Iron Core Inductor : Construction, Formula, Working & Its Applications

Inductors are used for the conversion of electrical energy in almost each power electronics circuit. These are active energy storage devices, used to provide stored energy in between different operating modes within a circuit. In addition, they can also work as filters, especially for switched current waveforms & also provides transient current limiting within snubber switches. Inductors are classified into different types depending on the specific materials & construction methods where every type of inductor has some benefits. So this article discusses one of the types of inductors like iron core inductor – working with applications.

What is Iron Core Inductor?

The fixed value inductor in which an iron core is used within the coil to increase the inductance value of an inductor is known as an iron core inductor. These inductors have a very low inductance value and the iron core of this inductor has very unique magnetic characteristics which strengthen the magnetic field. The iron core inductor symbol is shown below.

Iron Core Inductor Symbol
Iron Core Inductor Symbol

Iron Core Inductor Construction

The iron core inductor is designed with a conducting material coil-like insulated copper wire by wrapping around an iron core. This conducting material simply helps in amplifying the magnetic field of the inductor by making the inductor better at storing magnetic energy as compared to an air core inductor with the same number of turns.

In a conventional design, an iron core would wire around a geometric shape that encloses a helically constructed coil. Wires often include materials such as nickel nickel-iron alloys, magnesium, and cadmium. These wires are used in size ranges from 0.014 to 0.56mm, depending on the applications’ current levels and range of frequencies covered by the inductive component. The quantity of interwinding turns determines the electrical induction within the wire conductor system that is produced when voltage is applied across the component windings. 

A Traditional design of a magnetic core inductor utilizes an iron core and ferrite material that is wrapped with magnetic circuits to provide the desired inductance. A typical iron-core design consists of a geometry in which two or more parallel cylindrical partitions are wound most likely on a mandrel and then coated with an epoxy resin to create the necessary magnetic barrier around the inside of the cylindrical spaces. This longitudinal winding is usually connected to form a closed loop corresponding to the length of our core material pi.


Iron Core Inductor Construction
Iron Core Inductor Construction

Working Principle

The working principle of an Iron core inductor is based on the property that magnetic induction is proportional to the rate of change of magnetic flux through a circuit. So when an alternating current is passed through an iron-based one-turn coil the magnetic field of electricity in the coil tries to push past the axis which results in the eddy currents formed within the metal.  These currents create a magnetic field that acts against the primary, resulting in an opposite magnetic polarity and thus canceling out voltage from leaks in wires. The more turns there are in a coil and its resistance the more powerful this canceling effect is. This is why high amounts of electrical power can be fed into iron core conductors without any damage caused.


In addition, when the core is moved inside and outside of the wire coil, it can change the inductance. As compared to air core inductors, these inductors are superior at storing magnetic energy because the iron material assists in amplifying the magnetic field of an inductor.

Iron Core Inductor Vs Air Core

The differences between the iron core and air core inductors include the following.

Iron Core Inductor

Air Core Inductor

Iron core inductors utilize magnetic cores of ferrite/ iron.


Air core conductors may utilize ceramic, plastic, or other nonmagnetic materials; otherwise, they only have air within the windings.
These inductors have large inductance values. Air core inductors have low inductance values.
These inductors are superior in storing magnetic energy. These inductors are not superior in storing magnetic energy.
These inductors have normally some core loss.


These inductors are very efficient at high frequencies, so they don’t suffer from core loss.
These are large in size. These are small in size.
The inductors operate at up to several hundreds of MHz (megahertz) The inductors operate at up to 1GHz frequency.
These are frequently used in low-frequency-based applications like audio devices, power supplies in industries, inverter systems, etc. These are frequently used in high-frequency-based applications like TV & radio receivers.


Iron Core Inductor Formula

In the inductor, if the rod used is magnetic like iron or ferrite then it will increase the inductor’s inductance. Similarly, if the rod used is non-magnetic like copper or any other material, then it will decrease the inductor’s inductance. The formula for inductance calculation is;

L = µ0 µr N^2A/l


‘N’ number of turns.
‘l’ length.
‘µ0’ is the permeability of free space.
‘µr’ is relative permeability.
‘µr’ for iron is greater than 1 (>1)
‘µr’ for copper is less than 1 (<1)
‘A’ is an area of the coil.

How To Choose a Iron Core Inductor ?

Inductors have different properties & functions based on their shape, core material, or use. So, one should be aware of these functions & properties in order to select the correct inductor for a specific application. Thus, there are many factors that need to consider while selecting an iron core inductor like the performance of an inductor, requirements of the circuit, RF considerations, size and shielding of an inductor, percentage of tolerance, etc. So the factors which affect the inductance should be taken into consideration.

Affecting Factors

In any type of inductor, there are some factors that affect the inductance of the coil that are discussed below.

Number of Turns within the Coil

If the number of turns within the coil is more then the magnitude of inductance will be higher.

Length of Coil

When the coil length is longer, then the magnitude of the inductance will be smaller.

Core Material

If the magnetic permeability of the core material is greater, then the inductance will be greater.

Advantages and Disadvantages

The advantages of iron core inductors include the following.

  • These inductors have fewer losses.
  • Its size and construction are simple.
  • This type of inductor has a high Q-factor.
  • These inductors have a large inductance value.

The disadvantages of iron core inductors include the following.

  • In these inductors, the loss increases at high frequencies.
  • This inductor has complicated isolation.
  • These inductors have more eddy current & also harmonic current rating.


The applications of iron core inductors include the following.

  • These inductors are used in filter circuits to stabilize the ripple voltage.
  • It is extremely useful within AF applications & industrial power supplies.
  • These can be used as AF choke within fluorescent tube lights.
  • These are used in inverter systems.
  • These are used in rapid transit & power conditioning.

Thus, this is an overview of an iron core inductor – working with applications. Generally, many inductors include a magnetic core that is made with iron or ferrite arranged in the coil. The effect of the iron core in the inductor is to increase the magnetic field & thus the inductance. The inductance values of these inductors are very high because of their iron core. So they can handle maximum power although they are limited within high-frequency capacity. These are mostly used in low-frequency-based applications like audio equipment. Here is a question for you, what is an air core inductor?