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Filter Choke Design
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To: tesla-at-grendel.objinc-dot-com
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Subject: Filter Choke Design
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From: EDHARRIS-at-MPS.OHIO-STATE.EDU
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Date: Tue, 05 Mar 1996 18:22:15 -0500 (EST)
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>Received: from phyas1.mps.ohio-state.edu (phyas1.mps.ohio-state.edu [128.146.37.10]) by uucp-1.csn-dot-net (8.6.12/8.6.12) with ESMTP id QAA17169 for <tesla-at-grendel.objinc.COM>; Tue, 5 Mar 1996 16:22:18 -0700
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.
Suppose that a 100 turn choke sees:
10,000volts at 100kHz
reproducing the desing formula for flux density B:
8
V x 10^
B= ------------------
4.44 x f x N x A
where
B=peak flux density in gauss
V=rms voltage
f=frquency in Hz
N=number of turns
A=core area in sq cm
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).
Has anyone checked their chokes to see if they're becoming magnetized or if
the inductance has changed? Or am I missing something?
-Ed Harris
aside: Does anyone have info on the Bmax of powdered iron?