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Re: Continued Problems (fwd)
---------- Forwarded message ----------
Date: Fri, 22 May 1998 07:36:46 -0500
From: "Barton B. Anderson" <mopar-at-uswest-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Continued Problems (fwd)
Bert,
Thanks for taking the time. I think this is what Malcom was
indicating on his previous post. I have read many other posts indicating
the on/off situations regarding the gap, but for some reason, your post
hit home unlike the others. You presented each gap situation out very
well. This puts a whole new perspective (for myself) on the operation of
my own coil. The breakover at the gap is most definately the difference
between a conventional xfmr and the resonanat xfmrs we build.
Had a great time tonight. I added another 50 ft of 3/8 tubing to the
primary today and performed some point to ground test. I started at full
primary inductance (13 turns) and I got nothing but a sparkgap firing (
similar to Ed's delema which started this post). I came in a couple turns
and the coil started operating. I eventually ended up about 1.5 turns
beyond my previous primary extreme of 7.6 turns. The system appears in
tune at ~ 9 turns. At this point, I started getting arcs to the garage
ceiling. The coil is almost on the ground, and I couldnt' decrease it's
distance to the ceiling any further, so I decided it was a good night in
MN to set up outside the garage.
As soon as the sun went down, I fired it up. I tried to push it to it's
full voltage extreme and was getting some impressive and continuous 5t
foot arcs and once in a while, arcs beyond this range. One thing I did
notice was that when the arcs would find the strike ring, it remained for
an extended amount of time. I didn't expect the arc to remain as long as
it did, but as I kept attempting to pull full voltage, it hit the strike
ring and remained there for a significant amount of time (the arc was
extremely white and heavy). At one point, I tripped my 30A circuit breaker
(I'm surprised this is the first time a popped it, as I've been running 25
to 30A variation for some time). Looks like I may need to upgrade to 40's
to run full voltage. One nice change is that my primary rebuild and
secondary recoat has elliminated my first firing delema of the arc
traveling down the seconary winding. When it hits the strike ring, it is
now flaring out from the toroid and then back into the strike ring,
completely leaving the secondary unharmed.
One FUN night in MN, (the applause from neighbors was cool too),
thanks for the clarification,
Bart
Tesla List wrote:
> ---------- Forwarded message ----------
> Date: Sat, 23 May 1998 00:18:38 -0500
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Continued Problems (fwd)
>
> Tesla List wrote:
> >
> > ---------- Forwarded message ----------
> > Date: Fri, 22 May 1998 00:15:11 -0500
> > From: "Barton B. Anderson" <mopar-at-uswest-dot-net>
> > To: Tesla List <tesla-at-pupman-dot-com>
> > Subject: Re: Continued Problems (fwd)
> >
> > Malcolm (and all),
> >
> > Tesla List wrote:
> >
> > <snip>
> >
> > > > Just trying to understand this. I understand the tanks reactance is affected by added
> > > > inductance and therefore the resonant frequency changes, etc... , but are you saying
> > > > the secondary coil which has it's own reactance, would change due to an inductance
> > > > change on the input side of the tank?
> > > > Bart
> >
> > > <snip>
> > > A crude model of the transformer primary + choke while connected
> > > to the mains is that of the X of the choke at mains frequency
> > > connected directly to the transformer primary since the mains is
> > > effectively a short circuit (voltage source) in series with the two.
> > > In this situation, the transformer is transforming the choke
> > > impedance by the turns ratio squared to appear on the secondary side.
> > > A simple example to illustrate using a transformer with a stepup turns
> > > ratio of 1:2:
> > > Let Vp = 1V and the reflected load cause a current
> > > flow of 1A in the primary (assume no magnetizing current as this is
> > > separate from the load current and may be made infinitesimal by
> > > using a huge primary inductance). Then, Vs = 2V and Is = 1/2 Amp.
> > >
> > > Zp = 1 Ohm (1V/1A) and Zs = 4 Ohms (2V/0.5A) for Ns/Np of 2/1.
> > >
> > > One can model an equivalent circuit of the primary connected directly
> > > to the mains and a choke appearing in the secondary side modified as
> > > above. It is this effective choke that forms a resonant circuit with
> > > the Tesla primary cap.
> > >
> > > Malcolm
> >
> > I understand the above. However (here it comes),in a case of a tuned coil where the xfmr is
> > given added L (choke), Ls is seen as (xfmr L + choke L) x turns ratio squared. Tank C being
> > fixed (IMO) causes a change in the tanks resonant F in relation to any change in L before
> > the xfmr. Then, resonator vs. tank F would not be "tuned". The primary tap would then need
> > to be re-tapped so that Lp = original XL = original F?
> >
> > Bart
>
> Bart and all,
>
> Assume that the main gap is across the HV transformer. In a resonant
> charging system there are two independent resonant conditions at work.
> The first condition, low frequency resonant charging, ONLY occurs when
> the main gap is open, AND when the "effective" secondary inductive
> reactance of the HV transformer is close [in magnitude] to the
> capacitive reactance of the tank cap at the mains frequency of 50 or 60
> Hz. As long as the main gap is not conducting, the tank capacitor
> voltage and charging current will climb on successive mains half-cycles
> until the main gap fires {or the transformer or tank cap gets overvolted
> and fails). If the main gap fires, this "spoils" the Q of this resonant
> system, and the resonant charging process begins anew once the gap is
> extinguished. Ideally, the gap fires _at least_ once every half-cycle,
> reducing the possibility of "letting the smoke out of your system".
>
> The second condition occurs ONLY while the main gap is firing. In this
> case the heavily-conducting gap effectively "shorts out" the transformer
> L, leaving only the primary/tank inductance and capacitance to resonate
> at the operating frequency of the coil. The HV source is effectively
> "out of the picture", and will not influence the high frequency tuning
> of your system. While the two resonant conditions are basically
> independent and mutually exclusive, non-linearities (mostly transformer
> or choke core saturation) may also introduce chaotic operation and
> "bumping" in real-world coils...
>
> -- Bert --