RE: [TCML] 35 KVA Vacuum Tube Tesla Coil

["Phil Tuck" <phil@xxxxxxxxxxx>]

Wow that was news to me, I worked on the principle that the increased
current flow through the primary winding must cause more flux to be created
in the core. So either that is not the case, which I am not sure why, or it
does increase the flux, in which case if it is the latter would the
secondary flux increase cancel it out then? Otherwise what is happening?

Regards
Phil Tuck

www.hvtesla.com



-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Steve Ward
Sent: 07 July 2011 18:21
To: Tesla Coil Mailing List
Subject: Re: [TCML] 35 KVA Vacuum Tube Tesla Coil

Phil,

It is *magnetizing current* and NOT the *load current* that saturates a
transformer.  The magnetizing current is purely a function of the applied
voltage integrated over time, which essentially means that with 50/60 HZ
power there's just a specific input voltage at which the core will
experience magnetic saturation.  So drawing more power from your transformer
will NOT increase the chance of saturation, in fact its most likely to
saturate with no load as the line voltage will be highest then.

Roger,

Great to see some really high power VTTC work.  Some thoughts:

1) is it possible to increase the operating frequency of the system?  I
think you mention the Fres of 280khz, but have you actually measured the
oscillating frequency while making sparks?  I found that getting the Fop
above about 320khz tends to produce sparks that have straighter segments to
them which tends to make the spark length greater for the same input power.
I think the amount of plasma output is the same, but with the lower
frequency it tends to get all twisted up and becomes shorter.

2) What is the capacitance of your voltage doubler?  Could you furthermore
measure the leakage inductance of the power transformer feed, plus whatever
the ballast inductance is?  I have a strong suspicion that these "level
shifters" are really more just resonating with the total power supply
inductance at 60hz which gives you more through-put.  If you consider the
total energy storage of the level shifter cap, its often far too small to
supply even half the energy that the spark consumes in 1 cycle of AC.  I
think my tube coils had something like 10J worth of caps there, yet the
energy per spark was like 100J or something, in which case the capacitor
would end up looking like extra series impedance (aka, ballast).  But this
is not the case, because it *does* increase power throughput, so i think its
really that this series cap works to cancel out the series L of the power
circuit.

3) with regards to power measurement.  Can you simply get a line-type
current transformer and put a 1ohm resistor on the output (for example), and
use an oscilloscope to view the wave-shape and its relative phase with the
line voltage?  I expect the phase to be pretty good because the VTTC really
looks like a resistive load, but the shape may be kind of funky, and likely
asymmetrical due to the half-wave nature of the power supply.

Anyway, i also suspect the 35kVA figure is a bit high, but to see it
consuming 15-20kW (real power) would not be beyond my belief given the spark
output of this machine.  I cannot maintain that sort of spark length at
60pps on my QCW solid state machine, and ive seen the input power to that
machine get up to 10kW pretty easily.  These types of sparks require a lot
of power.

Steve

On Thu, Jul 7, 2011 at 10:26 AM, Phil Tuck <phil@xxxxxxxxxxx> wrote:

> PF issues aside, I would imagine the transformer core to be totally 
> saturated and most likely the ballast as well, unless it possess a 
> very substantial core size. The trouble then is that the sine wave 
> loses it's shape and the meter, depending on the sort used, will give 
> differing false results.
> Therefore, your coil is actually more impressive than what you though 
> for the power Roger!
>
> Regards
> Phil Tuck
>
> www.hvtesla.com
>
>
>
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