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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Ok, i used a voltage divider to capture these pics...
above: single yellow trace, from the 6kv-ground of NST. (10x probe)
above: yellow trace is same as previous pic. blue trace is 1x probe.
UPDATE: new waveforms.
blue trace is wall voltage/current divided down. yellow trace is as above.
Tick marks and lines for deltas.
EDIT:At least 1/0.016760s = 60Hz
my question is why is it not more sinusodal? i expected it to be a little noisy, but its so irregular.
let me do some math: if Vrms = Vp/root(2) then... 19.3/2 = Vp = 9.65V so... 9.65vp/root(2) = 6.82V as expected so 6.82V X 1000 = 6.82kV!!!
I dont know about this ...but perhaps its the magnetic core shunts, which are used to limit short-circuit current. They may allow a sort of linear rise until clipping, then it flips back and forth to approximate a sinusoid?
Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
Patrick wrote ...
I dont know about this ...but perhaps its the magnetic core shunts, which are used to limit short-circuit current. They may allow a sort of linear rise until clipping, then it flips back and forth to approximate a sinusoid?
That would be MY guess. I think you got it right!
Are there any transformer guru's who can confirm this?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Try looking at the mains voltage directly, it's never a pure sine wave.
Also, even if it was, the magnetic non-linearities in the NST will distort it, and the leakage inductance and self-capacitance of the secondary will ring from those distortion harmonics. Purity of output waveform was probably quite far down the NST designer's to-do list.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
I think these oscillograms are accurate, for the yellow trace (5 kV per div) at 19.3 kVp-p X 0.707 = 13.6 kVrms which is really close ( better then 2% ) of what the DMM + R divider said.
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Have NST Waveforms...Need Help.
