Re: SG electric control Idea - opinions wanted

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Speck by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dspeck-at-relex-dot-com>

Cory,
A triac won't work, 'cause it stays in conduction until the current passing
through it goes to zero.
You can turn it on, but not off.

You could theoretically turn off a large power transistor, but transistors
capable of the high currents
involved are large and very expensive.  They also tend to stand up poorly
to the severe electrical
environment of a TC tank circuit.

Big tubes and spark gaps just can withstand a lot more stress.

Dave

Tesla list wrote:

> Original poster: "Cory Roussel by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <imcuddlycory-at-yahoo-dot-com>
>
> Hello again,
>
> i have an idea: it is my understanding SCRs and TRIACs
> arent fast enough switching and dependable enough to
> handle TC spark gap replacement...  it is also my
> understanding that a single MOT is not useful as a TC
> trannie because it doesnt have near enough voltage for
> a reasonable gap, ide like to change this:
>
> My idea involves using a Triggered gap that uses a car
> coil to trigger powered by a dimmer switch to adjust
> the degree of the cycle it fires at.
>   this way you could have a  1" spark gap which would
> be MUCH easier to quench then a 1mm spark gap.
>
> secondly my idea involves using a Power TRIAC or
> simple transistor in series with the big ugly mot that
> is on all the time except a short ammount of time it
> turns off all current draw from the MOT shortly after
> the TC is done resonating,
>
> i have been told was about 30 cycles, according to my
> speedy calculations that is only about 2 degrees of
> the AC cycle.  so almost DIRECTLy after the trigger
> electrod fires the tranny is basically turned off
> untill the next cycle has begun and passed up some of
> the lower voltage components of (like 120-600V) it.
>
> problems this may encounter:
> - making a module to turn off the triac at the right
> time
> - protecting your car coil from the dangerous aperage
> of tha tank cap, anyone know how this is done?
> - low voltage = reduced primary tank energy :-/
>
> why this would be good:
> - beginners who dont have NSTs available ( i live in a
> pretty large city but i cant find a single one!  then
> again im also not really willing to buy one new )
> - MOTs are Free!
> - NSTs are very fragile i hear...
> - MOTs have good charging current- i forget the
> equasion to the time it takes to charge a cap (mabey
> somone can remind me) but i am pretty sure current is
> involved.. faster cap charging might = more BPS
> - More efficient?
>
> just an idea,
>
> Cory Roussel
> G1206
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Greetings - send holiday greetings for Easter, Passover
> http://greetings.yahoo-dot-com/