Hi Chris,
Only a little confusing, but not too bad. Anytime I start talking decrease
this, increase that, I personally have periodic cross-thought errors (type
just the opposite than I meant due to wondering off on a different
aspect).
There are of course losses associated with higher frequency. Usually, when
coilers are talking a high frequency coil, it's geometric size is small
and Q is not high. Here again now I've got to state, and yes log me down
for this statement: "higher frequency does not result in a higher Q coil".
Increase frequency by taking any coil and reduce it in 1/2. Thus, divide
the radius by 2, the height by 2, the wire size by 2, and keep the same
number of turns. Your frequency will double and Q will lower because the
AC losses begin to increase. If it were not for those losses, I would
expect the Q to remain the same.
In your case, there is a high Q due to the higher conductance. Eddy and
skin effects will not be hindered in your coil as it would in one of the
smaller high frequency coils. This should definitely not be related to Q,
but rather to the large wire size and it's low DC resistance and
unaffected AC resistances.
It should be true that as we reduce the number of transfers, the gap
losses should decrease. I'm not sure that higher frequency would help
ionization at the gap except that it will help to decrease the transfer
rate (so more energy over a shorter period).
The idea really is that a higher frequency should allow a higher current
pulse with upsetting the RSG too much. It was also my point about
"making sure" by decreasing the RSG dwell time. As higher current will be
harder to quench, then decrease the dwell time and it should help matters
also.
A lot of factors come into play, as pointed out by yourself, John, etc.
Though this was really the overview of the "high Q" system which I had in
mind. A lot of ideas and corrections brought up in all these posts thats
for sure!
Everyone has been down the classic road, wider coils, more inductance,
larger toroids... So I am thinking of a "new" direction instead....
But when you see certain aspects like Q increasing, look at what is
different. In your case, it's really the few turns of large wire over a
large area. This is a huge difference. Just take your coil and reduce the
wire size by half and you'll see Q start to drop without much affect on
frequency.
Another point which has not come into it yet, even though I mentioned it.
Higher frequency should also increase efficiency in it its own right
for example, running from a 12V test setup, at 15cm "range" ....
50hz =0
39khz =0.5mV
124khz=5mV
1mhz =50mV
1.2mhz =70mV
1.43mhz =120mV
1.87mhz =150mV
2mhz =200mV
But is that a result of the frequency or is that a result of the coil
geometry? Higher frequency is resulting in a shorter transfer rate and as
a result di/dt increases at the secondary which increases the amplitude
since the AC and DC losses are so low. But the same cannot be said for a
high frequency coil which is small. The losses are huge then. For your
particular geometry, I think what you said is true, but not across the
range of coils.
I was wondering if this would also apply to coupling efficiency. In a way
it looks like voltage is lost over the coupling. Tighter coupling would
in effect reduce my "range" figure and double up on the voltage.
I don't normally look at coupling as an efficiency number. Coupling will
always be 100% regardless. There are of course losses over time at the gap
and over the transfer. But yes, tighter coupling will increase di/dt.
After a lot of testing I drew up that double the frequency gave x4 the
voltage output. As a relation, 10 times the frequency gave double the
"range".
For your particular geometry.
Going by these figures, if a normal tesla coil used 1,000 turns at
100khz, then it suggests a magnetic field which runs "out of steam" at
1,000 turns. So increasing turns does nothing at all other than to gain a
few volts and increase resistance.... the point now that if we progressed
to 1mhz then we should be able to use 2,000 turns and the magnetic field
will run "out of steam" at the 2,000 turns mark.
In a normal coil, the losses in eddy and skin effects will come into play
and will be significant. But, if we go down the road of increasing the
wire size and coil size in order to achieve 10x the frequency and double
up on the turns, then yes, we can get reduce those losses. However, in
reality the coil would be physically to big to build.
Also as frequency goes up you get more voltage. take 124khz 0.5mV to
1mhz 50mV . This is all at 15cm "Range". When I say range, I mean the
distance between the primary and secondary. Remember only the frequency
changed and the voltage was constant at 12V.
You can only get more voltage if the di/dt is increased without
significant losses. For your particular coil which is really extreme I can
see that happening.
It is one of those odd things which also confuses me about tank energy
going from primary to secondary. My own tests show there is a voltage
drop... if we take 124khz I input 12V and got 0.5mV output.
Sure, there's always a voltage drop for any given point in time. No doubt
about that.
Another problem is that Q factor was not taken into account with the
secondary. I used a variable capacitor to tune the secondary to the
primary. So Q factor probably was going up.. Though in anycase frequency
increase gave way to higher Q factor coils and gave greater efficiency.
The cap in the secondary is a terrific approach on your coil. I agree, but
due to the few turns, large wire size, and coil size to accommodate the
wire size I believe is why. Your coil is so far outside the loss box that
the main loss in your system will be the gap. In a high voltage situation,
it would be interesting to see how the voltage stresses react.
Take care,
Bart
Even though I still have more tests to do. I got 16mhz as being the best
solution. I made me first think that the secondary coil over the loose
coupling would only obtain a fraction of the voltage. In which case
energy would be lost over the distance between the primary and secondary
coils.... always interesting none the less!
Chris
----- Original Message ----- From: "Barton B. Anderson"
<bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, November 24, 2007 8:01 PM
Subject: Re: [TCML] quench times again
Hi Chris,
Another correction I need to make.
As the number of cycles increases, the transfer rate will "decrease".
What you are doing is interesting and how you are going about looking at
how the frequency affects the transfer rate, efficiency, and gap
conduction. Very interesting subject to me.
Take care,
Bart
As the number of cycles increases, the transfer rate will increase.
Here is the relationship.
Total Energy Transfer = (0.5/((1/(1-k)^.5)-(1/(1+k)^.5)))*(1/fr)
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