[TCML] quench times again
Barton B. Anderson
bartb at classictesla.com
Sun Nov 25 13:03:42 MST 2007
I agree that this can be done to a point and about the trade-off of
losses in this system. The fact is no one has done this that I'm aware
of and it "is" new territory. At first, I wasn't sure. Too often a
coiler thinks he is doing something new only to find out it wasn't new.
In this case, I think it is new. The only one I know that has done
something along these lines is Dave Sharpe with is IDR coil, but that
really is in the primary area. Your secondary is completely different
and sets up a whole new set of issues as well as eliminating quite a few.
You have the ability to use a high frequency and keep the Q very high.
It will be interesting to see if you can apply this method to a high
voltage coil (plan B). I think you've thought this through very well and
it's been an eye opener for me. We don't really know what type of
problems will be encountered.
The ring up and how the energy is stored in the secondary and top
terminal will be interesting. Now I understand why you were looking at
dwell reduction. Unfortunately, that just doesn't help and I'm not all
that confident that a rotary is the best avenue for the coil. Have you
considered maybe an SISG approach?
Chris Swinson wrote:
> Hi Bart,
> I think some confusion is that when I mean higher frequency, I do not
> mean smaller coils.. my Q factors always go up with the larger wire
> with larger secondary coils.. Though you can only do this to a point
> as if you make the coil length longer to keep the same turns but
> thicker wire, then the HD ratio is a poor figure and chances are it
> will not couple correctly to the primary..
> So you are right in what you state, but it is not exactly what I am
> Higher frequency does increase losses in some parts, but in other
> parts losses can go down by a factor of 4... It is one huge epic
> counting up all these "new" pro's and con's, though overall the higher
> Q system comes out best..
> The other problem is higher Q( generally) is higher frequency, which
> needs a lower tank cap value, which reduces energy. So you cannot use
> large tank cap values.. I got around about 250khz before running into
> such problems.. So you have to rebuild and use a higher voltage to
> keep the same power input with a small tank cap. Joules input is a lot
> better at higher voltages and puts less current across the spark gap.
> IMHO, once you get to 100nF tank cap, the voltage should go up for a
> greater input power, not the tank cap value... In general 100-200nF is
> about the limits at say 10KV, but I think 100nF should be the largest
> tank cap which should be used. Rather than pumping more current, it
> should pump more voltage instead... once you start to pump more
> voltage input, you can use a lower value tank cap, so less current,
> and it opens up the doors to much higher Q coils.
> ----- Original Message ----- From: "Barton B. Anderson"
> <bartb at classictesla.com>
> To: "Tesla Coil Mailing List" <tesla at pupman.com>
> Sent: Sunday, November 25, 2007 3:53 AM
> Subject: Re: [TCML] quench times again
>> 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
>> 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
>>> 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,
>>> 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!
>>> ----- Original Message ----- From: "Barton B. Anderson"
>>> <bartb at classictesla.com>
>>> To: "Tesla Coil Mailing List" <tesla at pupman.com>
>>> 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,
>>>>> 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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