RU2369946C1 - Passive wideband electrodynamic filter - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention is aimed at higher noise immunity of electrotechnical equipment and radio electronic instrumentation, reduction of material costs with provision of efficient filtration in both directions (from network to apparatus and from apparatus to network). Specified technical result is achieved by the fact that passive wideband electrodynamic filter is arranged in the form of directional short connecting line with spatially distanced fixed geometry, of at least two multi-wire conductors made in a certain manner, enclosed in common dielectric shell.

EFFECT: technical result in local network circuit is achieved by application of method of filtration of wideband radio frequency electric noise with application of passive wideband electrodynamic filter made in the form of directional short connecting line.

4 dwg, 3 tbl

Description

The invention relates to products of the electrical industry, cable industry, to the section: “cables for special purposes” and can be used to connect electrical and radio equipment to power sources with voltage of both alternating (regardless of the number of phases) and direct current.

Analysis of the materials of the patent allows us to establish that the core of the device is a specially designed cable with conductive wires spaced in space with their corresponding geometry.

A high-quality 16 ampere network cable containing various filtering elements is known in the art. To achieve the broadest damping in the high-frequency region, up to nine different ferrite cores are used, and this exceptional broad-band filtering is achieved only by combining them. Filtering starts at relatively low frequencies, but is still noticeable even at frequencies above 1 GHz. Thanks to the use of carefully selected materials, a very effective filter was obtained for all high-frequency distortions. Unwanted RF signals arising on the crest of a pure sine wave AC power supply are simply converted to harmless heat (Fisch Cables, Germany. According to the catalog - reference book of the Tenth International Exhibition Hi-Fi Show & Home Theater '2006. Products presented by GONG -AB ").

Known network cable VALHALLA Reference company Nordost. This network cable uses seven mono-filament extruded silver conductors intertwined according to a special configuration, while the active and capacitive reactive components of the complex resistance of the line have tightly limited tolerances. The main task here is to minimize the active component of complex resistance through the use of drags. metal (Ag) (Nordost cables, USA. According to the catalog - reference book of the Tenth International Exhibition “Hi-Fi Show & Home Theater '2006”. Products presented by Barnsly Sound Org.).

All the previous technical solutions used in the construction of network cables, due to their relative broadband, have the same disadvantages, which lie in the absence of effective filtering and the complete insecurity of the electronic device from various electrical network interference and the insecurity of the network from interference from the power supply of the product itself.

The problem to which the proposed invention is directed is to create such a design of a passive broadband electrodynamic filter connecting line with distributed parameters and a method for filtering interference that would eliminate the above disadvantages.

The technical result achieved by the implementation of the invention is to increase the noise immunity of electrical equipment and electronic equipment, reduce material costs while ensuring effective filtering in both directions (from network to device and from device to network side).

The specified technical result is achieved in a passive broadband electrodynamic filter designed to connect electrical and radio equipment in local network circuits, made in the form of a connecting line consisting of at least two multi-wire conductors made taking into account the anisotropic properties of the metal by combining the physical principle their component wire, while the diameter d of the wire is in the range:

0,03≤d≤0,1 mm, and

the number n of wires selected from:

15≤n≤610,

moreover, the length H of the connecting line is selected from the interval:

H << λ,

where λ is the wavelength

and performed with spatially spaced fixed geometry by enclosing conductors in a common dielectric sheath, the distance between which is calculated on the basis of minimizing the running capacitance C _{shoulder straps.} , while C _{shoulder strap.} the connecting line is in the range:

C _{shoulder strap.} ≤2.5 pF.

The invention is illustrated by drawings, where figure 1 shows a cross section of a directional short connecting line (NKSL); figure 2 - calculation of the step of laying the conductors for the directional short connecting line; figure 3 - single-core copper mounting wire with insulation of fluoroplastic; 4 is a directional short connecting line.

The task is achieved due to the special geometry of the cable.

