RE: Another 942 run

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dave Kyle" <dave-at-kyleusa-dot-com> 

John,

I am not the expert as others on this list are but your popping a 20 amp
breaker with a 12KV -at- 120 with PFC caps is suspicious to me. I had a similar
experience with 15KV -at- 90 running a SRSG. My gap was about 90 degrees off
and caused me no end of blown 20 amp fuses until I corrected the timing. It
was later determined that due to my odd timing the NSTs were saturating and
drawing significantly higher currents than they would be normally limited.

Note that the coil appeared to perform normally despite the dramatic current
the NSTs were pulling. I was using Maxwell's and did not note any heating of
the caps or primary but my runs were very very short owing to the fuses
blowing almost immediately; perhaps saving my caps and NSTs for another day.

Can you measure the line current while the coil is running? Compare that to
the NST running a Jacob's ladder (non-inductive load). I bet if the
difference is substantial you have a SRSG phasing issue and if so maybe this
is the reason for the excessively high currents on you caps.

Dave

=========================================
Dave Kyle
Austin, TX USA
Email: dave-at-kyleusa-dot-com


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, March 08, 2004 9:56 PM
To: tesla-at-pupman-dot-com
Subject: Another 942 run

Original poster: "John Richardson" <jprich-at-up-dot-net>

Hello,

I replaced the cap that blew yesterday, and reset all of my safety
gaps.  7/32 on the NST and 1/4 on the SRSG.  I think that I will set the
RSG a little tighter than the NST gap, because if the RSG gap doesn't fire,
the NST gap will, popping the 20 amp breaker!  (Why?  Time to hook up my
Corcom?  Or is it because I don't have a dedicated RF ground?)  This is
with 300uf of PFC caps.  I did a quick alligator clip lash of of John's
phase controller, and with the 1/20 hp Teletype motor, about 50uf seems the
best.  The voltage rise is about five volts above line voltage, or
125.  Not sure if this matters.  75uf doesn't seem to make much more of a
difference than 50, except I get a lot more of a growl out of the
motor.  As I thought, the RSG phasing was pretty close before, but there is
a subtle difference in output.  Zero inductance to about 25% variac travel
seems to be the sweetest spot, anything more and the safety gaps fire like
crazy.  Primary is still getting warm, but not hot like it did with the
last bad cap.  The dog is going ape with this thing running, so I did have
to keep runs short.  Caps are getting slightly warm.  Re-checked RSG
spacing, and the 5/32 tungstens are starting to erode.  Is this normal for
such a short run time?  This is my first foray into SRSGs, so I don't
know.  This weekend or later this week, I plan on running for an extended
period of time to check for tank heating and more caps popping.  I have
found one cap with the "sand size piece" under the first layer, per David
Weiss.  Will see if that one goes first.  One more thing:  Anyone running
their coils in a basement have some stray streamers up and hit the house
wiring?  It's not a good thing, but sometimes hard to avoid in close
quarters.  All of the incandescent bulbs in the room, maybe six or seven,
light up when a streamer hit the 12-2 light wiring.  Each bulb had the
equivalent intensity of about a 25 watt unit.  Pretty neat, albeit rather
unsafe.  Obvious the toroid is too small, as I can get 46-50 inchers and
still have multiple streamers coming off of other areas of the toroid.

Thanks to all who are helping me.

John Richardson