CN108010701B - non-standard design method for UI and UU type powder magnetic core chopping inductance - Google Patents

Abstract

The invention relates to a non-standard design method for UI and UU type powder magnetic core chopping inductors, and belongs to the technical field of inductor design. The method is suitable for chopper inductors of buck, boost, buck-boost and the like. The invention takes average current of an inductor, ripple current of the inductor, switching frequency, target inductance, maximum length, width and height of the inductor, heat dissipation parameters and the like as input conditions, and obtains a minimum volume inductance structure which meets the inductance and the conditions of magnetic density, temperature rise and the like at the same time based on the free splicing of the existing powder magnetic core strips and no open air gap. The invention solves the problem of optimal design of free splicing of magnetic core strips based on a non-standard magnetic core.

Description

non-standard design method for UI and UU type powder magnetic core chopping inductance

Technical Field

The invention belongs to the technical field of power electronic inductor design, and relates to a non-standard design method of UI and UU type powder magnetic core chopping inductors.

background

(1) with the rapid development of power electronic technology, various power electronic devices are applied more and more widely in the fields of power systems, traffic, industry and the like, so that the requirement on the current quality is higher and higher, and the problem of solving harmonic waves is the most important problem at present. Unlike other electronic components, it is difficult for a user to select a suitable inductor, which is generally redesigned as desired. The specific design needs to take into account factors such as volume, weight, cost and the like.

(2) for a relatively large inductor, a proper standard magnetic core cannot be found under general conditions, and the magnetic core is formed by freely splicing magnetic core strips, so that the formation of a free splicing optimization algorithm is very important.

disclosure of Invention

in view of this, the invention aims to provide a non-standard design method for UI and UU type powder magnetic core chopper inductors, so as to implement programming of magnetic core strip splicing, greatly reduce a large amount of trial and error of designers, improve work efficiency, and reduce manual calculation errors.

in order to achieve the purpose, the invention provides the following technical scheme:

a non-standard design method for a chopping inductor of UI and UU type powder magnetic cores comprises the following steps:

s1: preparing magnetic core material parameters, and listing all magnetic core strips corresponding to a magnetic core material library according to the magnetic core material parameters;

s2: designating the width or thickness of the magnetic core strips as the sheet width, and arranging the magnetic core strips from small to large according to the sheet width;

S3: according to the sheet widths in the step S2, listing the corresponding magnetic core strip thickness or width under each sheet width, setting the thickness as a unit stack thickness, and arranging the magnetic core strips from small to large according to the unit stack thickness;

s4: setting, for each unit stack thickness, an integral multiple of the unit stack thickness as the magnetic core stack thickness according to the unit stack thickness in step S3;

s5: under the condition that the magnetic core strips listed in the step S4 are fixed in sheet width and magnetic core stack thickness, splicing the magnetic core strips in a single or double mode in the length direction, and arranging the spliced magnetic core strips from small to large according to the length;

S6: setting the length of the core bars obtained in the step S5 to a window height value for each core stack thickness according to the core stack thickness in the step S4, and arranging the spliced core bars according to the window height value from small to large at the core stack thickness;

s7: setting the length of the core bars obtained in step S5 as the core width for each window height value at which the spliced core bars are arranged from small to large according to the core width, according to the window height value in step S6;

s8: according to the sheet width of the step S2, the unit stack thickness of the step S3, the magnetic core stack thickness of the step S4, the window height value of the step S6 and the magnetic core width of the step S7, setting the initial sequence S to be 1, splicing the magnetic cores in sequence, and checking inductance space to obtain a magnetic core splicing table;

S9: calculating the size of the coil and the number of turns of the coil according to the size of the magnetic core in the magnetic core splicing table, and performing inductance check;

S10: judging whether the size of the magnetic core meets the termination condition, if not, S is equal to S +1, returning to the step S8, and if so, executing the step S11;

s11: and screening out a final splicing result according to the optimal volume.

further, the step S8 of performing spatial checking on the spliced inductors specifically includes:

length checking requirement: l is a + c is less than or equal to Ls;

Width checking requirement: wz is not more than 2a +2h and not more than Ws;

