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Re: [TCML] Terry Filter
Jim -
I had wondered about the inductance of large wire-wound resistors when used
in a Fritz Filter, and initially tried to find some non-inductive resistors
(monolithic "Carborundum" style) when I was building the filter for my
15/120
system. However, I was never successful in finding any surplus non-inductive
resistors with a value anywhere around 1K ohms, so in the end I just used
conventional wire-wound power resistors.
In answer to your question, I measured the inductance of several 1K ohm Dale
wire-wound resistors that I had laying around using a Sencore LC75
inductance analyzer. (I couldn't immediately locate my own Fritz Filter
with its 1K/100 watt Ohmite resistors.)
Length dimension is the actual winding length of the resistance wire, not
the overall resistor body length.
1K ohm 225W 9-1/4" long X 1-1/8" dia 160 micro-henries
1K ohm 55W 3-1/4" long X 3/4" dia 175 micro-henries
I was a bit surprised that the inductance values happened to be so close,
given the large difference in resistor physical size.
I'm not sure what you mean by "reverse RMF"; did you mean "back EMF"?
Regards,
Scott Hanson
----- Original Message -----
From: "Jim Mora" <jmora@xxxxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Monday, December 31, 2007 12:40 PM
Subject: [TCML] Terry Filter
Hello,
I am curious, has anyone ever measured the inductance of a 1K 100w Ohmite
resistor? I don't know if they are inductive canceling. The two inch spark
I
got while adjusting my unloaded Terry Filter is still a mystery. The gaps
were 1/8" each at the time and the center was grounded to the neon and
mains.
I am thinking reverse RMF from ramping up the variac too fast???
Jim
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