Inductor

The inductor is an element of an electrical circuit that contributes to the accumulation of magnetic field energy. With the use of products manufactured oscillatory resonant circuits. The coil is called because a wire is wound around the core reel. Often in radio engineering elements are called inductances. Fits the occasion, the designs sometimes a little resemble a coil.

The history of creating inductors

Inductors are wound with a fixed number of wires. This fact is hidden in the lessons of physics, avoiding the students scoring brains. Then the poor fellows guess, trying to catch the meaning of the term bifilar motor winding. There are more threads, they release inductors:

  • are trifilar;
  • tetraphilar;
  • pentafilar.

Conventional inductors are called unifilar - a single wire thread. Immediately a fair question arises - why constructions? The inventor of the inductor is unknown. Answers give, Tesla is guilty. .. Far from the truth.

Choke

One expert on Mail.ru - it’s possible, the admin of the resource - answered: Michael Faraday is the father of the inductors, allegedly opened magnetic induction( according to the English-language Wikipedia page).The conclusion suggests itself, the historian does not own the question. The main reason for criticizing “Answers” ​​Mile is incompetence. Faraday discovered induction by applying a toroidal transformer with two insulated windings. The design is much more complicated than the coil, the phenomenon was accompanied by the output of a current surge when the magnetic field of the core was changed.

Described in 1831, the first electromagnet was designed by William Sturgeon, a little-known in Russia. Do you know what the device looked like? That's right - an inductance coil of 18 turns of bare copper wire with a good varnished ferromagnetic horse-shaped horseshoe-shaped core. When passing through a current winding, iron in the area was attracted by the device. Historians consider 1824 to be the year when the first electromagnet was published. Earlier than Faraday began experiments.

Mentor Humphrey Davy considered plagiarism to work. The student did not dare to continue, to conflict openly. It turned out that in 1829 the untimely Humphrey Davy passed away, thanks to which Michael Faraday resumed work. We do not therefore consider as incorrect the runet’s meager information on the issue under consideration. The second reason lies in galvanometers: the first was designed on September 16, 1820 by Johann Schweiger. A year later, the great Ampère perfected the device, guess what was part of the novelty? That's right - an inductance coil composed of several turns of wire.

In 1826, Felix Savary discharged a Leyden jar through several turns of wire wrapped around a steel needle. Observing the residual magnetization of the metal. In fact, Savary created the first oscillating circuit, correctly drawing conclusions about the processes taking place.

Michael Faraday is powerless to become the inventor of inductance. Rather, the scientist worked in this direction, conducted some research, received a new law regarding electromagnetism. As a result, the question of the inventor of the inductor is left open. We venture to suggest that the subject has two fathers:

Laplace and Schweiger

  1. Laplace, on the basis of the report by Oersted, suggested that the effect of the current on the magnetic needle can be strengthened by bending the wire.
  2. Schweiger implemented what he heard in practice by creating the world's first galvanometer, using Ampere's reports on the dependence of the angle of deflection of the arrow on the amperage.

The design of the inductor

A circular magnetic field is created around a straight conductor with direct current. Tension lines resemble a spiral. Someone guessed to roll the wire into a ring so that the contribution of the elementary segments would be in the center. As a result, the magnetic field inside the structure is much higher than the outside. Lines are visually observed on iron filings. On Youtube, there are a lot of rollers, where current is passed through the inductance, demonstrating the orderly orientation of the metal dust at the moment of contact closure. The design is capable of storing a magnetic field for the future like a capacitor accumulating a charge. Coils are called inductances only, which contain the winding of varnished wire. In microstrip technology, the elements deposited for storing a magnetic field are logical to call inductances.

If in a coil, just like in the one used by seamstresses, arrange several turns of the wire one by one side by side so that the axis is common, the magnetic field strength lines are added. The simplest inductance capable of storing the energy of a magnetic field. With a sudden loss of voltage, the reverse-emf phenomenon is widely known to the technician. It is the cause of sparking collector engines. A lacquered( lacquered) copper wire of the desired cross section is used. The number of turns, the shape of the core are determined by preliminary calculations or by the existing sample.

Counter-EMF is parasitic, for extinguishing consistently with the coil include a larger size container, trying to underestimate the total reactance. The inductance impedance is entered with a positive sign, capacitance - with a negative one. Tesla invented the coil, took the patent. But the design was a flat spiral( labyrinth) with double winding. The scientist showed that inductance at the same time is characterized by significant capacitive resistance, with the disappearance of the voltage, the reverse EMF phenomenon does not manifest itself.

