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I need to make a dc dc converter and have some ferrite toroids but I don't have the datasheet of the cores so I need to know how much energy are capable do store the core and what current can they handle. I need an average current of about 6A at the output so the inductor current will be at least 6A probably 7 or 8A because of the efficiency and the conversion ratio.

Edit.

What would be a good test to know if the cores I have can handle a current of 8A with a switching frequency of 10KHz?

Nick Alexeev
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Luis Ramon Ramirez Rodriguez
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    Get some suitable cores with data. – Leon Heller Sep 22 '15 at 00:19
  • That sounds quite logic but in Venezuela we can't do that we don't have access to dollars and get it in a parallel market for buy an inductor will cost about a month salary. So I need to work with what I have. – Luis Ramon Ramirez Rodriguez Sep 22 '15 at 00:54
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    If these are really ferrite toroids, you will not be able to make an inductor with them. Ferrite has too high of permeability, and will saturate without a gap. You'll need some kind of distributed gap (low perm material) toroid, like powdered Iron or MolyPermalloy. – gsills Sep 22 '15 at 01:46
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    Very similar questions (with answers) here: http://electronics.stackexchange.com/questions/12594/measuring-ferrite-core-parameters and http://electronics.stackexchange.com/questions/70604/ferrite-or-iron-powder-how-do-i-tell-what-an-unknown-core-is-made-of. My rule of the thumb is that equipment required to characterize magnetics usually costs (far) more than buying the stuff with datasheet... As for arduino project google "arduino LCR meter" etc. But it's not exactly what you want. – Fizz Sep 22 '15 at 02:45
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    Here's a paper on (laboratory grade) core characterization: http://core.ac.uk/download/pdf/4876634.pdf I'm not aware of any arduino-like projects that attempt something like that. – Fizz Sep 22 '15 at 03:11
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    As for measuring/estimating core losses for SMPS purposes, that's a notoriously difficult problem, see http://eprints.soton.ac.uk/259070/1/tmag_hys.pdf for example. I don't think there is any shoestring budget method of doing that. – Fizz Sep 22 '15 at 03:25
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    Since you have a low budget, I think your best bet is to just test a toroid in the circuit. Use resistors to make a test load, so you can slowly increase the current being drawn. If it can't maintain the voltage, then you need more energy storage. Add another toroid in series or increase the switching frequency. If it overheats, then you need more current capacity. Another toroid in parallel should help with that. – Luke Sep 23 '15 at 22:21

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