave linearity range, and dB/dH reduces to the characteristic of air dielectric immediately so, and desirable BH curve promptly unshakable in one's determination can not be led;

(3) set actual BH family curve unshakable in one's determination;

The magnetic characteristic unshakable in one's determination of the various trades mark all is a smooth and continuous in the reality, and has linearity range, transition section and saturated section; This is different with the desirable BH curve of iron core, for inductance characteristic that the pairing saturable reactor of desirable BH family curve unshakable in one's determination is described is its limiting velocity, can add actual BH family curve unshakable in one's determination and illustrate that as a comparison promptly the limit inductance characteristic of saturable reactor meets physics law;

(4) obtain limit inductance characteristic unshakable in one's determination;

According to the structure of saturable reactor, can calculate the Distribution of Magnetic Field of saturable reactor under the range of linearity unshakable in one's determination by analytical Calculation or Numerical Calculation of Electromagnetic Field; At inner Distribution of Magnetic Field unshakable in one's determination, just can obtain the ideal or the limit inductance curve of saturable reactor; Promptly according to the inductance characteristic curve of iron core characteristics resulting saturable reactor under desirable BH curve; The core rule is being a local quantity for BH curve unshakable in one's determination for iron core then, and the saturated of iron core is progressively, stage by stage; As long as desirable BH curve means each part iron core and leaves linear zone that its magnetic characteristic disappears immediately, is equal to air; At this moment, promptly for BH curve unshakable in one's determination, need only iron core and leave linear zone, the inner close saturation magnetic induction that is equal to immediately of magnetic so unshakable in one's determination; Since unshakable in one's determination saturated be progressively stage by stage, this moment, the iron core of saturable reactor also had unsaturated zone, be not to decay to complete saturated section small inductor immediately from the big inductance of linearity range so for the inductance of saturable reactor, promptly the ideal behavior with the BH curve is different, corresponding dB/dH, be magnetic characteristic unshakable in one's determination is that high permeance from linearity range decays to no magnetic characteristic immediately and is equal to air, but have fading margin speed; This crucial rule of the fading margin speed of saturable reactor inductance be depend on the saturable reactor structure and with an irrelevant intrinsic propesties of used iron core characteristics.

Method of the present invention, quantitative, establish the external diameter R1=1 of reactor, R2=2, desirable BH curve is shown in formula (0.1):

$\left\{\begin{array}{c}\mathrm{dB}/\mathrm{dH}=a,H<H_0\\ \mathrm{dB}/\mathrm{dH}=0,H\&GreaterEqual;H_0\end{array}\right.---\left(0.11\right)$

When unsaturation, its inductance is:

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA00000238665600013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r\; h\; N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}h{N}^{}{}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.12\right)$

Wherein, Ur is the relative permeability of linearity range iron core, and h is a height unshakable in one's determination, and N is a coil turn, and R2 and R1 are external radius and inside radius unshakable in one's determination; So when inboard H unshakable in one's determination shown in formula (0.3), reach unshakable in one's determination saturated Ho after, iron core begins to enter state of saturation, this moment, corresponding electric current was I1:

$H_o=\frac{I_1}{2\mathrm{\&pi;}{R}_1}---\left(0.13\right)$

When the outside R2 H of place shown in formula (0.4), also reach Ho after, iron core is saturated fully, this moment, corresponding electric current was I2:

$H=\frac{I_2}{2\mathrm{\&pi;}{R}_2}---\left(0.14\right)$

Therefore at electric current during less than I1, the inductance of reactor is shown in formula (0.2); When electric current during greater than I2, the inductance of reactor is shown in formula (0.5):

${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{{\mathrm{\&mu;}}_0\mathrm{<figure-callout\; id="2"\; label="h\; N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">h</figure-callout>}{N}^{}{}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.15\right)$

When electric current was between I1 and I2, the inductance of reactor was between L1 and L2;

According to our principle and hypothesis, under desirable BH curve, L (I) curve is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r\; h\; N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}h{N}^{}{}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{r}\right)---\left(0.16\right)$

Such curve is exactly the limit of L (I) under all BH curve condition;

Consider the rule that r and I are same, therefore, the pass that is scaled I is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r\; h\; N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}h{N}^{}{}^2}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)---\left(0.17\right)$

This moment, we set 2D, and the inductance result who therefore calculates is unit head's result, so h=1 does not consider the effect of the number of turn herein, so consideration N=1, therefore, the relational expression of inductance is shown in formula (0.8):

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{80R_2}{i{R}_1}\right)---\left(0.18\right)$