This invention represents a definitely new and useful improvement in the cable for connecting electrical and radio equipment to power sources with voltage of both alternating (regardless of the number of phases) and direct current.

In this case, power sources must be understood as global network power systems designed for a large number of consumers, including all available types of power generation, and local networks using electromechanical, electronic and other voltage converters designed to ensure the operation of electrical equipment of a single consumer . By global network systems, it is necessary to mean large suppliers of electricity with their transmission lines and transforming substations. An example of a local network is a mobile diesel or gas generator, a battery, and also secondary sources of electricity based on electronic and electromechanical converters.

It is known that conductive lines designed to transmit electromagnetic waves with a frequency of 50 Hz and 60 Hz over long distances from the electricity producer to its consumers can repeatedly change the geometry of the conductor. This changes not only the cross-section and shape of the conductive elements, the distance between them, but also the types of dielectrics in their environment.

Open high-voltage power lines, cable glands in residential, office and industrial buildings, including wiring power to specific equipment, are a clear example of geometric metamorphoses of conductive structures.

Increasing demands on the quality of power sources supplying sophisticated radio equipment cannot ignore the issue of combating various network interference and eliminating the causes that cause them.

The rapid development of computer technology and various telecommunication systems has largely changed the nature of network interference.

The use of switching power supplies is accompanied by the emission of unwanted electromagnetic waves into the network in a wide frequency spectrum. There is a need to use special intra-structural technical solutions for filtering the mains voltage, which leads to higher cost of the product. A new class of equipment appears - network air conditioners. Practice shows that such complex implementations may not in all cases cope with the task assigned to them.

Practical observations of the operation of individual complex radio engineering devices draw attention to the following phenomena:

- the parameters of the global energy system, presented in the form of an oscillatory circuit, retain their values with enviable constancy in large time intervals and depend mainly on the daily activity of large consumers, which are industrial enterprises. If necessary, the electricity producer performs the correction (cosφ) (voltage drop from the nominal value of the "drawdown" was not initially taken into account);

- small consumers of electricity (ranging from 1-30 kW), as a rule, are connected to the power supply system through branches from the central feeder with a small cross-section cable. This fact leads to the formation of a local oscillatory circuit with its own characteristics.

Local circuit features

From a physical point of view, the branches from the main feeder are short connecting lines with conductive conductors of circular cross section 1-3 mm ² made of copper or aluminum, the distance between which varies from 1 to 3 mm, and the length from several meters to several hundred meters. Line resistance is complex. In this case, the linear inductance X _L as a component of reactance is determined by the number and thickness of the conductive conductors in the structure of the conductor and the winding coefficient, and capacitive X _C is the reduced surface area of the conductors, the distance between them and the dielectric parameters. The values of X _L and X _C in this local circuit are small and are unlikely to significantly affect the phase relations of the current and voltage of the supply network. However, a number of experiments in various office and industrial premises showed that by changing the nature of the reactivity and the value of the active component of the complex resistance of the line, good results can be achieved when filtering interference.

In the course of practical experiments, it was found that a decrease in X _C to several picofarads leads to a significant improvement in the operation of electronic equipment. The appearance of the model series of equipment with removable network cables made it possible to quickly and efficiently monitor the changes that occur when a standard connector is replaced with a test one.

The spectrum and magnitude of the interference thrown into the local circuit by pulse power supplies from a random sample of products was determined using an industrial interference verification system consisting of a selective voltmeter - SMV - 11 and the network equivalent - NNB - 111. Observation data led to the conclusion that that we are dealing with resonances at a number of harmonics, including in the radio frequency range.

The connection of additional equipment to the local power supply network led to a significant shift of these resonances in one direction or another in the frequency range. Changes in the operation of the equipment became noticeable even when unloaded extension cords were included in the network, in which the conductive wires were packed in such a way that the distance between them was determined only by the thickness of the dielectric. Therefore, the value of X _C in this case worked.

