The Different Types of Inductors and Their Affecting Factors

Different types of inductors are available based on sizes and ratings. Their physical sizes vary from tiny sizes to the huge transformer, depending on the power being handled and the frequency of AC being used. As one of the basic components used in electronics, inductors are extensively used in much wider application areas like signal controlling, noise elimination, voltage stabilization, power electronic equipments, automobile operations etc. Now a day’s, improvement of inductor design techniques enhances significant performance on rest of the circuit.

Types of Inductors

A diverse electronic component used in a wide range of applications requires various types of inductors. These are of different shapes, sizes including the wire wound and multilayer inductors. Different types of inductors include high-frequency inductors, power supply line inductors or power inductors and inductors for general circuits. Differentiation of the inductors is based on the type of winding as well as the core used.

• Air Core Inductors

  

In this type of inductor, core is completely absent. These inductors offer high reluctance path for the magnetic flux, hence less inductance. The air core inductors have larger coils to produce higher flux densities. These are used in high frequency applications including TV and radio receivers.

• Ferro Magnetic or Iron Core Inductors

Due to their higher magnetic permeability these have high inductance property. These are high power inductors but limited in higher frequency capacity due to the hysteresis and eddy current losses.

Transformer designs are the examples of this type.

• Ferrite Core Inductors

  

These are the different types of inductors which offer advantages of decreased cost and low core losses at high frequencies. Ferrite is a metal oxide ceramic based around a mixture of Ferric Oxide Fe2O3. Soft ferrites are used for the core construction to reduce the hysteresis losses.

• Toroidal Core Inductors

In these inductors, a coil is wounded on a toroid circular former. Flux leakage is very low in this type of inductor. However special winding machines are required to design this type of inductor. Sometimes ferrite core is also used to decrease the losses in this design.

• Bobbin based Inductors

  

In this type, coil is wounded on the bobbin. Bobbin wound inductor designs vary widely in terms of power rating, voltage and current levels, operating frequency, etc. These are mostly used in switch mode power supplies and power conversion applications.

• Multi Layer Inductors

A multilayer inductor contains two conductive coil patterns which are arranged in two layers in the upper part of a multi-layered body. The coils are connected electrically in a consecutive manner in series to two more conductive coil patterns disposed in the lower part of the multi-layered body. These are mainly used in mobile communication systems and noise suppression applications.

• Thin Film Inductors

  

These are completely different from the conventional chip-type inductors wound with copper wire. In this type, tiny inductors are formed using thin-film processing to create the chip inductor for high-frequency applications, which ranges from about nano Henry.

How Inductor Works?

An inductor is often referred to as AC resistor. It resists the changes in the current and stores energy in the form of the magnetic field. These are simple in construction, consisting of the coils of copper wire wounded on a core. This core might be magnetic or air.  Different types of inductors can be used in advanced applications like wireless power transfer.

Magnetic cores may be toroidal or E-type cores. Materials like ceramic, ferrite, powered iron are used for this core. The coil carrying the electric current produces the magnetic field around the conductor. More magnetic lines are produced if the core is placed inside the coil, provided high permeability of the core is used.

The magnetic field induces EMF in the coil which results in flow of current. According to Lenz’s law, the induced current opposes the cause, which is the applied voltage. Hence inductor opposes the change in input current that leads to change in the magnetic field. This reduction of the current flow due to the induction iscalled inductive reactance. Inductive reactance will increase if the number of turns in the coil is increased. It also stores the energy as magnetic field through charging and discharging processes and releases the energy while switching the circuit. Application areas of inductors include analog circuits, signal processing, etc.

Factors affecting the Inductance of an Inductor

Capability of producing magnetic lines is referred as inductance. Standard unit of inductance is Henry. The amount of magnetic flux developed or inductance of different types of inductors depends on four basic factors discussed below.

• Number of turns in a coil

If the number of turns are more, larger amount of magnetic field is produced, which results in more inductance. Fewer turns result in less inductance.

• Material of the Core

If the material used for the core has high permeability, more will be the inductance of an inductor. This is because high permeability materials offer the low reluctance path to the magnetic flux.

• Cross section area of the Coil

Greater cross section area results in greater inductance because this offers less opposition to the magnetic flux in terms area.

• Length of the Coil

Longer the coil less will be the inductance. This is because, for a given amount of the field, force opposition to the magnetic flux is more.

Fixed inductor doesn’t allow the user to vary the inductance once it is designed. But it is possible to vary the inductance using variable inductors by varying the number of turns at any given time or by varying the core material in and out of the coil.

Power loss in an Inductor

Power dissipated in inductor is mainly due to the two sources: inductor core and the windings.

Inductor core: Energy loss in inductor core is due to the hysteresis and eddy current losses. Magnetic field applied to the magnetic material is increased, goes to the saturation level and then decreases. But while decreasing it doesn’t traces the original path. This causes the hysteresis losses. Smaller value of the hysteresis coefficient of the core materials results in the low hysteresis losses.

The other type of core loss is eddy current loss. These eddy currents are induced in the core material due to the rate change of magnetic field according to the Lenz’s law. Eddy current losses are much less than the hysteresis loss. These losses are minimized by using the low hysteresis coefficient materials and laminated core.

Inductor Windings: In inductors, losses occur not only in the core, but also in the windings. Windings have their own resistance. When the current passes through these windings, heat losses (I^2*R) will takes place in the windings. But with increasing frequency, winding resistance increases due to the skin effect. Skin effect causes the current to concentrate on the surface of conductor than centers. So the effective area of the current carrying area decreases.

Also eddy currents induced in the windings causes the current to be induced in the neighboring conductors which is called proximity effect.

Due the overlapping conductors in the coils, proximity effect causes to increase the resistance of the conductor higher than in case of the skin effect. Windings losses are reduced with the advanced winding technologies like shaped-foil and litz wire windings.

I hope my article has been informative and intriguing. So here is basic question for you –What is the role of inductors in electrical circuits?

Please give your answer in the comment section below. You are also free to share your perceptions about this article and ideas.

Photo Credits:

Different Inductors by 1.bp.blogspot
Ferro magnetic or iron core Inductors by agilemagco
Ferrite core inductors by falconacoustics
How inductors work by dw-inductionheating
Inductor winding by stonessoundstudio