We set maximum induction is 1.44mH, and turns round at the 80A place, so Ho calculates as (0.9):

${\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="HSA00000238665600021.png,HSA00000238665600022.png"\; state="\{\{state\}\}">H</figure-callout>}}_0=\frac{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">I</figure-callout>}}{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000238665600013.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}=\frac{80}{2\mathrm{\&pi;}{R}_1}---\left(0.19\right)$

Correspond to a=0.01305, shown in formula (0.10):

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=1.44E-3\&DoubleRightArrow;a={\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r=\frac{1.44E-3*2\mathrm{\&pi;}}{\ln \left(2\right)}=0.01305---\left(0.20\right)$

The decline rate of inductance has the limit, promptly along with the wash one's face and rinse one's mouth increase of α of BH curve fitting, when iron core enter saturated after, the decline rate of inductance can be steeper, but along with the continuation of α increases, the decline rate of inductance is a fixing limit of trend, and this limit is determined by the structure of reactor;

The decline rate of inductance is to take all factors into consideration the magnetic linkage of reactor, though local saturated iron core is very fast almost is to enter saturated fully once breaking away from linear zone, but the iron core that does not break away from linearity range is still providing remaining inductance, and promptly the decline rate of inductance is by the structures shape of reactor.

The invention has the beneficial effects as follows:

1. the notion of limit inductance characteristic has been proposed;

2. disclosed the rule of limit inductance characteristic;

3. clarified the non-linear and nonlinear difference of reactor unshakable in one's determination;

4. provided the calculation procedure of limit inductance characteristic.

Description of drawings

Figure one is the fitting formula of BH curve unshakable in one's determination;

Figure two is that close coil on seamless iron core constitutes a reactor;

Figure three is for adopting the BH curve of different exponential fittings, and transverse axis is magnetic field intensity H (A/m), and the longitudinal axis is magnetic induction density B (T).

Figure four is for adopting the dB/dH curve of different exponential fittings;

Figure five is the inductive current curve of theoretical and simulation calculation;

Figure six is the process flow diagram according to method of the present invention.

Embodiment

Saturable reactor is a nonlinear inductance device, analyzes at a desirable saturable reactor, and is shown in figure two, close around a whole layer conductor on the iron core of a closed hoop.Adopt match mode for different unshakable in one's determination BH curves so as figure one.When the employing of the α in fitting formula different value, the BH curve that structure obtains can be seen corresponding dB/dH curve shown in figure four shown in figure three, and promptly the index correspondences of the different sizes of value iron core and entered saturated section speed fully by linearity range.Index α is high more, and it is fast more that dB/dH descends, and it is fast more that BH curve promptly unshakable in one's determination causes the zone of saturation to enter saturated fully speed.

Quantitatively, the reactor external diameter R1=1 shown in the figure two, R2=2.Desirable BH curve is shown in formula (0.1).

$\left\{\begin{array}{c}\mathrm{dB}/\mathrm{dH}=a,H<H_0\\ \mathrm{dB}/\mathrm{dH}=0,H\&GreaterEqual;H_0\end{array}\right.---\left(0.21\right)$

When unsaturation, its inductance is:

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA00000238665600013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.22\right)$

Wherein, Ur is the relative permeability of linearity range iron core, and h is a height unshakable in one's determination, and N is a coil turn, and R2 and R1 are external radius and inside radius unshakable in one's determination.So when inboard H unshakable in one's determination shown in formula (0.3), reach unshakable in one's determination saturated Ho after, iron core begins to enter state of saturation, this moment, corresponding electric current was I1.

$H_o=\frac{I_1}{2\mathrm{\&pi;}{R}_1}---\left(0.23\right)$

When the outside R2 H of place shown in formula (0.4), also reach Ho after, iron core is saturated fully, this moment, corresponding electric current was I2.

$H=\frac{I_2}{2\mathrm{\&pi;}{R}_2}---\left(0.24\right)$

Therefore at electric current during less than I1, the inductance of reactor is shown in formula (0.22); When electric current during greater than I2, the inductance of reactor is shown in formula (0.5).

${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{{\mathrm{\&mu;}}_0\mathrm{<figure-callout\; id="2"\; label="h\; N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">h</figure-callout>}{N}^{}{}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.25\right)$

When electric current was between I1 and I2, the inductance of reactor was between L1 and L2.

According to our principle and hypothesis, under desirable BH curve, L (I) curve is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{r}\right)---\left(0.26\right)$

Such curve is exactly the limit of L (I) under all BH curve condition.

