ES2312232B2 - PROCEDURE FOR PREDICTION AND CONTROL OF THE INDUCTANCE OF A BRAINED CABLE WITH DRAINAGE, SCREENED WITH DOUBLE LAYER SHEET AND WITH PROTECTIVE COVER, BY VARIATION OF THE BRAIDING PASS. - Google Patents

Abstract

Prediction procedure and control of inductance of a twisted pair cable with drain, shielded with double layer sheet with protective cover, by means of variation of braiding step.

The procedure allows prediction and control of the electrical inductance of a twisted pair cable determined by the dimensions and nature of the elements that conform it, and controlled by the step parameter of braided. The result of its application is to obtain a cable end of predefined inductance or the determination of design characteristics of the cable to be manufactured to meet a value of this electrical characteristic. The procedure and the product of your application are of interest in the industry manufacture of cable for signal transmission or electronic circuit power

Description

Prediction procedure and control of inductance of a twisted pair cable with drain, shielded with double layer sheet with protective cover, by means of variation of braiding step.

Technical sector

The invention is part of the technical sector of manufacturing processes and improvement of cable characteristics intended for the transmission of electrical signals or power supply electronic circuits.

State of the art

There are currently multiple types of cables intended to transmit electrical signals between electronic devices or to power electronic circuits of very different purposes. Due to the impact that electrical characteristics of the cables, as means of transmission, present in the quality of the signals to be transmitted, it is necessary to control them.

One of the most important electrical parameters of an electric transmission line is the inductance. The control of the inductance of a cable ensures certain behavior and integrity in the electrical signal that is intended to be transmitted by said physical medium. This parameter is usually obtained empirically in tests of final products already manufactured or approximately through little precise generic expressions, which they don't have in It counts the design parameters of certain special cables. One of the most used cables in signal transmission is the pair braided, which can have built-in shielding and covered. Each of these elements, depending on their dimensions and physical properties, and depending on the process of manufacturing through which they are incorporated into the final cable, provides a variation of the inductance to the set that is necessary Quantify and predict.

Cable signal transmission systems Standardized normally require a maximum allowed value of inductance, but they are usually oriented to very types of cables determined in terms of dimensions and materials. The control of this parameter for generic cables is open to determinations more precise

It is of great interest, therefore, to obtain a rationalization of the manufacturing process and a model of prediction and control of the inductance of a twisted pair as a function of the main design parameter thereof, the braiding step or also the number of turns per meter, and depending on the characteristics of the elements (screens, drains, covers) which are incorporated therein to form the final cable. The The present invention consists of a novel method that precisely sets the value of the inductance of a cable final (Fig. 1) from the selection of the elements that make up, and by varying the characteristics of the braided in the manufacturing process, which allows you to control your inductance.

Detailed description of the invention

The present invention relates to a new procedure for the control of inductance from the manufacture of a twisted pair cable, from the control of the relationship between the feed rate and collection of the final cable in the braiding machine, and the speed of rotation of the element that provides the twist to the individual cables to establish the final propeller The new method also predicts and quantifies the shielding influence, with flexible double layer tape and the cover provided by extrusion to the braided assembly, on the final cable inductance.

The first parameter that determines this procedure is the relationship between the advance and the turn of the conductors in the braiding process, that is, the number of turns per meter that has the final braid, which is also characterized by its inverse, the step (p = 1 / n), or also by the angle of advance of the propeller formed by the conductors. This The fundamental variable incorporates the parameters that define the shielding and protection features with cover insulating.

Single twisted pair

The analysis of the inductance variation of the twisted pair (Fig. 2) with respect to the number of turns per meter (n), or its inverse, the step (p = 1 / n), provides a tendency of increase in inductance dependent on the value of the cited variable (n). The term that expresses the variation of inductance regarding the increase in the number of turns per meter depends on the distance that separates the conductors and the surrounding environment, is that is, the thickness and magnetic permeability of the insulation. The terms in which this trend is shown are established according to the following criteria:

\ sqbullet

The twisted of a pair of conductors to obtain a final cable of predefined length it requires a length of these conductors greater than that of the cable final. That is, braiding implies an increase in length of the cables as the step is reduced to obtain a length established end cable. This aspect has an impact on the inductance value per unit of twisted cable length, that suffers an obvious increase.

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\ sqbullet

The form that originates from braiding the cables causes a variation of the inductance that It depends on the number of turns per unit length. The reduction of the twisting passage implies a deformation of the insulation that approximates the cable conductors with each other, that is, reduces the distance between them, and this aspect causes a decrease in inductance.