The height checking requirement is as follows: hs is less than or equal to Hz + b +2 h;

wherein, Lz is the length after the magnetic core that splices out adds the coil and forms the inductance, and Wz is the width after the magnetic core that splices out adds the coil and forms the inductance, and Hz is the height after the magnetic core that splices out adds the coil and forms the inductance, and Ls, Ws, Hs are the inductance maximum length and width height respectively, and a is kcx-2h, and kcx is the magnetic core width, and b is the window height value, and c is the magnetic core length, and h is magnetic core strip thickness.

further, the procedure of calculating the number of turns of the coil and performing inductance check in step S9 is as follows:

s91: calculating the lowest turn number according to the initial magnetic conductivity;

S911: calculating the sectional area of the magnetic core: ac ═ cxh, where c is the core length and h is the core strip thickness;

S912: calculating the length of the magnetic circuit: lc 2a +2b + pi h, where a is kcx-2h, kcx is the core width and b is the window height;

s913: calculating the initial turn number according to the initial magnetic permeability:

wherein, AL is single-turn inductance, mu 0 is vacuum permeability, mu r0 is initial relative permeability of the magnetic core material, N0 is initial turn number, and L0 is target inductance value;

s92: making the number of coil turns N equal to N0;

s93: calculating according to the number of turns of the coil to obtain a calculated inductance value;

wherein BI is the magnetic induction under average current, obtained from a magnetization curve (B-H curve), IL is the average current of the inductor, and Lso is the calculated inductance value;

S94: determining the number N of the final coil turns according to the deviation between the calculated inductance value and the target inductance value;

If the deviation type is +/-, when the deviation amount of the inductance value of the N turns is greater than N-1 turns for the first time, the number of turns N of the coil is equal to N-1, the step S95 is continued, otherwise, the number of turns N is equal to N +1, and the step S93 is returned;

If the deviation type is + and when the inductance value of N turns is greater than the target inductance value for the first time, the number N of turns of the coil is equal to N, continue to step S95, otherwise, N is equal to N +1, and return to step S93;

S95: and (3) carrying out inductance deviation checking, and when the calculated inductance value meets the following requirements:

wherein, L0 is a target inductance value, and RL is an allowable maximum inductance relative deviation;

s96: checking the maximum magnetic flux density, and judging whether the magnetic core is saturated or not;

s97: determining a wire parameter through the current density;

s98: calculating loss and carrying out temperature rise check;

S99: and filling the results of which the loss and the temperature rise meet the requirements into a temporary result list.

further, step S97 specifically includes:

s971: setting the initial current density as J to be 2.0;

S972: calculating the width and thickness values of the conducting wire, and judging whether the window width meets the requirements or not;

triangular wave chopping inductance current effective value:

sectional area of the wire:

width of the conducting wire: w is b-2Ld, wherein b is the height of a magnetic core window, and Ld is the end-to-end distance;

Thickness of the wire: hline Aw 0/w;

judging that ax is [ N multiplied by hline + (N-1) multiplied by hins ] < a, wherein ax is the required window width, and hins is the single-layer insulation thickness;

S973: if the current density does not meet the requirement, the next step of calculation is carried out without increasing the current density, and if the current density does not meet the requirement, judgment is carried out;

s974: if J is equal to or greater than 6.0, the flow returns to the main flow, and if J < 6.0, J is J +0.1, and S972 is executed.

Further, the termination conditions in step S10 are:

Kcx no longer continues to increase when a > Ws or a/b > 10;

when b > Hs or b/a >10, the b value does not increase continuously;

when c > Ls or c/h >20, the c value does not increase continuously;

wherein kcx is the core width, a is kcx-2h, b is the window height, c is the core length, Ws is the maximum width allowed, Hs is the maximum height allowed, Ls is the maximum length allowed.

the invention has the beneficial effects that: the method provided by the invention forms a set of standardized inductance design method based on infinite free splicing, and obtains the result of the inductance with the optimal volume. The method considers all possible splicing conditions, and can select the optimal result according to other requirements such as weight, copper-iron ratio, cost and the like. After programming, a large amount of trial work of designers can be greatly reduced, the working efficiency is improved, and the manual calculation errors are reduced.

drawings

in order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a flow chart of inductance parameter calculation and inductance verification according to the present invention;

FIG. 3 is a graph of the core dimensions after splicing in accordance with the present invention;

Fig. 4 is a schematic diagram of an inductor after splicing and molding according to the present invention.