This application is based on the foregoing and involves the creation of a directional short connecting line (hereinafter referred to as the NKSL), designed to act as a filter network cable for electronic equipment and electrical equipment operating in a local network circuit. An example of such a symbiosis can be the connection to a network of a computer, a plasma television panel, a DVD player, a refrigerator, an iron and an air conditioner, as well as incandescent lamps, etc.

Note

By a short connecting line is meant a conductive line whose length is less than the electromagnetic wavelength transmitted through it. ("Basic concepts and laws of the theory of electromagnetic fields and the theory of electric and magnetic circuits" Neumann AR 1981)

A special case is the proposed short line (0.000031-0.000062λ) at an alternating current frequency of the supply network equal to 50 Hz.

The filtering principle is implemented in a passive wide-band electrodynamic filter with distributed parameters, made in the form of directional short connecting lines (0.000031-0.000062λ) with spatially spaced fixed geometry of conductors used as network cables for connecting radio and electrical equipment.

Note

In the manufacturing process of NKSL, the anisotropic properties of the conductive core are taken into account. During machining, in particular during wire drawing, the crystal structure of the metal undergoes numerous changes. As a result, its physical properties in different directions become heterogeneous. Therefore, the finished product is supplied with appropriate markers in the form of arrow pointers and the logo of the manufacturer, while reading the text comes from the physical beginning of the conductive core.

In the 80s of the last century, many manufacturers of interconnect connecting lines turned their attention to the fact that the quality of the work of these products significantly depends on the direction of laying the conductors.

During my own experiments, I was able to make sure that network cables also significantly exhibit their anisotropic properties that affect the final result of the radio equipment.

Thus, the conductive line I designed has the following properties:

a) extremely limited bandwidth, especially in the radio frequency range,

b) the minimum value of X _C ,

c) at the same time, I made sure that the line did not warm up.

In the manufacture of the first samples, the calculation was carried out for currents up to 7 A and a network voltage of ~ 220 V, which corresponds to consumers with equipment whose power does not exceed 1500 W,

g) the line is flexible,

d) breakdown voltage exceeds 3500 V,

e) the dielectric provides high heat resistance and moisture protection,

g) the line does not have a high prime cost, while precious metals are absent in it.

Calculation of the capacity of the connecting line is carried out in the GHS system.

Figure 1 shows two conductors of circular cross section, presented in the form of a flat capacitor with parallel plates AA and BB.

To calculate the line capacitance, we use the formula of a flat capacitor:

where S is the area of the capacitor plates, d is the distance between them (in accordance with figure 1, this value is denoted as L). In the line WFD 001 it was 12 mm, the length of the line H = 0.000031, λ = 1.85 m. The diameter of the conductive core is specified in the range:

We abstract from the properties of the dielectric, because in these calculations, it is necessary to first of all evaluate the capacitance values of two types of connecting lines with their geometric proportions. In a first approximation, we represent a line skeleton made of an ideal dielectric, then in the GHS system the dielectric constant will take the following form:

Line sizes

at

and

at

The distance between the plates AA and BB (let's call it valid - L _action ) will be determined by the following expression:

and

In this case, the area of the capacitor plates can be represented by the expression:

After substituting the corresponding values, we obtain:

By the formula (1.1) we determine the value of the capacitance of the reduced capacitor:

Therefore, the linear capacitance with a diameter of the conductive core D = 0.4 mm will be close to 0.5 pF / m, and with D = 2 mm - 2.7 pF / m.

With an unsuccessful choice of the material of the dielectric of the frame, these parameters deteriorate. Therefore, the value of L can be increased (for example, by 25%), and it will be 15 mm. Then the calculated parameters for the cores:

take the following values: for D = 0.4 mm, the linear capacitance will be close to 0.38 pF / m, and at D = 2 mm - 2 pF / m.

Further spacing of conductive conductors in space is limited by economic inexpediency.

The tables below illustrate a number of relationships that are useful in the design of NKSL.

The calculation of the line resistance was carried out according to the formula:

with the corresponding dimension: L - in meters, ρ - ohm × mm ² / m; S - in mm ² .