So, the expression of inductance by unit of twisted pair length is initially set, and undeveloped, as shown in equation (1):

100

that, if the term develops which expresses the increase in length, is transformed in

one

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2

where the inductance (L) is formed by the external inductance (L e) and the inductance internal (L_ {i}) of the pair of drivers.

n = number of turns per meter of braiding

a = drivers radius

d = total diameter of each conductor, including insulation

µ = magnetic permeability of the medium

the = double forward angle propeller

s = multi-threaded factor or stranding factor

L Δ Ln (the) = term that expresses the variation of inductance as a function of braiding

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Foral inductance values differ between different cable models, with identical braiding conditions, depending on the section of the conductors and the particular dimensions of each cable (mean radius, insulation thickness). However, the tendency with which the inductance reduction is approximated with respect to the number of turns, or with respect to the angle of advance of the braid, is common to all of them. This trend is the one shown in equation (1) in the term ΔL (n). This term quantifies the influence of the twisted pair helical shape on the inductance of the wires. In order to establish a common model for all types of cables, we start with the case of parallel cables ( n = 0). The inductance value for each cable model under these conditions is taken as the threshold. By dividing the inductance value of each cable, stranded with a certain number of turns per meter, the ratio between the inductance of the cable in these twisted conditions and zero turns per meter is deduced between this threshold value. In a sufficiently broad spectrum (minimum 10) of samples, the tendency of variation of the inductance of each type of cable is obtained as a function of the variable n ; We call this model incremental model . The first and important contribution of this invention is the definition of the incremental model for the determination of the inductance of the cable, which reflects the increase in inductance with respect to the unbraided pair and which is adjusted with great precision by third order polynomials. The values of the coefficients of these incremental polynomials are established on the basis of tables of particular characteristics and graphs of each cable, but the manufacturer can obtain their values through inductance tests as described in the calculation section of the geometric polynomial . From this point on, each type of cable is defined by the incremental model, so that simply by knowing its dimensions it is possible to calculate the inductance value for a given number of turns per meter, and with a small estimation error.

The variation of the twisted pair inductance is defined in this incremental model by means of the geometric polynomial , which approximates the unitary variation of the inductance of the cable by varying the shape of the twisted pair's helix. Each geometric polynomial provides the approximation of the unit inductance variation (with respect to the threshold inductance, which is the inductance between two unbraided wires) due to the complex shape that the cables take in space, taking into account the deformation caused by the braided in the insulation (Fig. 3), and where the inductive effects are reduced as the distance between the conductors decreases, because with the braiding the initial theoretical magnetic field is approached and modified. Consequently, a behavior model is established for the increase of twisted pair inductance according to the term expressed below:

3

which, when replacing in the equation (1) gives rise to the following expression for inductance (by unit length) of the pair braided:

4

where I n, I ,, J n, J ,, K n, and K the are specific coefficients of each cable model, and They depend on the dimensions of the cable and the type of insulation material. The geometric polynomials include the influence of the geometric arrangement of the conductors in space in all its aspects and the deformation that originates the braiding (Fig. 4). The variables are ( n ) [Turns / m] or angle of advance of the twisted pair (the). The equivalent magnetic permeability is \ mu = \ mu_ {0} \ cdot \ mu_ {r}, whereby the above equation is established as follows:

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5

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or too

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6

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which are two equivalent expressions and whose difference is that the number of turns per unit of length ( n ) or the angle of advance (the) is used as a variable, which are related quantities by the expression n = \ frac {tg \ theta} {2 \ pi \ cdot r}.
{} \ hskip17cm The parameters \ mu_ {0} and \ mu_ {r} are, respectively, the magnetic permeability of the vacuum and the relative magnetic permeability of the medium surrounding the pair of conductors.

The equation that expresses this variation of inductance is then established as follows:

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7

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8

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Geometric polynomial calculation . The value of the geometric polynomial coefficients of each cable is obtained from tables (Table 1) and particular graphs for each cable model (Fig. 5).

TABLE 1 Coefficients of the geometric polynomials of different cables

9

If data is not available for a certain type of cable or for a new model, they can be obtained from tests, as indicated below. It will be necessary to prepare a set of braided cable samples with
{} \ hskip17cm a number of turns per meter variable from zero to a maximum of \ frac {0,1351} {r}, where r is the radius (in meters) of the cable
{} \ hskip17cm to braid. These samples must be representative of the range of turns per meter allowed, so the set must have a value of this characteristic properly distributed throughout the range of turns per meter, and the length of the same should not be less than one meter. In addition, the number of samples should not be less than ten to guarantee the validity of the results. The higher the number of samples, the greater the accuracy of the fit in obtaining the geometric polynomial. A minimum of three must be added to the samples made with parallel conductors ( n = 0) well connected. The purpose of this last step is to obtain a reliable inductance value of the parallel cable pair to use as a threshold value in the calculation process. Once the samples are obtained, the measurement of the inductance is carried out on a measuring device (network analyzer, impedance meter) calibrated and with an accuracy in the order of 1 to 10 [nH]. The tests measure inductance and must be carried out under stable conditions of humidity and temperature, for which the values of these characteristics must be set between 40% and 60% for the relative humidity and 23 [° C] ± 2 [° C] for temperature. The collection of results is analyzed with the composition of a mathematical function that provides the inductance value and the variable (n) [Turns / m]. To obtain a function of the incremental model, firstly, all the inductance values obtained are divided by the average inductance value of the parallel conductor samples (n = 0). In this way, percentage values of increased inductance are obtained with respect to the increase in the requirement of braiding. The new collection of values is subtracted from the term that represents, for each value of n, the increase in inductance due to the increase in the length of the conductors, as the twisting turns increase, which is expressed in equation (5 ). As a result, a set of incremental inductance values is achieved depending on the variable (n) [Turns / m]. From them, a continuous mathematical function is sought that accurately represents the trend of these values. This function is established by adjustment using a trend curve modeled with a polynomial of order 3. The function described is the geometric polynomial of the cable being tested. From this result the values of the coefficients are obtained, which can be stored in tables, graphs or any means that facilitate, in the future, the application of the procedure described in this patent. It is also possible to perform this process using the twist advance angle (the) as a variable. Under these conditions it is established that the twisted pair inductance in the incremental model responds to the expression shown in equation (7).

