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Home > Blog > Different types of inductors

Different types of inductors

  • April 16th, 2024
  • 142
Inductors are not only one of the basic electronic components but also a core component that affects circuit design and function realization. By delving into how inductors work, their diverse types, and their applications in different fields, we can better understand their irreplaceable role in modern technology. The main function of an inductor is to hinder the rate of change of current and store electrical energy as magnetic energy. This unique property makes inductors extremely valuable in AC signal processing. From high-frequency signal transmission to power management to radio frequency tuning and wireless charging technology, inductors are used in a wide range of applications, demonstrating their key role in achieving efficient and stable electronic systems.

Catalog

1. What Is an Inductor?
2. Types of Inductors
3. Skeleton Inductor
4. Air Core Coil Inductor
5. Ferrite Core Inductor
6. Laminated Core Inductor
7. Coupled Inductor
8. Toroidal Core Inductor
9. Shielded Adjustable Inductor
10. Surface Mount Shielded Inductor
11. Wireless Charging Coil
12. Multilayer Chip Inductor
13. Axial Inductance
14. Conclusion

Inductors
Figure 1: Inductors

What Is an Inductor?


Inductors are basic components used in electrical circuits. Its main function is to slow down sudden changes in electrical current and store electrical energy as magnetic energy. This feature becomes very important when dealing with alternating current (AC) signals. The ability of an inductor to store energy is quantified in Henrys (H). The term "Henry" refers to the inductor's ability to resist changes in current flow. Specifically, one Henry means that a change in current of one ampere per second will result in a change in voltage of one volt. This measurement helps understand how effective the inductor is at managing current changes and energy storage within the circuit.

Inductors
Figure 2: Inductors

Types of Inductors


Inductors come in a variety of shapes and sizes and are customized for specific functions in electrical systems. Generally, they are classified according to the frequency of the design application, such as high frequency, low frequency, decoupling, and filtering inductors. Each type is crafted with unique construction to best suit its intended use.

High-Frequency Inductor


High-frequency inductors are used in wireless communications, especially in devices that need to transmit and receive signals, such as radio frequency (RF) components. These inductors are designed to be small, which facilitates installation into the tight spaces typically found in mobile devices. They excel at managing high-speed signals, minimizing energy loss, and maintaining signal integrity during rapid transmission.

High-Frequency Inductor
Figure 3: High-Frequency Inductor

Low-Frequency Power Line Inductors


Low-frequency power line inductors are primarily used in power supply systems to handle high voltages and currents. Their larger size allows for greater energy storage capacity and is suitable for smoothing the flow of electricity in power lines. This type of inductor plays a role in efficiently converting and distributing electricity in a wide range of power systems.

Decoupling Inductor


The purpose of a decoupling inductor is to protect sensitive circuit components by filtering out high-frequency noise that can disrupt circuit operation. These inductors are often located at the power entry points of microprocessors or digital circuits, helping to stabilize the power supply and ensuring that changes and noise in other parts of the circuit do not affect critical components.

Decoupling Inductor
Figure 4: Decoupling Inductor

Filter Inductor


Filter inductors are essential components in audio and broadcast equipment, specifically designed to eliminate unwanted noise or fluctuations that can interfere with signal quality. By filtering out frequencies outside the expected range, these inductors help maintain the clarity and stability of transmitted or received signals, ensuring the output remains clean and undistorted.

Filter Inductor
Figure 5: Filter Inductor

Skeleton Inductor


The bobbin inductor is a widely used inductor characterized by a coil of wire carefully wound around a bobbin or coil former. The bobbin is typically made of ferrite, a material known for its excellent magnetic properties such as high magnetic permeability and minimal hysteresis losses. These characteristics make bobbin inductors very effective for applications requiring efficient power management, such as power adapters and electronic filters.

Skeleton Inductor
Figure 6: Skeleton Inductor

The core of the bobbin inductor is the ferrite element, which acts as the backbone of the coil winding. The process involves tightly wrapping wire around a ferrite core to create a compact and efficient electromagnetic path. When current flows through this coil, the ferrite core amplifies the magnetic field produced by the wire, thereby enhancing the inductor's ability to increase its inductance value. This amplified magnetic field helps the inductor effectively block high-frequency interference and ensure smoother power output, which can maintain the performance and reliability of the power system.

