RE: [TCML] NST Measurements

["Lau, Gary" <Gary.Lau@xxxxxx>]

Since the HV side of the NST was tied directly to the mains voltage, I have no reason to think that I should be loading that with a resistor, as the rest of my house is already doing that.  Measured line voltage was 123.6V.

The voltage on the LV side of the NST without any resistive loading was 0.807V.  With a 1K load resistor, it was 0.804V, and with a 510 Ohm resistor, 0.800V.  So the predicted NST secondary voltage with a nominal 120VAC input varied between 18.4kV with no resistor on the LV winding, and 18.5kV with a 510 Ohm resistor (actually worse).  Weird.

Regards, Gary Lau
MA, USA


> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of David Speck
> Sent: Monday, January 19, 2009 9:40 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] NST Measurements
> 
> Guys,
> 
> If you are using a modern high input impedance DVM for your
> measurements, you might try loading the winding you are measuring with
> something between 1K and 10K ohms, and see if your measurements make
> more sense.
> 
> A couple of years back, I was trying to figure out the windings of a
> band saw blade welder transformer with a Fluke industrial DVM.  It
> should have been a real simple job, but I wasted an entire day getting
> readings that were all over the place, unrepeatable, and totally
> inconsistent with the way I "knew" the transformer had to work.
> 
> After I loaded the winding under test with a 1K power resistor, all the
> measurements made sense and were much more consistent.  Might be an
> issue with these NST measurements as well.
> 
> Dave
> 
> mddeming@xxxxxxx wrote:
> > 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.
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