[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: MOT Testing

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...