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Re: Optimal Quench Tests

Subject: 
            Re: Optimal Quench Tests
       Date: 
            Mon, 31 Mar 1997 09:10:01 -0800
       From: 
            Skip Greiner <sgreiner-at-wwnet-dot-com>
Organization: 
            Greiner, Ltd.
         To: 
            Tesla List <tesla-at-pupman-dot-com>
 References: 
            1


Tesla List wrote:
> 
> Subject:
>         Optimal Quench Tests
>   Date:
>         Sun, 30 Mar 1997 19:56:25 -0500 (EST)
>   From:
>         FutureT-at-aol-dot-com
>     To:
>         tesla-at-pupman-dot-com
> 
Hi John
Great design and it's really proving out the ability to quench without
major effort on the gap. One Question...What is the cap value.

Skip

> All,
> 
> I set up a small 360 VA (12kV, 30ma neon) coil for quench testing.
> Steady
> first notch quenching was achieved at k = .11, k = .12, and at k = .18,
> spark
> length was 36".
> 
> Specs are as folllows;     Primary is #12 standed pvc ins, 15 degree
> inverted
> cone, tapped at 33 turns  (448uH).  C = 0.007uF, polypropylene.
> Secondary is
> 6- 1/2" by 23" plastic form wound with #28 formvar, L = 108mH.  Resonant
> frequency without toroid is 130 kHz, with toroid is probably about 100
> kHz or
> so.  Toroid is 4" by 17" aluminum dryer duct.  Gap is a 120 BPS
> synchronous
> 12 point super-series quench rotary (the spark snakes through 12 gaps
> during
> each firing).  There are 12 spinning and 12 stationary electrodes, all
> electrodes are 1/8" dia. stainless steel.  Motor is 3600 rpm, 1/10 HP
> salient
> pole design with ~7" rotor.  Six of the gaps are "offset".  Maximum
> voltage
> applied to the Tesla coil transformer is 125 volts.
> 
> First test:       Secondary was set at 2 1/4" above center of primary, k
> =
> .11, spark was 36"  and quench occured at first notch.  Quench was
> monitored
> using a solid state o-scope in the next room with an antenna type
> pickup.  To
> obtain the 36" spark, it was necessary to attach a small aluminum foil
> "bump"
> to the toroid to force it to emit from that point only.  Without the
> bump,
> multiple streamers formed but were shorter.  Ringdown was near-linear,
> and
> took about 40uS.  First notch quenching was achieved for 2 to 3 foot
> spark.
>  At lower power levels (1 foot spark length), the gap quenched
> intermittently
> on 1st notch since the coil was not loaded enough, and too much energy
> reflected back from the sec. to the primary.
> 
> Second test:       Sec. was set at 1 3/4" above pri, k = about .12,
> results
> were the same as in first test.
> 
> Third test:      Sec. was set at  1 1/2" above pri, k = about .13,
> results
> were similar, but gap quenches mostly on the first notch but
> occasionally on
> the second.  Spark may have appeared slightly stronger, but still just
> reached 36"
> 
> Forth test:     Sec. was set at 1 1/8" above pri, k = about .15, still
> quenched on first notch most of the time, but a second toroid streamer
> formed, so sparks were shorter.   Probably a slightly larger toroid
> would be
> helpful.
> 
> Fifth test:      Sec. was set at 1/4" above pri, k = about .18, quenched
> at
> second notch, and the multiple streamers were strong, but not quite 36".
>  Racing sparks started to appear on the secondary at this k value.
> 
> Sixth test:     Sec was set at 9/16" above pri, k = about .18, quenched
> steadily at first notch.  Here I no doubt "hit" the exact (.18) needed
> magic
> k value.  In some of the above tests, I no doubt "passed by" some of the
> exact magic k values, I'll have to go back and check in smaller sec.
> height
> adjustment increments of 1/4".    No racing sparks occured.  Multiple
> streamers were strong but did not hit 36" but hit 35- 1/2" one time.  A
> slightly larger toroid would probably reduce the number of streamers and
> give
> a longer spark.
> 
> The next test will be to try for k = .22, but to accomplish this, I will
> have
> to lower the secondary 1/2" or so below the primary.  Failure to quench
> here
> on the first notch will cause my secondary coil to be destroyed by
> racing
> sparks.  The primary/secondary as presently physically configured,
> cannot
> couple tighter than k = .22.  I may also try using a smaller capacitor
> with a
> higher rotary break rate for comparison, but this may destroy the neon
> transformer.     Comments welcomed.
> 
> Towards optimal coiling,
> 
> John Freau