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How to calculate Saturation current of a torroid?

picstudent

Aug 22, 2009
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Aug 22, 2009
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I have to wind a inducor which will have 330uH and can carry 2Amps.

I got the formula for toroid cores and the calculation was found practically accurate in a inductance meter measurement.

But that is inductance only. How to determine the core size for the required current, 2Amps in my case?
This is to be used in the output of a simple switcher(LM2576).

Thanks
 

Zipslack

Sep 15, 2009
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Sep 15, 2009
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It's been many years since I've done any coil designs, but you need to worry more about having the wire handle the amps instead of the core material. However, the choice of core material (permeability) and size drastically affects the inductance and how many turns you will need. Don't be surprised if you have to play around with a few different scenarios to get the proper combination of wire size/turns/core. You can usually find the formulas easily enough on the core manufacturer's site or catalog. I recommend setting up a spreadsheet to easily play with the values. If you already have a core you plan to use, go for it and try it out. Like I said, make sure the WIRE can handle the current first. Two amps isn't a tremendous amount of current to deal with, but you want to be careful about heat.
 

Resqueline

Jul 31, 2009
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Jul 31, 2009
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I was never able to figure out how to use the manufacturers formulas and figures to find the saturation current. One should think it ought to be as easy as supplying an Ampere-Turns figure for a specific core, but alas..
I finally built a pulse generator capable of 50A peak current, and using an oscilloscope to monitor the current it was easy to find the saturation point (& the inductance).
But it could be done as easy as Zipslack suggests; if the core has room for the wire size and turns needed then it's not likely go into saturation (if it's intended for dc use).
 
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