Detailed Description

preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

the invention relates to a non-standard design method of UI and UU type powder magnetic core chopper inductors, which comprises the following steps:

1, preparing and calculating material parameters, wherein before entering a main flow, the magnetic core material parameters required by calculation need to be prepared:

(1) initial relative magnetic permeability mu r0 and saturation magnetic induction Bsat;

(2) B-H curve or D-C offset curve, B-P curve;

(3) Calculation of steinmetz parameters Kc, α, β:

Taking points: two B-P curves closest to the working frequency f are selected as calculation bases, and the two extracted B-P curve parameter point formats are N points in total, such as (f1, B1, Pv1), (f2, B2 and Pv2). (fN, Bn and Pvn).. the. (fN, BN and Pvn).

and (2) equivalence:

the steinmetz equation is as follows: Pv-Kcf Alpha B beta

taking logarithm of both sides, logPv ═ logKc + alpha logf + beta logB

order: r is logf, s is logB, t is logPv, u is logKc

Then there are: t ═ α × r + β × s + u

The B-P curve points are converted into: (r1, s1, t1), (r2, s2, t 2.)

(iii) for t ═ α × r + β × s + u, there is a set of values (α, β, u) such that the 2-norm of the residual is minimal:

Even at a minimum

the minimum is required, and the partial derivatives of α, β, and u are separately calculated and made equal to 0, i.e.:

the following system of equations can be obtained:

when the linear system of equations is solved to obtain a solution (α, β, u), Kc ═ eu.

2 magnetic core strip and splice thereof

the core strip is spliced as shown in the flow chart of fig. 1, as shown in fig. 1,

(1) listing all magnetic core strips corresponding to the magnetic core materials, wherein the magnetic core strips comprise three parameters of height, width and length;

(2) firstly, designating the h value as the width or the thickness of the magnetic core strip, and circulating from small to large;

(3) at a specific h value, the corresponding thickness or width of the magnetic core strip is set as c0, and the cycle is from small to large;

(4) the value of c is composed of n c0, n is a positive integer, and the length c of the magnetic core is increased from 1 time of c 0;

(5) The iron silicon strips under specific h and c0 have different length specifications, and are spliced (1 or 2) in the length direction, so that two iron silicon strips are allowed to be spliced, and are arranged into a length series from small to large;

(6) under the specific values of h and c, the minimum value of the designated length series is the window height b, and the cycle is from small to large;

(7) At a specific value of b, the minimum value of the specified length is kcx magnetic core width, a is kcx-2h, and the cycle is from small to large;

(8) under the specific magnetic core sizes (a, b, c and h), the calculation of the coil size and the number of turns and the inductance check are completed;

(9) after circulation is finished, the result is screened according to the optimal volume;

3 end condition of magnetic core strip splicing

see the main flow, wherein Ls, Ws, Hs are the maximum allowable length, width and height:

(1) Kcx no longer continues to increase when a > Ws or a/b > 10;

(2) When b > Hs or b/a >10, the b value does not increase continuously;

(3) when c > Ls or c/h >20, the c value does not increase continuously;

4 inductance spatial check

fig. 2 is a flow chart of inductance parameter calculation and inductance verification according to the present invention, and as shown in fig. 2, the specific flow is as follows:

fig. 3 is a size chart of the magnetic core after splicing, as shown in fig. 3, the actual length, width and height Lz, Wz and Hz of the inductor are calculated according to the determined parameters h, a, b and c, and compared with the required maximum length, width and height Ls, Ws and Hs:

length checking requirement: ls is equal to a + c

width checking requirement: wz is equal to 2a +2h and is less than or equal to Ws

the height checking requirement is as follows: hs is not more than Hz b +2h

if the space check meets the requirement, subsequent calculation and check are carried out; otherwise, entering the main flow, and continuing to perform magnetic core parameter circulation.

