Do-it-yourself inductor for generation. Manual winding and calculation of the inductance of coils "Universal. Calculation of the frequency of the oscillatory circuit

In order to create a magnetic field and smooth out interference and impulses in it, special storage elements are used. Inductors in AC and DC circuits are used to store a certain amount of energy and limit electricity.

Design

The main purpose of GOST 20718-75 inductors is the accumulation of electrical energy within a magnetic field for acoustics, transformers, etc. They are used to develop and design various selective circuits and electrical devices. Their functionality, dimensions and area of ​​use depend on the design (material, number of turns), the presence of a frame. Devices are manufactured in factories, but you can make them yourself. Home-made elements are somewhat inferior in reliability to professional ones, but are many times cheaper.

Photo - scheme

The frame of the inductor is made of a dielectric material. An insulated conductor is wound on it, which can be either single-core or stranded. Depending on the type of winding, they are:

1. Spiral (on a ferrite ring);
2. screw;
3. Screw spiral or combined.

A notable feature of an inductor for electrical circuits is that it can be wound both in several layers and nirovanno, i.e., with scraps. If a thick conductor is used, then the element can be wrapped without a frame, if thin, then only on the frame. These frames of inductors come in various sections: square, round, rectangular. The resulting winding can be inserted into a special case of some electrical device or used in an open form.

Photo - design of a homemade element

Cores are used to increase the inductance. Depending on the purpose of the element, the rod material used varies:

1. With a ferromagnetic and air core, they are used at high current frequencies;
2. Steel are used in low voltage environments.

Based on the principle of operation, there are such types:

1. Contour. They are mainly used in radio engineering to create oscillatory circuits of the board, they work together with capacitors. The connection uses a serial connection. This is a modern version of the flat Tesla coil;
2. Variometers. These are high-frequency tunable coils, the inductance of which can be controlled, if necessary, with the help of additional devices. They are a connection of two separate coils, while one is movable and the other is not;
3. Twin and trim chokes. The main characteristics of these coils are low DC resistance and high AC resistance. Chokes are made of several coils connected by windings to each other. They are often used as a filter for various radio devices, installed to control interference in antennas, etc.;
4. Communication transformers. Their design feature is that two or more coils are installed on one rod. They are used in transformers to provide a certain connection between the individual components of the device.

The marking of inductors is determined by the number of turns and the color of the case.

Photo - marking

Operating principle

The scheme of operation of active inductors is based on the fact that each individual winding coil intersects with magnetic field lines. This electrical element is necessary in order to extract electrical energy from a power source and convert it to store it in the form of an electric field. Accordingly, if the circuit current increases, then the magnetic field expands, but if it decreases, the field will invariably shrink. These parameters also depend on frequency and voltage, but in general, the action remains unchanged. Turning on the element produces a phase shift of current and voltage.

Photo - the principle of operation

In addition, inductive (frame and frameless) coils have the property of self-induction, its calculation is based on the data of the nominal network. In a multilayer and single-layer winding, a voltage is created that is opposite to the voltage of the electric current. This is called EMF, the definition of the electromotive magnetic force depends on the indicators of inductance. It can be calculated using Ohm's law. It is worth noting that regardless of the mains voltage, the resistance in the inductor does not change.

Photo - connection of individual terminals of elements

The relationship between inductance and the concept (change) of EMF can be found by the formula And if the rate of change of electrical energy is equal to dI/dt = 1 A/c, then L = ε c .

Video: inductor calculation

calculation

Formula - the formula of the oscillatory circuit

Where L is the element itself, which accumulates magnetic energy.

At the same time, the period of free oscillations of this circuit is calculated by:

Formula - period of free oscillations

Where C is a capacitor, a reactive circuit element that gives off the accumulating electrical energy of a particular circuit. The value of the inductive reactance in such a circuit is calculated from X L \u003d U / I. Here X is the capacitance. When calculating a resistor, the basic parameters of this element are inserted into the example.

The inductance of the solenoid is determined by the formula:

Formula - solenoid coil inductance

In addition, the level of inductance has a certain dependence on the temperature on the board. Parallel connection of several parts, changes in the density and size of the turns of the winding and other parameters affect the basic properties of this element.

