Re: Theory - primary cap duty -transformer output current

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

Original poster: "PotLuck by way of Terry Fritz <twftesla-at-qwest-dot-net>" <potluckutk-at-earthlink-dot-net>

PotLuck is my gaming name. I play Unreal Tournament.
Anyway, I'm a newbie here (Does it show? :)  ) so excuse my ignorance of
using my handle.
BTW, PotLuck came as my handle because it's shear potluck if I win a match.

The name is Richard Williams, I go by Rick. From Salt Lake City. Been into
electronics for 30+ years, professionally for 16 years.

I'll set up another Email account with my real name. .

I gotta tell ya! I really hadn't expected all the replies I recieved and the
wealth of info and links!
Thanks to all who replied. Greatly appreciated, believe me! :D

Thanks all!!!

Rick W.


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, July 03, 2001 11:41 AM
Subject: Re: Theory - primary cap duty -transformer output current


> Original poster: "Jason Petrou by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jasonp-at-btinternet-dot-com>
>
> Pot Luck? (plz use your name on the list :)
>
> > My inquiry focuses on transformer current and the primary cap.
> > My understanding is that once the primary cap is charged and the firing
> spark
> > occurs that the transformer's current during the HV pulse and "ringing"
> are no
> > longer a factor, that the energy stored in the primary cap becomes the
> sole
> > provider of current in the tank circuit. Once that arc is quenched then
> the
> > primary cap is again charged.
> Yes. The primary capacitor charges, and then discharges through the spark
> gap, as you rightly say. The current produced in this pulse can be in the
> tens of hundred of amps, depending on the capacitor. The output current of
a
> transformer is at most 1A, and is completely insignificant to the actual
> magnetic induction in the TC system. the 50 (or 60) Hz line is also not
part
> of the resonant system so there could be no effect on the resonant rise of
> the system. The transformer is shorted out through the spark gap (hence
the
> need for current limiting and quenching).
>
> > So how does transformer current fit into the
> > scheme of things?
> Simply - it doesnt. Its sole purpose is to charge the primary cap and to
> fire a static gap.
>
> > If that cap is allowed to charge within 90% of the voltage
> > available before discharge then where does transformer current fit in?
> Does
> > higher current allow quicker charge time?
> It's not a case of the cap charging to the voltage (which it obviously
does)
> but a case of storing the energy that the transfomer puts out. As the cap
> reaches its peak capacity the voltage across the transformer increases as
> the circuit becomes more and more open. Finally the voltage that occurs at
> full charge will cause the air in the gap to conduct and then the resonant
> rise process will begin. Higher current does allow a quicker charge time,
> but the capacitors need to reach their peak charge as the AC line reaches
> its peak. In this way, the maximum energy is transferred into the primary
> inductor. Therefore your capacitors need to be matched to your power
supply,
> to get the correct charging rate. If you have a variable ballast and you
> turn the curent up, then the TC performance will rapidly fall, because the
> current supply is no longer matched to the capacitor. THIS IS ASSUMING A
> SELF TRIGGERENG STATIC GAP. Practically any cap value can be used if an
> async adjustable rotary gap is used. Generally if you are going to use an
> async rotary, then the bigger the capacitor, the faster a break rate you
> will need. For a 50z line you cannot use a break rate lower than 100BPS,
and
> for a 60Hz line, 120BPS, logically.
>
> > I can see where firing at zero-crossing is also advantageous, allowing
the
> cap
> > to "see" the full transformer output voltage and eliminates shorting the
> > transformer secondary during discharge.
> Kinda. Firing at zero allows the cap to store the full amount of ENERGY
from
> the transfomer, not voltage. However you need to use a sync. rotary to
> achieve this, as a standard static gap will fire at the peaks, not at
zero.
> Also your cap needs to be double the size (i think) to accomodate the
extra
> half of the AC sine wave.
>
> If you are building your first coil, I would suggest that you go for a
> static gap, or if you decide to use a rotary, then have a static gap
across
> the rotary, so that any misfirings caused by bad calculations/logic will
not
> damage your transfomer or caps.
>
> Regards,
> Jason
>
> Geek # 1139 Rank G-1
> www.thegeekgroup-dot-org
>
>
>