5 wire turn number determination

(1) calculating the sectional area of the magnetic core and the length of the magnetic circuit:

sectional area Ac ═ c × h

magnetic path length lc ═ 2a +2b + pi h

(2) Firstly, the initial turn number is inversely calculated according to the initial permeability:

Single turn inductance:

initial number of turns:

(3) determining the actual number of turns of wire:

generally, the actually required number of turns is larger than the initial number of turns N0; the number of turns cycles from small to large starting from N0, see fig. 2:

if the deviation type is +/-, when the deviation amount of the inductance value of N turns is greater than N-1 turns for the first time, the turn number N of the coil is equal to N-1;

If the deviation type is + and when the inductance value of N turns is greater than the target inductance value for the first time, the number of turns of the coil is equal to N;

(4) and calculating the inductance when the number of turns of the coil is N:

magnetic field strength at average current H:

magnetic induction at average current B: BI ═ f (hi)

Where IL is the inductor average current, f is a function of B as a function of H, the B-H curve, which generally consists of more than 5 coordinate points (H, B), is first taken at two points (H1, B1) closest to the HI value (H2, B2), and then the BI value is calculated using linear interpolation or extrapolation methods:

actual rated inductance:

6 inductance deviation checking

as shown in fig. 2, after the number of turns N of the coil is determined, inductance deviation checking is performed:

where L0 is the target rated inductance and RL is the maximum allowable relative inductance deviation.

if the inductance deviation checking meets the requirements, subsequent calculation and checking are carried out; otherwise, entering the main flow, and continuing to perform magnetic core parameter circulation.

7 maximum magnetic flux Bmax checking

When the inductance reaches the requirement, the magnetic core is also saturated, so after the inductance deviation meets the requirement, the maximum magnetic density Bmax check is needed, as shown in fig. 2:

(1) peak current:

(2) magnetic field strength at peak current:

(3) magnetic induction at peak current: bmax ═ f (hmax), where f is a function of B from H;

(4) checking: if Bmax is less than or equal to Bsat multiplied by Rb, the requirement is met, wherein Bsat is the saturation magnetic density of the magnetic core material, and Rb is the magnetic saturation rate of the limited material;

If Bmax check meets the requirement, subsequent calculation and check are carried out; otherwise, entering the main flow, and continuing to perform magnetic core parameter circulation.

8 wire parameter calculation and window width check

as shown in fig. 2, the copper foil conductor parameter calculation and window width check are performed, and it is assumed that there is only one copper foil conductor per layer:

(1) first, assume that the wire current density J0 is 2.0;

(2) determining the wire size according to the current density:

triangular wave chopping inductance current effective value:

sectional area of the wire:

width of the conducting wire: w is b-2Ld, wherein b is the height of a magnetic core window, and Ld is the end-to-end distance;

Thickness of the wire: hline Aw0/w

(3) checking the window width:

when the window width is required to meet the following conditions:

a＝[N×h+(N-1)×h]≤a

If a is the width of the magnetic core window, the requirement is met, the subsequent calculation is carried out without continuously increasing the current density, otherwise, the current density is continuously increased, and the wire size calculation and the window width check are repeatedly carried out;

(4) If the current density is increased to 6.0, the window width can not meet the requirement, the current density is not required to be increased continuously, the main flow path is directly entered, and the magnetic core splicing circulation is continued;

9 loss calculation

as shown in fig. 2, after the size of the magnetic core of the inductor and the parameters of the lead are determined, loss and temperature rise check are performed, and loss calculation is performed first:

9.1 core loss calculation

(1) calculating delta B value under rated ripple

maximum and minimum current at rated ripple:

maximum H and minimum H at rated ripple:

maximum B and minimum B at rated ripple:

B＝f(H)；B＝f(H)

wherein f is a function for solving B according to H;

calculating the delta B value under rated ripple:

ΔB＝B-B

(2) magnetic core loss calculation

Magnetic core volume:

V＝A×(2a+2b+4h)

the core loss per unit volume is as follows:

P＝k|ΔB|f[D+(1-D)]

Wherein D is the duty cycle;

magnetic core loss:

P＝P×V

9.2 winding DC loss

(1) wire DC resistance calculation

average turn length: MLT 2h +2c +0.5 pi a

total length of wire: lcu-MLT × N

Direct current resistance:

(2) DC loss calculation

9.3 skin Effect loss calculation

(1) ripple current fourier decomposition (radian system), where Δ IL is the ripple current peak-to-peak value:

(2) Skin depth at each harmonic frequency:

(3) For the copper foil wire, the skin effect ac resistance corresponding to each harmonic frequency is as follows (radian):

(4) the skin effect loss is:

9.4 proximity effect loss

(1) Fundamental frequency skin depth:

(2) Inductance alternating current component current effective value:

(3) effective value of current derivative of alternating current component of inductor:

(4) proximity effect ac resistance:

wherein

(5) proximity effect loss:

9.5 total loss of inductance

total loss of the winding:

P＝P+P+P

Total loss of inductor

P＝P+P

10 temperature rise calculation and check

the temperature rise of the inductor is calculated according to the known heat exchange coefficient hc and the surface area of the inductor:

(1) the surface area of the inductor, namely the area of a cube enveloped by the actual length, width and height of the inductor:

A＝2(L×W+W×H+L×H)

(2) Temperature rise: wherein hc is the heat transfer coefficient;

(3) working temperature: twork ═ T0+ Δ T, where T0 is ambient temperature;

(4) temperature checking:

when Twork is less than or equal to Tmax, the inductance result meets the temperature rise requirement, a temporary result list is written, the main process is returned, and the magnetic core splicing circulation is continued; otherwise, the inductor does not meet the temperature rise requirement, the result is given up, the main flow is returned, and the magnetic core splicing circulation is continued.

11 best results

and optimizing and selecting the result according to the inductance volume index. Fig. 4 is a schematic diagram of the inductor after splicing molding according to the present invention, and according to the main flow, after the core cycle is completed, the temporary result list may have more than 1 result, and if the material selection is not appropriate, there may be no result, so the result with the smallest inductor volume is selected as the final result.

finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims (1)

1. a non-standard design method for a chopping inductor of UI and UU type powder magnetic cores is characterized by comprising the following steps: the method comprises the following steps:

s1: preparing magnetic core material parameters, and listing all magnetic core strips corresponding to a magnetic core material library according to the magnetic core material parameters;

s2: designating the width or thickness of the magnetic core strips as the sheet width, and arranging the magnetic core strips from small to large according to the sheet width;

s3: according to the sheet widths in the step S2, listing the corresponding magnetic core strip thickness or width under each sheet width, setting the thickness as a unit stack thickness, and arranging the magnetic core strips from small to large according to the unit stack thickness;

s4: setting, for each unit stack thickness, an integral multiple of the unit stack thickness as the magnetic core stack thickness according to the unit stack thickness in step S3;

s5: under the condition that the magnetic core strips listed in the step S4 are fixed in sheet width and magnetic core stack thickness, splicing the magnetic core strips in a single or double mode in the length direction, and arranging the spliced magnetic core strips from small to large according to the length;

s6: setting the length of the core bars obtained in the step S5 to a window height value for each core stack thickness according to the core stack thickness in the step S4, and arranging the spliced core bars according to the window height value from small to large at the core stack thickness;

s7: setting the length of the core bars obtained in step S5 as the core width for each window height value at which the spliced core bars are arranged from small to large according to the core width, according to the window height value in step S6;

s8: according to the sheet width of the step S2, the unit stack thickness of the step S3, the magnetic core stack thickness of the step S4, the window height value of the step S6 and the magnetic core width of the step S7, setting the initial sequence S to be 1, splicing the magnetic cores in sequence, and checking inductance space to obtain a magnetic core splicing table;

s9: calculating the size of the coil and the number of turns of the coil according to the size of the magnetic core in the magnetic core splicing table, and performing inductance check;

s10: judging whether the size of the magnetic core meets the termination condition, if not, S is equal to S +1, returning to the step S8, and if so, executing the step S11;

