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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