inductance calculator, by
Serge Stroobandt, ON4AA
Round wire coil with dimensions and its current-sheet approximation D
mm Mean diameter of the air core coil, measured from wire centre to wire centre N
Number of turns ℓ
mm Lenght of the coil,
measured from the connecting wires centre to centre
d
mm Wire or tubing diameter
Cu, annealed
Cu, hard-drawn
Ag
Al
Plating material ρ
nΩ·m Plating conductivity μ
_{r}
Plating permeability f
MHz Design frequency
INTERMEDIATE RESULTS: p
mm Winding pitch Φ
Proximity factor according to empirical Medhurst data
^{[2,3]}
D
_{eff}
mm Effective coil diameter according to Stroobandt (see below) Correction factors: k
_{L}
Field non-uniformity correction factor according to Lundin
^{[2,4]}
k
_{s}
Round wire self-inductance correction factor according to Rosa
^{[2,5,6]}
k
_{m}
Round wire mutual-inductance correction factor according to Grover and Knight
^{[2,7]}
Wire: ℓ
_{wire, phys}
mm Physical wire length ℓ
_{wire, eff}
mm Effective wire length δ
_{i}
µm Skin depth at design frequency Sheath helix waveguide mode ψ
° Effective pitch angle β
rad/m Axial propagation factor of n=0 sheath helix waveguide mode at design frequency
^{[1,8]}
Z
_{c}
Ω Characteristic impedance of n=0 sheath helix waveguide mode at design frequency
^{[1]}
Effective circuit equivalent at design frequency
L
_{eff,s}
µH Effective series inductance
at design frequency
from Corum & Corum's sheath helix
waveguide formula,
corrected for field non-uniformity and round wire
^{[1,2,4-7]}
X
_{eff,s}
Ω Effective series reactance of round wire coil at design frequency R
_{eff,s}
Ω Effective series AC resistance of round wire coil at design frequency Q
_{eff,ul}
Effective unloaded quality factor of round wire coil at design frequency Lumped circuit equivalent at design frequency
L
_{s}
µH
Frequency-independent
series inductance from the current-sheet coil
geometrical formula,
corrected for field non-uniformity and round wire
^{[2,4-7]}
X
_{L,s}
Ω Series reactance of round wire coil R
_{L,s}
Ω Series AC resistance of round wire coil at design frequency Q
_{L,ul}
Unloaded quality factor of round wire coil at design frequency C
_{L,p}
pF Parallel stray capacitance at design frequency
^{[1]}
Self-resonant frequency: f
_{res,L}
MHz λ/4 (parallel) self-resonant frequency of n=0 sheath helix mode
^{[1,8]}