Air Core Flat Spiral Inductance
Calculate the inductance of an air core flat spiral coil in nanohenries.
The flat spiral air core inductor holds a prominent place, finding its application in various devices like Tesla generators, RFID tags, and proximity detectors. These inductors come in different planar spiral coil designs, such as square, rectangular, hexagonal, and octagonal, often used in high-frequency applications and integrated onto PCB as tracks.
The advantages of air core inductors are numerous, including a higher Q-factor, improved efficiency, enhanced power handling, and reduced distortion. However, they require more turns or larger coil sizes to attain a specific inductance value, leading to larger physical dimensions, lower self-resonance, and higher copper loss.
Understanding Air Core Flat Spiral Inductance
Design and Uses
These inductors are commonly found in proximity detectors, RFID tags, and the main coil of Tesla generators. In addition, they are present in:
- Resonant circuits
- Low pass filters
- Antenna matching units
- Crystal sets
- Antenna traps
- Wireless charger designs
Air Core Inductors
Air core inductors employ air as the core, as opposed to inductors wound on a bobbin constructed of ferromagnetic materials. This indicates that their inductance is independent of the current they carry and that they lack the ferromagnetic core characteristic of non-linearity in the magnetization curve.
Advantages and Disadvantages
Because they don't have core saturation and are linear, air core inductors are useful in some situations. To get a given inductance value, they need more and/or larger turns, which might result in larger coils, lower self-resonance, and higher copper loss at higher frequencies.
Characteristics
| Characteristic | Description |
|---|---|
| Inductance unaffected by current | Unlike ferromagnetic core inductors, these do not see a change in inductance in response to variations in current |
| No core loss | No energy loss from magnetic saturation since there is no ferromagnetic material present |
| Higher self-resonance | Often have a higher self-resonance frequency due to interwinding capacitance |
| Larger coils required | Frequently need more turns and larger coils to obtain a given inductance value, which might increase copper loss |
Design Considerations
| Parameter | Effect |
|---|---|
| Inner Diameter | Influences the self-resonance frequency and inductance value |
| Distance Between Windings | Influences the self-resonance frequency and inductance value |
| Wire Diameter | Influences copper loss and the inductance value |
| Number of Turns | Influences the self-resonance frequency and inductance value |
Advantages and Disadvantages
| Advantages | Disadvantages |
|---|---|
| High frequency operation with minimal core loss | Higher manufacturing cost than conventional inductors |
| Low power loss due to absence of core loss | Limited inductance range — may not suit high inductance applications |
| Compact, lightweight design possible | Sensitivity to environmental factors like humidity and temperature |
Conclusion
Air-core flat spiral inductors are a special kind of inductor with notable benefits such as compact design, minimal power loss, and high frequency operation. They do, however, have certain drawbacks including increased cost and a limited inductance range. Design considerations and performance-influencing aspects must be taken into account while creating an Air Core Flat Spiral Inductor.
Use the online calculator below to assist in designing your next pancake-shaped flat spiral air core coil inductor. Inputs such as inductance, inner diameter, wire diameter, number of turns, and distance between windings are usually needed for these computations.
Formula
where:
- = Air Core Flat Spiral Inductance
- = Number of turns
- = Outer diameter
- = Inner diameter
- = Dimension factor — if unit is mm, if unit is mils
Inputs
Outer diameter of the spiral coil
Inner diameter of the spiral coil — must be less than outer diameter
Total number of turns in the spiral coil