Photo - temperature dependence

To find out the parameters of the inductor, you can use various methods: measure with a multimeter, test on oscilloscopes, check separately with an ammeter or voltmeter. These options are very convenient in that they use capacitors as reactive elements, the electrical losses of which are very small and may not be taken into account in the calculations. Sometimes, in order to simplify the task, a special program for calculating and measuring the necessary parameters is used. This greatly simplifies the selection of the necessary elements for circuits.

You can buy inductors (SMD 150 μH and others) and wires for winding them at any electrical store, their price varies from $ 2 to several tens.

Sergey Komarov, UA3ALW

To perform “Universal” winding, you need an enameled winding wire in silk or lavsan insulation of the PELSHO, PESHO, LESHO, PELO, LELO types. Additional fibrous insulation performs two functions: it prevents the wire from slipping off the frame and from each other with oblique turns, and allows subsequent impregnation with polystyrene varnish, paraffin or ceresin to rigidly fix the arrangement of turns of the multilayer coil, which ensures high stability of its inductance.

With some skill, winding is easily done by hand. To do this, mark the frame itself, as shown in Figure 1, or wrap it with cable paper with markings applied to it. At the place of winding, two circular lines are drawn, the distance between which will determine the width of the winding. Next, two diametrically opposite lines AB and CD are drawn. The distance between them should be exactly equal to half the turn. If it is planned to wind several sections or inductively coupled coils on the frame, then marking is done immediately for all windings. Marking should be done with a non-conductive electrical dye (a simple pencil is not suitable, since its lead is made of graphite).

Next, with adhesive tape outside the markup, we fix the wire at the beginning of the winding so that it passes through point A, and with a slight tightness, lay it obliquely along half the circle from point A to point D. At point D, we bend the wire at an obtuse angle and, holding corner with a thumbnail (it works especially well for girls and young wives), with less interference, we lay the wire obliquely in the opposite direction to point A. Arriving at point A, we cross the wire of the beginning, pressing it with a new turn, and immediately bend it under a blunt corner, but now in the opposite direction and begin to lay the second turn close to the first, to the right of it. At the same time, again, with the thumbnail, we hold the angle of the bend of the wire from its sliding to the center of the winding. With the acquisition of skill, this can be done with the wire of the next turn, first bending it slightly to the outside (to tighten the angle of the previous turn) and only then, pressing it with a fingernail, at an obtuse angle, inward, and laying it parallel to the previous turn.

In the process of winding, with each bend of the wire, it is necessary to tighten the bend angle to the annular marking line. Since the turns of the winding are oblique, and the winding tends to narrow when the wire is pulled, the winding is carried out with a slight tension. To obtain an even section of the winding, it is necessary to lay all the corners of the bends of the wire exactly on the line of ring markings, and make the bend sharp, holding the wire with the thumbnail of the left hand.

Before you start winding the Universal coils with a thin winding wire, you should practice such cross winding, for example, on the MGShV-0.2 mounting wire, winding it on any round rod or tube with a diameter of 15 ... 20 mm and marking the winding width 12…15 mm. To do this, you need to take a wire 3.5 ... 4 meters long and wind a narrow, high and even winding section exactly according to the markup - a kind of “pancake”, putting the entire length of the wire into the winding (Fig. 2).

After several attempts, the winding will begin to turn out even, and the necessary skills will appear, as they say, “at your fingertips”. Now you can try to wind 150 turns into a section 5 mm wide with PELSHO-0.25 ... 0.3 wire on a frame with a diameter of 8 ... 10 mm. For thinner wire, the winding width should be taken proportionally smaller. But you should not immediately get carried away with thin wires and narrow sections, without still having well-established skills. This winding requires patience, accuracy, attentiveness, fine coordination of finger movements, and if you rush, you can find frustration instead of skills. If the section turns out to be even, neat and exactly according to the markup, you can assume that you have learned how to wind the coils with the Universal winding.

