Question 1

How do I calculate DC resistance of a wire winding?

Accepted Answer

Use the formula R = ρ × L / A, where ρ is the copper resistivity (1.724×10⁻⁸ Ω·m at 20°C), L is the total wire length in meters, and A is the cross-sectional area of the wire. To find the wire length, multiply the number of turns by the mean length per turn (MLT).

Question 2

What AWG wire gauge should I use for my inductor?

Accepted Answer

The AWG gauge depends on your current requirements and acceptable DCR. For high-current applications, use thicker wires (lower AWG numbers like AWG 18-22). For small signal inductors, thinner wires (AWG 28-36) are suitable. Balance between winding space, DCR loss, and skin effect at your operating frequency.

Question 3

What is MLT (Mean Length per Turn)?

Accepted Answer

MLT is the average length of wire required to complete one turn around the magnetic core. It depends on the core size and bobbin dimensions. For a toroidal core, MLT ≈ π × (OD + ID)/2 + 2 × height. Core manufacturers typically provide MLT values in their datasheets.

Question 4

How does temperature affect wire DCR?

Accepted Answer

Copper resistance increases with temperature. The calculator uses 20°C as reference. For other temperatures, use: R(T) = R(20°C) × [1 + 0.00393 × (T - 20)]. At 100°C, resistance is approximately 31% higher than at 20°C.

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