Re: Sparklength inquiry

To: tesla-at-pupman-dot-com
Subject: Re: Sparklength inquiry
From: Greg Leyh <lod-at-pacbell-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Thu, 24 Sep 1998 16:55:13 -0600
Approved: terryf-at-verinet-dot-com
> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>


> >>   Bart, Greg -
> >>
> >> I agree the equation (Vs/1000/65)^1.43 is not correct. It should 
> >> be(Vs/65000)^1.43 where Vs is the secondary volts or
> >> (KVs/65)^1.43 where KVs is the secondary kilovolts.  -JHC
> >
> >The revised equation is also incomplete, since it still does not
> >account for the effects of BPS on spark length, which are 
> >significant. -GL
> >
> >> To my knowledge this is the best equation presently available for 
> >> TCspark length. It will probably change when more accurate data 
> >> from coilers becomes available. It appears to be working well at 
> >> present.  -JHC
> >
> >Except that the equation blows up completely if the break rate is
> >altered.  This should be fixed.  -GL
> 
>   Greg -
> 
> Not true. Note that the Vs is a function of BPS in the equation
>    Vs = sqrt(2 watts/(Cs BPS))
> The spark lengths are for controlled sparks. Streamer sparks can be 
> 2 to 3 times longer depending on the guestimate of the coiler.
> 
>   John Couture


Again, the algebra is lacking here.  In the above equation,
Vs would only be a function of BPS if the quantity "watts" 
was a constant.  But since watts is an inverse function of
BPS, the above equation simply reduces down to Vs = SQRT(2Es/Cs).

At this point, I should once again offer the following test data
from my old coil:

Primary capacitor is 0.225uF, Vpri = 26kV. 
The Vpri is *not* adjustable in this design, which means that Ep, Es
and ultimately Vs are independent of the break rate.  

At a BPS of   1 and a Vpri of 26kv, sparks are about 2.5 ft long.
At a BPS of  80 and a Vpri of 26kv, sparks are about 4.0 ft long.
At a BPS of 350 and a Vpri of 26kv, sparks are about 25. ft long.

Since I have an oscilloscope and a HV probe, I am able to determine
that the maximum jitter on the 26kV value is less than 2kV at any
break rate.  With a current probe, I can also determine that the
peak secondary base current of 27A has a jitter of less than 3A,
confirming that Es does not vary considerably either.

I am quite convinced that Vs is *not* an inverse function of BPS.
(unless the charging circuit is broken)

But you might not believe my measurements.  So I should ask if
anyone else on the List has data from *actual operating coils*
which might indicate whether Vs, and therefore Vpri, varies as
an inverse function of BPS.

Comments?
-- 


-GL
www.lod-dot-org