At long wavelength frequencies, where there are hundreds of turns to achieve the desired inductance, it makes sense to wind a winding with a double pattern across the winding width (cross-over) and wind twice as wide. (Fig. 3).

The marking of the frame is almost the same as in the first case, but in the middle of the winding we draw another annular line. Winding is done like this. We fix the wire with adhesive tape at the beginning of the winding so that it passes through point A, and with an interference fit, lay the wire obliquely along half the circle from point A to the middle of the CD line. Next, we continue winding so that a full turn of wire ends at point B. Bend the wire at an obtuse angle and, holding the corner with a thumbnail, continue winding to the middle of the CD line, where we cross the wire of the previous turn and continue winding further. We finish the second turn at point A, where we cross the wire of the beginning of the winding, immediately bend it at an obtuse angle and lay the third turn close and parallel to the first, to the right of it. Then we continue winding, laying the wire of the new turn parallel and to the right of the previous one, and crossing the previous one at points A and B. In the middle of the CD line, the turns will intersect without a kink, and as the number of winding turns increases, the point of each new intersection will shift towards the winding. When the displacement reaches a full turn around the carcass, further winding will continue with the second layer on the already wound turns of the first layer. Here, as in the first case, it is necessary to constantly tighten the bending angles of the wire to the side lines of the ring marking and acquire the skill of maintaining the required wire tension force so that the coil turns out to be dense and so that it does not narrow from turn to turn and from layer to layer.

To fix the outer output of the coil, 10 ... 15 turns before the end of the winding, a double-folded cotton sewing thread, No. 20 thick, is placed across the turns, as shown in the figure, and winding is continued on top of it.

The location of the thread on the winding circumference must be guessed so that the end of the last winding turn is exactly in the place and from the edge where the thread loop is located. The end of the wire is cut off with a margin of the desired length and threaded into a thread loop. After that, pulling the output, tighten the loop on the reverse side of the winding and tie both ends of the thread together into two knots. The thickness of the double knot will prevent the thread from jumping out to the other side of the winding between the turns that pressed it. Fixing the external output is simple and durable.

After winding, it is advisable to impregnate the turns of the coil to choose from: liquid polystyrene varnish (a solution of polystyrene in acetone or dichloroethane), paraffin (melting a part of a household lighting candle in a tin larger than the coil, heating the jar on a soldering iron and dipping the wound coil into liquid paraffin) or ceresin ( same technology). The coil should not be impregnated with other compounds in order to avoid deterioration of the frequency properties.

If such coils are often used in your radio circle or by you personally, it makes sense to make a home-made manual machine for winding Universal coils, descriptions and drawings of which have been repeatedly published in Radio magazine. A detailed description of the work with the machine and the methodology for setting it up for a specific winding are also given in the articles.

It will not be possible to buy such a machine for anyone or for every radio circle. Nobody produces them, and those that are produced are intended for large factories, designed for mass production of the same type of coils, take up a lot of space, are excessively functional, incredibly difficult to operate, cost astronomical sums and are absolutely inappropriate in a radio circle, and even more so, in a home radio laboratories.

Now about the inductance of coils wound with "Universal". Knowing the overall dimensions of the coil and the number of turns, it is possible to calculate its inductance with very high accuracy. Figure 4 shows the calculation formula, size ratios and a table of practical values ​​for the inductance of actually wound coils.

This table was compiled as follows: 150 turns of the "Universal" winding were wound on the frame of the specified diameter D1 with the specified wire; the outer diameter of the resulting winding was measured with a caliper and its inductance with an E12-1A device. Then, 10 turns were unwound and measurements were repeated 11 times until the remaining 50 turns. And so four times, with different wires, on different frames. Thus, four columns of the table were compiled.

Since with inductances of 20 ... 40 μH or less, it is better to use a single-layer winding, and it is hardly reasonable to wind less than 50 turns into a coil with the "Universal" winding, measurements with a smaller number of turns were not carried out. However, calculations of the inductances of coils with a smaller number of turns can be easily carried out using the above formula. With careful winding along the markup, the inductance calculation gives a good match (about 1% accuracy) with the measurement results.