Air Core Coil Inductor


Air core coil inductors are unique in that they use air in their design rather than a solid core such as ferrite or iron. This choice of structure results in a lower energy storage capacity but could prove advantageous in applications operating at high frequencies, such as radios and televisions.

Air Core Coil Inductor
Figure 7: Air Core Coil Inductor

To construct an air-core coil inductor, wire is carefully wrapped around a mold made of a nonmagnetic material, such as plastic or ceramic. This setting defines the shape and size of the inductor while ensuring that the core remains non-magnetic. The absence of magnetic materials means these inductors do not suffer from magnetic saturation, a common problem with solid inductors that can cause signal distortion. Therefore, air-core coil inductors are particularly effective at managing high-frequency signals and maintaining signal integrity by avoiding the nonlinear distortion typically associated with magnetic cores. This makes them ideal for ensuring clear, consistent performance in high-frequency electronic equipment.

Ferrite Core Inductor


Ferrite core inductors are ideal for use in high-frequency environments due to their impressive performance characteristics. Ferrite, the core material of these inductors, is made by mixing iron oxide with various metal oxides and then heating them to high temperatures. This compound has significant magnetic permeability, high resistivity, and minimal eddy current losses, making it suitable for devices requiring fast switching (such as modern electronic filters and high-speed equipment).

Ferrite Core Inductor
Figure 8: Ferrite Core Inductor

The manufacturing process of ferrite involves the detailed selection of iron oxides and other metal oxides such as nickel and zinc. These materials are mixed thoroughly and then sintered or heated so that they combine at a molecular level to form a strong ceramic. This high-temperature process not only bonds the materials together but also fine-tunes the microstructure of the ferrite. This improvement is key to optimizing its magnetic and electrical properties. The result is a ferrite material with excellent magnetic properties and high resistivity that reduces energy losses due to eddy currents when the magnetic field changes rapidly. This makes ferrite core inductors particularly suitable for efficiency and speed applications.

Laminated Core Inductor


Laminated core inductors are suitable for applications requiring high reliability and efficiency under heavy loads, such as electric vehicle chargers and circuits that filter noise. These inductors are characterized by their layered core construction, which is made of specially designed steel and often includes insulating material sandwiched between layers to minimize eddy current losses.

Laminated Core Inductor
Figure 9: Laminated Core Inductor

To build the core of a laminated core inductor, several steps need to be followed carefully. First, the steel plate was chosen for its excellent magnetic properties. These boards are then subjected to a heat treatment process to enhance their magnetic permeability and reduce hysteresis losses, which can maintain efficiency in handling high frequencies and larger current loads. After heat treatment, the sheet is coated to further protect and optimize its surface for better performance.

Assembling these steel panels into a multi-layered core requires careful alignment and layering, ensuring each layer is insulated from its adjacent layers to prevent energy loss due to eddy currents. This layered structure not only improves the inductor's magnetic efficiency but also enhances its ability to manage the intense demands of high-power applications. Through this precise engineering, laminated core inductors achieve a balance of performance and durability, making them ideal for critical and intensive applications.

Coupled Inductor


Designed to facilitate the efficient transfer of energy within a circuit, coupled inductors feature a unique arrangement of two or more wires wrapped around a single magnetic core. This configuration enables them to meet different circuit requirements by employing different connection strategies (series, parallel, or transformer-type), which makes them particularly useful in applications such as flyback, SEPIC, and Chuuk converters.

Coupled Inductor
Figure 10: Coupled Inductor

Central to the functionality of coupled inductors is the shared magnetic core. Each winding wound around this core is capable of carrying current independently. The proximity of these windings to each other, combined with the shared magnetic core, allows efficient energy exchange between them via magnetic coupling. This setup not only enhances the inductor's ability to handle energy flow but also improves circuit efficiency and responsiveness, which is particularly beneficial for circuits operating at high frequencies. Careful arrangement of the windings and strategic placement of the core ensures optimal magnetic interaction for the inductor's ability to efficiently manage and transfer electrical energy.

Toroidal Core Inductor


Toroidal core inductors stand out due to their distinctive ring-shaped design, which plays a pivotal role in minimizing magnetic field leakage and enhancing energy efficiency in electronic devices. These inductors are typically crafted using ferrite, a material known for its high magnetic permeability, allowing the inductor to operate effectively with fewer coil turns and thereby reducing overall resistance.

