Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
If you want to pass 20amps RMS through an inductor you need an inductor that's rated for a minimum of... 20 amps =) I'm not sure where you're getting 28.28
For AC it's resistance is the least of your problems, inductors generally don't let AC pass without some reactance, which is dependent on the frequency of the AC signal you're trying to pass.
28.2A is 20A RMS? What do you mean? 20 amps RMS is 20 amps... 28.2 peak amps maybe but it's RMS that's important for valuing components for AC. I'm not sure what you're talking about ESR. Reactance + Resistance = total impedence if that's what you're looking for. Without the frequency and value of the inductor we can't answer the question.
The current limit is in DC, meaning if i apply AC current on inductor, i need to match the AC current with the DC current limit, therefore to do this match, should i take the peak value of the AC current and make sure the the peak current is under the DC current limit?
In datasheet its said: MAX DC RESISTANCE IS 0.9ohm.
What is MAX DC RESISTANCE?
I thought I was clear electricity, you don't use the peak value, you use the RMS value for AC, and inductor can handle MANY times it's 'maximum' current for short durations so the peak value is irrelevant as long as the RMS current is within it's specs. If the frequency allowed it you could probably put 10 times the rated current through that inductor for very short periods of time.
Datasheet for what your inductor? It sounds like the ohmic resistance of your coil is .9 ohms.
If i need to apply 20Arms current for long periods of time, then how do i need to match the AC current (20Arms) to the MAX DC Current limit ?
meaning for 20Arms long period AC current, what should be the MAX DC current limit (they dont show in datasheet MAX AC Current limit).
Here is the info about the inductor (didnt find datasheet): PA0135.102NLT
What is then the ohmic resistance (not reactance) in AC, 50Hz?
This ESR should be depended on frequency right?
It's not usually called ESR for inductors, but yes. The ESR as you call it depends on frequency and the inductance of the coil. I'm not sure how to derate the inductor for power AC applications like that, it depends on what the core material of the inductor is, you'd have to ask the manufacturer.
The ohmic resistance is listed and you've already said it twice now. It's .9ohms resistance, AC or DC ohmic resistance is always the same.
You're not looking for ESR, you're looking for bulk (ohmic) resistance.
Just a language mix up =)
I wasn't thinking the DC maximum thing through sorry for shooting you down so fast. The problem with AC VS DC signal is the ripple. There's going to be heat loss in the core under AC conditions which could cause it to over heat faster than just the ohmic resistance, only the maker of the inductor can tell you what the effects of AC are. Someone else here might have a better idea of how to derate the inductor for AC use.
Because the physical construction of a capacitor and an inductor are VERY different not just their function.
A capacitor has a voltage limit because after a certain voltage their dielectric (internal insulators) break down and conduct, destroying the cap.
Inductors are wires wrapped around ferromagnetic cores mainly, the insulation of most inductors is significantly thicker than that of the dielectric of a capacitor so it can withstand a much higher voltage before the dielectric breaks down. A capacitor's insulator has to be thin because the closer the plates are together the higher the capacitance. With an inductor the insulator is just there to prevent short circuits. Air core inductors don't even need insulation if they're spaced far enough apart.
What SCeadwian told you about AC current through an inductor is WRONG!. The maximum current rating for an inductor states the peak current, which if exceeded, will cause the inductor's core to saturate.
If the rated peak current is 20A, then you can pass 20A dc, or 20/1.414= 14.1A rms.
If you need to pass 20 A rms, then buy an inductor rated for 28.3A dc, assuming of course that your waveform is sinosoidal.