Re: Toroid inductance

>Date:          Sat, 1 Jun 1996 12:25:04 -0600
>From:          Tesla List <tesla-at-poodle.pupman-dot-com>
>To:            Tesla-list-subscribers-at-poodle.pupman-dot-com
>Subject:       Re: Toroid inductance
>Reply-to:      tesla-at-pupman-dot-com
>>From jim.fosse-at-bdt-dot-comSat Jun  1 07:46:13 1996
>Date: Sat, 01 Jun 1996 05:09:27 GMT
>From: Jim Fosse <jim.fosse-at-bdt-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Toroid inductance
>>>From chip-at-grendel.objinc-dot-comFri May 31 21:34:48 1996
>>Well, I finally got a (not really a)VOM and used it to measure the inductance
>>of the 400Hz 10A 3ph. variac core this morning.  
>>I measured 69.984542848319856 mH.  
>Are you sure that you transcribed that number right? didn't drop any
>>The problem is that the last significant
>>digit kept changing. 
>Thats the problem with digital engineers (oops) meters they can't make
>up their minds! Now an analog LCR bridge will give you a nice stable
>70mH +- 10%;)
>> I think I'm going to return the meter -- it's not stable :-)
>>Seriously, it works great and displayed a value of about 70 mH.
>Take it back. It's not accurate enought;) 69.984542848319856 mH
>>I hope the value is high enough.  I've been reading about values in the 300mH
>	you've got 3 sections. Put them in series. 3 * 70mH = 210mH!
>If that isn't enough, get 2 pole pigs and put their primaries in
>series with you neons. That way, you can also use their secondaries as
>110V/220V isolation xformers. GDAR
>	Highest Regards,
>	jim

Anyone mind if I butt in here?  Chip, if you are planning to employ those 
variac cores in your HV supply line as an RF choke, or if Jim is 
trying to make you,  you both might want to consider that their winding
to conductive core insulation is only designed by the manufacturer for a few
hundred volts and as such these sections if used as RF chokes will not be
capable of holding off high RF voltages end to end, or either end to core.  
The dry air core chokes I wind (and which I now custom build for market)
can hold off  Tesla RF voltages capable of 3 inch long air sparks from either
end to the other, or grounded mounting surface without internal or surface
breakdowns.  They can do this in part because there are no conductive 
materials anywhere in or too near near the winding form.

Oh yeah, that other small magnetic hysterisis and eddy current loss problem
encountered trying to use  60 Hz transformer iron in the RF Zone shouldn't be
too obscure.

Did I miss something fundamental earlier on this thread?  I apologize 
if  I misunderstood the question here.  I certainly don't want to offend the
parties involved,  your intelligence and technical knowledge are above 
I've just returned from the Rochester, N.Y. Hamfest and am trying to 
review my favourite mail.   My own cognitive
(and being able to keep my eyes open) functions are definitely in question!

Good nite, rwstephens