[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

streamer impedance matching, was Re: Fwd: Re: Calculating streamer breakout of top-loads



Original poster: "Sean Taylor" <sean.s.taylor-at-comcast-dot-net> 

Hi all,

I have a few problems/questions with this argument, interspersed throughout.

 > Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz>
 >
 > On 13 Sep 2003, at 10:33, Tesla list wrote:
 >
 >  > Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >  >
 >  > I wondered this myself,  If you have a source with say a fixed source
 >  > impedance and you vary the load impedance, then the maximum power
transfer
 >  > is with the Zload = Zs.

First, with complex load and source impedances, the max power transfer is
Zload = Zs*, that is the complex conjugate.

However, if the load impedance is fixed and the
 >  > source impedance is varied, then the maximum power transfered is with
Zs = 0
 >  > to get maximum voltage on the load.

Zs = 0 for max power, and we're relatively close to that for a TC.  First,
the voltage is high, and the DCR low enough to allow for 100+ amps.  Second,
we're purposely running at resonance, or close to it - i.e. Xl = -Xc.
Sometimes systems are out of tune a bit, it's not easy (possible) to get
*perfect* tuning.  Also, many people detune to account for streamer
loading - the added capacitance of the from the streamers.  This is just
taking the extra capacitance into account to meet the resonance condition,
Xl = -Xc, more C, need a lower frequency to increase Xc, and decrease Xl.

 > Suppose the idea is a goer. The challenge is then on to build a
 > secondary whose output impedance remains a conjugate of 220k - jnwC
 > where n is expected spark distance in feet and C is the 1pF. At least
 > I'd consider it a challenge. Just meeting the 220k requirement would
 > be a nightmare.


Well, to match the 220k part would be pretty easy, just throw a resistor on
top of the coil, or bottom, (a HV rateed one) :-)  The resistance wouldn't
be distributed like it is from the wire resistance, but you don't need it to
be.  It would also waste a WHOLE lot of energy, and as was already pointed
out, with a fixed load impedance, max power into the load occurs when Zs = 0
.  We can't get that, but we can get as low as possible.  Low R, and zero
complex impedance.  But changing the inductance is where you'll mess things
up.  The tuning of the coil will be thrown off, and you'd have to retune to
get the same output.  But by retuning, you've just changed the frequency so
once again, Xl = -Xc.  Guess we need to add another inductor :-)  You can
see where this is going . . . a never ending cycle of more inductance and
tuning.  Just tuning for the added streamers will cause the complex
impedance to be minimized - that's the whole idea of resonance.

Feel free to send any comments/questions/flames.  As a disclaimer, this is
just me view of what's going on, and may be a little, or more than a little
off :-)

Sean Taylor