When calculating a multi-section coil, it is necessary to take into account the mutual inductance between the sections. With the same winding direction, the total inductance of two sections located close to each other (one section is partially in the magnetic field of the other) is determined as follows:

L total =L1+L2 + 2M

If there are three sections under the same conditions, then: L total =L1+L2+L 3 + 2M 1-2+2M2-3+2M 1-3; where:

M 1-2- Mutual induction between the first and second sections;

M 2-3- Mutual induction between the second and third sections;

M 1-3- Mutual induction between the first and third sections.

If the sections are arranged in a row, one after the other, at the same distance, then M 1-2 =M 2-3. Mutual induction through the section, - M 1-3 will be very small due to the large distance between the sections and the quadratic nature of the decrease in the magnetic field strength depending on the distance between them. When calculating the inductance of multi-section coils with practical accuracy, the mutual inductance between sections located at a distance greater than their outer diameter can be safely neglected. The mutual inductance of coils spaced at a distance greater than their diameter should be taken into account only in those cases when communication between the circuits is carried out through it.

It follows that in order to obtain the maximum inductance of a multi-section coil, the sections must be located as close to each other as possible, then, with the same number of turns and active resistance of the wire, the total inductance will be greater due to mutual inductance. However, sections should not be located at a distance closer than 2 mm, since when winding the next section close to the previous one, it is very difficult to lay turns and bend the wire accurately.

The optimal ratio of the coil shape to obtain the minimum active resistance at maximum inductance is when the section width is equal to the winding thickness, and the average winding diameter is 2.5 times the section width. It should be noted that at high frequency the optimum for the minimum active resistance does not coincide with the optimum for obtaining the maximum quality factor, and for coil sizes acceptable for compact design, there is a tendency to increase the quality factor with an increase in the average diameter, while maintaining the same width and thickness of the winding.

For example, let's calculate the inductance of a five-section choke with "Universal" winding with a section width of 5 mm, a distance between sections of 2.5 mm, containing 100 turns of PELSHO - 0.25 wire in each section, wound on a resistor VS-2W with R ≥ 1MΩ.

Since the surface of the resistor is slippery, we wrap it with two layers of cable paper 37 mm wide, 55 mm long and mark the winding sections on it. At the same time D 1 = 8.5 mm. For the PELSHO-0.25 wire, the insulation diameter is 0.35 mm, the winding looseness coefficient k n= 1.09 (experimental value; can be calculated from the table in Fig. 5).

Winding dimensions: C =n (k nd) 2 /l = 100 x (1.09 x 0.35) 2 / 5 = 2.9 mm. D2=D1+2C= 8.5 + 2 x 2.9 = 14.3 mm. D = (D2+D1) / 2= (14.3 + 8.5) / 2 = 11.4 mm; l= 5 mm = 0.5 cm;

Inductance of one section (Fig. 4) :

L 1 \u003d 0.0025 πn 2D 2 / (3D+9l + 10 c)= 0.0025 π 100 2 11,4 2 / (3x11.4 + 9x5 + 10x2.9) = 94.3 μg.

Interestingly, measuring the inductance of a coil wound according to the indicated dimensions gives a result of 95 μH (Fig. 5). Given the inaccuracies in manual winding, this is a very good match.

To determine the mutual inductance between the sections, we calculate the ratio (Fig. 6):

r 2 / r 1 = √([(1 - a /A) 2 + B 2 /A 2 ] / [(1 + a/A) 2 + B 2 /A 2 ]) for five pairs of points.

Average section radius: a = (8.5 + 14.3) / 4 = 5.7 mm;

For points 0-1: A = a = 5.7 mm; B = 7.5 mm.

r 2 /r 1 = √{(7,5 2 / 5,7 2 ) / [(1 + 1) 2 + 7,5 2 / 5,7 2 ]} = √(1,7313/5,7313) = 0,5496;

Calculation and manufacture of an inductor, choke. Typical electronic circuits with chokes. How to make an inductor with your own hands (10+)

Choke, inductor - Design, manufacture, application

Choke manufacturing

First, let's decide on the material of the magnetic circuit (core). If the frequency is more than 10 kHz, then we use ferrites, if less than 3 kHz, then iron, if between these values, then we decide based on specific conditions.