Toroidal Core Inductor
Figure 11: Toroidal Core Inductor

The key to the effectiveness of toroidal core inductors lies in their circular structure. This shape encloses the magnetic field more uniformly compared to other designs, significantly reducing leakage and minimizing external electromagnetic interference. The utilization of high-permeability ferrite material not only boosts this containment but also enhances the inductor's efficiency by facilitating a more compact coil configuration. As a result, toroidal core inductors are highly efficient and reliable in applications that demand precise magnetic field control, such as in medical imaging machines, power conditioning systems, and sophisticated electronic controllers. The strategic design and material choice make these inductors an optimal choice for maintaining stability and efficiency in high-performance electrical environments.

Shielded Adjustable Inductor


Shielded adjustable inductors have an internal magnetic core that can be moved by the user to precisely adjust the inductance value. This feature is particularly valuable in applications that require fine control of inductance, such as in automotive electronic systems with stringent performance standards. These inductors are versatile, with cores made of either ferrite or brass, depending on the magnetic properties required for specific frequency scaling and signal processing operations.

Shielded Adjustable Inductor
Figure 12: Shielded Adjustable Inductor

The operation of a shielded adjustable inductor involves the user adjusting the position of the magnetic core within the coil. This is accomplished by rotating or sliding the magnetic core, allowing the inductor's characteristics to be fine-tuned to meet specific operating needs. Additionally, these inductors are encased in a metal shield to suppress any external electromagnetic interference. This design ensures that the inductor's functionality is not affected by external interference, thereby improving device accuracy and stability in sensitive applications. The ability to physically adjust the core provides users with the flexibility to optimize performance and adapt to varying electronic conditions.

Surface Mount Shielded Inductor


Surface mount shielded inductors are designed to significantly reduce electromagnetic noise, making them ideal for use in electronic equipment that requires quiet operation. These inductors involve the process of wrapping wire around a bobbin and then encapsulating it within a ferrite housing, which not only enhances shielding but also helps suppress noise. This configuration is particularly advantageous for applications involving circuit board integration.

Shield Surface Mount Inductors
Figure 13: Shield Surface Mount Inductors

The production of surface-mount shielded inductors follows a detailed sequence:

Wrapping the Coil: Start by selecting a wire that meets your thickness and conductivity requirements. These wires are then carefully wound around a spool made of a non-conductive material such as plastic or paper, forming the core component of the inductor.

Encapsulation: Next, the coil is placed inside a protective shell made of ferrite or other high-permeability material. The enclosure provides the physical shielding needed to block external electromagnetic interference.

Curing and Testing: After encapsulation, the components will go through a curing process. This step solidifies the structure and ensures the inductor remains stable under operating stress. After curing, comprehensive electrical performance testing is performed to verify that the inductor meets all operating specifications. These tests check efficiency, durability, and noise immunity, ensuring each inductor is ready for integration into electronic systems.

Wireless Charging Coil


Wireless charging coils enable efficient power transfer in wireless charging systems, significantly reducing energy waste in the process. The coil is constructed of stranded wire and is supplemented with ferrite plates to enhance its performance. These components work together to increase the coil's inductance, focus the magnetic field more effectively, and reduce energy loss. Wireless charging coils are not only suitable for charging devices but are also widely used in communications, medical, and industrial equipment due to their efficiency and versatility.

Wireless Charging Coil
Figure 14: Wireless Charging Coil

The manufacture of wireless charging coils involves several meticulous steps:

Coil structure: The coil is braided from multiple strands of thin wire. This braiding technique increases the flexibility and durability of the coil, making it suitable for a variety of applications where mechanical stress is a factor.

Enhanced magnetic field concentration: Around the braided coils, ferrite plates are strategically placed. These plates play a key role in enhancing the focus of the magnetic field produced by the coil. A more concentrated magnetic field translates into more efficient energy transfer.

Optimization: By adjusting key parameters such as coil diameter, number of wire turns, and wire thickness, the performance of the coil can be customized to meet specific requirements. These adjustments allow the coil to optimize its compatibility with different charging standards and device specifications, ensuring that the coil meets the precise needs of various electronic devices.

