Advanced Proximity Effect Loss Calculator

Analyze round wires or layered windings with practical engineering assumptions. Review losses, ratios, and depth. Size conductors wisely before heat and efficiency problems appear.

Calculator Inputs

Calculation model

RMS current (A)

Frequency (Hz)

Conductor length (m)

Operating temperature (°C)

Relative permeability

Resistivity at 20°C (Ω·m)

Temperature coefficient (1/°C)

Wire diameter (mm)

Center spacing (mm)

Adjacent conductors

Geometry factor

Conductor width (mm)

Conductor thickness (mm)

Number of layers

Use the round model for wire bundles in external fields. Use the Dowell model for layered windings or foil conductors.

Example Data Table

Case	Model	Current (A)	Frequency (Hz)	Main geometry	Observed design takeaway
Transformer lead pair	Round wire	12	20,000	0.8 mm wire, 3.5 mm spacing, 2 neighbors	Comfortable spacing keeps field coupling moderate.
Tight choke winding	Round wire	18	80,000	1.2 mm wire, 2.0 mm spacing, 4 neighbors	High frequency and crowding sharply increase AC loss.
Planar secondary	Dowell	25	150,000	10 mm width, 0.2 mm thickness, 5 layers	More layers can dominate total copper heating.

Formula Used

This calculator offers two engineering approaches because proximity loss depends strongly on conductor shape and winding arrangement.

Common equations

Angular frequency: ω = 2πf

Temperature-adjusted resistivity: ρ_T = ρ₂₀ × [1 + α(T − 20)]

Skin depth: δ = √[2ρ_T / (ωμ₀μ_r)]

Round wire transverse-field model

Cross-sectional area: A = π(d/2)²

DC resistance: R_DC = ρ_TL / A

Peak field intensity: H_pk ≈ k × n × I_pk / (2πs)

Peak flux density: B_pk = μ₀μ_rH_pk

Approximate proximity loss: P_prox ≈ (π²B_pk²d²f²V) / (16ρ_T)

Dowell multilayer winding model

Dimension ratio: x = t / δ

Skin factor: F_skin = (x/2) × (sinh x + sin x) / (cosh x − cos x)

Proximity factor: F_prox = ((m² − 1)/3) × x × (sinh x − sin x) / (cosh x + cos x)

Effective AC resistance ratio: R_AC / R_DC = F_skin + F_prox

The round model is useful for early wire-spacing studies. The Dowell model is widely used for transformer and inductor winding estimates.

How to Use This Calculator

Select the model that best matches your conductor arrangement.
Enter RMS current, operating frequency, conductor length, temperature, and material values.
For round wire, add diameter, center spacing, nearby conductor count, and geometry factor.
For layered windings, add width, thickness, and the number of stacked layers.
Press Calculate to display the result block beneath the header.
Review proximity loss, total AC loss, AC to DC resistance ratio, and skin depth.
Use the CSV or PDF buttons to save the computed summary.
Compare multiple cases by changing spacing, thickness, or layer count.

FAQs

1. What is proximity effect loss?

It is extra conductor loss caused by magnetic fields from nearby conductors. Those fields push current toward limited regions, increasing current density and raising AC resistance.

2. Why does frequency matter so much?

Higher frequency reduces skin depth. As current crowds into thinner regions, both skin and proximity effects intensify, which increases copper loss and temperature rise.

3. When should I use the round-wire model?

Use it for quick estimates of circular conductors exposed to nearby alternating fields. It works well for comparing spacing, neighbor count, and wire diameter during early design screening.

4. When is the Dowell model more appropriate?

Use Dowell for transformer or inductor windings with layered rectangular conductors or foil. It is especially helpful when thickness and layer count strongly affect AC resistance.

5. Does this replace finite-element analysis?

No. This calculator is intended for engineering estimates and comparisons. Final validation for critical hardware should still use detailed field simulation or laboratory measurements.

6. Why is temperature included?

Resistivity increases with temperature. A hotter conductor has higher resistance, so both DC loss and AC-related loss predictions should be adjusted for realistic operating conditions.

7. How can I reduce proximity effect loss?

Increase spacing, reduce conductor thickness, split current among strands, lower layer count, use litz wire where suitable, and optimize winding arrangement to weaken transverse magnetic fields.

8. What does the AC to DC resistance ratio show?

It shows how much effective resistance rises under AC conditions. A value of 2 means the conductor behaves like it has twice the DC resistance at that frequency.