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I'm trying to design a tank circuit which has a large solenoid coil as the inductor but I'm stuck with the "proximty effect".
I chose the dimensions as to fit the conditions required in "Wheeler's coil inductance equation". As far as I could understand, the impedance is the total of the DC resistance, the skin effect losses due to decreased effective cross-sectional area, and the proximity effect which seems to be very similar to the skin effect (eddy currents and back EMF).
The calculations for the proximity effect is too complex, hard to find and seem to vary widely. I thought, whatever it's equiations are, they must be somehow contributing to the power consumed by the coil (ohmic heating). And the question turned into "how much power could an inductor take safely?".
I analised the standart AWG chart and calculated the "maximum (ohmic) power for safety" per 1 meter of wire and per 1 m^2 cross-sectional area of wire to be Pmax < 13 x 10^4 (Watts/m^3).
Impedance of the solenoid is easily calculated as I have a very accurate equation for the coil inductance. I'm going to use only the frequecies at which there is no skin effect (%100 skin depth frequency limit as listed in the AWG charts). Knowing the max power allowable and the impedance of the solenoid, I thought I had a reasonably safe method to calculate the coil dimensions and operating conditions.
That was until I remembered that in a RLC circuit (parallel or series) when resonance occurs, the only loss is the resistive one. So where is the proximity effect gone then? Does a capacitor somehow negate the mutual inductance between the coil turns? That doesn't make sense. The proximity effect results as cornering the current into a tighter area of the wire, when the current is rising. Even when the capacitor is "helping" the voltage source with the push, the effect would still be the same, wouldn't it?
When calculating the maximum safe power in a coil at resonance, is it P=[ I(rms)^2 ] x Z(coil impedance)] or P=[ I(rms)^2 ] x R (coil DC resistance) ?
Thanks for your time. I just don't want to burn or explode something.
I chose the dimensions as to fit the conditions required in "Wheeler's coil inductance equation". As far as I could understand, the impedance is the total of the DC resistance, the skin effect losses due to decreased effective cross-sectional area, and the proximity effect which seems to be very similar to the skin effect (eddy currents and back EMF).
The calculations for the proximity effect is too complex, hard to find and seem to vary widely. I thought, whatever it's equiations are, they must be somehow contributing to the power consumed by the coil (ohmic heating). And the question turned into "how much power could an inductor take safely?".
I analised the standart AWG chart and calculated the "maximum (ohmic) power for safety" per 1 meter of wire and per 1 m^2 cross-sectional area of wire to be Pmax < 13 x 10^4 (Watts/m^3).
Impedance of the solenoid is easily calculated as I have a very accurate equation for the coil inductance. I'm going to use only the frequecies at which there is no skin effect (%100 skin depth frequency limit as listed in the AWG charts). Knowing the max power allowable and the impedance of the solenoid, I thought I had a reasonably safe method to calculate the coil dimensions and operating conditions.
That was until I remembered that in a RLC circuit (parallel or series) when resonance occurs, the only loss is the resistive one. So where is the proximity effect gone then? Does a capacitor somehow negate the mutual inductance between the coil turns? That doesn't make sense. The proximity effect results as cornering the current into a tighter area of the wire, when the current is rising. Even when the capacitor is "helping" the voltage source with the push, the effect would still be the same, wouldn't it?
When calculating the maximum safe power in a coil at resonance, is it P=[ I(rms)^2 ] x Z(coil impedance)] or P=[ I(rms)^2 ] x R (coil DC resistance) ?
Thanks for your time. I just don't want to burn or explode something.
