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[TCML] NST rebuild good
My NST rebuild worked out very well. The procedures I used were very
similar to the ones that Bart has on his site.
Originally the transformer was 120mA @ 15kv. During surgery I had to
remove almost 1/2 pound of overheated
secondary wire. The damage was too great to count layers, so I used a
scale to make both secondary windings
equal. The shunt stack was originally 3/4" thick. I reduced it to 3/8"
thick and installed spacers to fit the windings
Now the transformer is 100:1 with about 4% difference in the secondary
voltages. Note that I do not have a
suitable voltage divider, so my next statements are "figgered". My
voltmeter goes to 600. I applied 5 volts to
the primary and got 248v from one side and 252v from the other side, 500v
across the secondaries, so i figure
100:1 or 12kv @ 120v in. The current on the primary side is 26 A at 120v
with an arc drawn. This is where
I may be mistaken, but simple math would indicate that the transformer is
now 260mA @ 12kv
Am I making mistakes in my calculations?
Here is the next part. I set the safety gap according to the
recommendations of list members, the gap is now
fixed at 0.250" I have not changed my capacitors yet, they add up to
0.033mfd, which, if my transformer calcs
are correct, is a way too small cap. I wired the variac to 120v to stay on
the safe side, and fired up the coil.
Now, when I turn the power up to about 80v, the safety gap fires like a
string of firecrackers. Is this because
the cap is way too small? Adjusting the sync. on the rotary gap has some,
but very little effect.
If I get past the safety gap issue and rewire the variac to 140v then my
NST primary current would be 30 amps!
Do you think power correction caps may be in order?
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