10

Influence of the drain conductor

The influence of the drain conductor on the inductance is not as important and obvious as over others magnitudes, such as capacity. The highest parameters importance for the modification of the inductance value are the magnetic permeability and distance between effective centers of the conductors that form the cable.

Although when introducing the driver of drainage modifies the set configuration (Fig. 6), both parameters that determine the value of the cable inductance They are barely affected. The equivalent permeability of said set is altered by having introduced the new driver, but its  influence is negligible; consequently, the Variation in value without fear of introducing appreciable errors. Copper is a diamagnetic material with a susceptibility value of value -0.98E-05. Therefore, still being all space surrounding the conductors of the pair of this material, its serious influence of the following order:

\ mu = \ mu_ {0} \ cdot (1 + \ chi_ {m}) = \ mu_ {0} \ cdot (1 + (-0.98 \ cdot 10-5)) = \ mu_ {0} \ cdot (1 - 0.0000098) = \ mu_ {0} \ cdot 0.9999902, which is practically the same as considering the magnetic permeability of the empty. This value will be closer to one if you consider that it only occupies a small region of the entire area surrounding the torque drivers Therefore, it is concluded that the influence of The permeability variation is negligible.

The second of the parameters that determine the Cable inductance is the distance between the conductors. He effect provided by the drain conductor from a point of view geometric, in general, is reduced to the modification of the initial braiding distribution (single pair); increase the radius of cable twist, but nevertheless the distance between the conductors varies little from the initial (d). By entering the drain in samples of low number of turns per meter, you get a higher twisted pair packing; that is, drainage helps a greater compaction of the set, which, although it is obvious that the theoretical distance between conductors is constant, the actual distance it is reduced (the drainage does not allow so much deviation in the contact of the drivers). As a consequence, in these cases the inductance It is slightly lower (no more than 5%) than the single pair. To the increase the number of turns per meter in the samples, it goes reducing this effect, and even the relationship is reversed, because the existence of drainage does not allow drivers to pack both together and deform your privacy so notably. The reason is that the drain conductor withstands large part of that deformation (it has no insulation, and its shape is not so rigid) (Fig. 7).

In summary, the value of the inductance the following expression:

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eleven

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where L threads is the inductance of the pair of parallel cables, ΔL {Δl} is the increase in inductance due to the increase in length due to the twisting effect and ΔL {Δn} is the term that reflects the geometric polynomial The physical parameters that give rise to these terms are the average distance between conductors and the relative position of both. The last term (\ Delta L drain {}) is merely varying the parameters just discussed to introduce the drain wire; It does not imply any new parameter or concept, but is due to the variation of the characteristics of the equation (6) .

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When considering the variation of characteristics as described, the following equation is posed:

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12

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in which it is possible to neglect the increase in permeability of the set (Δ \ mu_ {r_ {d}}) and where Δ d d is the variation
of the theoretical distance between the conductors, and r p + d is the radius of the triple helix formed, of theoretical value:
1200 where e is the thickness of the insulation and d the diameter of each cable.

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Variation of the distance between conductors (\ Deltad_ {d})

The variation of the distance between conductors \ Deltad_ {d} follows a linear approximation model, just as It is expressed in the following expression:

101

where

D 0 and D 1 are dimensionless coefficients that depend on the rigidity of the insulation

d = initial distance between conductor centers (equal to the initial diameter of each cable)

n = number of turns per meter of braiding

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The value of the coefficients D {0} and {1} D can be determined from specific tables and for each cable model (Table 2) or by assays dimensional graphics.

TABLE 2 Adjustment coefficients of the average distance between drivers

13

If values for these coefficients are not available, they can be obtained as indicated below. A set of twisted cable samples with a number of turns per meter is required, varying from zero to
{} \ a maximum of \ frac {0,1351} {r}, where r is the radius (in meters) of the cable to be braided; you can use those used to
{} \ jskip17cm determine the coefficients of geometric polynomials, if this procedure has been followed. As in the aforementioned case, the samples must be representative of the range of turns per meter allowed, so that the set must have a value of this characteristic properly distributed throughout the range of turns per meter, and the length thereof It should not be less than one meter. In addition, the number of samples should not be less than ten to guarantee the validity of the results. The greater the number of samples, the greater the accuracy of the adjustment according to the model described. Precision cuts must be made on these samples that allow to obtain sections of the insulation of the cables of the pair without modifying the shape that the braiding has determined. These sections must be less than 1 mm (1E-03 m) thick and the average diameter is measured. The accuracy of this procedure is directly conditioned by the equipment and the measurement method used. After obtaining the values it proceeds to perform the calculations adjustment D {0} and {1} D model described; The value of the distance increase is obtained by comparing the measured value for each section with the theoretical value. The collection of results is linearized or approximated by a mathematical function such as that described for Δd d and with variable the parameter ( n ) [turns / m]. As a result, an expression of the variation in the distance between conductors that is given to equation (9) is established, so that it concludes

14

It is also possible to obtain the values of these coefficients indirectly if measurement tests of inductance of twisted pair samples with similar drainage as described for the determination of the coefficients of the geometric polynomial and clear of the expression indicated in the equation (10).

