ilmainduktori

Ilmainduktori, also known as air-core inductor, is an electrical inductor that uses air or another non-magnetic material as its core rather than a ferromagnetic substance. The term is used in Estonian as ilmainduktori and refers to inductors designed to avoid magnetic core materials, offering stable operation over a wide frequency range.

Construction and design

An air-core inductor consists of insulated copper wire wound around a non-magnetic form, such as a plastic spool. The winding may be arranged as a cylindrical solenoid or as a toroid, among other shapes. Since no magnetic material is inside the coil, the inductance is determined primarily by the number of turns, the cross-sectional area of the coil, and the coil length. For a long solenoid, the inductance can be approximated by L ≈ μ0 N^2 A / l, where μ0 is the permeability of free space, N is the number of turns, A is the cross-sectional area, and l is the length.

Characteristics and performance

Air-core inductors exhibit low core losses and better linearity over temperature compared with ferrite or iron cores, making them suitable for high-frequency applications. They typically offer a wide usable frequency range, but their inductance density is lower than that of core-based inductors, so achieving high inductance often requires larger coils. The performance is influenced by parasitic capacitance between turns, leading to a self-resonant frequency at which the inductor stops behaving as an inductor.

Applications and considerations

Ilmainduktori are commonly used in RF tuning circuits, VHF/UHF receivers, signal generators, and measurement equipment where stable inductance at high frequencies is important and core losses must be minimized. Designers balance size, inductance value, Q factor, and self-resonance when selecting an air-core inductor for a given application.