[TCML] Racing sparks - question
joe at killerowls.com
Sat Aug 7 21:50:49 MDT 2010
I've been down this route in the past few weeks. I have my 15/90 running pretty smoothly, though if I increase the voltage on the variac much past 110V I start getting racing sparks.
I was getting racing sparks first at about 70V on the variac. Ok, so I reduced the coupling - first by surgically slicing out the inner 2 turns of my refrigeration tubing primary - which I might add I painfully threaded through 6 stanchions only a few months ago. Such is the life of a coiler looking to make progress, I suppose. Nothing is sacred. This stopped any arcing between the primary and secondary, but I was still getting the racing sparks at the higher voltages.
I noticed a couple other things:
1) As John mentioned a few weeks ago - if you are connecting your primary anywhere but the very first turn and taping very last turn, then you have turns "left over", and they're still somehow electrically active. In fact, I was getting arcing from my outmost turn of my primary (turn 15, after cutting off the inner 2 turns) to the ground rail. My tap point was at turn 7.5. So there was a lot more copper not engaged in the tuning than was engaged, but it was still energized. I managed to relocate things so the arcing stopped between the last turn and the strike rail - and believe it or not - this reduced the racing sparks. Could be a coincidence...but I don't discount anything anymore.
2) I got more racing sparks when my SRSG was not timed correctly than when it was. WHich is to say that when my SRSG safety gap fired, it was almost always in conjunction with some sort of arcing or racing sparks. Fixing the timing also fixed that problem.
3) Finally, I got less racing sparks by decoupling further, which in my case was raising the secondary because I didn't want to cut any more permanently out of my primary.
Now, as Gary mentions, coupling (as I remember from my "electric motors and transformer"s class, EE101) is energy transfer. So reducing the coupling has got to reduce the energy transfer, which means less going into the secondary from the primary. Resonance or no resonance, there's just less going from primary to secondary with a lower k, and so that, to me, is equivalent to running it at a lower voltage/power level.
The engineer side of me thinks: yeah, you stopped the racing sparks but you haven't solved the problem.
So I tried messing with the top loading. My secondary is 4.5" diameter, 23inches of 26ga. The top load is a 4.5x18 toroid. I happened to have a 3x12 toroid laying around from my smaller coil attempts. I stacked these - separating them by 5".
As far as I can tell it made the coil look cooler and changed the tuning point on the primary, but did absolutely nothing for spark production or modification of the racing spark issue. What seems to have absolutely killed the racing sparks was raising the secondary an additional 1/8" (it is now 5/8" higher than the primary). Spark production is to my eyeballs about the same as it was before I raised the secondary.
So as we are not quantifying spark production and measuring our success by objective energy output measurements - if it looks cool and nothing detonates and everybody is safe, then we have succeeded as coilers - far as I can tell in this eclectic hobby of ours.
I guess reducing the k works, though to me it's the same as running it at a lower voltage on the variac.
On Aug 7, 2010, at 8:04 PM, Gary Lau wrote:
> I also get racing sparks on my coils if I don't have a breakout point, so I
> just use one. I could reduce the coupling, but fear that sparks from a
> point would be reduced.
> One thing you can try is to add a spacer between the two toroids.
> Regards, Gary Lau
> MA, USA
> On Sat, Aug 7, 2010 at 8:43 PM, <otmaskin5 at aol.com> wrote:
>> Hi coilers. Life's been busy the last few months & not much time for
>> coiling, although I still read the pupman postings. Anyway, I did find the
>> time to roll out my coil tonight & run it, but I kept running into on an old
>> problem I've had in the past. Using a screw or ball bearing for a breakout
>> point, my 15/60 coil produces good sparks, and the coil runs well with no
>> problems. If I remove the breakout, I still get sparks from the toroiod,
>> but eventualy start getting racing sparks.
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