Shielded twisted pair

A more appreciable effect on the variation of the inductance is provided by the shielding of the torque cable braided. From a qualitative point of view, the value is expressed of the inductance of the new configuration (Fig. 8) of the following form:

fifteen

where? L screen expresses a term that reduces the value of the inductance of the cable more appreciably than in the previous case. The reason for this reduction is due to a decrease in the actual distance that separates the conductors from the torque. Although it is considered a constant theoretical distance, the actual distance is reduced because the shield exerts a compression force on the surrounding torque. This effect, less important in the case of capacity, for example, is quite appreciable in the measure of inductance. Therefore, the highlighted term in the previous equation represents the contribution of this twisted pair packing, caused by shielding, to the reduction of the inductance (Fig. 9). As in the previous case, the contribution of the screen to the variation of the magnetic permeability of the set is considered negligible. The inductance equation for this case is expressed as follows:

16

Δ \ mu_ {t_ {pant}} = increase in relative magnetic permeability when entering the screen; be considered close to zero, so it is possible to avoid consideration.

\ D {Delta} = pant variation of the distance between the shielding conductors of the pair; It is negative, and represents the reduction of the distance between the conductors (with respect to the theoretical or nominal distance) due to the packing imposed by the screen.

\ _ {? R} = pant variation of the average radius of each due to the deformation of the insulation (result of the pressure exerted by the screen) wire; its value is negative, because it represents the reduction of the turning radius.

The distance reduction effect due to shielding is less noticeable, and tends to be null, when It greatly increases the number of turns per meter. The reason is that in these conditions the torque drivers maintain a distance constant because the demanding braid to which they have been subjected it reaches a degree of little deformable packing. The drivers of the pair adopt a form that presents greater difficulty for warp and that a greater approximation is possible without considerably deform the insulation (maximum tendency packing) In this situation, the tape that is wrapped over the torque in the manufacturing process, implies very little approximation Additional drivers. The concept of variation of the nominal distance per screen effect is displayed so graphic in figure 9.

Equation 12 approximates as can be seen in The following equation:

17

Variation of the distance between conductors (\ Deltad_ {pant}) and of the twist radius of twisting (\ Deltar_ {pant})

The variation of the distance between conductors \ Delta d {pant} when a screen type is introduced laminar wrapping the twisted pair follows a pattern of quadratic approximation which depends on the parameter (n) [revolutions / m], as indicates in the following expression:

18

which is a negative term (decreases the distance between conductor centers), and in which D 0, D 1 and D 2 are dimensionless coefficients that depend on the rigidity of the insulation and n is the number of turns per meter of the braid.

The value of the coefficients D 0 and D 1 and D 2 is established from tables and graphs specific to each cable model (Table 3) or by dimensional tests.

TABLE 3 Adjustment coefficients of the average distance between drivers

19

If there are no values available for these coefficients can be obtained by the same procedure as provides for the calculation of the distance increase for the pair braided with drain; the only difference is that the Approach to the model is second order instead of a model linear. In this way the coefficient values are calculated of the model expressed in equation (13), and shown with more detail in equation (14).

twenty

As in the previous case, it is also possible get the values of these coefficients indirectly if you perform inductance measurement tests of torque samples shielded braid, analogously to what is described for determination of the coefficients of the geometric polynomial and it they clear the expression indicated in equation (14).

The deformation of the insulation due to the strain caused by the shielding causes a reduction in the distance from the effective center of each conductor to the point of contact between the two wires of the twisted pair. That is, in addition to a reduction in the distance between centers of the conductors, there is a reduction in the radius of rotation of the propeller that forms said pair. Therefore, if the approach described (\ d {pant Delta}) has a certain value,
{} \ hskip17cm reduced turning radius in the twisted is equal to the half of it, then \ _ {? r} = pant \ frac {\ Delta} d {pant} {2}. Therefore, the expression to apply in this case will be:

twenty-one

Shielded twisted pair with drain conductor

When performing the shielding process of the twisted pair with drain conductor (Fig. 10) originates a variation of the inductance, with respect to the case of the pair of conductors parallel, quantifiable and predictable. In a generic way states that

22

The difference is of consideration with respect to trailed torque with drainage, because the average distance between the conductors between which the inductance is measured, as it is He explained in the previous section. The expression that shows this Behavior is set as follows:

2. 3

but where \ Delta \ mu_ {r_ {pant + d}} approaches zero. The value of ( r + Δ r pant + d) has a theoretical value equal to 24 (if the drain were rigid); but nevertheless, 25 and the approximation of ( r + Δ r pant + d) to the value of r introduces a minimum error. The term Δ d pant + d is similar to Δ d pant in the previous section; The contribution of the drain to the inductance is minimal and, in addition to presenting the same behavior as the one explained with respect to the simple pair, it is also observed that its contribution is almost negligible. If a very precise approximation is sought in the attainment of an inductor value of the foral cable, the difference can be quantified as explained in this section, but it can also be considered under the same conditions as the shielded twisted pair. The drainage slightly reduces the inductance with low values of n , and also increases it in a reduced way as high values of n are achieved in a percentage value less than 2%. The reason for its low influence is the good adaptation to the shape of the assembly, which is mainly determined by the screening (Fig. 11). The consideration of the pair plus shielded drainage is equivalent to that of the shielded pair. In the application of the procedure presented, the distance variation of the shielded torque is considered.