Chokes are made with a gap in the core. The correct thickness of the gap, combined with the correct number of turns, provides the desired choke parameters.

Here is a selection of materials for you: Inductor reactance An ideal inductor does not have the classic ohmic resistance, the DC resistance of the inductor is zero. But if an alternating voltage is applied to the inductor, then due to the periodic accumulation of energy in the magnetic field and its subsequent return, a finite current will flow in the circuit. Moreover, the current through the inductor does not depend on the voltage at the current moment, but depends on the history of voltage changes, that is, it is determined by the primitive of voltage versus time. So, if a sinusoidal voltage is applied to the inductor, then the current will have the form of a minus cosine. It is due to this phase shift that thermal energy is not dissipated on an ideal inductor. On real inductors and in the circuits around them, thermal energy, of course, is dissipated, since they all have non-zero ohmic resistance. That's where the power is dissipated. If we consider a sinusoidal voltage and operate in terms of effective voltage and current, then we can write a formula that resembles Ohm's law for resistors. [ Effective current through the choke] = [Actual voltage at the throttle] / [Z], where [ Z] = (2 * PI * [ voltage frequency] * [Choke inductance]). This formula is useful in calculating inductive AC voltage dividers and high and low pass filters. Features of the use of chokes in circuits Chokes can be connected in series and in parallel. [Inductance of series-connected chokes] = + [Inductance of parallel connected chokes] = 1 / (1 / [Inductance of the first choke] + 1 / [Inductance of the second choke]) The figure shows typical circuits on inductors. (A) - Inductive AC voltage divider. [ Lower throttle voltage] = [Input voltage] * / ([lower choke inductance] + [top choke inductance]) (B) - High pass filter. (B) - Low pass filter. Unfortunately, errors occur periodically in articles, they are corrected, articles are supplemented, developed, new ones are being prepared. Subscribe to the news to stay informed. If something is not clear, be sure to ask! Ask a Question. Article discussion. messages. And what is E in the first formula, it just turns out to be a huge amount of inductance. In the first formula, it is plausible if the inductance is in microhenries. If I understand correctly, then, for example, E-3 means 0.001?

What do you imagine under the word "coil"? Well ... this is probably some kind of “figovinka” on which threads, fishing line, rope, whatever! The inductor is exactly the same, but instead of a thread, fishing line or something else, ordinary copper wire is wound there in insulation.

The insulation can be made of clear varnish, PVC insulation and even cloth. Here the chip is such that although the wires in the inductor are very tight to each other, they still isolated from each other. If you wind inductors with your own hands, in no case try to take an ordinary bare copper wire!

Inductance

Any inductor has inductance. The inductance of a coil is measured in Henry(GN), denoted by a letter L and measured with an LC meter.

What is inductance? If an electric current is passed through a wire, it will create a magnetic field around itself:

where

B – magnetic field, Wb

I-

And let's take and wind this wire into a spiral and apply voltage to its ends

And we get this picture with magnetic field lines:

Roughly speaking, the more magnetic field lines cross the area of ​​this solenoid, in our case the area of ​​the cylinder, the greater the magnetic flux will be. (F). Since an electric current flows through the coil, it means that a current passes through it with a current strength (I) and the coefficient between magnetic flux and current strength is called inductance and is calculated by the formula:

From a scientific point of view, inductance is the ability to extract energy from a source of electric current and store it in the form of a magnetic field. If the current in the coil increases, the magnetic field around the coil expands, and if the current decreases, then the magnetic field contracts.

self induction

The inductor also has a very interesting property. When a constant voltage is applied to the coil, the opposite voltage appears in the coil for a short period of time.

This opposite voltage is called EMF of self-induction. This depends on the value of the inductance of the coil. Therefore, at the moment the voltage is applied to the coil, the current strength smoothly changes its value from 0 to a certain value within fractions of seconds, because the voltage, at the moment the electric current is applied, also changes its value from zero to a steady value. According to Ohm's Law:

where

I- current in the coil, A

U– voltage in the coil, V

R– coil resistance, Ohm

As we can see from the formula, the voltage changes from zero to the voltage supplied to the coil, therefore the current will also change from zero to some value. The coil resistance for DC is also constant.

