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Air Core Inductor Calculator
Calculation of power handling and temperature of air core inductors.
Calculate values and power handling of an air core inductor
Which air core inductor for my crossover?This calculator determines the maximum power handling of an inductor
based on its heat distortion temperature.
Further explanations can be found below the calculator.
| Enter inductor values | ||||
| Value: | mH | Wire diameter: | mm | |
| Resistance: | Ohm | Material: | ||
| Size | Calculate Outer Ø | |||
| Select an inductor or enter dimensions manually below | ||||
| Inner Ø | mm | Outer Ø | mm | |
| Winding Height | mm | Max Temp. | °C | |
| Calculated Values | ||||
| Turns: | x | Layers: | x | |
| Turns per Layer: | x | Wire Length: | m | |
| Si: | (m²*K) | Wire Length approx. (R): | m | |
| Calculated Power Handling (Inductor in series with chassis) | ||||
| Ambient Temp. | °C | ΔT | °C | |
| Variable Heat Transfer Coefficient | ||||
| HiFi Applications | PA Applications | |||
| Prms 2Ω | W | Prms 2Ω | W | |
| Prms 4Ω | W | Prms 4Ω | W | |
| Prms 8Ω | W | Prms 8Ω | W | |
| Prms 16Ω | W | Prms 16Ω | W | |
| Max Current | A | Max Current | A | |
| With Sine Wave Signal | ||||
| Max Current | A | Pmax 2Ω | W | |
| Power Dissipated at Inductor | W | |||
| Calculate Manual Temperature Rise | ||||
| Load Impedance | Ohm | Power Load (RMS) | W | |
| Tmax Sine | °C | ΔT Sine | °C | |
| 6dB Crest | °C | 6dB Crest | °C | |
| 9dB Crest | °C | 9dB Crest | °C | |
| 12dB Crest | °C | 12dB Crest | °C | |
| Inductors in Series | |||||
| L1 | + | L2 | = | Ltotal | |
| mH | + | mH | = | mH | |
| Inductors in Parallel | |||||
| L1 | + | L2 | = | Ltotal | |
| mH | + | mH | = | mH | |
Explanation:
| General Information | |
| This calculator serves as an approximation for the maximum power handling of air core inductors. We evaluated an empirical test series of over 300 measurements for this purpose. To determine the coefficients, the inductors were loaded with a 100 Hz sine wave (3 dB crest) for 40 to 360 minutes with currents ranging from 2 to 16 A across a 2-ohm load resistor, measuring the temperatures on both the inside and outside of the winding. Deformations of the ABS bobbin were observed between 100–105 °C after 30 to 50 minutes, meaning continuous operation at 85 °C (with approx. 10 °C headroom) is perfectly safe. |
|
| Tips | |
| If more headroom is desired—for example, in PA applications where black speaker cabinets sit in direct sunlight for hours— increase the ambient temperature setting from 20 °C to 40 °C, or alternatively, reduce the target heat distortion temperature. |
|
| Inductor Values | |
| Material | Only required for "Wire length (R)" |
| Wire length (R) | This is just a rough approximation based on the resistance R and should yield a similar result to "Wire length" for copper. |
| Size | Pre-selection of typical Intertechnik air core inductors |
| Outer Ø | Manual entry (by deactivating the checkbox) provides slightly more accurate results. |
| Heat Distortion Temp. | Maximum temperature of the former/bobbin; for typical ABS, this is 85 °C |
| Calculated Values | |
| Values | The physical values are self-explanatory. |
| Si | Effective cooling surface of the inductor (in m2) to determine heat transfer (Fixed value) |
| Power Handling | |
| Ambient Temp. | Typically, we choose 20 °C as the starting baseline value. |
| ΔT | The temperature delta. Temperature rise of the inductor. |
| Heat Trans. Coeff. | Deactivate for a fixed heat transfer coefficient. Useful for continuous, long-term loads over many hours in non-audio applications. |
| Power Handling | HiFi applications are calculated with a 12 dB crest factor, PA applications with a 9 dB crest factor. For a 6 dB crest factor, simply halve the PA values. Sine wave values are for a continuous load with a constant sine wave, making them less relevant for crossovers and audio applications. |
| Power Dissipated at Inductor | The power dissipated by the inductor (converted into heat) during a sine wave signal with 3 dB crest. |
| Manual Calculations | |
| Impedance | Impedance of the load, e.g., the speaker chassis in series with the inductor. |
| Power Load max | Maximum power handling (RMS load) of the load, e.g., the speaker chassis. |
| Tmax | Maximum total temperature of the inductor, depending on the ambient temperature. Arranged vertically for sine wave and for music signals with crest factors. |
| ΔT | The temperature rise of the inductor, arranged exactly like Tmax. |
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