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Re: Filter Choke Design

tesla-at-grendel.objinc-dot-com On Wed, 6 Mar 1996 08:30:40 +0700, you wrote:

>>From EDHARRIS-at-MPS.OHIO-STATE.EDU Tue Mar  5 18:13 MST 1996
>I',m curious about another issue in filter choke design. Namely, are people 
>considering the saturation flux density (Bmax) of their chokes? If not, then
>the inductance of a choke which is exceeding Bmax is not the same value one 
>measures beforee the choke is actually used in  tesla coil circuit. 
>
Oops, no.

>Suppose that a 100 turn choke sees:
>10,000volts at 100kHz
It may be worse that. The spice simulation I'm using (ftp to
ftp.bdt-dot-com/home/jim.fosse/tank.*) shows my 2mH inductor with almost
20Kv across it with a 15kV starting voltage!
>
>reproducing the desing formula for flux density B:
[snip]
>then assuming the torriod has a square cross section A=1cmxcm
>
>B=22,000 gauss
>
>which is about 9x bigger than the Bmax for type 43 ferrite (Marlin P Jones 
>ferrite torroids).
>
mine are 4.2 cm^2, but that may still be overloaded.
>
>Has anyone checked their chokes to see if they're becoming magnetized or if 
>the inductance has changed? Or am I missing something?
>
It may be a good thing, for the neon, to operate the core close to
saturation. I'm throwing this idea out for comment, please feel free
to correct me! The core losses go up, reducing the power to the
primary, but by the same token, you don't generate 36Kv to 45Kv across
your neon. These were some of the numbers I've generated by spice
simulation on my tank circuit. I may, however, be GIGO by using a bad
model. Comments? corrections?
>-Ed Harris

>aside: Does anyone have info on the Bmax of powdered iron?

>
Ed,
	any particular core? I've got more catalogs at work. Tonight
all I'm able to come up with is ferrite pot cores.

	jim