Re: [TCML] Terry Filter Resistors

[mddeming@xxxxxxx]

Hi Gary, All,

I think part of the problem is that most LC meters don't measure Inductance directly. They actually measure the Z of the device and assume Z=XL, and therefore L=Z/2pif, which for most inductors is close enough. For a wire-wound resistor though, this is not a good approximation, since actually Z=sqrt(R^2+XL^2), and R is no longer negligible. You could use the L?shown by the meter to calculate what Z it actually read by Z=2pifL, then using the known resistance, calculate a corrected XL? from XL=sqrt(Z^2-R^2)and from that, determine the corrected L by L=XL/2pif. 

Matt D.


-----Original Message-----
From: Lau, Gary <Gary.Lau@xxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, 28 Jan 2009 8:50 am
Subject: RE: [TCML] Terry Filter Resistors



Bart,

Please confirm "I just checked the resistor in question and it measured 146mH at 
1kHz."  146 mH sounds about a million times too high for the inductance of a 
wirewound resistor.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Tuesday, January 27, 2009 6:09 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Terry Filter Resistors
> 
> My point was that the inductance of the resistor does not appear to be
> part of the design (that I'm aware of) as opposed to say using an
> inductor on the hv side of a transformer. I just checked the resistor in
> question and it measured 146mH at 1kHz. What inductance values do you
> use on the hv side? There may be some filtering there going on, but I
> still don't know if it is by design or by accident.
> 
> Take care,
> Bart
> 
> DC Cox wrote:
> > As current moves thru the inductor, the rising magnetic field causes the
> > peak currents to reduce.  It takes a bit of time to produce the magnetic
> > field, and
> > this clamps the peak currents.  Commonly used in series with large Marx
> > generators when testing HV insulators, transformers, etc.
> >
> > Dr. Resonance
> >
> >
> >
> >
> > On Mon, Jan 26, 2009 at 6:28 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> >
> >
> >> Hi Jim,
> >>
> >> I've never heard mention of the resistors for LC filtering in the Terry
> >> filter. Given the application and various configurations of the 
transformers
> >> and tank C with no change to the resistor, I don't see how the inductance
> >> can play a part in the filtering.
> >>
> >> Take care,
> >> Bart
> >>
> >> Jim Mora wrote:
> >>
> >>
> >>> The Terry Resistors handle some fair power. Terry selected the Ohmites for
> >>> the "small air core inductance they add" to the filter.
> >>>
> >>> Jim Mora
> >>>
> >>>
> >>>
> >> _______________________________________________
> >> Tesla mailing list
> >> Tesla@xxxxxxxxxxxxxx
> >> http://www.pupman.com/mailman/listinfo/tesla
> >>
> >>
> >
 _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
> >
> >
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla