An inductor or wire coil that does not have a magnetic core is called an air core inductor.
In this article, we will discuss the air core inductor, its construction, working, formula of inductance, and applications. So let us start with the basic introduction of inductors.
What is an Inductor and its Types?
An inductor is an electric circuit component that stores electrical energy in the form of a magnetic field. A simple inductor is formed by twisting a wire of finite length into a coil. Thus, an inductor is made up of a conducting wire.
The property of the inductor by which it stores electrical energy in the form of a magnetic field is referred to as the inductance of the inductor. The inductance is usually denoted by the symbol L and is measured in Henry (H).
The circuit symbol of a typical inductor is shown in Figure 1. An inductor has a coil-form structure and it has a finite number of turns.
Based on the core used at the center of the inductor, there are several types of inductors such as air core inductors, iron core inductors, etc.
What is an Air Core Inductor?
An air core inductor is one that has no magnetic material as the core at the center of the inductor coil, rather it has free space, i.e. air as the core. Since air is considered a non-magnetic material, thus the air core inductor is a non-magnetic core type inductor.
These inductors are used in applications that require low inductance and a high frequency of magnetic reversal. In simple terms, an inductor coil without a magnetic core is termed an air-core inductor. These inductors provide a very low inductance. However, the presence of air in the core allows this type of inductor to operate at very high frequencies.
The circuit symbol of an air-core inductor is shown in figure-1
The air core inductors do not have any core losses (hysteresis loss and eddy current loss) because there is no magnetic core present. However, the number of turns in the inductor coil should be large to give a significant inductance. For this reason, the air core inductors demand high magnetomotive force (MMF).
Construction of Air Core Inductor
The construction of an air core inductor is quite simple. Rather, it is the simplest type of inductor. It is simply constructed by twisting a conductor wire of finite length into a coil as shown in figure 2.
The construction figure shows that an air core inductor has a gap (air) inside the winding.
Working of Air Core Inductor
When the terminals of this inductor are connected to a source of electric supply source, an electric current starts flowing through the turns of the inductor. Due to the magnetic effect of electric current, a magnetic field is established through the air gap.
As we know, the air is a poor conductor of the electric current and magnetic field, thus the air core inductor will have very low inductance. Hence, the magnetic field produced by this type of inductor is also weak.
Difference between Air Core Inductor and Solid Core Inductor
| Air Core Inductor | Solid Core Inductor |
| Lacks a solid core in the coil. | It has a solid core in the coil. |
| Smaller in size compared to a solid core inductor. | Larger in size. |
| Has a lower inductance value. | Has a higher inductance value. |
| More cost-effective than solid core inductors. | More expensive. |
Inductance Formula of Air Core Inductor
Let,
Then, the inductance of the air core inductor can be calculated using the following formula.
Also, we can determine the inductance of the air core inductor using the following formula,
Where N is the number of turns in the coil, A is the cross-sectional area of the coil, l is the mean length of the coil, and µ0 is the permeability of air = 4π × 10-7 H/m.
Air Core Inductor Example
Examples of air core inductors include:
- Audio Crossover Networks: Used in hi-fi speaker systems to minimize distortion.
- Radio Transmitters: Helps suppress harmonics.
- RF Tuning Coils: Found in radio and television receivers.
- Filter Circuits: Utilized in high-frequency applications.
- Snubber Circuits: Designed for high-frequency applications.
Advantages of Air Core Inductor
The following are the major advantages.
- The construction of this inductor is simple.
- This type of inductor is saturation-free.
- It has no core losses.
- It can be designed to operate at high frequencies.
- At high frequencies, it has no core losses or distortion.
- It is relatively inexpensive.
Disadvantages of Air Core Inductor
The following are the major disadvantages.
- This inductor requires many turns, which makes its size larger.
- t has a very low Q-factor.
- It cannot provide high values of inductance.
- It has low magnetic permeability.
Air Core Inductor Applications/Uses
The following are the important applications.
- These inductors are used in designing radio frequency (RF) tuning coils.
- These are essential for various applications, including computers, electronic gadgets, televisions, communication systems, mobile chargers, and DVDs.
- They are used in snubber circuits and filter circuits.
- They are used in radio and TV receivers.
- They are used for inter-stage coupling.
- These inductors are used to ensure low peak inductance.
- They are used in radio transmitters to reduce harmonic vibrations caused by electromagnetic interference.
Conclusion
Air core inductors are core-free inductors. These are suitable for such applications where low inductance is required, but they are supposed to function at high frequencies like in TV and radio receivers, and RF tuning circuits.
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