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

Re: NST Variations

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Matt,

For thier intended use, NSTs don't need to be made very accurately at all.
For our use, even NSTs of different voltages can be mixed to a point like
putting a 12/30 with a 15/30.  They don't add perfectly but it works.
Different manufacturers make NSTs as they please and no two are really
alike.  Core size, wire size, number of turns, how the shunts are done,...
it all points to some pretty large variations to get to the same end.  I
don't think such differences matter too much since the outputs are pretty
similar in the long run.



At 01:37 PM 5/17/2002 -0400, you wrote:
>Hi All,
>       While doing preliminary resistance testing on a set of 15/60 NSTs of 
>different origins, I noticed a couple of anomalies that might or might not 
>have some significance. I expected to find some variation in coil resistance 
>among different manufacturers, but a variation in secondary DC resistance of 
>up to 32% seemed unusual:
>Franceformer: 4696 Ohms, Transco: 5897 Ohms, and Allanson 6612 Ohms. 
>       More puzzling perhaps, was the consistent variation between left and 
>right halves of the same secondary. For consistency, I defined the "right 
>side" as the one with the primary terminals. In France and Allanson cases, 
>the right side had 3% higher resistance than the left side. In the Transco 
>case right was 5.5% higher than left. Readings were checked at two different 
>times with three different meters: Radio Shack 22-174B, Fluke 8000A, Fluke 
>8275A with filtering. Repeatability variation was <0.4%. I realize that with 
>only 3 transformers there is still a 1 in 8 chance of the left/right 
>variation being simple random error. 
>       I am wondering if these simple tests could indicate compatibility for 
>use in an NST "farm". If so, it could save people time and money (and 
>strain). Has anyone else encountered this phenomenon? I will be running AC 
>tests this weekend.
>Matt D.