Variation of the distance between conductors (\ Deltad_ {Pant + d}) and twist radius of twist (\ Deltar_ {pant + d})

The variation of the distance between conductors Δd d , when a drain conductor and a laminar type screen that surrounds the triple helix are introduced follows a quadratic approximation model that depends on the variable ( n ) [turns / m], as expressed in the following expression, in a similar way to the above for the case of the simple twisted pair:

26

which is a negative term (decreases the distance between conductor centers), and in which D 0, D 1 and D 2 are dimensionless coefficients that depend on the rigidity of the insulation and n is the number of turns per meter of the braid. The contribution of the drain conductor limits the approximation between the conductors to which the screen is forced. In a comparison with the case of the shielded pair, it can be established that for braids of reduced number of turns per meter ( n ), the drain contributes to the compaction of the cables, thereby slightly reducing the inductance. However, by raising the torque requirement of the triple helix (increase in n ), the drain adapts its shape to that of the assembly but hinders the approach of the cables of the pair; The effect in the latter case is that of slightly higher inductance values compared to the case taken as a reference.

The value of the coefficients D 0 and D 1 and D 2 is established from tables and graphs specific to each cable model (Table 3) or by dimensional tests.

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TABLE 3 Adjustment coefficients of the average distance between drivers

27

If there are no values available for these coefficients can be obtained by the same procedure as provides for the calculation of the distance increase for the pair braided with drain; the only difference is that the Approach to the model is second order instead of a model linear. In this way the coefficient values are calculated of the model expressed in equation (17), and shown with more detail in equation (18).

28

As in the previous case, it is also possible obtain the values of these coefficients indirectly, if perform inductance measurement tests of torque samples shielded braid, analogously to what is described for determination of the coefficients of the geometric polynomial, and they clear the expression indicated in equation (18).

Cover Influence

Bringing a cover to the cable does not notably affects its inductance. How has it detailed in the preceding sections, the different steps taken for the conformation of the final cable they contribute in greater or lesser measured at a small reduction in inductance. The cover provides  rigidity to the set, and does not allow the deformation of the braid. In addition to providing a constant distance between the drivers of the pair (the cover is usually made of solidified plastic material in volume to the previous set), does not allow the deformation of what it covers. The main advantage of this feature is the great stability which is achieved in the inductance measurement values.

The procedure described herein document focuses from two different points of view, in Function of the variables and departure requirements. In this sense, It is possible to anticipate or modify the parameters already indicated cable manufacturing process in question, which allow to obtain a predefined inductance value, but it is also possible determine the inductance from the cable dimensions and the variables specified for the manufacturing process. The application of the prediction and control procedure described in this description, it is specified more specifically in a set of stages necessary for the correct application of it. The following are summarized and with consideration of the two commented approaches:

Procedure (I) :

Determination of the inductance of the final cable from the characteristics of the elements that compose it and through the variable (n) [turns / m]

one.

Determination of the type of cable . Definition of the type of cable depending on the selection of the elements that are introduced in the manufacturing process, such as the screen, the drain and the cover. In this phase it is decided if the cable is a simple braid, a braid with a screen, if it has a drain and if a cover is included.

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2.

Analysis of the dimensional characteristics and types of materials of the selected cable . Selection of the dimensions and materials used in the manufacture of the cable according to the needs and requirements of mechanical type, insulation resistance, fire propagation and any other predefined condition. That is, the design requirements prior to the determination of the characteristics, if they exist, are applied in this phase.

3.

Choice of the shape and parts of the cable . Depending on the requirements analysis of sections 1 and 2, the characteristics, dimensions and particular types of the elements to be used are established; that is, conductors, insulations, screens and drainage.

Four.

Obtaining the parameters of the model . Depending on the characteristics of the cable chosen in the previous phases, the coefficients of the geometric polynomial and the other parameters of the cable are obtained according to the exposed model.

4.1.

Tables and statistical models .

quad

If there are tables and graphs with the data above, the determination of the commented values is immediate.

4.2.

Measurement tests

quad

The other option is to perform the measurement tests necessary to determine the characteristics of the cable to be used in the procedure and of which no values are known. This step is only necessary when testing one type of cable new.

5.

Determination of the value or range of values of turns per unit of length desired . Define the twisting step (p) or the number of turns per meter (n = 1 / p) desired.

6.

Obtaining the inductance value of the cable to be manufactured . By applying the method described in this procedure, the inductance value per unit length of the designed cable is determined. In the event that the value obtained is not admitted as valid, the process can be restarted by returning to point 1. It is also possible to rethink the process from points 2 and 3 because the influence of the aspects described in them is known. the final result.

7.

Deduction of the manufacturing process control algorithm to establish the braiding requirement obtained in the previous point . When an acceptable inductance value is achieved, the information necessary to obtain the data to adjust the manufacturing process is entered into the control algorithm. The information that is incorporated is that of the relationship between advance and winding of the braided conductors, and the dimensions and arrangement of the other components.

8.

