Air Core Flat Spiral Inductance

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. Additionally, they may generate a greater stray field radiation and susceptibility to external pickups.

Outer diameter
mm
Inner diameter
mm
Number of turns

Formula

\[Air Core Flat Spiral Inductance = \frac {(4.921 * N^2(d_1 + d_2)^2)}{(15d_1 – 7d_2)} * dimension\]

where :

  • N = the number of turns
  • d1=outer diameter
  • d2=inner diameter
  • if the dimension unit is mm then dimension=1. if the dimension unit is mils then the dimension is 0.0254

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