In AC circuits, chokes, that is, inductive reactances, are used to limit the load current. Such devices provide significant energy savings, do not allow overload and excessive heating.
A choke is one of the types of inductors, the main purpose of which is to delay the influence of current on a specific frequency range. Moreover, a sharp change in the current strength in the coil is impossible, since the law of self-induction works, as a result of which additional voltage is created. Let us consider in detail the principle of operation, types and purpose of chokes.
Purpose
Many are interested in what a throttle is and how it looks. The device is made in the form of an iron transformer, the only difference is the presence of one winding. The coil is wound on a transformer steel core, with the plates separated and not in contact with each other in order to reduce eddy current.
Electronic choke characterized by a high level of inductance up to 1H, the coil effectively counteracts current changes in the electrical circuit. When the current decreases, the coil maintains it, and in the event of a sharp increase, the coil provides limitation and prevention of a sharp jump.
Considering what a throttle is for, the following goals should be named:
- interference reduction;
- smoothing of electric current ripples;
- accumulation of energy in a magnetic field;
- separation of parts of the circuit at high frequency.
Why do you need a throttle? Its main purpose in the electrical circuit is to delay the current of a specific frequency range on itself or to store energy in a magnetic field.
The importance of the choke is explained by the fact that fluorescent discharge lamps (eg household lamps, street lights) do not function without a choke. It acts as a voltage limiter applied to the electrodes of the discharge lamp.
Also, throttling devices form the starting voltage required to create an electrical discharge between the electrodes. This ensures that the fluorescent lamp is switched on. The starting voltage is designed for only a fraction of a second. Thus, the choke is a device responsible for turning on the lamp and its stable operation.
Principle of operation
The electronic choke has a simple configuration and a clear operating principle. It is a coil of electrical wire, which is wound on a core of a special ferromagnetic material. The principle of operation is based on the self-induction of the coil.When considering the design of the inductor, it becomes clear that it works like an electrical transformer, with only one winding.
The core and ferromagnetic plates are insulated to prevent Foucault currents from causing significant interference. The coil has a large inductance, and directly acts as a protective fence during sudden voltage surges in the network.
However, this design is considered low-frequency. Alternating current in household networks fluctuates over a wide range, so fluctuations are divided into three categories:
- low frequencies within 20Hz-20kHz;
- ultrasonic frequencies from 20 kHz to 100 kHz;
- ultra-high frequencies over 100 kHz.
In high-frequency devices, a core is not provided; plastic frames or standard resistors are used instead. And the throttle itself in this case has a multilayer winding configuration.
In the process of calculations and drawing up diagrams, how to connect the inductor, its parameters and the characteristics of the network in which it is necessary to maintain the operation of the lamps are taken into account. When connecting, special attention must be paid to the stage when the lamp begins to glow, when it is necessary to break through the gaseous medium by means of a discharge. At this point, a high voltage is needed, and after that the device acts as a voltage-restraining element.
Main characteristics
For the most part, chokes have significant dimensions. To make devices compact without compromising performance, the inductor is replaced by a stabilizer, which is essentially a powerful transistor. The result is an electronic throttle.However, this type of device is a semiconductor, so it is not advisable to use it in high-frequency devices.
An electronic choke must be selected according to several parameters, the main of which is the inductance, measured in H. Also important technical characteristics of the devices are:
- resistance, which is taken into account at direct current;
- voltage change within acceptable limits;
- bias current - the nominal value is used.
When choosing a device, first of all, it is necessary to focus on goals and objectives, for which a choke is needed in circuit diagrams. The use of magnetic cores in electric chokes makes it possible to ensure the compactness of devices while maintaining the same inductance values. Ferrite and magnetodielectric compositions, due to their low capacitance, can be used in wide frequency ranges.
Varieties of chokes
The following types of electric chokes are distinguished, based on the types of lamps in which they are used:
- single-phase - suitable for household and office lighting systems that operate on a 220 volt network;
- three-phase - designed for networks of 220 and 380 volts. Such chokes are suitable for DRL and DNAT lamps.
The electronic choke may belong to one of the categories depending on the installation location:
- embedded or open. They are mounted in the luminaire housing, which provides protection from external factors;
- closed - differ in tightness and moisture protection. Such devices can be installed outdoors in open areas.
Depending on the purpose, the chokes are divided into types:
- alternating current. They are used to limit the voltage in the network, for example, at the time of starting an electric motor or impulse IVEP;
- saturation. Mainly installed in voltage stabilizers;
- smoothing - to reduce the ripple of the rectified current;
- magnetic amplifiers. Such inductors assume the presence of a magnetizable core due to the presence of direct current in the network. When adjusting its parameters, you can change the values of inductive resistance.
Throttles can maintain their performance over a long service life if used correctly. The device is designed to limit sudden power surges, which allows you to secure both devices and the entire network.
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