What is Inductor, and what are the types of inductors?

 INDUCTORS

The electronic component (mostly a coil) which opposes the change of current in circuit is named an inductor. the power of the coil or inductor thanks to which it opposes the change of current flowing through it's referred to as its inductance. The inductance of an inductor can also be defined because the ability of an inductor (coil) to supply induced voltage when the present varies through it. The unit of inductance is henry which is known as after Henry . The schematic symbol of fixed and variable inductor.

An inductor may be a component which offers high impedance to a.c. but very low impedance (opposition) to d.c. the standard function of an inductor, within the electronic circuit, is to dam a.c. signal but to pass d.c. signal (or voltage). The variable inductors are utilized in tuning circuits (for changing the resonant frequency) for radio frequencies. These also are used for impedance matching.

TYPES OF INDUCTORS

The inductors, like resistors and capacitors, can be classified broadly as fixed and variable inductors.  The different types of inductors are available for different applications and are briefly described below:

1. Filter Chokes : A filter choke is an inductor used in the fiiter section of a d.c. power supply. It blocks the a.c. signal (voltage) and allows the d.c. signal (voltage)  to pass through it. A typical filter choke has  many turns of wire wound on an iron core.

The two major ratings of a filter choke are the inductance and current rating. Most of the power supplies use filter chokes having inductance ranging from about 1 henry to 50 henry, capable of carrying current upto 0.5 ampere.

2. Radio-Frequency Chokes : These are smaller  in size as compared to filter chokes. Air-core coils for RF applications have very small value of inductance.

For example, an RF coil for the radio broadcast band of 535 to 1605 KHz may have an inductance of 250 µH or 0.25 mH.

Variable Inductors

Variable inductors (or coils) are used in tuning circuits for radio frequencies. The winding is placed  over a fiber or ceramic former and to change the  inductance, a ferrite core is employed. By changing the position of screwed ferite core the inductance can be changed. 

Transformers

A transformer is just similar in appearance to an inductor (filter choke). Basically, it consists of two inductors (coils) having the same core. The coil to which supply is connected, is called primary winding and the coil to which load is  connected is called secondary winding. When an a.c. supply is applied to an e.m.f. is induced in the primary, secondary side. Thus, transformer is a static device which transfers power from one circuit (primary) to the other circuit (secondary). Depending upon the number of turns on and secondary primary side, a transformer may be step up (secondary turns > primary turns) or step down (secondary turns < primary turns). In electronic circuits, the transformers which are generally used are known as power transformers, output transformers and intermediate-frequency transformers.

1. Power Transformers : Power transformers are used to step-up and step-down the supply voltage as per requirement in vacuum-tube circuits (radio receivers). These are also employed in power supplies. 

2. Output Transformers : These are used, generally, in the radio receivers at the output stage for impedance matching i.e. at the output stage of power amplifiers. 

3. Intermediate Frequency Transformers : It is known as an intermediate frequency transfomer because it is used in the intermediate frequency amplifier section of radio and TV receivers. It consists of two windings placed on a fiber or ceramic former with air core. Generally, both the primary windings and secondary are tuned to the operating frequency by mica compression trimmer capacitors. In some IF transformers, ferrite lugs are used to tune the windings to the desired frequency.

TROUBLES IN INDUCTORS

The most common trouble in inductors is that it may open.

Checking of Inductor : The leads of the ohmmeter are connected across the inductor. The ohmmeter reads infinite resistance for  an open circuit. It does not matter whether the inductor is an air core or an iron core. When the inductor is  open, it cannot conduct current and therefore, has no inductance. The inductor should be disconnected from the circuit while checking otherwise any parallel path may affect the ohmmeter's resistance reading.