Power Inductors, Chokes and Reactors FAQ

Power inductors can be classified in several ways: by inductance value, by power or current rating, by type of application, by type of construction, by industry, by material and others. Choke and reactor are other names for power inductors. Inductors limit the flow of electrical current in A.C. or transient applications. This allows them to reduce the voltage reaching the intended load. Since an inductor’s impedance increases with frequency, they are good for blocking (suppression) of high frequency electrical noise. Inductors are frequently used for electrical/electronic filtering. You can find inductors in tuning and most types of bandwidth filters. Saturable inductors can be used in signaling circuits to create time delays. Boost inductors, flyback inductors, and buck inductors are inductors used in some switching power supplies. Inductors are also used in switching power supplies to smooth out ripple voltage and ripple current.

Inductors store energy. Transformers are not intended to store energy (but do store some). Coupled inductors are used in some multi-output switching power supply designs to improve voltage regulation. In this case, the inductor is also acting as a transformer because there is transformer coupling occurring between the multiple outputs. In contrast, a (link: flyback transformer) is technically an inductor. A coil winding is used to create a magnetic field thereby storing energy in the field. The stored energy is then released to the output. There is no direct (simultaneous) coupling of energy.

What are the construction types of inductors?

Bobbin wound inductors, toroidal inductors, air core (no core), tube wound, foil wound, wound with litz wire, encapsulated (potted), laminated, powdered core, and others. An Inductor’s core material is heavily influenced by the application’s frequency range. Line frequency applications usually use a laminated or tape wound silicon steel core stack. Low frequency audio applications may use laminated (link: nickel-iron core) stack or possibly (link: powdered core materials). High frequency applications generally use a (link: ferrite material).

What are the shapes of bobbin wound inductors?

Pot cores: round, “RM”, or square pot cores, “RS”, or round slab pot cores, and “DS”, or double slab pot cores.
Other core shapes: “EP”, “PQ”, “E”, “EI”, “EEM”, “EFD”, “U”, “UI”, “EC”, “ETD”, “ER”, “EER”, and some others including custom shapes.

How are bobbin wound inductors mounted?

Pin-through, surface mount, or chassis mount.

Toroidal inductors are usually preferred when high efficiency and optimum performance are desired. Tube based construction tends to be more customized hence a variety of inductor shapes are possible.