[AMPS] Chokes

[measures]

>
>Hi Marv,
>
>> permeability, it was likely greater than 100.  Thus, the core is
>> intercepting relatively little of the magnetic field compared to a tight
>> winding.  Additionally, rod cores with their open magnetic structure are
>> very difficult to saturate compared to a toroid or other closed loop form.
>
>Heating is always more of a problem than saturation, because of 
>the finite Q of soft-iron cores. The usual exception is pulse duty. 
>Most off the shelf rods have too much loss tangent at HF. They 
>look like a resistor in series with an inductor. 
>
>If you tell me the core material type number (assuming it is a 
>standard number), I can tell you the Q or ratio of resistance to 
>reactance. I'd bet it is pretty poor with an off-the-shelf rod at the 
>high end of HF.  
>
>>   Since relatively little RF current flows through this coil, if things
>> are working correctly, the DC component probably creates more flux.  
>
>The "dc" flowing through the core is time-varying at an RF rate. 

Mr. Rauch --  Please explain the difference between ''varying'' and 
''time-varying"".
thanks


>I'm afraid no matter what the impedance, you are stuck with a certain 
>number of ampere-turns that are changing at an RF rate. 
>
>>   A tuned circuit is a much more demanding application... probably
>> requiring something in the neighborhood of 100x the power handling
>> capability.
>
>It always translates to volt-turns at a certain impedance, or ampere 
>turns at a certain frequency. Q of a resonant system multiplies the 
>problem because of increased VAR power.
>
>I would be skeptical of using random ferrite materials in a HV, high 
>current application at RF. Ferrites do not get rid of heat well.
>
> 
amen, Tom.  And, as an added bonus, sellers of ferrite materials 
typically have  better specs. .than manufacturers.  

later 
>
>


-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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