In this case, the ρ value for copper is taken to be 0.0175 ohm × mm ² / m.

From tables 1, 2 it can be seen that with a large cross section of the core, its resistance decreases, and in the place with it the filtering properties change when working in a local circuit. However, with a decrease in the cross-section of the bar constituting the core, the resistance of the line increases, and the filtering capabilities in short sections of the line also increase. At the same time, I want to note the fact that the last three cores in table No. 2 are very suitable for network wiring from the distribution panel to the consumer outlet. They perfectly form a filter at a length of 10-15 meters.

Thus, the method of effective filtering is the exact calculation of the parameters of the line itself.

Optimization of all these parameters cannot be solved in isolation from economic and technological factors. That is why the MGTF family of wires was chosen, the manufacture of which has long been mastered by domestic manufacturers. These cables have very suitable properties, including dielectric properties, for organizing local network circuits.

Below will be described a special case of a two-wire line. In this case, lines with a large number of conductive conductors are performed in a similar way.

As the main component of this development, an existing sample of domestic cable products is used, which is an assembly wire - an assembly flexible heat-resistant in a fluoroplastic sheath (MGTF) with a conductive core cross section of 0.12 mm ² . We are talking about changing its purpose and amending the technological cycles of production without significant additional costs. This refers to the laying of the wire in accordance with its physical beginning and end.

The following are some characteristics of the MGTF wire family. Copper mounting wires are used to make electrical connections both inside and between devices and apparatuses. One of the applications for mounting wires is to lengthen the terminals of resistance thermal converters to connect them to measuring instruments.

MGTF is a single-core copper mounting wire with fluoroplastic insulation (Fig. 3), where position 3 is fluoroplastic insulation, position 4 is twisted copper core. The cross section of the core is selected from the following series: 0.03, 0.05, 0.07, 0.12, 0.35 mm ² . Operating temperature from -40 ° С to + 200 ° С.

Key Specifications

The MGTF mounting wire is rated for a rated voltage of 250 V AC with a frequency of up to 5 kHz.

The dependence of the electrical resistance of the MGTF wire on the cross section of the conductor core is given in table No. 3.

Table number 3 Conductor cross section, mm The number and diameter of wires in the conductive core, mm Electrical resistance of a conductive core 1 km of wire, Ohm, no more 0,03 7 × 0.08 569.45 0.05 10 × 0.08 398.69 0,07 14 × 0.08 271 0.12 24 × 0.08 174.4 0.2 19 × 0.12 one hundred 0.35 19 × 0.15 60

The fact that the core was formed by a wire cross section of 0.08-0.12 mm, largely determined this choice. With such a cross section of the conductors that make up the core, the cable cannot have a wide passband and save the frequency-time parameters of the signal.

The fight against X _C can be conducted in two directions: firstly, you can increase the distance between the conductive conductors, and secondly, if possible, reduce the reduced surface of the capacitor, in this case we are talking about optimizing the diameter of the core.

Thus, the structure of the NKSL looks like that shown in figure 2, where position 1 is the MGTF wire section, position 2 is the dielectric frame.

Fixation of conductors in space is provided by a dielectric frame. The distance L is selected depending on the diameter of the core and the dielectric parameters of the frame, indirectly related to the magnitude of the transmitted currents through the line, and the voltage of the local network.

Russian cable engineers are familiar with this geometry. The manufacturing technology of the so-called ribbon cables was mastered in the 80s of the last century.

The first samples of the NCL were made by me manually in 2004 on the basis of a frame made of Whatman drawing paper, and have been working successfully in high-end sound systems to this day. Below is presented figure 4, which depicts one of the first models. This line is called by me “cable with spatially spaced, fixed geometry of conductors (Wires fixed in distance - WFD)”.

If necessary, the calculation of L can be performed according to the formula (1.1) for given values of the linear capacity of the line. (L calculation for the trunk is carried out in the GHS system.)

