[TCML] quench times again

Sat Nov 24 20:53:12 MST 2007

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 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,
>> 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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