And the second phenomenon in the inductor is that if we open the circuit of the inductor - the current source, then our self-induction EMF will be added to the voltage that we have already applied to the coil.

That is, as soon as we break the circuit, the voltage on the coil at this moment can be many times greater than it was before the circuit was opened, and the current in the coil circuit will quietly fall, since the self-induction EMF will maintain a decreasing voltage.

Let's draw the first conclusions about the operation of the inductor when a direct current is applied to it. When an electric current is applied to the coil, the current strength will gradually increase, and when the electric current is removed from the coil, the current strength will smoothly decrease to zero. In short, the current in the coil cannot change instantly.

Types of inductors

Inductors are divided mainly into two classes: with magnetic and non-magnetic core. Below in the photo is a coil with a non-magnetic core.

But where is her heart? Air is a non-magnetic core :-). Such coils can also be wound on some kind of cylindrical paper tube. The non-magnetic core inductance is used when the inductance does not exceed 5 mH.

And here are the core inductors:

Mostly use cores made of ferrite and iron plates. Cores increase the inductance of the coils at times. Cores in the form of a ring (toroidal) allow you to get more inductance than just cores from a cylinder.

Ferrite cores are used for coils of medium inductance:

Coils with a large inductance are made like an iron core transformer, but with one winding, unlike a transformer.

Chokes

There is also a special kind of inductors. These are the so-called. A choke is an inductor whose job is to create a high resistance to AC current in a circuit in order to suppress high frequency currents.

DC current passes through the inductor without problems. Why this happens, you can read in this article. Typically, chokes are included in the power circuits of amplifying devices. Chokes are designed to protect power supplies from high-frequency signals (RF signals) entering them. At low frequencies (LF) they are used in power circuits and usually have metal or ferrite cores. Below in the photo are power chokes:

There is also another special type of chokes - this. It consists of two counter-wound inductors. Due to counter winding and mutual induction, it is more efficient. Dual chokes are widely used as input filters for power supplies, as well as in audio technology.

Experiments with a coil

On what factors does the inductance of a coil depend? Let's do some experiments. I wound a coil with a non-magnetic core. Its inductance is so small that the LC-meter shows zero to me.

Has a ferrite core

I begin to insert the coil into the core to the very edge

The LC meter reads 21 microhenries.

I introduce the coil into the middle of the ferrite

35 microhenry. Already better.

I continue to insert the coil on the right edge of the ferrite

20 microhenry. We conclude the largest inductance on a cylindrical ferrite occurs in its middle. Therefore, if you wind on a cylinder, try to wind it in the middle of the ferrite. This property is used to smoothly change the inductance in variable inductors:

where

1 is the coil frame

2 are coil turns

3 - a core with a groove on top for a small screwdriver. By screwing in or unscrewing the core, we thereby change the inductance of the coil.

The inductance has become almost 50 microhenries!

And let's try to straighten the turns around the ferrite

13 microhenry. We conclude: for maximum inductance, the coil must be wound “turn to turn”.

Reduce the turns of the coil by half. There were 24 turns, it became 12.

Very little inductance. I reduced the number of turns by 2 times, the inductance decreased by 10 times. Conclusion: the smaller the number of turns, the lower the inductance and vice versa. The inductance does not change in a straight line to the turns.

Let's experiment with a ferrite ring.

We measure the inductance

15 microhenries

Separate the turns of the coil from each other

We measure again

Hmm, also 15 microhenries. We conclude: turn-to-turn distance plays no role in a toroidal inductor.

We wind more turns. There were 3 turns, it became 9.

We measure

Wow! I increased the number of turns by 3 times, and the inductance increased by 12 times! Conclusion: inductance does not change in a straight line between turns.

