The Definitive Guide to Inductors

Inductors are passive electrical components found in a variety of devices and equipment. Playing a critical role in signal processing, sensing operations, transformers, and more, inductors are an important technology to understand. In this blog, we will highlight the design, function, and practical applications of inductors.

The design of an inductor is to optimize the magnetic flux through a circuit. Magnetic flux may be represented by the simple physical equation B=L*I, where “B” is the flux, “I” represents the current based on the circuit's shape, and “L” is the inductance. Therefore, to increase the magnetic flux through a current, inductors contain an insulated copper wire which is shaped in a helix or a coil to create a higher inductance. They also typically include ferromagnetic cores made from iron, nickel, or molybdenum to further enhance magnetization. This basic design may be scaled up or down as needed, with many being printed directly onto circuit boards.

While all inductors more or less share similar properties, there are several different types to be aware of. Some of the most common are described below:

Air-Core Inductor

Instead of implementing a ferromagnetic core, air-core inductors are designed with nonmagnetic cores. Such materials may include plastic or ceramic, while others are designed with no core at all. They are preferred over ferromagnetic inductors in high-frequency applications since they are less prone to core losses. However, inductors lacking a core may experience microphony, which occurs when the windings vibrate and cause fluctuations in the level of inductance.

Variable Inductor

Variable inductors account for a majority of models in current use. They are designed with a ferromagnetic core that can be adjusted within the confines of the coil or removed altogether. This configuration is valuable for radio applications because the user can tune the inductor to whatever value is necessary. Variometers also fall into this category, which replaces the core with another wound coil attached to a shaft. As the inner coil turns, it creates a magnetic field that is either moving in the same or different direction than the outer, creating a variance in the inductance.

Toroidal-Core Inductor

Toroidal cores feature a ferromagnetic core that is shaped similar to a donut, which limits the amount of magnetic flux to escape from the component. This design prevents potentially damaging magnetic interference, making these inductors particularly useful in appliances. Although they are generally much larger than other inductors, they are the preferred type in aerospace and nuclear applications since both could have devastating consequences from excess electromagnetic interference.

Inductors are used in several specific applications, including choking, energy storage, and impedance matching. A choke filter blocks high-frequency AC currents while allowing DC and low- to mid-frequency AC currents to pass. Furthermore, inductors may also store electrical energy in the form of magnetic energy. Additionally, street lights implement inductive loops to sense cars as they approach the line. When the vehicle rolls over the inductive loop, there is an immediate change in the magnetic field that is picked up and relayed to the traffic light, causing it to change.

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