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About coils and chokes
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Structure and function of the components
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Where are coils and reactors used?
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What was to be considered when purchasing?
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Bottom line
Structure and function of the components
Simple coils consist of a copper wire , which is often wound in such a way that the windings are close together . It flows into two contacts at both ends, with which the coil is connected in the circuit.
If a current is applied to the coil, a multi-overlapping magnetic field is created around the wound conductor, which depends on the dimensions, current and number of windings of the coil. The more windings are located next to each other in as small a space as possible, the more the magnetic field of the individual conductors overlaps and the larger the accumulated field of the coil. It is also referred to as a higher inductance of the coil .
This phenomenon is called self-induction and can be used many times. If current is applied to the coil, it first builds up its magnetic field before it forwards the current. If a current is applied to a circuit with built-in inductance, an induction voltage is generated in the coil caused by the self-induction of the coil. This voltage depends on the change in current and inductivity of the coil. It is counter-directed to its origin, i.e. the applied voltage, and thus ensures that the current in the circuit is not abrupt but slowly activated t. The same is true for a drop in current. The current does not fall radically, but decreases gradually. For alternating current with constant voltage change, a coil acts as an inductive resistor , which provides a phase shift in which the current is trailing the voltage.
The inductance of the coil and thus the strength of the effect depend on several factors. This includes not only the number of windings and the dimensions of the coil, but also the material inside the component. The wire is often wound around a ferromagnetic material, i.e. magnetizable. These are often iron, but zinc can also be used as an example. This increases the inductance compared to a so-called air coil, which does not require such a Kern. This means fewer turns are needed, was the result of which the costs were reduced. However, at high AC frequency or high current, a Kern coil may "saturate" . This ensures that Kern loses its effect and that the inductance drops considerably. The advantage of air coils is that their inductance is always constant.
The inductance is therefore a compact summary of the electrical properties of a coil and combines all these properties as one value. This ensures easy comparability.
Apart from self-induction, a foreign production can also be generated. If two coils are held together and one current is applied to one of them, an induced current can be measured for the other coil. This effect can be used for wireless transmission of current, such as inductive charging of cars or for transforming current to lower or higher voltages.
There are also different types of inductors. There are both round wound toroidal coils and rod coils , where the wire is placed around a cylindrical Kern. Conrad SMD coils can also be mounted directly on the PCB. These are suitable for different applications.
Where are coils and reactors used?
The application area of coils and chokes is very diverse. Reactors are used in AC power networks for reactive power compensation. They compensate for the reactive power that is caused by capacitive loads, for example caused by earth cables. The reactor acts as a reactive resistor . . It can therefore also be used to deliberately cause a phase shift in which the current of the voltage is behind.
Coils also occur in transformers. If two coils are installed in parallel, the voltage is transformed in relation to the two wind numbers. If the primary coil has 50 windings and the secondary 100, the voltage is doubled.
The principle of external induction is also used for ignition coils. The secondary coil has a significantly higher number of windings, so that a low voltage is transformed into a very high voltage, which is used to generate sparks. This can ignite gas that is leaking.
Coils are also used in oscillating circuits. There, energy is periodically exchanged between a capacitor and a coil. Such oscillating circuits are used in radio or radio technology, for example, to select certain frequencies and are also known as LC elements. Similar circuits also occur in high-pass filters and are used to filter certain frequencies.
What was to be considered when purchasing?
Which coil is best suited for you depends on the application area in which it is to be used. In order to find the perfect component for your application, it is worth paying attention to some key data.
Depending on how the reactor is manufactured – how many windings it has, from which the ferromagnetic Kern is made or which conductor cross-section the wire has – it has a different high inductance . The height of this value is decisive for the reactor. If you need a reactor in your circuit, you should calculate the inductance that you must have and then select the correct component from Conrad. The unit for inductance is Henry.
For this purpose, refer to the on the product page for the nominal current and nominal voltage for which the respective coil is designed. This is the maximum current value that can be passed through the coil. This value must not be exceeded, otherwise the copper wire will overheat and the component will be damaged. There is a risk of fire.
It is also worth paying attention to the ohmic resistance (R in Ohm) of the coil. This is the resistance of the copper wire. This limits the maximum nominal current and ensures, for example, that the phase shift does not succeed by exactly 90 degrees in the AC circuit. In transformers, it ensures efficiency losses. It should therefore be as small as possible.
SMD inductors are recommended for PCB mounting. SMD stands for surface mounted device and refers to coils that have been specially designed for this purpose.
Bottom line
The inductive effect of coils and reactors can be used in many ways with alternating and direct current. From the transformer to the phase shift in alternating current to the crossover, there are many different areas of application. Conrad has the right component for every application.