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Re: NEW break-rate/power tests
In a message dated 99-02-24 05:40:59 EST, you write:
<< Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net>
>>Hello John, all,
><SNIP>
>>Next I replaced the 1500 watt 14.4kV potential transformer with (2)
> >1500 watt 7.2kV potential transformers in series for a "stiffer" power
> >supply. With this set-up I got 54" sparks at 1000 watts at 120 bps.
> >At 400 bps, the sparks were very bright, but never reached 54" but
> >they hit the ceiling a lot and seemed more powerful than with the
> >one transformer.
> After hearing so many comments about low voltage/ high current
> setups having higher losses and probably not so good an output
> AND NOT being able to agree (because I have found it not to be
> true, for me), this brought a smile to my face. During Johnīs
> low voltage xformer test, he gets 54" sparks at 1000W (as
> compared to 54" at a "HV" 1370W). This is the exact opposite
> of what high voltage coilers are saying (:o)) !! A low voltage
> coil may need more construction thoughts, but IT
> DEFINATELY does NOT perform worse!!
Reinhard, all,
I placed the (2) 7200 volt transformers in series, so my voltage
is still 14.4kV, the same as with the one transformer. I'm sorry
if I didn't make this clear enough. If I had actually used 7200
volts, I would have had to increase the cap size by four times to
keep the power input the same at a given break-rate.
>snip
> I think the higher the primary tank current is, the bigger the topload
> should be (at least this seems to work for me).
Yes, but if the primary voltage is increased without increasing the
primary current, you'll still need a larger toroid. Toroid size must
match bang size or input power IMO.
>> My formula above uses true input wallplug power. I
>>measure the power before any variacs, ballasts, etc.
> I agree with John here. I, myself, have used the VA ratings
> somewhat carelessly (although never the printed rating).
> I am not using a reso cap. I have always wondered about the
> NST (coiler) VA ratings. If you have a 7.5kV NST with say
> 75mA rating, the formula V*A = 7500*0.075A = 562VA.
> HOWEVER, the NST will give you EITHER 7500V OR 75mA,
> but never both. The 75mA rating is a short circuit rating, which
> means the voltage is zero or almost zero! Every shunt limited
> xformer works this way. The input current is (unless
> compensated) not a very good way to measure actual input
> VA, because you are not considering all losses. The best way
> would be to measure the HV xformerīs secondary voltage and
> current, which probably isnīt an easy task (voltage and current
> are constantly surging up and down), either. So, the primary
> (mains input) VA will always be a lot higher than the actual
> VA that is feeding the coil. Comparing coils and results this
> way is okay, but it does NOT (I think) give you an accurate
> view of what the real VA is, that is feeding the coil.
It depends on what you want to measure. I want to know
how efficient the entire system is, so I use wall plug power. If you
want to analyze the efficiency of the cap-to-spark section of the
TC, then I agree with you.
>snip
> This I find extremely interesting. The spark LENGTH does
> NOT change with BPS. The 120bps 1050VA created a
> 58" streamer and the 400bps 2000W was barely able to
> come up with the same results. (Which is pretty much what
> John wrote) I, for myself, am always looking for longest and
> NOT "best looking" sparks.
True, the higher bps did not give longer sparks, but the voltage
on the caps was much lower at high bps, because resonant
charging voltage build-up did not occur. If the cap voltage had
been equal for both high and low bps, then the high bps spark
would have been much longer as shown by Greg Leyh's and Larry
Roberson's coils. I too am looking for longest sparks for the most
part.
>snip
> I also think the low voltage,
> high current setups benefit from the high Lsec to Lpri ratios.#
> I know resonance believers wonīt like this, tho :o).
High ratios are good, but I acheive them by using a lot of L in
both primary and secondary. This reduces my relative gap losses.
> I havenīt been able to give this much thought, but it seems a
> universal sparklength equation (Johnīs empirical equation
> seems to work great) has to take the following parameters
> into account:
> a.) LRatio (pri to sec)
> b.) Primary tank current
> c.) Ctopload
> d.) Input joules
> e.) Breakrate
> I donīt think the higher the TC output voltage necessarily
> means the longer the spark is. The ability of the coil to
> feed and keep up a created ion channel leads to long
> sparks (in my opinion).
>>For a high break-rate system to outperform, it has to make up for
>>all the above losses and then some more by using ion channel
>>spark-growth----can it do it? Obviously, not in coils of the size I'm
>>testing (up to 2000 watts). I do not know how much of the high
>>break-rate under-performance results from losses, and how much
>>may be inherent to high break-rates (if any). I would not be
>>surprised if the losses at high break-rates are much lower
>>(relatively speaking) in large coils compared to small ones.
> Might it be possible that it has something to do with the
> cap DISCHARGE time? In a high break rate system one
> should consider that not only does the cap have very little
> time to charge (which is why the cap value has to go down
> for a given xformer VA rating at higher BPS values), but it
> also has very little time to discharge.?!?
I don't see how the break-rate would affect the cap discharge
time in a typical TC.
Regards,
John Freau
>Coiler greets from germany,
>Reinhard
>>