Application to the manufacturing process . The implementation of the results of point 7 consists in the realization of the manufacturing process with the deduced conditions. The relationship between lead and winding of the conductors in the braid is applied in the relationship between the speed of rotation (Vg), the element that exerts the torsion on the propeller that is formed with the two cables, and the speed of advance of the final cable (Va). That is, if for example the two conductors are twisted at a speed of rotation of Vg = 50 [turns / s] and the cable advances in line at the rate of Va = 5 [m / s], then the foral cable has a twisted of 10 [revolutions / m] (Vg / Va). The most obvious application is the control of the speed of the motors that cause the rotation and the advance described. However, this application is not restricted to a particular type of braiding machine, and describes the control of the process parameters.

Procedure (II) :

Determination of the variable (n) [turns / m] of the braiding of a final cable from the characteristics of the elements that make up and the desired inductance value between the drivers

one.

Determination of the type of cable . Definition of the type of cable depending on the selection of the elements that are introduced in the manufacturing process, such as the screen, the drain and the cover. In this phase it is decided if the cable is a simple braid, a braid with a screen, if it has a drain and if a cover is included.

2.

Analysis of the dimensional characteristics and types of materials of the selected cable . Selection of the dimensions and materials used in the manufacture of the cable according to the needs and requirements of mechanical type, insulation resistance, fire propagation and any other predefined condition. That is, the design requirements prior to the determination of the characteristics, if they exist, are applied in this phase.

3.

Choice of the shape and parts of the cable . Depending on the requirements analysis of sections 1 and 2, the characteristics, dimensions and particular types of the elements to be used are established; that is, conductors, insulations, screens and drainage.

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Four.

Obtaining the parameters of the model . Depending on the characteristics of the cable chosen in the previous phases, the coefficients of the geometric polynomial and the rest of the coefficients that define the cable according to the exposed model are obtained.

4.1.

Tables and statistical models .

quad

If there are tables and graphs with the data above, the determination of the commented values is immediate.

4.2.

Measurement tests

quad

The other option is to perform the measurement tests necessary to determine the characteristics of the cable to be used in the procedure and of which no values are known. This step is only necessary when testing one type of cable new.

5.

Determination of the value or range of desired inductance values for the final cable . Define the inductance value per unit length that is intended to be set for the final cable.

6.

Obtaining the value of turns per unit length in the braid of the cable to be manufactured . When applying the method described in this procedure, the value of turns per unit of length is determined, or the step, which must be carried out to meet the requirements imposed in point 5. In the event that the value obtained is not admitted as valid, The process can be restarted by returning to point 1. You can also return to points 2 and 3 because the influence of the aspects described in them on the final result is known.

7.

Deduction of the manufacturing process control algorithm to establish the braiding requirement obtained in the previous point . When a desired inductance value is achieved, the necessary information is entered into the control algorithm to achieve that value in the manufacturing process. The information that is incorporated is that of the relationship between advance and winding of the braided conductors, and the dimensions and arrangement of the other components.

8.

Application to the manufacturing process . The implementation of the results of point 7 consists in the realization of the manufacturing process with the deduced conditions. The relationship between lead and winding of the conductors in the braid is applied in the relationship between the speed of rotation (Vg), the element that exerts the torsion on the propeller that is formed with the two cables, and the speed of advance of the final cable (Va). That is, if, for example, the two conductors are twisted at a rotation speed of Vg = 10 [turns / s] and the cable advances in line at the rate of Va = 0.5 [m / s], then the final cable it presents a braid of 20 [turns / m] (Vg / Va). The most obvious application of the process to achieve the number of turns per meter of the cable to be manufactured is that of the speed control of the motors that cause the rotation and the advance described. However, this application is not restricted to a particular type of braiding machine, and describes the control of the process parameters.

Description of the figures

Figure 1 represents a twisted pair cable with screen, cover and drain conductor.

Figure 2 represents a twisted pair simple.

Figure 3 shows the deformation effect that occurs in the wires of the pair when performing the process of braided. The effect is more important as the requirements, that is, as the number of turns increases by subway.

Figure 4 shows the concept of deformation of the insulation provided by the twisted pair of cables.

Figure 5 represents the polynomials geometric twelve wires, different in size and type  of isolation. The variable with respect to which these are represented polynomials is the angle of advance of the twisted helix (\ theta).

Figure 6 provides a fragment of pair cable braided with drain conductor and a high number of [turns / m].

Figure 7 provides two images that allow compare the effect of drainage deformation on the shape of the set. The image above represents the section of a pair Ideal braided with drain conductor. In the image below you shows an equivalent section in which the drain conductor it is deformed by the effect of the stresses applied in the process of braided.

Figure 8 represents a twisted pair cable With flexible tape display.

Figure 9 provides a fragment of pair cable high number of twists [turns / m] with drain conductor and screen

Figure 10 shows two views of a pair braided with drain (triple helix) and laminar type screen.

Embodiments of the invention

The invention presented in this document It is illustrated by the following examples, which summarize the conclusions obtained by applying the procedure outlined. These examples are not intended to limit the scope or scope of application of the invention, but simply intended to provide A sample that illustrates its conclusions.

