2015-12-24
Self-capacitance of single-layer inductors. The formula for calculating
This work suggests the optimal formula for calculating the self-capacitance of single-layer coils of inductively. There are various approaches to this problem are described in [1]—[4], which are quite complicated formulas that are not always covering the whole range of different shapes of the coil design.
It is known that in a narrow range of relationship length to the winding diameter of the coil, the formula for the calculation of its own capacity is quite simple:
C = 0.46 \, D,
where: C — capacity of the coil in picofarads, and D — diameter of coil in inches. Formula with acceptable accuracy within a range of 0.5 < \frac {L} {D} < 2,
where: L — length of winding in inches. For a wider range of attitudes \frac {L} {D} the author suggests the following formula: C = \frac {D} {2} \bigg ( \frac {\pi} {7} + k \frac {\pi} {14} + \frac {0.25} {k^{0.75}} \bigg ),
where: k = \frac {L} {D}. Below shows the graphs constructed by the above formula. On them: f(k) = \frac {C} {D}, \varepsilon = 1. 
The materials used
- [1] A. J. Palermo. Distributed Capacity of Single-Layer Coils.
- [2] G. Grandi. Stray Capacitances of Single-Layer Solenoid Air-Core Inductors - Grandi, Kazimierczuk, Massarini and Reggiani. 1999
- [3] David W Knight. The self-resonance and self-capacitance of solenoid coils.
- [4] Details of the circuits of radio equipment, calculation and design. V. A. Volkov. 1954