Re: [TCML] quench times again

["Chris Swinson" <list@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Hi Bart,

> 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.

Ok... So the coil was half the inductance, which halved the mutual 
inductance which doubled the trasnfer rate which as a result frequency was 
increases....







> 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).

In my testing I kept the coil geometry the same, by using thicker wire and 
less turns, but physically the coil was the same size...

Repeating my self a little here.....

200khz  DCR 0.010  L=61uH  ML=134uH  27.5uS
400khz  DCR 0.005  L=15uH  ML=33uH   13.7uS

So you are saying that *if* the 400khz coil still ran at 200khz then the ML 
was still the same, that it would still take 13.7uS to transfer... A little 
confused.. Still play with some JavaTC figures on that one so I can 
understand what you are getting at a little better....


> 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).


So 2 things are altering coupling (K factor) then ? one the physcial aspects 
of the coils, but also the mutual inducation.. such as you could  have a 8" 
dia secondary and 12" primary and just assume this has a K=0.1  , Though are 
you saying if the secodnary is kept the same size, but reduced in turns and 
thicker wire, that the mutual inductance would be lower and K would increase 
?

If so, then the 12" dia primary would have to be 24" in dia to get back to 
coupling K=0.1 ?!


> 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.

Right, so I think frequency is related, but its the actual mutual inductance 
which is the casue of the decrease in mutual coupling....

It is confusing..... as you can also reduce coupling by physically making 
the primary larger which decreses coupling again, but makes the transfer 
time longer ?!

But if you decrease the secondary turns and use larger wire, it also 
decreases coupling but energy takes less time

*confuzzled look*


> I'm not sure if that makes you rethink frequency effects, but the 
> situation above is rather important to understand.

I think I see your point to a point... higher frequency really is just a 
by-product of altering all other factors... all those other factors such as 
mutual inductance are the real "engine" behind the transfer rate change...

There would have to be a difference between coupling and mutual induction, I 
always took these as the same, but decreases in coupling is a decrease in 
mutual induction which take more time to transfer, but reducing mutual 
induction by spec's of the secondary also decrease mutual induction but the 
transfer time takes less time... seems a conflict between the two, can't be 
both ways ?!

Cheers,
Chris





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