S11: screening out a final splicing result according to the optimal volume;

the step S8 of performing spatial check on the spliced inductor specifically includes:

length checking requirement: l is a + c is less than or equal to Ls;

width checking requirement: wz is not more than 2a +2h and not more than Ws;

the height checking requirement is as follows: hs is less than or equal to Hz + b +2 h;

Wherein Lz is the length of the spliced magnetic core and the coil after forming the inductor, Wz is the width of the spliced magnetic core and the coil after forming the inductor, Hz is the height of the spliced magnetic core and the coil after forming the inductor, Ls, Ws and Hs are the maximum length, width and height of the inductor respectively, a is kcx-2h, kcx is the width of the magnetic core, b is the window height value, c is the length of the magnetic core, and h is the thickness of the magnetic core strip;

in step S9, the number of turns of the coil is calculated, and the flow of performing inductance check is as follows:

s91: calculating the lowest turn number according to the initial magnetic conductivity;

S911: calculating the sectional area of the magnetic core: ac ═ cxh, where c is the core length and h is the core strip thickness;

s912: calculating the length of the magnetic circuit: lc 2a +2b + pi h, where a is kcx-2h, kcx is the core width and b is the window height;

s913: calculating the initial turn number according to the initial magnetic permeability:

wherein, AL is single-turn inductance, mu 0 is vacuum permeability, mu r0 is initial relative permeability of the magnetic core material, N0 is initial turn number, and L0 is target inductance value;

s92: making the number of coil turns N equal to N0;

s93: calculating according to the number of turns of the coil to obtain a calculated inductance value;

wherein BI is the magnetic induction under the average current, obtained from the magnetization curve, i.e. B-H curve, IL is the average current of the inductor, Lso is the calculated inductance value;

s94: determining the number N of the final coil turns according to the deviation between the calculated inductance value and the target inductance value;

If the deviation type is +/-, when the deviation amount of the inductance value of the N turns is greater than N-1 turns for the first time, the number of turns N of the coil is equal to N-1, the step S95 is continued, otherwise, the number of turns N is equal to N +1, and the step S93 is returned;

if the deviation type is + and when the inductance value of N turns is greater than the target inductance value for the first time, the number N of turns of the coil is equal to N, continue to step S95, otherwise, N is equal to N +1, and return to step S93;

s95: and (3) carrying out inductance deviation checking, and when the calculated inductance value meets the following requirements:

wherein, L0 is a target inductance value, and RL is an allowable maximum inductance relative deviation;

S96: checking the maximum magnetic flux density, and judging whether the magnetic core is saturated or not;

s97: determining a wire parameter through the current density;

s98: calculating loss and carrying out temperature rise check;

s99: filling results of which the loss and the temperature rise meet the requirements into a temporary result list;

step S97 specifically includes:

S971: setting the initial current density as J to be 2.0;

s972: calculating the width and thickness values of the conducting wire, and judging whether the window width meets the requirements or not;

triangular wave chopping inductance current effective value:

sectional area of the wire:

width of the conducting wire: w is b-2Ld, wherein b is the height of a magnetic core window, and Ld is the end-to-end distance;

thickness of the wire: hline Aw 0/w;

Judging that ax is [ N multiplied by hline + (N-1) multiplied by hins ] < a, wherein ax is the required window width, and hins is the single-layer insulation thickness;

s973: if the current density does not meet the requirement, the next step of calculation is carried out without increasing the current density, and if the current density does not meet the requirement, judgment is carried out;

S974: if J is greater than or equal to 6.0, returning to the main process, if J is less than 6.0, J is J +0.1, and executing S972;

the termination conditions in step S10 are:

kcx no longer continues to increase when a > Ws or a/b > 10;

when b > Hs or b/a >10, the b value does not increase continuously;

when c > Ls or c/h >20, the c value does not increase continuously;

wherein kcx is the core width, a is kcx-2h, b is the window height, c is the core length, Ws is the maximum width allowed, Hs is the maximum height allowed, Ls is the maximum length allowed.