Power Inductors, Chokes and Reactors

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 inhibit the flow of electrical current in A.C. or transient applications.  Inductors are used in some A.C. circuits to reduce the voltage reaching the intended load.  Inductors may be used to limit the amount of A.C. current flow. 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 purposes.  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 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.

Types or inductor construction include bobbin wound, toroidal, 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 nickel-iron core stack or possibly powdered core materials.  High frequency applications generally use a ferrite material. 

Inductors are available in a variety of shapes.  Bobbin wound inductor shapes include pot cores (round), “RM” (square pot cores), “RS” (round slab pot cores) and “DS” (double slab pot cores), “EP”, “PQ”, “E”, “EI”, “EEM”, “EFD”, “U”, “UI”, “EC”, “ETD”, “ER”, “EER”, and some others including custom shapes.  Bobbins often provide a convenient method of mounting; pin-through, surface mount, or chassis mount.  Toroids are well known.  Toroids 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.

Butler Winding can makes power inductors and custom transformers in a wide variety of materials and sizes with pin-thru, surface mount, and/or flying leads terminations.  Butler Winding also does “tube wound” inductors and air core coils.  Our upper limits are 40 pounds of weight and 2 kilowatts of power.  We have experience with foil windings, litz wire windings, and perfect layering.  For toroids, we provide sector winding, progressive winding, bank winding, and progressive bank winding.  Butler winding has a variety of winding machines, bobbin/tube and toroid.  Butler Winding has vacuum chamber(s) for vacuum impregnation and can also encapsulate.  To ensure quality, Butler Winding purchased two programmable automated testing machines.  Most of our production is 100% tested on these machines. For more information on Butler Winding’s capabilities, click on our “capabilities” link.

Also, feel free to contact Butler Winding and ask for technical or engineering assistance.