Example 1

Foral cable formed by two conductors single helically joined in a braiding machine. In based on items 1, 2, and 3 of procedures (I) and (II) detailed in the description of the invention are provided the Cable characteristics to use:

- Copper conductors, middle section of 0.50 [mm2] (5E-09 [m2]) and formed by 16 threads

- Insulation of each cable with a medium thickness 0.41 [mm] (0.00041 [m])

- Insulation material: PVC

- Coefficients of the geometric polynomial: obtained from Table 1. Their values are as follows:

In = 3.55E-03; Jn = -4.86E-05; Kn = 3.19E-07. If of not having values for the coefficients it is necessary perform the calculation procedure explained in the description of the invention

For a braid of 20 [turns / m] (step = 50 [mm] = 0.05 [m]) the method provided predicts a value of 710.1 [nH / m] lead wire conductor inductance (71.01 E-08 [H / m]).

Under these conditions, the relationship between the feed speed of the cable in the manufacturing line (Va, with unit [m / s]) and the speed of rotation for braiding (Vg, expressed in [revolutions / s]) has an approximate value
equal to 29

The method allows to control the characteristic inductance in the manufacturing process. In this way, if modify the relationship between the two magnitudes that control the braided (Va and Vg) at a value of 55 there is a decrease in the final cable inductance up to a value of 702.0 [nH / m] (70.2 E-08 [H / m]).

If a shield is added using the rolled up of a double layer tape, aluminum-polyester, thickness 0.01 [mm] (1E-07 [m]), width of 14 [mm] (0.014 [m]), angle of advance equal to 20.5º, and taking into account the coefficients of distance reduction model due to the shielding of the Table 3 (D_ {0} = - 5,2167E-01, D_ {1} = 6.299E-03, D 2 = 2,9653E-05), then, the value of  inductance of the set at 651.3 [nH / m] (65.13 E-08 [H / m]). The introduction of a drain in the braiding process implies, with a copper drain conductor, with section 0.50 [mm2] (5E-09 [m2]) and without insulation, a inductance value equal to 638.1 [nH / m] (63.81 E-08 [H / m]). The modification of this cable by the application of an extrusion process to provide a cover PVC sheath, with an average thickness of 0.45 [mm] (45 E-05 [m]), implies a stabilization of the value anterior inductance.

Example 2

End cable consisting of two conductors single helically joined in a braiding machine. In based on items 1, 2, and 3 of procedures (I) and (II) detailed in the description of the invention, the Cable characteristics to use:

- Copper conductors, middle section of 0.35 [mm2] (35E-09 [m2]) and formed by 7 threads.

- Insulation of each cable with a medium thickness 0.32 [mm] (0.00032 [m]).

- Insulation material: PVC.

- Coefficients of the geometric polynomial: obtained from Table 1. Their values are as follows:

In = 3.35E-03; Jn = -4.41E-05; Kn = 2.35E-07. If of not having values for the coefficients it is necessary perform the calculation procedure explained in the description of the invention

It is intended to manufacture a final cable formed by a twisted pair according to the characteristics shown and a PVC protective cover. The thickness of the cover should approach 0.44 [mm] and the required material is PVC. In these conditions, it is intended to obtain the control parameter of the braided in the manufacturing process, which ensures a value of conductor inductance for the focal wire of a value Approximately 702 [nH / m] (70.2 E-08 [H / m]).

The method predicts the value of the variable ( n ) [rounds / m] to satisfy this characteristic of the final product, and for this case a value of n = 22 [rounds / m] is concluded, which is equivalent to a step of 45 , 45 [mm] (0.04545 [m]). Consequently, in the braiding process the relationship between the advance and the twist in the cables must be established at a value of 22. That is, in a conventional braiding machine, the relationship between the mentioned speeds 1300 Control of machine parameters is immediate; if, for example, the speed Va is constant, the control of the characteristic is reduced to the control of the speed of rotation of the braiding element according to the expression: Vg ( rpm ) = 22 [ turns / m ] \ cdot 60 \ cdot Va [ turns / m ]. In a generic case where these conditions are control solution arises in the expression Vg [rpm] = n [revolutions / m] \ cdot 60 \ cdot Va [m / s], where n is obtained by applying the method described .

In the present invention it is not intended to limit the type of braiding machine to a particular type or model, but that the parameters of the same that condition the Results that arise. That is, it has been established as control parameter, in examples 1 and 2, the relationship between the cable feed in production line and twist with the one that is braided. This parameter refers, in short, to final step of braiding the cable to be manufactured, which is a fact that indirectly determined also by the number of turns per meter or the angle of advance of the propeller for cables known dimensions. Nor is the type of control of forward and turn speeds to a particular model but it extends to any type of mechanical or electronic control that Perform the same function.

Industrial application of the invention

The industrial application of the invention is immediate in the technical sector that has been established at Beginning of this description. Said invention provides an improvement of great interest in the electrical cable manufacturing sector and allows the inductance control in this product line industrial through the variation of braiding parameters that are described

Claims (4)

1. New procedure for the prediction and control of the electrical inductance of a twisted pair cable in the manufacturing process according to a predefined value and determined by the dimensions and nature of the elements that make it up and controlled by the step parameter of the twisted, or also the equivalent parameters number of turns per meter and angle of advance of the propeller, in the braiding machine, and where said procedure is characterized by the twisting stage of the pair of conductors comprising the calculation of the inductance value end of the cable from an incremental model, which reflects the increase in inductance with respect to the unbraided pair and which is adjusted with great precision by third order polynomials, as indicated in the following expression: 30 The determination of the coefficients of Geometric polynomial can be obtained from tests such and as follows.

