Re: tesla coil power ?! (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 27 Sep 2007 14:14:20 -0700
From: David Dameron <ddameron@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: tesla coil power ?! (fwd)

Hi Ed,
Yes, I was very surprised when I first heard of their "new" work! They
claimed 40% efficiency (coupling?) I understand everything you wrote,
except the last sentence.
A 60 watt 120V bulb is about 240 Ohms, and that isn't a high Q load for a
LC circuit with a coil inductance in the range of 25 -50 uH. (series or
parallel) at 3.5 or 10 MHz.  I used bare #12 AWG wire (~ 2mm diam.) and
varied the coupling coefficient by the spacing, looking for "critical
coupling".  I don't know if the unloaded receiver coil Q approached 1000.
For a HV connection, the voltage obviously can be increased by increasing
the effective parallel impedance, up to a point where the unloaded Q
becomes a factor. It wasn't clear in the MIT photo that the xmit or
receiving coil had any taps or links. I guess I could use a resistor load,
which could be much higher than an incand. lamp, for higher voltage and Q.
I guess it would be cheating to come up with a high-power regenerative
receiver for high Q.
-Dave D.


> [Original Message]
> ---------- Forwarded message ----------
> Date: Wed, 26 Sep 2007 17:09:52 -0700
> From: Ed Phillips <evp@xxxxxxxxxxx>
> 	That work is trivial trash but the Q's sound reasonable enough. 
Certainly one can build coils with equal or higher Q at the 10 MHz
frequency they used - just takes large size and large conductors.  Remember
that their coils were 2 feet in diameter - expected unloaded Q would be
much greater than 1000 - I think they expected 2500 and that sounds OK.  As
for the loaded Q, that is adjusted by varying the coupling of the load to
the resonant circuit.
>
> Ed
>
>
>