Consider the rule that r and I are same, therefore, the pass that is scaled I is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)---\left(0.27\right)$

This moment, we set 2D, and therefore the inductance result who calculates is for unit head's result, so h=1.Do not consider the effect of the number of turn herein, so consider N=1, therefore, the relational expression of inductance is shown in formula (0.8).

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{80R_2}{i{R}_1}\right)---\left(0.28\right)$

We set maximum induction is 1.44mH, and turns round at the 80A place, so Ho calculates as (0.9).

${\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="HSA00000238665600021.png,HSA00000238665600022.png"\; state="\{\{state\}\}">H</figure-callout>}}_0=\frac{I}{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000238665600013.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}=\frac{80}{2\mathrm{\&pi;}{R}_1}---\left(0.29\right)$

Correspond to a=0.01305, shown in formula (0.10).

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000238665600022.png"\; state="\{\{state\}\}">r</figure-callout>}}}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=1.44E-3\&DoubleRightArrow;a={\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r=\frac{1.44E-3*2\mathrm{\&pi;}}{\ln \left(2\right)}=0.01305---\left(0.30\right)$

The decline rate of inductance has the limit, shown in figure five.Promptly along with the wash one's face and rinse one's mouth increase of α of BH curve fitting, when iron core enter saturated after, the decline rate of inductance can be steeper, but along with the continuation of α increases, the decline rate of inductance is a fixing limit of trend, and this limit is determined by the structure of reactor.

The decline rate of inductance is to take all factors into consideration the magnetic linkage of reactor, though local saturated iron core is very fast almost is to enter saturated fully once breaking away from linear zone, but the iron core that does not break away from linearity range is still providing remaining inductance, and promptly the decline rate of inductance is by the structures shape of reactor.This part work provides favourable explanation for the limit inductance curve, has also proved the correctness of this patent of invention.

More than be in order to make those of ordinary skills understand the present invention; and the detailed description that the present invention is carried out; but can expect; in the scope that does not break away from claim of the present invention and contained, can also make other variation and modification, these variations and revising all in protection scope of the present invention.

Claims (2)

1. a method that obtains the limit inductance characteristic of saturable reactor for converter valve is characterized in that comprising selected structure, sets desirable BH family curve unshakable in one's determination, sets actual BH family curve and limit inductance characteristic unshakable in one's determination; Provide analysis and checking to the saturable reactor limit inductance characteristic, and the limit inductance characteristic that obtains saturable reactor for converter valve and even general nonlinear inductance device, specifically may further comprise the steps:

(1) selected structure, the structural parameters of setting saturable reactor;

Only relevant at the limit inductance characteristic of saturable reactor with the reactor structure, and with irrelevant this rule of magnetic characteristic unshakable in one's determination, the structural parameters of at first selected saturable reactor;

(2) set desirable BH family curve unshakable in one's determination;

There is the limit in the decline rate of the inductance that limit inductance characteristic and magnetic characteristic unshakable in one's determination be irrelevant to be meant saturable reactor from the big inductance of linearity range unshakable in one's determination to saturated section small inductor; This limit corresponds to desirable magnetic characteristic unshakable in one's determination, i.e. Tie Xin desirable BH family curve;

Desirable BH curvilinear characteristic unshakable in one's determination is that unshakable in one's determination have high permeance at linearity range, do not have transitional region directly to enter saturated section; Being converted to the dB/dH description then is, at linearity range, iron core has constant high permeance, enters saturated section in case leave linearity range, and dB/dH reduces to the characteristic of air dielectric immediately so, and desirable BH curve promptly unshakable in one's determination can not be led;

(3) set actual BH family curve unshakable in one's determination;

The magnetic characteristic unshakable in one's determination of the various trades mark all is a smooth and continuous in the reality, and has linearity range, transition section and saturated section; This is different with the desirable BH curve of iron core, for inductance characteristic that the pairing saturable reactor of desirable BH family curve unshakable in one's determination is described is its limiting velocity, can add actual BH family curve unshakable in one's determination and illustrate that as a comparison promptly the limit inductance characteristic of saturable reactor meets physics law;

(4) obtain limit inductance characteristic unshakable in one's determination;

