Parallel Inductance Calculator

Parallel Inductance Calculator

H mH µH nH

H mH µH nH

H mH µH nH

H mH µH nH

Total Equivalent Inductance (L_eq):

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Understanding Parallel Inductance

In electrical engineering, when inductors are connected in parallel, the total inductance decreases, similar to how resistors behave in parallel. This configuration is commonly used in RF circuits, power supplies, and filter design to achieve specific inductance values that aren't available as standard component ratings.

The Parallel Inductance Formula

For inductors connected in parallel where there is no mutual inductance (magnetic coupling) between them, the total equivalent inductance (L_eq) is calculated using the reciprocal formula:

1 / L_eq = 1/L₁ + 1/L₂ + 1/L₃ + … + 1/L_n

If you only have two inductors in parallel, you can use the simplified product-over-sum formula:

L_eq = (L₁ × L₂) / (L₁ + L₂)

Practical Example

Suppose you have two inductors in parallel with values of 100 µH and 200 µH. Using the formula:

• L1: 100 µH
• L2: 200 µH
• Calculation: (100 × 200) / (100 + 200) = 20,000 / 300 = 66.67 µH

Notice that the equivalent inductance (66.67 µH) is always smaller than the smallest individual inductor in the parallel network.

Key Rules to Remember

1. Mutual Inductance: This calculator assumes that inductors are shielded or placed far enough apart that their magnetic fields do not interact. If magnetic coupling exists, the calculation becomes much more complex.
2. Units: Always ensure all values are converted to the same unit (e.g., all in Henries or all in Microhenries) before performing manual calculations.
3. Decrease in Value: Adding an inductor in parallel to an existing circuit will always decrease the total inductance.

function calculateInductance() { var val1 = parseFloat(document.getElementById('val1').value); var unit1 = parseFloat(document.getElementById('unit1').value); var val2 = parseFloat(document.getElementById('val2').value); var unit2 = parseFloat(document.getElementById('unit2').value); var val3 = parseFloat(document.getElementById('val3').value); var unit3 = parseFloat(document.getElementById('unit3').value); var val4 = parseFloat(document.getElementById('val4').value); var unit4 = parseFloat(document.getElementById('unit4').value); var totalReciprocal = 0; var count = 0; if (!isNaN(val1) && val1 > 0) { totalReciprocal += 1 / (val1 * unit1); count++; } if (!isNaN(val2) && val2 > 0) { totalReciprocal += 1 / (val2 * unit2); count++; } if (!isNaN(val3) && val3 > 0) { totalReciprocal += 1 / (val3 * unit3); count++; } if (!isNaN(val4) && val4 > 0) { totalReciprocal += 1 / (val4 * unit4); count++; } if (count < 2) { alert("Please enter at least two valid inductor values."); document.getElementById('results-area').style.display = 'none'; return; } var leq = 1 / totalReciprocal; document.getElementById('res-h').innerHTML = "Henries (H): " + leq.toExponential(4); document.getElementById('res-mh').innerHTML = "Millihenries (mH): " + (leq * 1000).toFixed(4); document.getElementById('res-uh').innerHTML = "Microhenries (µH): " + (leq * 1000000).toFixed(4); document.getElementById('res-nh').innerHTML = "Nanohenries (nH): " + (leq * 1000000000).toFixed(2); document.getElementById('results-area').style.display = 'block'; }