To calculate L - the distance between the current-carrying conductors of the line - we use the flat capacitor formula, giving it the following form:

where S is the area of the plates of the reduced capacitor, d is the distance between them (in accordance with figure 1, this value is denoted as L).

The diameter of the conductive core is set based on considerations of permissible current density in accordance with the energy consumption of the consumer. In our case:

We abstract from the properties of the dielectric, and set the value of the linear capacitance within 0.4 pF / m. In a first approximation, we represent a line skeleton made of an ideal dielectric, then in the GHS system the dielectric constant will take the following form:

Line sizes

at

and

at

The distance between the plates AA and BB (let's call it valid - L _action ) will be determined by the following expression:

and

In this case, the area of the capacitor plates can be represented by the expression:

where H is the length of the connecting line (in our case, equal to 1.85 m).

After substituting the corresponding values, we obtain:

Substitute these values in the formula (1.2), we obtain:

NKSL APPLIES

1. As a power cable:

- equipment of land-based stationary and mobile radar systems,

- equipment intended for the collection and processing of telemetric information,

- sonar devices,

- accurate time storage systems.

2. As a power cable for television receivers and computer monitors.

3. As a power cable for digital and measuring equipment.

4. As a power cable for sound recording and reproducing equipment (household and studio equipment).

5. As a network cable for household appliances: refrigerators, washing machines, dishwashers, heating devices, air conditioners, lighting devices, battery chargers, telephone "bases", cell phone chargers, household fans, food processors, mixers, coffee grinders and other electrical equipment.

ADVANTAGES OF NKSL CONNECTORS

1. The use of NKSL for the components of the sound path allows you to get a deeply echeloned and well-structured space of the scene while observing the absolute tonal and timbral balance. Achieving such results is not possible with traditional network cables.

2. The observed changes in image quality on the screens of television receivers and on the displays of computer monitors can be described as follows:

- The contrast depth of the image improves. Events in the foreground are very well separated from events in the background of the video image,

- emphasizes the volume of individual objects and the image as a whole,

- the eye of the observer begins to capture the texture of the material from which the objects falling into the field of view of the lens are made,

- The perception of fast-moving objects improves markedly. There is a possibility of better recognition and identification when watching sports,

- The improvement in the quality of visual illusions in projection technique is especially noticeable when the image is transferred to large screens.

3. An improvement in the shape of complex signals generated by the generators of measuring equipment was noted.

4. I believe that the effect of NCLS on the performance of computer systems should be investigated in appropriate laboratories.

5. The load on the human visual apparatus is reduced, which is an important factor in the long-term operation of the personal computer operator.

6. NKSL does not contain precious and rare earth metals.

7. With a line length of 0.000031λ, interference suppression in the radio frequency range is at least –5 dB.

8. The leakage current under voltage of 3500 V is - 0.12 mA.

9. The line resistance is 9 megohms (measurements were made at the installation for checking electrical safety - GPI - 745 A).

10. The copper content in one NKSL is 7-8 times less than that which is currently spent on the manufacture of products for similar purposes.

NKSL with minimal material costs provides effective filtering in both directions (from network to device and from device to network side).

A private significant feature of the NKSL is: flat geometry with widely spaced conductive conductors.

Claims (1)

A passive wide-band electrodynamic filter designed to connect electrical and radio equipment in local network circuits, made in the form of a connecting line consisting of at least two multi-wire conductors made taking into account the anisotropic properties of the metal by combining the physical principle of the component of their wire, with this diameter d of the wire is in the range:
0.03≤d≤0.1 mm, a
the number of n wires selected from:
15≤p≤610,
moreover, the length H of the connecting line is selected from the interval:
H << λ,
where λ is the wavelength
and performed with spatially spaced fixed geometry by enclosing conductors in a common dielectric sheath, the distance between which is calculated on the basis of minimizing the running capacitance C _{shoulder straps.} , while C _{shoulder strap.} the connecting line is in the range:
With _{shoulder straps.} ≤2.7 pF / m.

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