What is an Inductor?
An inductor is an electronic device that stores electrical energy when current flows through it, in the form of a magnetic field. inductor is made of a coil of conducting wire, usually made of copper and wound around a core, which can be air, iron, or ferrite.
The main function of an inductor is to resist sudden changes in current. L is the symbol of an inductor in a circuit diagram, and its unit is Henry (H). Inductors play an important role in power management, noise filtering, signal integrity, and electromagnetic interference (EMI) suppression.
Inductor Working Principle
An inductor works on the principle that it stores energy in the form of a magnetic field when an electrical current passes through it. This behaviour is governed by Faraday’s Law of Electromagnetic Induction and Lenz’s Law.
Resistance against the sudden change in current makes the inductor useful for filtering and smoothing electrical signals.
The voltage across the inductor is derived by the formula:
V(L) = L (dl/dt)
Where:
V(L) is the voltage across the inductor.
L is the inductance (Henrys)
dl/dt is the rate of change of current
Types of Inductors
Inductors are classified based on the core material, construction, and application. Following are the types of inductors:
1. Air Core Inductor
This type of inductor uses non-magnetic material like plastic or ceramic as the core, as this inductor has no magnetic core.
This inductor has low inductance values and has no core saturation, which is ideal for high-frequency applications.
Air inductors are used in RF circuits, high-frequency filters, and communication devices.
2. Iron Core Inductor
To enhance the inductance, these inductor uses laminated iron as the core material.
This inductor has a high inductance value, and core saturation is possible in that inductor.
Used in audio equipment and power supplies (low-frequency applications).
3.Ferrite Core Inductor
To provide the high magnetic permeability and low electrical conductivity, these inductor uses ferrite (a ceramic compound) as the core.
This inductor has high inductance and can reduce eddy current loss, and is effective in high-frequency circuits.
These inductor is used in switch-mode power supplies, RF transformers, and EMI filters.
4. Toroidal Inductor
A toroidal inductor is usually made of ferrite or powdered iron and is wound on a ring-shaped magnetic core.
It is a compact-sized sized having low electromagnetic interference and has efficient magnetic flux containment.
It is used in power electronics, medical devices, and industrial control systems.
5.Laminated Core Inductor
To reduce eddy current losses, these inductors are constructed using stacked layers of magnetic material like silicon steel.
These inductors are suitable for high power applications, which reduce core losses.
Laminated core inductors are used in transformers, power amplifiers and electric drives.
6.Variable Inductor
The name itself suggests that its inductance can be adjusted manually or electronically.
Used in frequency-selective circuits like radio tuners, oscillators, and signal generators because of its tunable inductance.
7.Multi-layer Chip Inductor (SMD)
This is a compact-sized surface mount device inductor that is built using multilayer technology.
This is a surface mountable device with high frequency performance.
Used in mobile phones, IoT modules, and microcontroller-based PCBs.
Functions of an Inductor
1. When the current flows through the inductor, the electrical energy stored in the form of a magnetic field.
2. To pass the specific frequency ranges, inductors are used in filter circuits.
3. Inductors allow DC current to pass easily by opposing high-frequency AC signals.
4. Inductors create inductive reactance in AC circuits, used for impedance matching and signal tuning.
5. They are used in circuits for shaping digital pulses and delaying signals.
6. Inductors suppress unwanted high-frequency electromagnetic noise in sensitive circuits.
Inductors in Series
When we connect inductors in series,
The total inductance is the sum of the individual inductances, and the inductance increases.
The same current flows through all inductors.
The formula for deriving the total inductance when there is no mutual inductance is:
L(total) = L1 + L2 + L3 + … + Ln
If the inductors are magnetically coupled, then we consider the mutual inductance as:
L(total) = L1 + L2 + 2M (if aiding is there)
L(total) = L1 + L2 – 2M (if opposing is there)
M is the mutual inductance between the coils.
The inductors in a series configuration are mostly used in power supplies, filter design, tuned circuits, and choke circuits.
Inductors in Parallel
When inductors are in parallel, the inductors are connected across the same two points, which provides multiple paths for current to flow. When we connect the inductors ina parallel configuration,
The voltage across each inductor is the same.
The total current is the sum of individual currents.
The formula for deriving the total inductance when there is no mutual inductance is,
(1/ L(total)) = (1/L1) + (1/L2) + (1/L3) + … + (1/Ln)
If there is mutual coupling, mutual inductance M is considered for deriving total inductance.
L(total) = (L1L2 – M^2) / (L1 + L2 – 2M) (when there is aiding)
Mutual inductance can either increase or decrease total inductance based on magnetic coupling orientation.
The inductors in a parallel configuration are used in current sharing, lower inductance requirements, compact power filtering, and impedance control.
Applications of Inductors
1. For smooth current flow and filtering, voltage inductors are used in switch-mode power supplies.
2. For controlling signal frequency, inductors are essential in low-pass, high pass, band pass, and band stop filters.
3. Inductors are used in transformers to transfer energy between circuits via magnetic coupling.
4. Inductors are used in RF filters, oscillators, and antenna tuning circuits.
Frequently Asked Questions
1.What is the function of an inductor?
The function of an inductor is to store energy in a magnetic field and oppose changes in current in an electrical circuit.
2.Can an inductor store energy?
Yes, an inductor can store energy in the form of a magnetic field when current flows through it.
3.Is an inductor used in AC or DC?
An inductor is used in both AC and DC circuits, but it mainly affects AC by opposing changes in current.
4.What is the SI unit of inductance?
The SI unit of inductance is the henry (H).
5.Where are inductors commonly used?
Inductors are commonly used in power supplies, filters, transformers, RF circuits, and energy storage systems.