If you believe the formulas for calculating inductances, inductance depends on "turns squared". I will not post these formulas here, because I do not see the need. I can only say that the inductance also depends on such parameters as the core (what material it is made of), the cross-sectional area of ​​\u200b\u200bthe core, and the length of the coil.

Designation on the diagrams

Series and parallel connection of coils

At series connection of inductors, their total inductance will be equal to the sum of the inductances.

And when parallel connection we get like this:

When connecting inductances, the rule is that they be spaced apart on the board. This is due to the fact that if they are close to each other, their magnetic fields will influence each other, and therefore the readings of the inductances will be incorrect. Do not put two or more toroidal coils on one iron axle. This can lead to incorrect total inductance readings.

Summary

The inductor plays a very important role in electronics, especially in transceiver equipment. Various electronic radio equipment are also built on inductors, and in electrical engineering it is also used as a current surge limiter.

The guys from the Soldering Iron made a very good video about the inductor. I advise you to take a look at:

Inductor - a helical, spiral or helical coil of a coiled insulated conductor, which has a significant inductance with a relatively small capacitance and low active resistance. As a result, when an alternating electric current flows through the coil, its significant inertia is observed.

To increase the inductance, cores made of ferromagnetic materials are used: electrical steel, permalloy, fluxtrol, carbonyl iron, ferrites. Cores are also used to change the inductance of coils within a small range.

There are also coils whose conductors are implemented on a printed circuit board.

Inductor in an electric circuit it conducts direct current well and at the same time resists alternating current, since when the current changes in the coil, an EMF of self-induction arises, which prevents this change.

The main parameter of an inductor is its inductance, which determines what kind of magnetic field flux the coil will create when a current of 1 ampere flows through it. Typical values ​​of coil inductances are from tenths of µH to tens of H.

Losses in wires caused by three reasons:

· Winding wires have ohmic (active) resistance.

· The winding wire resistance increases with increasing frequency due to the skin effect. The essence of the effect is the displacement of current into the surface layers of the wire. As a result, the useful cross section of the conductor decreases and the resistance increases.

· In the wires of the winding, twisted into a spiral, the effect of proximity is manifested, the essence of which is the displacement of current under the influence of eddy currents and a magnetic field to the periphery of the winding. As a result, the cross section through which the current flows takes on a crescent shape, which leads to an additional increase in the resistance of the wire.

Dielectric loss (wire insulation and coil cage) can be classified into two categories:

· Losses from the dielectric of an interturn capacitor (interturn leakage and other losses characteristic of capacitor dielectrics).

· Losses due to the magnetic properties of the dielectric (these losses are similar to losses in the core).

In the general case, it can be seen that for modern coils of general application, the losses in the dielectric are most often negligible.

Core loss are the sum of eddy current losses, hysteresis losses and initial losses.

Eddy current loss . The current flowing through the conductor induces an emf in the surrounding conductors, for example, in the core, screen, and in the wires of adjacent turns. The resulting eddy currents become a source of losses due to the resistance of the conductors.

Varieties of inductors

Loop inductors . These coils are used in conjunction with capacitors to form resonant circuits. They must have high stability, accuracy and quality factor.

Communication coils. Such coils are used to provide inductive coupling between individual circuits and cascades. Such a connection makes it possible to separate the base and collector circuits by direct current, etc. There are no strict requirements for quality factor and accuracy for such coils, therefore they are made of a thin wire in the form of two windings of small dimensions. The main parameters of these coils are inductance and coupling coefficient.

Variometers.These are coils whose inductance can be changed during operation to rebuild the oscillatory circuits. They consist of two coils connected in series. One of the coils is stationary (stator), the other is located inside the first and rotates (rotor). When the position of the rotor relative to the stator changes, the value of the mutual inductance changes, and, consequently, the inductance of the variometer. Such a system makes it possible to change the inductance by a factor of 4–5. In ferrovariometers, the inductance is changed by moving the ferromagnetic core.

Chokes . These are inductors with high AC resistance and low DC resistance. They are used in power circuits of radio engineering devices as a filter element. For power networks with frequencies of 50-60 Hz, they are made on cores made of transformer steel. At higher frequencies, permalloy or ferrite cores are also used. A special kind of chokes are noise-suppressing ferrite barrels (beads) on wires.

