An inductor is an inductor of a specific design and rating intended for installation in electrical and electronic circuits. The electric choke must be distinguished from the analog used in electronic devices, taking into account their design features. To understand what the differences are between these two products, you will have to familiarize yourself with the principle of operation and the existing varieties.
Principle of operation
The principle of operation of chokes in an electrical circuit can be explained as follows:
- when alternating current flows through the inductive element, the rate of its rise slows down, which leads to the accumulation of energy in the magnetic field of the coil;
- this is explained by the action of Lenz's law, according to which the current in an inductance cannot change instantly;
- violation of this rule would lead to an unacceptable increase in tension, which is physically impossible.
Another distinctive feature that explains the principle of operation of inductance is the self-induction effect, theoretically substantiated by Faraday. In practice, it manifests itself as guidance in the coil of its own EMF, which has the opposite polarity. Due to this effect, a current begins to flow through the inductance, preventing the growth of the field formation that caused it.
This property allows the use of inductive elements in electrical engineering to smooth out low-frequency pulsations. For them, inductance appears to be a lot of resistance.
Used in other technical areas (in high frequency devices, for example) the choke provides decoupling of the main electronic circuit from the auxiliary (low frequency) circuits.
Specifications
The main technical parameter of a choke in electrical engineering and electronics, which fully characterizes its functionality, is the value of inductance. In this way, it resembles a conventional coil used in various electrical circuits. In both cases, Henry is taken as the unit of measurement, designated as Mr.
Another parameter that describes the behavior of an inductor in various circuits is its electrical resistance, measured in ohms. If desired, it can always be checked using a conventional tester (multimeter). To complete the description of the operation of this element, you will need to add the following indicators:
- allowable (limiting) voltage;
- rated bias current;
- the quality factor of the contour formed by the coil.
The specified characteristics of the chokes make it possible to diversify their assortment and use them to solve a variety of engineering problems.
Varieties of chokes
By the type of electrical circuits in which the choke elements are installed, the classification is as follows:
- low frequency inductors;
- high frequency coils;
- chokes in DC circuits.
Low-frequency elements outwardly resemble a conventional transformer, which has only one winding. Their coil is wound on a plastic frame with a transformer steel core placed inside.
The steel plates are reliably insulated from one another to reduce the level of eddy currents.
LF choke coils usually have a high inductance (more than 1 H) and prevent the passage of currents of mains frequencies of 50-60 Hertz through the sections of the circuits where they are installed.
Another type of inductive product is high-frequency chokes, the turns of which are wound on a ferrite or steel core. There are varieties of HF products that work without ferromagnetic bases, and the wires in them are simply wound on a plastic frame. With sectional winding, used in mid-range circuits, the turns of the wire are distributed in separate sections of the coil.
Electrical products with a ferromagnetic core are smaller than simple chokes of the same inductance. For operation at high frequencies, ferrite or dielectric cores are used, which differ in their low intrinsic capacitance. Such chokes are used over a fairly wide frequency range.
Some of them are made in the form of thick twisted wire, which does not have a frame at all.
A DC choke is mainly used to smooth out ripples that appear after it has been rectified in special circuits.
Application of inductive elements and their graphic designation
Electric chokes operating in AC circuits are traditionally used in the following cases:
- for decoupling the secondary circuits of switching power supplies;
- in flyback converters or boosters;
- in ballast circuits of fluorescent lamps, providing quick start;
- for starting electric motors.
In the latter case, they are used as inrush and braking current limiters.
Electrical products installed in electric drives with a power of up to 30 kW resemble a classic three-phase transformer in appearance.
Power supplies with such elements are still found in electrical engineering. To start fluorescent lamps, "electronic" ballast is increasingly used, gradually replacing winding products. Its use is explained by the following advantages:
- low weight;
- operational reliability;
- no hum characteristic of conventional chokes.
To designate a choke on electrical and electronic circuits, icons are used, which are a piece of a twisted conductor. For coils with a core, a dash is additionally placed inside the winding, but in the frameless version it is absent.