Bifilar coils are widely used today. As for the back EMF, it causes the ignition of discharge lamps( daylight).Let's return to the design. In the first electromagnet, the wire is bare, modern inductors are wound varnished. Thin insulation, if necessary, can be easily removed( for example, with toxic formic acid); in the initial state, it reliably protects the structure against short circuits.

Inside the coil is a core of ferromagnetic material. The shape is not important, the cross section is better to take. At high frequencies, the magnetic flux( see Voltage Converter) reaches the surface of the core, the meaning of using ferromagnetic alloys disappears, sometimes brass is used( even composite materials, dielectrics).Reduces inductance, at high frequencies, the power stored over a period is small. The trick is passing. Many have a question - why do we need a core?

The core of the inductor acts as a support, durable frame, strengthening the magnetic field. Induction is associated with the field strength through the constant magnetic permeability of the medium. In ferromagnetic materials, the parameter is truly large. Thousands of times more than air, most metals. With increasing frequency, the need for a core decreases, some negative effects occur, two of which are especially important:

Magnetic field lines formed by

  1. sawdust The alternating magnetic field induces eddy currents through which induction tiles function. Imagine the result: what kind of core heating will cause. The cores of power transformers are assembled from special electrical steel with high resistance, broken into thin sheets, mutually insulated with a layer of varnish. Charging will greatly reduce the influence of eddy currents.
  2. The second effect is called magnetization reversal. It takes energy field, causes the material to heat. The phenomenon is characteristic of ferromagnetic materials, eliminated by the use of brass.

The microstrip technology provides for the implementation of inductances in the form of flat spirals: the conductive material is sprayed onto the substrate through a stencil( a possible method).Reminds construction Nikola Tesla. The value of the inductance coil is very small, otherwise it is not necessary at microwave frequencies. The calculation is carried out according to special directories, although they are mainly used by design engineers.

For winding inductance make special devices, resembling a spinning reel. The core is put on the axis with the limiter on the sides, rotating the knob, the master carefully considers the number of revolutions, measures the desired length. Slowly, according to the method of the shuttle, the hand moves left-right, the turns exactly lie in sequence.

Why use bifilar inductors

Sometimes a coil is wound in two or more wire filaments. Tesla design applied to increase the capacitive qualities. As a result, it became possible to save materials - as mentioned above. Regarding the state at the present stage of technology development, the reason for creating bifilar coils may be the following:

Bifilar inductors

  1. One winding is grounded. Eliminates parasitic counter-EMF, causing sparks, some other negative effects. When the voltage drops abruptly, the magnetic field for the most part induces a current in the grounded winding, since the resistance of the circuit is the lowest. The effect of counter-emf is extinguished. In impulse relays, the auxiliary winding is short-circuited. The field energy is small, dissipated by the active resistance of copper in the form of heat.
  2. Tesla ideas are not forgotten. Often in the form of bifilar coils small resistors are manufactured. Resistance often have a similar structure. For example, the famous MLT, tape wound on a ceramic base. The idea is to increase the capacitance by compensating the inductance. The impedance of the resistor becomes purely active. The meaning of the event is great when working on alternating current. In the circuits of the constant imaginary part of the impedance( reactance) does not matter.
  3. In pulsed power supply units, the voltage of one polarity varies in amplitude. The bifilar transformer will allow to protect from the phenomenon of parasitic counter-emf, rescues the key transistor from breakdown. Additional winding is grounded through the diode, in normal mode does not affect the operation of the device. Counter-EMF has the opposite direction. As a result, the p – n junction opens, the potential difference is limited by direct voltage drop. For silicon semiconductor diodes, the value is 0.5 V. Clearly, the voltage can not penetrate the key transistor of almost any type.
  4. Tesla's ideas are used in the creation of perpetual motion machines( in the literature: CE - superunit devices, with efficiency higher than 1).The opportunity to eliminate the reactance is used to idealize the work process.

. Parameters of inductors.

. The main characteristic of coils is called inductance. Physical quantity, in SI, measured Gn( Henry), characterizing the magnitude of the imaginary component of the resistance of the structure. The parameter indicates how much magnetic field the coil will store. For simplicity, the period energy is considered proportional to the product of LI2, where L is the inductance, and I is the current flowing in the system.

Inductance Calculation Formula

The theoretical calculation of the main parameter of the coils is strongly defined by the design. Special methodological aids are issued, the formula( see figure: S is the winding cross-sectional area, l is the coil length, N is the number of turns of the wire, in the formula is the magnetic constant and magnetic permeability of the core) shown in the picture, a particular variant. When inductance resembles a coil. There are special programs for the personal computer that simplify the process.

The secondary parameters of inductors include:

  • Quality factor. Characterizes the loss of active resistance.
  • Own inductance( see above).
  • Temperature stability parameters.
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