[Amps] Silly Inductor Question

[Will Matney]

A couple of sources for gapped toroids are below;

http://www.elnamagnetics.com/catalogs/

http://www.alphacore.com/cores.htm

Might help if you end up needing them.

Will


On Wed, 09 Feb 2005 16:40:27 +0100, Angel Vilaseca <avilaseca at bluewin.ch>  
wrote:

> You can stack some cores, but maybe a more elegant solution would be to
> cut a small gap with a fret saw into the core. That would interrupt the
> magnetic path and prevent saturation. Fill the gap with a drop of glue.
> Now to obtain .5 mH it will take much more than just one or two turns.
> To know how many, you will need some way of measuring inductance. Add
> windings until you reach your target value.
>
> Angel Vilaseca HB9SLV
>
> Dan Levin wrote:
>>
>> Suppose that I want an inductor of 5 mH that will handle 1500 watts  
>> into a
>> 3:1 SWR from 1.8 to 30 Mhz (to build an L network antenna tuner, at the
>> output of a solid state amplifier, say).
>>
>> 12 turns on a T-400A-2 powdered iron core will give me something like  
>> 5.2 uH
>> at a maximum flux density of 70 gauss at 500 volts at 1.8 Mhz (with no  
>> DC
>> current flowing).  70 gauss is acceptable at 1.8 Mhz (and it gets better
>> relative to the spec as you get higher in frequency).  Fine, I'm a happy
>> camper.
>>
>> Now suppose that I want an inductor of .5 mH, all else the same.  4  
>> turns on
>> the same core gets me .58 mH, close enough - but the flux density is now
>> 210, well beyond acceptable limits.  Things get worse for smaller  
>> inductors
>> - the flux density goes through the roof for just 1 or 2 turns.
>>
>> I can't buy a bigger core easily - so what do I do?  Is my only option  
>> an
>> air core inductor (which I then have to shield...)?  It seems more  
>> likely
>> that I am being dense, as usual :-)
>>
>> Thanks!
>>
>>                         ***dan, K6IF
>>
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