This simple calculator will estimate the inductance of a flat pancake coil used in induction heaters, based on:
- Number of turns (
N) - Spacing between turns (
s) in millimeters - Wire diameter (optional, we’ll assume it’s negligible unless you want it)
- Coil outer and inner diameter (to get average radius)
Formula to Estimate Inductance (Pancake Coil)
We’ll use an approximate formula derived from the Wheeler formula for spiral coils:
L = (μ₀ * N² * r²) / (8r + 11w)
Where:
L is inductance in Henries
μ₀ = 4π × 10⁻⁷ H/m (permeability of free space)
N = number of turns
r = average radius of the coil in meters
w = radial width of the coil (outer radius - inner radius) in meters
We can calculate:
w = (N - 1) * spacing
r = (inner_diameter + outer_diameter) / 4
Calculator by homemade-circuits.com