Multilayer Chip Inductor


Multilayer chip inductors are important components of contemporary electronic devices, enabling miniaturization without compromising performance. These inductors are particularly important in small technologies such as wearable devices, wireless networks, and Bluetooth technology. Their design uses alternating layers of a special metal paste and ferrite material on a printed metal coil, resulting in a compact structure that maintains high functionality and reliability.

Multilayer Chip Inductor
Figure 15: Multilayer Chip Inductor

The production of multilayer chip inductors includes several detailed steps:

Coil Design and Printing: Initially, coil patterns are carefully designed to meet specific electrical and space requirements. These metal coils are then deposited onto a substrate using precision printing techniques, setting up the basic layout of the inductor.

Application of Metal Paste and Ferrite Layers: After the initial coil printing, special metal paste and ferrite layers are alternately applied directly onto each printed coil layer. This step enhances the inductor's magnetic properties, specifically its efficiency and effectiveness in electronic circuits.

Lamination and Sintering: Once lamination is complete, the structure goes through a lamination process where all the layers are stacked and pressed together. The component is then subjected to a high-temperature sintering process. Sintering involves heating the assembled inductor at high temperatures, fusing the layers into a strong and cohesive unit. This process not only cures the inductor but also ensures that its layers are seamlessly integrated, thereby enhancing its overall magnetic properties and structural integrity.

Axial Inductance


Axial inductors are often referred to as color ring inductors and can be easily identified by their unique color-coded ring, which allows engineers to quickly determine their inductance value. These inductors consist of wire, usually copper, wrapped around a dumbbell-shaped ferrite core. The color coding system simplifies the identification process, making these inductors very useful in electronic designs that require accurate inductance measurements, such as filters, power amplifiers, and other electronic projects.

Axial Inductance
Figure 16: Axial Inductance

Creating an axial inductor involves a precise series of steps:

Core material selection and winding: The first step is to select a suitable ferrite core with magnetic properties suitable for the inductor. Selected copper wire is then wrapped tightly and evenly around this core to ensure consistent magnetic flux throughout the inductor.

Color ring coding: After the winding is completed, the inductor body will be marked with a color ring. The rings follow a standardized color-coding system, where each color corresponds to a specific number, representing the inductance value. This encoding enables fast visual identification and reduces the risk of errors when selecting the correct components during assembly or repair.

Encapsulation and Inspection: After winding and coding are complete, the inductor is encapsulated, usually in a durable resin or plastic. This packaging protects the precision windings from physical and environmental damage, increasing the inductor's durability and reliability. The final phase involves thorough electrical testing to ensure each inductor meets the required specifications and operates reliably in its intended application.

Conclusion


With the continuous advancement of electronic engineering technology, the design and application of inductors are also constantly innovating and expanding. Whether they are traditional wire-wound inductors, inductors with special core materials, or air-core inductors for high-frequency applications, each plays an integral role in its specific field. In the future, with the development of new materials and new technologies, as well as the improvement of performance requirements for electronic equipment, the design of inductors will be more refined and the application fields will be wider. From high-performance computing and advanced communications devices to wearable technology and smart home systems, inductors continue to drive technological innovation and improve the quality of human life. By in-depth understanding and application of inductors, engineers and designers can bring more innovative solutions to this digital era.






Frequently Asked Questions [FAQ]


1. Do Inductors Store Current or Voltage?


Inductors don't hold electricity like a battery. They work with electric currents to create a magnetic field. This field stores energy. The more current, the more energy is stored. Think of it like this: when electricity flows through an inductor, it builds a magnetic storage area for energy.

2. Does an Inductor Allow AC or DC?


Yes, inductors work with both AC (back-and-forth current) and DC (one-way current). For DC, once the magnetic field is set up, inductors just let the current flow easily. But for AC, inductors resist the current more as it speeds up. This resistance is because inductors don't like changes in how much or how fast the current is moving.

3. Do Two Inductors Make a Transformer?


Not by themselves. A transformer needs two inductors wrapped around a shared core. This setup lets energy move from one inductor (primary) to the other (secondary) through the magnetic field. This energy transfer changes the voltage. So, it's not just having two inductors; it's how they share and transfer energy that counts.

4. What Is the Q of an Inductor?


The "Q" stands for Quality Factor. It shows how good an inductor is at storing energy without losing much. A higher "Q" means less energy is wasted. Think of "Q" as a score that tells you how efficient an inductor is at its job, with higher scores being better, especially for devices that need precise energy control.

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