Aircoils
Benefit of aircoils
Air coils are inductors without ferromagnetic core. The magnetic field closes around the winding over air. This eliminates the often-problematic effect of nonlinearity. Only the relatively low permeability constant uo = 0.4 * Phi * 10E-06 contributes to the inductance value because the relative permeability of air ur = 1.
As advantage the inductance remains almost constant regardless of frequency and current.
Air coils are characterized by high linearity.
Manufacturing of air coils at InduComp
In terms of design, windings of air coils with enameled copper wire can either be wound on a wide variety of bobbins.
Or the winding of an air coil is made with bonding wires. The bonding magnet wire is formed around a polished winding tool and often bonded during the winding process. Depending on the type of bonding varnish wire, the bonding can be done with solvents such as alcohol (IPA) or by hot air.
If the bonding layer, which is located above the base enamel is heat sensitive, there is also the possibility of bonding the air coil with current heat after winding, while inside of the winding tool. The bonding current causes a power loss in the ohmic winding resistor and heats and bonds the bonding wire.
In both cases, the air coil must be removed from the bonding tool (often identical to the winding tool).
A huge variety of geometrical shapes can be realized this way (depending on the geometry and complexity of the winding tool).
To calculation air coils, approximate formulas for inductance can be used. They are available for round or rectangular air coils.
More options and designs
For example:
- Formula for toroid with circular cross-section
- Toroid with strip-type conductor cross-section
- Rectangular coil with square cross-section
- Square flat coil
- Multilayer coil with round cross-section
- Single layer coil with round cross-section
- Toroidal core with rectangular cross-section
Single-layer or multi-layer round air coils (ring coil or elongated cylindrical coil) are special forms of baked lacquer coils and can also be produced for SMT (Surface Mount Technology).
Even high frequency bonding lit wires (twisted pairs of small strands of bonding wire) can be used to reduce the skin effect at high frequencies.
