RE: blowing fuses: troubles with a new system

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

Original poster: "Dave Kyle by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dave-at-kyleusa-dot-com>

I experienced exactly the same symptoms in a similar sized coil and it
turned out my SRSG was way out of phase. My John Freau phase controller did
not have sufficient range to correct for this. Only after a manual
adjustment to my SRSG was I able to dial things in and the massive over
current issue disappeared.

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, June 26, 2003 10:19 PM
To: tesla-at-pupman-dot-com
Subject: blowing fuses: troubles with a new system

Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>

HI everyone,

its been awhile since ive built a spark gap coil (ive been doing VTTC and
SSTC work), so i put a new one together.  But im having problems in that
the coil appears to have terrible power factor!  Here are the specs:

15/120NST (was a France 15/60, but i removed shunts (left 12 leaves in each
packet for a rough estimate of 120ma))

238uf of PFC (its too small, maybe my problem???)

.045uf MMC (also a bit too small for the system)

120BPS sync gap

7.5" ID 23"OD flat primary, 14 turns 1/4" tube, tapped at 11.

6.3"OD x 24" winding of 24awg magnet wire for a secondary

4.5"x30" toroid.

So far, ive been using the phase controller that John Freau has on his site
(variable inductance and an extra capacitor with a small sync motor).  The
SRSG is similar to a Terry Blake setup, it uses a 7" tungsten rod with 4
electrodes spaced around it.  Would be similar to an 8" SRSG disc.

Ok, so when i test with power, i can get up to about 50% input on the
variac, then the 20A fuse blows!  The coil puts out 3-4 feet of sparks at
that point.  Ive noticed that, as i turn up the power, i need to reset the
phase controller (lower the inductance) to keep the coil happy (otherwise
the safety fires, and the coil looses the synchronous tone).  Though, im
sure the motor is still spinning sync, since its fine at a lower
level.  Ok, so i get to about 50% and adjust the RSG for maximum output
(which is JUST before it starts to flash on the safety gap) and
watch.  Then the fuse blows.  It seems that, when i turn up the power
without adusting the phase controller, the SRSG pulses or surges, but i
dont know why.  Though John Freau told me this is common ( the need to
reset the phasing at higher powers).  I notice that if i adjust the phasing
in the other direction, the sparks get shorter, and there is a wide area of
settings that will work fine (and this does not seem to blow the fuse), but
the spark output is MUCH weaker :o(  So does anyone have some advice for me
besides get a bigger fuse??  (by the way, its it ever ok to put a 30A fuse
inplace of a 20 ;) ).
Im actually going to hire my uncle (electrician) to wire me my own power
box off of the mains with a 240V and high current 120V line, but that wont
be for a while.  So i need answers now!

here are my thoughts on a possible solution. 1) put all of the shunts back
into the NST and run it at 60ma (though im sure the setup will pull much
more power out of it).  Im not sure how effective it would be with a .045uf
cap.  I could run .030 uf i guess, but i want big sparks!  2) add more PFC?
I think i really need like 450uf or something like that for this amount of
power. 3) whatever anyone else could suggest!!

Thank you all in advance.

Steve Ward.