Re: Why does running an NST on an async gap kill it?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Mark,

At 10:05 PM 8/7/2003 -0500, Mark Broker wrote:
>...
>
>The wirewound resistors in Terry's filter design do have a fairly large 
>inductance.  I remember trying to measure it once (the 1kohm, 100W 
>Ohmites), but the RLC meter I was using had issues with the large 
>resistance, and wouldn't give me reliable results.

I measured one of the Ohmite L100J1K0  100W 1K ohm resistors here.

I get a DC resistance of 1000.88 ohms (pretty good for a cheap space heater 
resistor ;-)) and an inductance of 884nH.  I resonated it at 307kHz with 
two 0.15uF caps of our favorite kind ;-)  I used the HP signal generator 
and Tek scope to resonate the set.

The Elenco LCR-1801 gives 997 ohms at 1.121uH.

At say 250kHz, 1uH has a reactance of 1.57 ohms.  Insignificant in terms of 
the filter's operation.  So I think it is safe to say the series inductance 
of the resistors is insignificant in the filter's case.

Odd that it messed your meter up, but some LCR meters don't like series 
resistance at all when measuring inductance.  Depends on how they work 
inside...

Cheers,

         Terry