[TCML] quench times again
Barton B. Anderson
bartb at classictesla.com
Fri Nov 23 22:14:12 MST 2007
You mentioned frequency and energy transfer times. I just wanted to
The frequency has nothing to do with it. The reason transfer time
changed from 200us to 400us is due to the mutual inductance which
changed when you halved the turns which changed the geometry.
To quickly verify, just run my default coil and look at the transfer
time and number of 1/2 cycles. Then, change the secondary wire size to
18 awg at 516 turns (this will keep the geometry the same and raise the
frequency). You'll find the transfer time will change from 17.16us to
17.29us (hardly a change). Look how much L changes and yet transfer time
barely changes. You will find secQ increases and ACR decreases (that big
18 awg wire wound in that geometry is why).
Then if you want, use the 24 awg wire and reduce the turns to hit the
same frequency as the 18 awg wire size case above (use 291 turns with
the 24 awg size and secondary change "height2" to 29.55). This will be a
geometric change at near the same frequency. Transfer time will now
decrease to 10.65us. Note what I did here was change the geometry to
cause a transfer time reduction and simply set it for near the same
frequency as the 18 awg frequency using 24 awg wire. In order to do
that, the secondary geometry needed to change (less wire, get smaller).
You can easily increase transfer time by changing relative position
between the two coils or by changing the geometry of the coils
themselves. Anytime coupling increases, transfer time decreases. It's
easy to do either of these. The problems however are the stresses
involved which often culminate into premature breakout (any breakout not
at the top terminal).
I just wanted to clarify this situation between geometry (coupling) and
transfer time. Frequency is simply a result of the LC changes. Note that
coupling has increased! Geometry and position is why, not the frequency.
I'm not sure if that makes you rethink frequency effects, but the
situation above is rather important to understand.
Chris Swinson wrote:
>> sparks to air are different than ground strikes. Only ground
>> strikes drain
>> energy quickly overall (if the strike happens early in the bang).
> I think Richie's waveforms show that after about cycles the voltage
> broke out and arced to ground which pretty much killed the tank
> energy. There is still some left and it rings down very slow. So I
> assume here that there was no voltage breakout and the ring down was
> just down to losses.
> I was wondering if the secondary was less inductance, the frequency
> would be higher, so the secondary should be easier to "soak up" the
> tank energy than a higher inductance one ?
> I ran some figures and got that when you half the turns, it doubles
> the frequency and the inductance goes down by a factor of 4 (approx).
> According to JavaTC, 200khz is 27.5uS transfer time, and 400khz 13.7uS.
> Idea is that if you can transfer the energy quicker by using a higher
> frequency, then breakout will happen a lot sooner and drain the tank
> cap a lot faster...
> I think there are a lot of complications though. For one, if the coil
> sparks to ground, lets just say the tank is empty and the RSG dwell
> time is not important (since there is zero in the tank left
> anyway)...... Now normally lets say the spark gap quenches at the 4th
> notch which lets say is 400uS at 200khz... Then at 400khz the gap
> would still take 400uS to quench ? I think as the cycles are running
> faster that the quench time would also half to 200uS for the 4th notch...
> Frequency is a tricky one to think in terms of notches and quench
> times. I expect frequency would not alter things other than the amount
> of time to take to transfer the energy. Such as 200khz 400uS or 400khz
> 200uS. In both cases ( all other factors being the same) that it would
> still quench at the 4th notch.....
> At first I thought that 200khz or 400khz the gap would still take
> 400uS to quench, as I was thinking more mechanical dwell times. So the
> higher frequency would quench at the 8th notch and drain more power...
> But I think I as realise now, other factors can cause the gap to
> quench ( like arcs to ground) anyway, so its really irrelevant anyway....
> So assuming a arc to ground which assuming it drains the tank to zero,
> it would not matter if it was 200khz or 400khz, as it would still take
> the same amount of cycles to complete the transfer (say 4) but the
> higher frequency of 400khz just does it in 200uS and not 400uS as in
> I am also trying to work out, that other than coupling and frequency
> which effect the tank "transfer speed" to secondary... can the
> secondary itself become "easier to drive" to make the transfer quicker
> ? this is why I thought that a lower inductance would take less time
> to "charge" and the energy transfer would be quicker than a lower
> inductance.... though this could just be down to a higher frequency...
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