Inductors are passive electronic components that store electrical energy in a magnetic field when current flows through them. There are various types of inductors designed for specific applications. Here are some common types of inductors.
Air Core Inductor
Construction
- An air core inductoris an inductor formed by winding several turns of enameled wire around a non ferromagnetic cylinder. The cylinder may be made up of simple cardboard. It is possible to remove the cylinder after the wire is wound around the core.
- Since there is the air inside the cylinder, the inductor is called air core inductor.
Applications
- It is used for IF & RF tunning coil.
- It is used for coupling.
Advantages
- The inductance is independent of the electrical current, because there is no ferromagnetic core to be saturated as the current increases.
- There are noiron losseswhich affect ferromagnetic cores, then you can get betterQ Factorand lower distortionas frequency increases.
- They can be used to operate well up to frequencies about 1 GHz.
Iron Core Inductor
Construction
- Iron-core inductors use a magnetic core made of a ferromagnetic or ferrimagnetic material such as iron or ferrite to increase the inductance.
- A magnetic core can increase the inductance of a coil by a factor of several thousand, by increasing the magnetic field due to its higher magnetic permeability.
Applications
- It is used in filter circuits.
- It is used in fluorescent tubes.
- It is used in RF applications.
Ferrite Core Inductor
Construction
- For higher frequencies, inductors are made with cores of Ferrite is a ceramic ferrimagnetic material that is nonconductive, so eddy currents cannot flow within it.
- The formulation of ferrite is xxFe2O4where xx represents various metals. For inductor cores soft ferrites are used, which have low coercivity and thus low hysteresis losses.
Applications
- It is used in High and Medium frequency.
- It is used in ferrite rod antenna.
Slug Tuned Inductor
Construction
It is a variable inductor. The value of inductance increases when slug is moved into the coil winding and it decreases when slug is moved out of coil winding. The slug can be moved by the screw driver.
Applications
It is probably used inbandpass filters in the intermediate frequency (IF) section of radio receivers to filter out interference from radio stations near in frequency to the desired station.
Colour Codes of Inductor
For Four bands Inductor
Band | 1 | 2 | 3 | 4 |
Meaning | 1stDigit | 2ndDigit | Multiplier (No. of zeros) | Tolerance % |
Black | 0 | 0 | x1 (No Zeros) | +/-20% |
Brown | 1 | 1 | x10 (0) | |
Red | 2 | 2 | x100 (00) | |
Orange | 3 | 3 | x1000 (000) | |
Yellow | 4 | 4 | x10000 (0,000) | |
Green | 5 | 5 | ||
Blue | 6 | 6 | ||
Violet | 7 | 7 | ||
Grey | 8 | 8 | ||
White | 9 | 9 | ||
Gold | x 0.1 (divide by 10) | +/-5% | ||
Silver | x 0.01 (divide by 100) | +/-10% |
Note: If no Band 4 is used, tolerance is +/-20%.
Summary
- Air Core Inductors:
- Core Material: None (air).
- Characteristics: Air core inductors have no magnetic core; instead, they rely on the surrounding air for the magnetic field. They are lightweight and have low inductance values. These inductors are used in applications where high Q-factor (quality factor) and minimal magnetic interference are essential.
- Ferromagnetic Core Inductors:
- Core Materials: Iron, ferrite, or other magnetic materials.
- Types:
- Iron Core Inductors: Iron core inductors are relatively common and provide moderate inductance values. They are used in various electronic applications.
- Ferrite Core Inductors: Ferrite cores are commonly used in high-frequency applications due to their ability to operate at elevated frequencies while minimizing energy losses.
- Laminated Core Inductors:
- Core Material: Thin layers of magnetic material laminated together.
- Characteristics: Laminated cores reduce eddy current losses in high-frequency applications. The laminations are insulated from each other to prevent the circulation of eddy currents that can result in energy losses and heat.
- Toroidal Inductors:
- Core Shape: Toroidal (doughnut-shaped).
- Characteristics: Toroidal cores offer high inductance with low electromagnetic interference. They are commonly used when a compact and efficient design is required, such as in power supplies and audio equipment.
- Bobbin Wound Inductors:
- Core Construction: Wound on a bobbin (spool).
- Characteristics: These inductors are commonly used in power supplies and transformers. The winding is often done around a magnetic core material, and the bobbin helps in holding the wire in place.
- Variable Inductors:
- Core Construction: Typically air or ferrite core.
- Characteristics: These inductors have an adjustable core or winding, allowing for the variation of inductance. They are used in tunable circuits where the inductance needs to be adjusted.