Dual chokes two counter-wound inductors are used in power filters. Due to the counter winding and mutual induction, they are more effective for filtering common-mode interference with the same dimensions. Dual chokes are widely used as power supply input filters; in differential signal filters of digital lines, as well as in audio technology. Those. are designed both to protect power supplies from ingress of induced high-frequency signals into them, and to avoid clogging the power supply network with electromagnetic interference. At low frequencies, it is used in power supply filters and usually has a ferromagnetic (made of transformer steel) or ferrite core.

Application of inductors

· Inductors (together with capacitors and/or resistors) are used to build various circuits with frequency-dependent properties, such as filters, feedback circuits, oscillatory circuits, etc.

· Inductors are used in switching regulators as an element that stores energy and converts voltage levels.

· Two or more inductively coupled coils form a transformer.

· An inductor fed by a pulsed current from a transistor switch is sometimes used as a high voltage source of low power in low-current circuits, when creating a separate high supply voltage in the power supply is impossible or not economically feasible. In this case, high voltage surges occur on the coil due to self-induction, which can be used in the circuit, for example, by straightening and smoothing.

· Coils are also used as electromagnets.

· Coils are used as an energy source for excitation of inductively coupled plasma.

· For radio communications - the emission and reception of electromagnetic waves (magnetic antenna, ring antenna).

o Loop Antenna

o DDRR

o induction loop

· For heating electrically conductive materials in induction furnaces.

· As a displacement sensor: the change in the inductance of the coil can be varied over a wide range by moving (pulling out) the core.

· The inductor is used in inductive magnetic field sensors. Induction magnetometers were developed and widely used during World War II.

Efficient winding methods developed at our enterprise:

Allow to remove restrictions on the ranges of applied voltages, currents and temperatures. Reduce wire cross-section, cost and weight of coils under the same operating conditions. Or they allow you to increase voltages, currents and operating temperatures with the same wire cross section.

Our long-term researches have shown that the most effective way of cooling is air. The use of additional types of insulation is sometimes undesirable and worsens the properties of the windings. Instead of insulation, we use the division of the winding into sections. We strive to increase the area of ​​contact of the wire with powerful air flows.

1. Split winding.

The best alternative for additional insulation. The winding is divided into any number of sections connected in series. The potential between sections is divided by the number of sections. The potential between layers is divided by the number of sections times the number of layers. The potential between adjacent turns in one layer is divided by the number of sections multiplied by the number of layers and the number of turns in the layer. Thus, any dangerous breakdown voltage can be reduced to the electrical protective performance of an ordinary enameled wire without the use of special electrical insulating measures. The more individual sections, the better you can organize the cooling.

2. Non-contact winding.

The coils of the winding are suspended in the air on special braces. They do not have mechanical, electrical and thermal contact with any other materials of the coil, neither with the frame, nor with the body, nor with electrical insulation. The most efficient air cooling, heat and electrical insulation.

3. Body in the form of a snail.

We consider air to be the most effective way to cool the windings. The use of such a case with fans and a miscalculation of aerodynamic characteristics provides significant advantages.

4. Full-wave winding.

Everything new is well forgotten old. The division of the winding into two arms and switching on through the diode bridge gives the alternate switching on of the arms with the mains frequency. In one half-cycle, one shoulder works, the other rests. This allows the use of windings with a smaller cross section. A full-wave winding is especially relevant where it is required to place a very powerful winding with such a thick wire in small dimensions that it is impossible to bend at the required angles without damage. Or the industry does not produce such thick tires, and thus it is possible to switch to a smaller section.

5. Pipeline winding.

For work at especially high temperatures. As a wire, a copper pipe, circulating liquid, pumps, heat exchangers, coolers, tanks are used.

6. Filling with compounds with impurities based on boron nitride and others to increase the thermal conductivity of the compound. Or vibration-resistant stretching using special technical plates. It is used in complex vibro-impact modes of operation.

Our experts will develop the most effective way to solve your problems. We will be glad to cooperate with you.

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