Re: Why tesla coil is air-cored to operate efficiently at high freq?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: BunnyKiller <bunikllr@xxxxxxx>

answers are after your questions....



Tesla list wrote:

> Original poster: d a <btoc3000@xxxxxxxxxxxx>
>
>
> Hi all,
>
>
>
> I have three theoretical questions here:
>
>
> I read this from a website: "A normal transformer users an iron core 
> in order to operate at low frequencies, whereas the Tesla Coil is 
> air-cored to operate efficiently at much higher frequencies".
>
>
>
> I understand that a normal transformer relies on turn ratios and the 
> air core is there to reinforce the magnetic flux.
actually, air gaps cause a loss in flux flow, thats why we use air 
gaps in the EI core inductors to reduce the current capacity



> May I then ask, why is an iron core only required in low frequency 
> operation and why do we use an air-core for high frequency operation?


in iron core transformers there is something called flux, it is a 
magnetic field that travels thru the iron ( it actually causes the 
electron spin to change direction a tad) and this flux has a sorta 
kinda mass to it   once the flow gets going it is difficult to 
reverse it instantly and to do so takes power and if you increase the 
frequency of the directional swapping   the iron core will heat 
up   kinda like induction heating process   with an air core 
transformer, the magnetic field is still there but not as tightly 
confined as in iron core trannies   with no iron core in the way, the 
magnetic field can change direction rapidly  with very little energy 
required to swap directions.



> Lastly, I read this from another website: " In the Tesla "swing", 
> the kick is supplied by the AC electrical current moving back and 
> forth". Can someone elaborate on this please? Is it actually 
> referring to the LC circuit - both the secondary and primary 
> operating at the same frequency that reinforce each other?

there are two AC voltages used in a tesla coil   the first one 
charges the cap and then the spark gap conducts creating a "new" AC 
voltage that is created when the cap discharges thru the inductor ( 
the primary coil)  and the combination of cap value and inductor 
value will create a circuit that will oscillate at a specified 
frequency due to the cap and inductor...  change either the cap or 
inductor and the frequency changes.  The idea behind a Tesla Coil is 
to create an LC circuit ( cap and primary) and power it up and let 
the gap connect to create the oscillating wave. The secondary is made 
to recieve the hi frequency magnetic wave produced by the cap and 
primary during spark gap conduction. But to make a secondary and 
toriod to match the frequency of the cap and primary would not be 
easy. So what is done is that we create a secondary and toroid, get a 
rough idea of its natural frequency and then get caps and design the 
primary to match the secondary and toroid set.   This is why we end 
up having a moveable tap point on the primary....   its alot easier 
to change the tap point on the primary than it is to change the 
windings on the secondary or change the toroid size.

as far as the increased voltage,  it works on the theory that as the 
spark gap conducts the cap primary produces an enormous magnetic flux 
( this magnetic field/fluxx is made due to the primary coil) that 
feeds into the base of the secondary, as the voltage ( electrons) 
work their way up to the top of the coil and deposit a good portion 
of them on the toroid, a reversal of current begins to travel back to 
the base of the secondary. The primary /cap LC circuit if in tune 
with the secondary toroid will supply another pulse of power to the 
portion of existing power that is returning to the secondary base. 
The combination of both the existing and new pulse adds more 
electrons to the system,  and this happens 100+ thousand times a 
second. Eventually the continual addition of power will increase the 
voltage to a point that the toroid can no longer hold it and it is 
then released to the closest "ground" .

Scot D





> Thank you very much for your kind attention.
>
>
> Regards
> Sam