I'm looking to buy some inductors, axial or radial ones. What I need to know is the difference between measured dc current and ac current. Modeled in multisim, the max dc current through the inductor is about
1mA but the max ac current approaches 1A. I know inductors have max current values, so do I use the 1mA or the 1A to decide which one to buy?
RMS current is what's important, because the issue is self-heating of the coil (and its contacts). In your case, the DC current is so small it's negligible compared to your AC current. Is this current at high frequency or low frequency? If it's high frequency, you may need to derate it because heating increases with frequency.
Its for a Colpitts oscillator at around 1-2MHz. So should I go with a higher rated inductor? What does derate it mean?
Sounds pretty high for the steady-state current in an oscillator, even for the resonator coil.
Derate means you must reduce the current rating as a function of AC frequency. Calculate the self-heating due to resistance at DC with the rated current. The coil can be operated at that power dissipation at AC, but not higher. Calculate the heating of the coil due to AC current and calculate the I^2*R loss. AC resistance is always higher than DC resistance for a coil. How much higher should be on the data sheet.
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