Formula Used
AWG diameter: d = 0.127 x 92^((36 - AWG) / 39) mm.
Single strand area: A = pi x (d / 2)^2.
Total conductor area: A total = strand area x strand count x parallel bundles.
Effective length: L effective = length x (1 + twist allowance / 100).
DC resistance: R = rho x L effective / A total.
Temperature correction: R temperature = R20 x [1 + alpha x (temperature - 20)].
Skin depth: delta = sqrt(rho / (pi x frequency x mu0)).
Estimated AC resistance: R ac = R temperature x skin factor x proximity factor.
Voltage drop and loss: V = I x R ac. Power = I^2 x R ac.
How To Use This Calculator
Enter the wire length first. Choose meters or feet. Select AWG when the strand gauge is known. Select diameter when a manufacturer gives strand size in millimeters.
Add the number of strands in one bundle. Add parallel bundles if the winding uses several equal conductors together. Choose the conductor material. Use custom resistivity for special alloys.
Enter temperature, frequency, twist allowance, proximity allowance, and current. Press calculate. The result appears above the form. Use CSV or PDF buttons to save the current calculation.
A Practical Guide to Litz Wire Resistance
Litz wire helps reduce alternating current loss in coils. It uses many insulated strands instead of one solid conductor. Each strand carries part of the current. The design lowers skin effect when strand diameter is chosen well.
Why Resistance Matters
Resistance controls voltage drop, heating, and usable power. A small error can change a winding design. High resistance can overheat a transformer. Low resistance can improve efficiency and stability. The calculator gives a quick estimate before a final prototype is tested.
Important Design Inputs
Length is the first input. Longer wire increases resistance. Strand diameter is also important. Smaller strands usually help at high frequency. More strands increase total copper area. More area lowers direct current resistance. Twist allowance adds extra conductor length. This makes the result more realistic. Temperature matters because metal resistance rises when the winding gets hot.
Frequency And Skin Depth
At higher frequency, current moves toward the strand surface. Skin depth estimates how deep current flows. A strand should often be smaller than about two skin depths. That rule keeps the litz advantage useful. If a strand is too thick, the calculator raises the estimated alternating current factor. This is only an engineering estimate. Real coils may need lab measurements.
Using Results Wisely
Use the resistance value to estimate voltage drop. Use power loss to judge heat. Compare several strand counts and gauges. Look for a balance between loss, price, and winding space. Very high strand counts can be difficult to terminate. They can also increase cost. Good designs consider copper area, frequency, insulation, cooling, and manufacturing limits together.
Limits Of The Estimate
The tool does not replace detailed electromagnetic simulation. It cannot fully model proximity effect, winding layers, terminations, or imperfect strand transposition. The proximity allowance helps include extra loss. Use it when conductors are packed tightly. For critical equipment, validate the calculation with measurements. Still, this calculator is helpful for early design, comparison, and documentation.
Good Documentation Practice
Record every assumption beside the result. Save material, length, gauge, strand count, and temperature. Exporting the table helps compare options later. Clear notes also support purchasing, testing, and maintenance work across repeated winding projects during future design reviews safely.
FAQs
What is Litz wire?
Litz wire is made from many individually insulated strands. It reduces high frequency losses caused by skin effect. It is common in transformers, inductors, wireless power coils, and resonant converters.
Why is strand diameter important?
Smaller strands help current use more conductor area at high frequency. A large strand can behave more like solid wire and increase alternating current resistance.
Does this calculator include skin effect?
Yes. It estimates skin depth from resistivity and frequency. It then applies a simple AC factor when strand radius becomes larger than skin depth.
What is twist allowance?
Twist allowance adds extra conductor length caused by strand lay and bunch construction. A value between two and five percent is often useful for early estimates.
What is proximity allowance?
Proximity allowance represents extra loss from nearby conductors and magnetic fields. Increase it when turns are packed tightly or current is high.
Can I use custom material?
Yes. Select custom material and enter resistivity in ohm meters. This helps with special alloys, plated conductors, or vendor supplied values.
Why does temperature change resistance?
Metal resistance usually rises as temperature increases. The calculator applies a linear temperature coefficient referenced to twenty degrees Celsius.
Is the result enough for final design?
Use it for estimation and comparison. Final designs should be checked with measurements, thermal review, winding layout analysis, and manufacturer data.