Re: Measured INDUCTANCE of my welding reactor
- From: jmeyer@xxxxxxxxxxx
- Date: Sat, 15 Oct 2005 15:36:49 GMT
On Sat, 15 Oct 2005 06:12:28 GMT, Ignoramus3498
<ignoramus3498@xxxxxxxxxxxxxxxxxxx> wroth:
>I am not yet completely sure of my numbers.
>
>I used this schematic:
>
>and made several measurements. I assumed internal resistance r of my
>wavetek to be 50 Ohm. At first, I forgot about that r and got bad
>results (clearly increasing L as function of R).
>
>The results show a relatively clear pattern, that my welder's
>inductance is between 2 and 5 mH. That's not bad.
Your inductor also has a parasitic capacitance associated with it. Each
turn is a conductor acting like a capacitor plate with respect to adjacent
turns.
The method you used ignored that capacitance.
A "better" method to estimate the inductance would be to purposly add an
external capacitor across the inductor's terminals and make the R very large
(10K to 100K, it isn't at all critical) so that your generator/R combination
acts like a current source. Then sweep the generator's frequency looking for a
resonant peak in the voltage across the L/C combination. Make the added
capacitor's value much larger than the inductor's own parasitic capacitance.
About .1 uF should do it.
Once you have that *single* frequency measurement, the inductance should
"fall out" of a simple calculation.
Jim
.
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