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1.6: Inductor Sizing Equation

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    The Inductance Formula


    Wheeler’s formulas for inductance of air core coils which follow are useful for radio frequency inductors. The following formula for the inductance of a single layer air core solenoid coil is accurate to approximately 1% for 2r/l < 3. The thick coil formula is 1% accurate when the denominator terms are approximately equal. Wheeler’s spiral formula is 1% accurate for c>0.2r. While this is a “round wire” formula, it may still be applicable to printed circuit spiral inductors at reduced accuracy.


    The inductance in henries of a square printed circuit inductor is given by two formulas where p=q, and p≠q.


    The wire table provides “turns per inch” for enamel magnet wire for use with the inductance formulas for coils.


    This page titled 1.6: Inductor Sizing Equation is shared under a GNU Free Documentation License 1.3 license and was authored, remixed, and/or curated by Tony R. Kuphaldt (All About Circuits) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.