According to the structure of saturable reactor, can calculate the Distribution of Magnetic Field of saturable reactor under the range of linearity unshakable in one's determination by analytical Calculation or Numerical Calculation of Electromagnetic Field; At inner Distribution of Magnetic Field unshakable in one's determination, just can obtain the ideal or the limit inductance curve of saturable reactor; Promptly according to the inductance characteristic curve of iron core characteristics resulting saturable reactor under desirable BH curve; The core rule is being a local quantity for BH curve unshakable in one's determination for iron core then, and the saturated of iron core is progressively, stage by stage; As long as desirable BH curve means each part iron core and leaves linear zone that its magnetic characteristic disappears immediately, is equal to air; At this moment, promptly for BH curve unshakable in one's determination, need only iron core and leave linear zone, the inner close saturation magnetic induction that is equal to immediately of magnetic so unshakable in one's determination; Since unshakable in one's determination saturated be progressively stage by stage, this moment, the iron core of saturable reactor also had unsaturated zone, be not to decay to complete saturated section small inductor immediately from the big inductance of linearity range so for the inductance of saturable reactor, promptly the ideal behavior with the BH curve is different, corresponding dB/dH, be magnetic characteristic unshakable in one's determination is that high permeance from linearity range decays to no magnetic characteristic immediately and is equal to air, but have fading margin speed; This crucial rule of the fading margin speed of saturable reactor inductance be depend on the saturable reactor structure and with an irrelevant intrinsic propesties of used iron core characteristics.

2. the method for claim 1 is characterized in that:

Quantitatively, establish the external diameter R1=1 of reactor, R2=2, desirable BH curve is shown in formula (0.1):

$\left\{\begin{array}{c}\mathrm{dB}/\mathrm{dH}=a,H<H_0\\ \mathrm{dB}/\mathrm{dH}=0,H\&GreaterEqual;H_0\end{array}\right.---\left(0.1\right)$

When unsaturation, its inductance is:

$L_1=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{N}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.2\right)$

Wherein, Ur is the relative permeability of linearity range iron core, and h is a height unshakable in one's determination, and N is a coil turn, and R2 and R1 are external radius and inside radius unshakable in one's determination; So when inboard H unshakable in one's determination shown in formula (0.3), reach unshakable in one's determination saturated Ho after, iron core begins to enter state of saturation, this moment, corresponding electric current was I1:

$H_o=\frac{I_1}{2\mathrm{\&pi;}{R}_1}---\left(0.3\right)$

When the outside R2 H of place shown in formula (0.4), also reach Ho after, iron core is saturated fully, this moment, corresponding electric current was I2:

$H=\frac{I_2}{2\mathrm{\&pi;}{R}_2}---\left(0.4\right)$

Therefore at electric current during less than I1, the inductance of reactor is shown in formula (0.2); When electric current during greater than I2, the inductance of reactor is shown in formula (0.5):

$L_2=\frac{{\mathrm{\&mu;}}_{0}h{N}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{R_1}\right)---\left(0.5\right)$

When electric current was between I1 and I2, the inductance of reactor was between L1 and L2;

According to our principle and hypothesis, under desirable BH curve, L (I) curve is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{N}^2}{2\mathrm{\&pi;}}\ln \left(\frac{R_2}{r}\right)---\left(0.6\right)$

Such curve is exactly the limit of L (I) under all BH curve condition;

Consider the rule that r and I are same, therefore, the pass that is scaled I is:

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{r}h{N}^2}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)---\left(0.7\right)$

This moment, we set 2D, and the inductance result who therefore calculates is unit head's result, so h=1 does not consider the effect of the number of turn herein, so consideration N=1, therefore, the relational expression of inductance is shown in formula (0.8):

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r}{2\mathrm{\&pi;}}\ln \left(\frac{80R_2}{i{R}_1}\right)---\left(0.8\right)$

We set maximum induction is 1.44mH, and turns round at the 80A place, so Ho calculates as (0.9):

$H_0=\frac{I}{2\mathrm{\&pi;}{R}_1}=\frac{80}{2\mathrm{\&pi;}{R}_1}---\left(0.9\right)$

Correspond to a=0.01305, shown in formula (0.10):

$L=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r}{2\mathrm{\&pi;}}\ln \left(\frac{2\mathrm{\&pi;}{H}_0{R}_2}{i}\right)=1.44E-3\&DoubleRightArrow;a={\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r=\frac{1.44E-3*2\mathrm{\&pi;}}{\ln \left(2\right)}=0.01305---\left(0.10\right)$

The decline rate of inductance has the limit, promptly along with the wash one's face and rinse one's mouth increase of α of BH curve fitting, when iron core enter saturated after, the decline rate of inductance can be steeper, but along with the continuation of α increases, the decline rate of inductance is a fixing limit of trend, and this limit is determined by the structure of reactor;

The decline rate of inductance is to take all factors into consideration the magnetic linkage of reactor, though local saturated iron core is very fast almost is to enter saturated fully once breaking away from linear zone, but the iron core that does not break away from linearity range is still providing remaining inductance, and promptly the decline rate of inductance is by the structures shape of reactor.

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