Re: Wire-wound resistors as dummy test load

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Original poster: "Brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ka1bbg-at-webryders-dot-net>

Hi, well maybe i can shed some light. first each manufacturer of "Nichrome"
resistance wire has its own spec's as well as diameter and thickness. The
ohms per foot vary all over the lot too. I wound a bunch of braking
resistors from 2 completely different manufacturers products. One set of
resistors had 5 1/2 turns of wire across 4 inches, the other had 11 turns
across 4 inches. As for inductance the 2 resistors are very different ie.
one has 11 turns and one has 5 1/2 turns so the inductance has to be quite
different yet both resistors measured wattage and resistance the same.. I
watched a line of resistors being made at a resistor co. and there were 3
lines in view as i worked, all 3 making the same resistors but using
different "nichrome wires" so all 3 resistors had much different inductance
values. This type of thing happens all the time, they wind them according to
watts, and resistance so the number of turns and the spacing depends on what
wire is used. you can order resistors made and tested for a certain
inductance however they cost 4 times more than regular resistors! cul brian
f.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, October 01, 2002 1:51 PM
Subject: RE: Wire-wound resistors as dummy test load


> Original poster: "Mccauley, Daniel H by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
>
> A wise guy wrote:
> > the reason wirewound resistors aren't used in pulse-type
> > applications etc... because they are so inductive.
>
> I dare say Matt realises that :)  He's asking why the
> variation in inductance.  They're all the same type, so why
> a factor of two variation in the L?
>
> > Your inductance values seem normal for what you have.
>
> If such variation is normal, what is altering by a factor of
> two from one component to the next?
>
>
> >>>>>>>>>>My guess is that the meter he is using to measure this is
getting
> confused by the large amount of series
> resistance.  I'd use a better meter.
>
> Also, for his application (steady-state) load, i wouldn't worry about the
> inductance.
>
> Dan
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> Paul Nicholson
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