Inductors are available in several types and each of them plays a crucial role when used in electronic devices. They are used for different purposes like noise suppression, high-power applications, radio frequency signals, etc. Here we are giving some major types of inductors along with their applications, advantages, and disadvantages.
1. Air-Core Inductor
Air-core inductors, also known as ceramic-core inductors, are made with ceramic materials. They are used in high-frequency applications where low inductance value is required. As they contain no cores, there are no core losses, such as eddy current and stray losses. However, these inductors need to take more turns as compared to inductors with cores. They use non-magnetic cores, which is why their inductance decreases.
Applications：Radio Frequency
Advantages: low core losses at high operating frequencies
Disadvantages: Mechanical vibration can affect their inductance
2. Iron-Core Inductor
Iron core inductors are those that are produced using ferromagnetic material, like iron cores. The magnetic cores of these materials are used to increase the inductance of the coil. They have high magnetic permeability, so they increase the magnetic field of the coil. These inductors are the best choice for areas where low-space inductors are required. They have high power and high inductance value, but a limited frequency capacity. These inductors have a few applications only.
Applications：Audio Equipment
Advantages: Ideal for low-space areas Have high power and high inductance
Disadvantages: limited applications; limited high-frequency capacity; Core losses, including eddy current loss & hysteresis loss
3. Ferrite Core Inductor
Ferrite core inductors are produced using ferrite materials as cores. The ferrite cores have high magnetic permeability and are made from a combination of manganese, zinc, nickel, barium, etc. Ferrites are of two types: Soft Ferrites and Hard Ferrites.
(i) Soft Ferrites
They can change their magnetization with ease, and they are an excellent conductor of the magnetic field. They reverse their polarity with no external energy. Hence, they are used in inductors and transformers, i.e. Toroidal cores and E cores.
(ii) Hard Ferrites
These materials are used in permanent magnets because they don't demagnetize properly. They don't change their polarity even after the removal of the magnetic field. They carry high hysteresis losses; hence, they are not used in inductors.
Applications: Medium and High Frequencies; PI Filters; Switching Circuits; Ferrit Rod Antennas; Telecommunications
Advantages: low electrical conductivity Low eddy current losses
Disadvantages: high hysteresis losses
4. Iron Powder Inductor
Iron powder inductors contain iron oxide. They are produced using pure iron powder. They are very solid when they are compressed under high pressure and mixed with a binder. They have air gaps, so high magnetic flux can be stored.
Due to this, a higher DC current level passes through the inductor. Therefore, the permeability of the cores used in these inductors is quite low, below 100. Hence, these inductors enjoy high-temperature stability.
Applications: Switching Power Supplies
Advantages: Have air gaps to store high magnetic flux
Disadvantages: The permeability of the cores is quite low
5. Laminated Core Inductor
In Laminated core inductors, there are several laminations on the cores. It means the cores are made of thin sheets that are placed on top of each other. These laminations may contain different materials and thicknesses.
The sheets have insulation coating to increase electrical resistance and avoid eddy current losses. This is why the losses decrease in these types of inductors. The design of the inductors is also flexible and has high power levels.
Applications: power filtering devices; low-frequency detectors
Advantages: decreased eddy current losses; flexible structure; high power levels
Disadvantages: difficulty in determining different materials & thicknesses
6. Toroidal Core Inductor
Toroidal Core Inductors contain toroidal cores that are ring-shaped. These cores are produced with ferromagnetic materials, such as powdered iron or tape wound. They have low magnetic flux leakage, which is why there is a high magnetic field. The inductance of these inductors increases as compared to rod-core inductors or others. They contain high energy-transferring abilities and high inductance values.
Applications: Medical Devices, Switching Regulators, Refrigerators, Air Conditioners, Telecommunications, and Musical Instruments
Advantages: low magnetic flux leakage, high magnetic field, high inductance values
7. Power Inductor
Power Inductors are ultra-compact components that handle high currents while reaching the area of magnetic saturation. They help reduce core losses in applications that need voltage conversion. They can be used in a magnetic field to receive or store energy, filter noise caused by Electromagnetic Interference (EMI), and reduce the loss of signals. To reduce the EMI, these power inductors are used, along with proper self-shielding.
Applications: Power Supply Circuits, like DC-DC Converters; AC Inputs
Advantages: Reduces core losses. Provides low leakage magnetic flux. Filters EMI noise.
8. Coupled Inductor
When two conductors are connected by electromagnetic induction, they are called coupled inductors. They have two windings around a magnetic core. In these types of inductors, the AC current flowing in one inductor produces a voltage in the other inductor, thus providing us with the concept of mutual inductance. They can be used to separate two circuits electronically by releasing impedance through the circuit.
These inductors can be used for a variety of applications, depending on their windings. Common uses are electrical isolation and adding series inductance.
Application: Energy conversion circuits
Advantages: very few active components; low noise operation; iron core double winding
Disadvantages: higher output voltage ripple; limited bandwidth for control loops
9. Moulded Inductors
Moulded inductors have an insulating coating, such as moulded plastic or ceramic. Their cores are made of ferrite material. Their windings are available in a variety of designs and shapes, such as cylindrical, bar and axial. Inductors are small, lightweight, and easy to use.
Applications: printed circuit boards; mobile devices; computers
Advantages: small size and light weight
Disadvantages: Limited number of shapes available
10. Variable Inductors
Variable inductors are those that allow the inductance to vary. They are designed in a variety of ways, such as using removable ferrite cores inside and outside the inductor windings. In these inductors, the ferrite core is located in a threaded structure. This increases or decreases the core permeability, affecting the inductor.
The inside of the inductor is filled with a magnetically shielded metal case. On the other hand, the resin-molded design provides protection for the windings and high reliability. They are well suited for RF applications.
Application: For RF applications
Advantage: Reliability
11. Bobbin Wound Inductors
Bobbin-wound inductors are wound on a cylindrical bobbin, which is why they are so named. They are mainly used in printed circuit boards. They contain two types of leads: axial and radial. These inductors are available in a variety of designs in terms of characteristics such as power rating, impedance matching, voltage and current levels, bandwidth, operating frequency, packaging and other parameters. They operate in the 60 Hz to MHz frequency range.
Their core materials are selected with operating frequency in mind, ranging from ferrite core materials to silicon steel laminations.
Applications: Printed Circuit Boards; Switch Mode Power Supplies; Power Conversion; Filter Circuits
Advantages: Operating at different frequency levels; multiple applications
Disadvantages: Space constraints; AC losses in high-frequency applications
12. Thin Film Inductors
Thin film inductors use small thin film coils shaped like spirals with a limited maximum value. These films are primarily used to demonstrate how applications such as conductors are manufactured from ferrite or magnetic materials, as well as aluminium oxide. The material ensures compact and highly accurate performance.
Key benefits of using thin-film inductors include reduced noise, heat resistance and improved stability. These thin inductors are ideally suited for DC/DC converters that power smartphones and other mobile devices.
Applications: power suppliers; amplifiers; wireless and LAN; impedance matching; mobile devices
Benefits: Multilayer construction; stable inductors; high Q factor (quality factor); high-performance compact chips
