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RE: [TCML] NST Measurements



Hi Gary, Bart, All,


?


Back in Oct '07 I measured the Vin/Vout ratio forward and backward on a 15/30 Transco NST using an old Triplett 630-Aanalog meter, which has a 6KVAC scale. The forward ratio was 124:1 at 48.4 Vin implying 14880 Vout at 120 Vin, but the reverse ratio was only 37:1 with 120 Vin on the secondary. These results are very inconsistant.?I will have to rerun it when I get a chance, but it seems to indicate that the reverse method doesn't work well for an NST


?


Matt D.










-----Original Message-----

From: Lau, Gary <Gary.Lau@xxxxxx>

To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>

Sent: Sun, 18 Jan 2009 6:54 pm

Subject: RE: [TCML] NST Measurements





Hi Bart,    As often as I have dispensed the same advice to measure and feed the mains   voltage into the NST secondary and measure the primary to determine the sec/pri   ratio, I don't recall ever having actually done that to mine.  So, I just pulled   out a 15/30 and a 15/60 NST.      The 15/30 measured a ratio of 153X, so assuming a 120V primary, predicts a   18.3kV secondary.    The 15/60 measured a ratio of 145X, so assuming a 120V primary, predicts a   17.4kV secondary.    The meter that I used is a simple Fluke DMM, not RMS.  But given that the NST is   going backwards, I wouldn't think that it's getting near saturation and the   associated waveform weirdness.  Unfortunately I don't own a HV probe that I   would trust to measure it in the normal operating sense.  Have you done this and   gotten closer to the faceplate voltage rating?    Regards, Gary Lau  MA, USA      > -----Original Message-----  > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On  > Behalf Of bartb  > Sent: Sunday, January 18, 2009 5:37 PM  > To: Tesla Coil Mailing List  > Subject: Re: [TCML] NST Measurements  >   > Hi Jeremy,  >   > How you perform a measurement depends largely on the equipment you have  > on hand and what it is you want to identify. So my first question is  > what meters do you have hand to make measurements? Obviously, a HVac  > probe would be ideal, but not absolutely necessary to simply identify  > rough specs. If you have say only a digital rms meter handy, hook up  > 120Vac to the output side and measure voltage on the primary. This will  > do fine for identifying your turns ratio (Vout/Vin). Then you can just  > figure wall plug AC volts x turns ratio for the output. Current more  > complicated.  >   > If you want to look at "more" and get to know the transformer for what  > it really is, two meters are helpful. One to read current and the other  > to read voltage along with a HV probe. I'm not a big fan of reverse  > wiring t

he transformer to gain transformer characteristics other than  > the basic turns ratio. When normal current is flowing, it will be  > different from the reverse wired situation because the secondary voltage  > applied is never the output volts (but some far lower voltage). If you  > could, a hv probe would be needed. But at that point, you may as well  > feed low voltage high current to the primary for ease of measurements.  >   > So again, what equipment do you have on hand?  >   > Bart  >   > Jeremy wrote:  > > Ok, wait, so how exactly do you guys propose measuring NST outputs for  > dummies? i have  9kV 30mA unit as well as a large unlabelled unit atm, and the  > unlabelled one arcs at over half an inch so i'm guessing it's at least 15kV   60mA. I  > need the measurement on the unlabelled unit. I was thinking of using a 10V   input to  > the NST, then further stepping down the output by 20x to be measured by a  > voltmeter. Is this workable? (all components rated at 240V input)  > >  > >  > _______________________________________________  > Tesla mailing list  > Tesla@xxxxxxxxxxxxxx  > http://www.pupman.com/mailman/listinfo/tesla  _______________________________________________  Tesla mailing list  Tesla@xxxxxxxxxxxxxx  http://www.pupman.com/mailman/listinfo/tesla  

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