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Re: [TCML] Cold Sparks and Hot Sparks
Hi Jeff,
It looks to me like the "cold" sparks represent a lower duty cycle,
disruptive discharge while the "hot" sparks represent a more con-
tinuous higher duty cycle and higher current discharge. The cold
sparks look more like the disruptive discharge of a SG driven coil
whereas the hot sparks look more like the CW discharge of a
vacuum tube driven Tesla coil. I've noticed the output of my x-ray
transformer will make the "cold" sparks when I heavy ballast its in-
put and the current draw is actually quite low. However, when I open
the ballast up and allow much more unfettered current flow into its
primary side, the arcs get much more bushy and flaming and of course,
the current draw incereased dramatically. It's also quite difficult to
ignite
paper with the cold sparks but very easy with the hot ones. On a side
not, the capacitance of those HV cables that are used to access an
x-ray transformer's HV output can also cuase the loud and snappy
cold sparks.
David
----- Original Message -----
From: "Jeff Behary" <electrotherapy@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, August 02, 2008 7:52 AM
Subject: [TCML] Cold Sparks and Hot Sparks
Hey All,
Last night I was preparing the place for some guests, and I decided to take
some pictures of two simple things with Tesla Coils. I think they are
interesting though, because they show two extremes of Tesla Coil
discharges - one a cold, crackling spark and one a hot fiery one.
If you watch the videos, please turn on your speakers to maximum volume -
the sound (at least on my computer) at this level is close to what the real
thing sounds like. The cold sparks are unusually loud, and hot sparks are
unusually quiet. Tesla mentioned in the lectures that one sounded like gun
shot, and the other the hissing of a low frequency arc. I think he was
right! In the hot spark, it was taken from a bipolar 9" Pancake arrangement
powered by a MOT, .05 mfd oil-filled cap, and 4 series 1/2" tungsten spark
gap. The cold spark photos were taken with the recently made Kinraide Coil
repro, .096 mfd, single 1/4" tungsten spark gap, and around 2kV also for the
tank xfmr.
The hot spark photos had two steel dischargers, around .080" in diameter.
They actually flare up in little arcs once in a while and started to melt at
the tips...both poles were active. The cold spark photos were between two
spheres, 6" sparks. One was simply an aluminum pipe that touched the
primary coil, the other was the active terminal from the coil. The hot
sparks required about 1200 watts, and the discharge could be drawn to around
8" maximum, but the flare ups ceased at over a 2" distance. The cold sparks
were about 150 watts of power.
To take either spark to a metal rod held in your hand a bit unpleasant. The
hot coil makes your whole hand and half of your arm heat up (diathermy), the
cold spark causes occasional muscle contractions, some really unpleasant.
Pictures:
http://www.electrotherapymuseum.com/2008/BipolarFire/Fire.htm
Movies:
http://www.electrotherapymuseum.com/2008/BipolarFire/TBKCrackle.wmv
http://www.electrotherapymuseum.com/2008/BipolarFire/Fire.wmv
Jeff Behary
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