I am experimenting with the simple circuit shown below and was wondering how to ensure that the inductor used would handle the inrush current.
My reasoned solution is the following:
I solved for current to Voltage transfer function and applied a step response to get the inrush current (over one second interval), then multiplied by 15 (for 15V input). This gives a peak of around 2.2A which is approximately the current where my bench supply stopped tripping the limiter, so far so good. (ESR was left off of this btw, since it is something like 60mOhm according to the datasheet)
The inductor is rated for 500mA, saturation current is 560mA (datasheet is here). I'm assuming it's heat that kills inductors, so assuming continuous operation at max rating (35C temp rise, according to the datasheet), and internal resistance of 1.7Ohms, that gives 0.425W, or 0.425 J/sec max allowable dissipation.
I then calculated power dissipated in the 1.7Ohms over the 1 second inrush period and integrated. I end up with 0.1408 J, lower than the continuous rating.
However, during inrush the inductor becomes saturated, and I know this generally has a heating effect, which wasn't taken into account in my calculation, and I'm not exactly sure if it is just from the excess heat dissipated in the resistance, or if I need to account for it in some other way.
So my questions:
1) Is this a reasonable way to think about inductor sizing and current handling during inrush, or is there a more common/different/better way?
2) Do I need to take into account any energy dissipated in saturation beyond just the resistance to solve for the total heat dissipation under these conditions?
3) If this is reasonable, would it be applicable to sizing of common-mode chokes at the supply as well? It seems overkill to put in a 2.5A rated CM choke when the system is only drawing a small amount of current.