The inductors (also called as a coil or choke) is a passive two-terminal electrical component that stores magnetic energy when an electric current is passed through it. It’s an insulated wire wound into a coil around a core of some material (air, iron, powdered iron, or ferrite material) in a spiral form.
The inductor is denoted by inductance ‘L’ and the measuring unit is Henry (H). Inductors have values that typically range from 1 µH to 2000 mH.
When the time-varying current flows through an inductor, the magnetic field is created which induces an electromotive force (e.m.f.) (voltage) in the inductor. Voltage V, across an inductor of inductance L, is given by:
V = L di/dt
That is, there is a voltage across the inductor only if the current through it is changing; DC produces no voltage through an inductor. In general, inductor blocks the AC and passes the DC.
The energy stored in an inductor with value ‘L’ Henries is given by;
E = 1/2 Li² energy E is in Joules, and I is in ampere.
An ideal inductor has zero resistance and zero capacitance. However, real inductors have a small value resistance associated with the winding of the coil and whenever current flows through it, energy is lost in the form of heat.
Application of inductors
- In buck/boost power regulators
- In filter circuits in DC power supplies
- Isolating signals
- In transformer to step up/down the AC voltage level
- In oscillator and tuning circuits
- For generating voltage surges in fluorescent lamp sets
Types of inductors
Inductors are mainly classified depending on the core material used and operating frequency. The following are the different types of inductors and available in through-hole as well as SMD package based on the construction.
- Iron cored inductors
- Air cored inductors
- Powdered iron cored inductors
- Ferrite cored inductors
- Variable inductors
- Audio frequency inductors
- Radio frequency inductors
Inductor selection parameters
While selecting an inductor in any circuit user needs to take care of the following parameter apart from the application/usage.
- Inductance value
- Maximum current rating
- Shielded and non-shielded
- Q ratings
- Frequency range
- The resistance of the inductor
- Type of core used
Manufacturers: Murata, TDK, Bourns Inc., Abracon Electronics, AVX corporation, Schaffner, Signal Transformer, etc.