Re: MOT Testing

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Brian" <ka1bbg@xxxxxxxxxxxxx>

look over the section for inductive reactance(resistance at frequency) will
be helpful for making an inductance to limit current something like 1/2pie
fl will give you the resistance at frequency. cul brian f.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, April 25, 2005 2:47 PM
Subject: Re: MOT Testing


> Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>
>
> Mark,
> Thanks a lot. You have been extremely helpful. While at the appliance
> repair shop, I grabbed a bunch of stove top heating elements and oven
> heating elements. All of them test good. I thought they would make great
> low ohm, high watt, low inductance resistors. Other than looks, is there
> any reason I shouldn't use these as resistors this way?
>
> I saw that business about Z^2=Z1^2+Z2^2+Z3^2+... and I don't know where
> this came from. I checked my copy of The Art of Electronics by Paul
> Horowitz and Winfield Hill, second edition and on page 32 it says that
> series impedance is calculated as Z=Z1+Z2+Z3+.... Where did I miss the
> boat? I know you guys are way ahead of me, so I figure there is something
> I'm not taking in to account. The Electric Engineering professor at the
> local university told me that this book is just about the best electronics
> reference available, so I feel like I can trust it, especially on
something
> as basic as this. I hope someone can explain this to me, please.
> BTW, was "sum" discussion a pun?
>
> Now, I'm reading full tilt about constructing inductors. I'm sure I'll
find
> plenty in the archives.
>
> Paul
> Think Positive
>
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Monday, April 25, 2005 11:21 AM
> Subject: RE: MOT Testing
>
>  > Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>
>  >
>  >
>  > Paul:
>  >
>  > I agree with your approach.  Not certain why you get a different result
>  > when you check the secondary as opposed to the primary.  Maybe at these
>  > low test voltages the resistance of the secondary is affecting the
>  > results.  Most of my MOT secondaries have about 60 ohms of resistance.
>  >
>  > For current limiting you indicate you want 15 amps (now this calc is
for
>  > 1 MOT mind you, not a bank of 2 or 4) so your total impedence needs to
>  > be 120V/15amps = 8 Ohms.
>  >
>  > You have 4.75 Ohms already in the MOT so you need 3.25 Ohms of
impedence
>  > from your current limiting inductor(Note - follow current limiting
>  > inductor thread discussion going on.  There is sum discussion about
>  > whether Z=Z1+Z2 or Z^2=Z1^2+Z2^2. If the latter then you need 6.5
Ohms).
>  >
>  > Now for the moment assume R=0 for the inductor, then X^2 = Z^2 - R^2 so
>  > X = Z.  Then L = X/(2*Pi*60).
>  >
>  > So you have L = 3.25/(2*Pi*60)=.00862 H or 8.62 mH for your cuurent
> msnip...