Transformer Inductance

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Bruno2000
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Transformer Inductance

Post by Bruno2000 » Wed Mar 10, 2010 4:23 pm

I need a fairly large inductance in a small package, so I thought about using a miniature audio transformer with the windings connected in series. Is there a way to figure out what the inductance would be, knowing the impedance and the DC resistance (or should I just buy one and measure it)?
Thanks!
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JR.
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Re: Transformer Inductance

Post by JR. » Fri Mar 12, 2010 11:07 am

I have no practical experience with this. I don't know if you can use transformer action to get something for nothing. I wouldn't think there is an easy substitute for copper and iron to give large LF signal handling.

When in doubt, try it and see what happens.

JR
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Re: Transformer Inductance

Post by emrr » Fri Mar 12, 2010 12:04 pm

I think you'll have to buy a meter. I think there are some ways you can rig a meter set-up, but owning a meter is probably worth it in the long run. I think CJ or PRR may have posted a method at PP.
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Bruno2000
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Re: Transformer Inductance

Post by Bruno2000 » Fri Mar 12, 2010 3:57 pm

Thanks folks,
Looks like plan B. Buy the transformer and measure it.
I've seen some LC meters on eBag that will go up to 20H for about $30. Anybody ever used one of these?
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JR.
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Re: Transformer Inductance

Post by JR. » Sat Mar 13, 2010 12:02 pm

I'm not sure what your application is but perhaps prototype up the circuit you want to use the transformer/inductor in, and see how it acts.

I suspect there may be no free lunch here.

JR
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mediatechnology
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Re: Transformer Inductance

Post by mediatechnology » Fri Mar 19, 2010 11:19 am

Bruno2000 wrote:I need a fairly large inductance in a small package
How big and how small?
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JR.
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Re: Transformer Inductance

Post by JR. » Fri Mar 19, 2010 4:48 pm

Thinking out loud, without knowing what you are trying to do, it is common to use opamps with a small capacitor to mimic a large capacitor, perhaps a similar trick could multiply a small inductor to look like a bigger one.

Also gyrators, use opamps with small caps to mimic inductors, perhaps another option.

If dealing with a lot of current or voltage, you may need to use a real inductor.

JR
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mediatechnology
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Re: Transformer Inductance

Post by mediatechnology » Sat Mar 20, 2010 9:38 am

I have a hunch we may be making a vintage inductor-based EQ based on a popular design.
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JR.
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Re: Transformer Inductance

Post by JR. » Sat Mar 20, 2010 10:56 am

Funny I still have some inductors back in my lab I bought to build a 5 band GEQ from a kit in popular electronics back in the '70s. I never built it or any Inductor based EQ, and don't even like the common gyrator based EQs (gyrator as shunt to ground between opamp + and - inputs).

If trying to recreate a classic design, I suspect it would be useful to use the same general components. It's not nice to fool father physics.

JR
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