Types of Inductors and Cores

Inductors, devices that transmit and measure current in relation to the amount of voltage applied, are essentially elecotromagnets that store and release an electrical current. As the current is applied, an inductor coil stores the current to establish a magnetic field. Eventually, the coil builds a field and current is transmitted through the coil until the magnetic field collapses and the process must begin again. Inductors are commonly used in radio frequency applications to transmit a current and minimize feedback and interference, and can also be used in circuits to moderate electrical flow.

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Types of Inductors

As with many electrical devices, different models exist for specific applications. Coupled, multilayer, ceramic core, and molded inductors are all common types found in commercial and industrial applications:

• Coupled Inductors

Coupled inductors exhibit magnetic flux that is dependent on other conductors to which they are linked. When mutual inductance is needed, coupled inductors are often used. A transformer is a kind of coupled inductor.

• Multi-Layer Inductors

This particular type of inductor consists of a layered coil, wound multiple times around the core. As a result of the multiple layers and the insulation between them, multi-layer inductors have a high inductance level.

• Ceramic Core Inductors

Although there are numerous kinds of cores, a ceramic core inductor is unique in having a dielectric ceramic core, meaning it cannot store a lot of energy but has very low distortion and hysteresis.

• Molded Inductors

These inductors are molded using plastic or ceramic insulation. Often used in circuit boards, they can assume either a cylindrical or bar formation, with windings featuring terminations at each end.

Types of Cores

Aside from ceramic core inductors, other core materials can be used to achieve certain results. Because the core is the material the coil winds around, it directly affects inductance. Coils wound around iron-based cores yield greater inductance than those wound around non-iron-based cores.

• Air Core

In this configuration, there simply is no core. The lack of a metal core results in very little distortion, but by the same token, the coil must be very long to carry high amounts of inductance, resulting in a large inductor.

• Steel Cores

For low resistance, high inductance applications, steel cores are a step above air cores. The denser the steel core, the less of a problem the core will encounter with magnetic saturation.

• Solid Ferrite Cores

When it comes to offering the highest resistance, solid ferrite cores are at the top of the list. However, when dealing with high inductance they are not always reliable and tend to reach their magnetic saturation level relatively quickly. Ferrite cores will use a different ferrite material based on the application, such as manganese zinc for certain kinds of antenna rods, with various materials offering a different set of advantages. Powdered ferrite cores are available, which are denser and offer greater linearity than solid ferrite cores.

Inductors in Circuits and Preventing Kickback

Because inductors do not sustain a continual level of voltage between terminals, it is not possible to suddenly stop the current. If a current is running through a closed-switch circuit, the inductor will allow the current to flow and build an electromagnetic field. If the circuit switch is then opened, the inductor will continue in its attempts to transmit current and in doing so one of the inductor’s terminals may switch charges, from negative to positive. This will eventually cause the terminal contact to overload. If the contact is overloaded, the switch will experience interference and damage, resulting in a shorter life cycle. This kind of problem can be avoided by simply using a diode, though for high-speed applications a resistor may be preferable.

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