?

Prepare a set of samples of braided cable with a number of turns per variable meter from {} \ hskip17cm zero to a maximum of \ frac {0,1351} {r}, where r is the radius (in meters) of the cable to be braided. These samples must be {} \ hskip17cm representative of the range of turns / meter allowed, so the set must have a value of this feature properly distributed throughout the range of turns / meter, and the length of them should not be less than one meter. In addition, the number of samples should not be less than ten to guarantee the validity of the results. The greater the number of samples, the greater the accuracy of the adjustment in obtaining the geometric polynomial. To the samples made a minimum of three must be added with parallel conductors (n = 0) well united. The purpose of this last step is to obtain a reliable inductance value of the parallel cable pair for use as threshold value in the calculation process.

?

Once the samples are obtained the inductance measurement is carried out in a device calibrated measurement and with an accuracy in the order of 1 to 10 nH The tests must be carried out under stable conditions of humidity and temperature, for which the values of these characteristics must be set between 40% and 60% for the relative humidity and around 23ºC + 2 [ºC] for temperature. The collection of results is analyzed with the composition of a mathematical function that provides the inductance value and the variable (n) [turns / m] (n).

?

To obtain a function of incremental model, first all the values of the inductance obtained between the average value of the inductance of parallel conductor samples (n = 0). In this way obtain percentage values of increased inductance regarding the increase in the requirement of braiding (number of turns per meter). The new collection of values is subtracted from term that represents, for each value of n, the increase of inductance due to the increase in conductor length as braiding turns increase. As a result it is achieved a set of incremental inductance values depending on the variable (n) [turns / m].

?

From the set of values incremental inductance a mathematical function is established continues to accurately represent the trend of these values by a trend curve modeled with an order polynomial 3. The function described is the geometric polynomial of the cable that is rehearse and indicated below:

31 2. New procedure for the prediction and control of the electrical inductance of a twisted pair cable with drain conductor in the manufacturing process according to a predefined value and determined by the dimensions and nature of the elements that make it up and controlled by the braiding step parameter, or also the equivalent parameters number of turns per meter and angle of advance of the propeller, in the braiding machine, and where said procedure is characterized by the braiding stage of the pair of conductors comprising the calculation of the inductance value of a twisted pair cable with drain conductor from the following expression: 32 The determination of the coefficients of polynomial D 0 and D 1 can be obtained from tests as indicated below.

?

Prepare a set of samples of braided cable with a number of turns per meter that can vary {} \ hskip17cm from zero to a maximum of \ frac {0,1351} {r}, where r is the radius (in meters) of the cable a braid. Samples can be used {} \ hskip17cm used to determine the coefficients of the polynomials geometric, as indicated in claim 1, if Followed this procedure. As in the aforementioned case, the samples must be representative of the range of turns per meter allowed, so the set must have a value of this characteristic properly distributed over the entire range of turns per meter, and their length should not be less than one subway. In addition, the number of samples should not be less than ten to guarantee the validity of the results. The greater the number of samples, the greater the accuracy of the adjustment according to the model described

?

About these samples are due make precision cuts that allow obtaining sections of the insulation of the pair's wires without modifying the way the Braided has determined. These sections must be of a thickness less than 1 mm (1E-03 m) and of them the medium diameter The accuracy of this procedure is directly conditioned by the equipment and the measurement method used

?

Once the values are obtained, proceeds to perform the adjustment calculations of D_ {0} and D_ {1} at model described; the value of the distance increase is obtained when comparing the measured value for each section with the value theoretical.

?

The collection of results is linearize or approximate through a mathematical function such as described for \ Deltad_ {d} and depending on the variable (n) [turns / m] and the initial diameter of each cable (d), as Indicate below:

33 3. New procedure for the prediction and control of the electrical inductance of a shielded twisted pair cable without drainage conductor in the manufacturing process according to a predefined value and determined by the dimensions and nature of the elements that make it up and controlled by the braiding step parameter, or also the equivalent parameters number of turns per meter and angle of advance of the propeller, in the braiding machine, and where said procedure is characterized by the braiding stage of the pair of conductors comprising the Calculation of the inductance value of a shielded twisted pair cable without a drain conductor from the following expression: 3. 4 The value of the coefficients D_ {0} and D_ {1} and D_ {2} can be obtained by the same procedure that is provided for calculating the distance increase for the twisted pair with drain, set forth in claim 2; the only difference resides in that the approximation to the model is second order instead of a linear model. 4. New procedure for the prediction and control of the electrical inductance of a shielded twisted pair cable with a drain conductor in the manufacturing process according to a predefined value and determined by the dimensions and nature of the elements that make it up and controlled by the braiding step parameter, or also the equivalent parameters number of turns per meter and angle of advance of the propeller, in the braiding machine, and where said procedure is characterized by the braiding stage of the pair of conductors comprising the calculation of the inductance value of a shielded twisted pair cable, and with a drain conductor from the following expression: 35 The value of the coefficients D_ {0} and D_ {1} and D_ {2} can be obtained by the same procedure that is provided for calculating the distance increase for the twisted pair with drain, set forth in claim 2; the only difference resides in that the approximation to the model is second order instead of a linear model.