Re: MOT Powered SSTC - First Tests Successful!!

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

Original poster: "chris swinson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>

Captain,

This sounds like a really good project. Will you take some scans of it all
in action ? I've been trying to keep up with all the posts and still not
sure how its actually working over a normal SSTC design. Will you be Selling
the PCB's for this when all is sorted out ?

cheers,
chris




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, March 30, 2003 8:14 PM
Subject: Re: MOT Powered SSTC - First Tests Successful!!


 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<dhmccauley-at-spacecatlighting-dot-com>
 >
 >  >  > To get big output on a SSTC, you need big voltage input.
 >  >
 >  > Dan I love your design, the high voltage definately seems to work and
 >  > all, but I absolutely disagree that using HV input (like from a MOT)
 >  > is the only route to huge arcs.
 >  >
 >  > Input POWER is what is needed, regardless of the input voltage or
 >  > current.
 >  >
 >  >  > But this design is flawed as it extremely limits the output of your
 >  >  > SSTC as input voltages are relatively low
 >  >
 >  > I don't think it's that limited at all...sure, impedance matching is
 >  > a little more difficult with low input voltage (4 turn primary vs. 20
 >  > turns), but 6 foot + arcs arcs are WELL within the capabilities of
 >  > the H-bridge topology for an SSTC.
 >  >
 >  > Recipe For Huge Arcs: 3 turn primary, 4" tall 6" O.D., 4" secondary
 >  > with #28, 240Vrms 1/2 wave DC input, and an H-bridge using 60+ amp
 >  > MOSFET's.
 >
 > I wasn't saying that huge arcs are impossible with a full-bridge SSTC.  I
 > was trying to say it would be extremely difficult and a relatively complex
 > and expensive
 > device.  Perhaps when those 10kV FETs (single packages) come out in the
next
 > decade or so, a simple full-bridge would be capable of 6 ft arcs rather
 > easily.
 > But at this time, it would be very difficult to get anything more than 24
 > inches from a 240VAC driven full-bridge SSTC.  Case and point is that with
 > all the full-bridge SSTCs already
 > out there, no-one has really exceeded 24" yet.  I've hit beyond that using
 > my full-bridge SSTC, but I was pushing almost 480VAC.  And that was before
 > catastrophic destructions of
 > all my FETs ! ! ! !  So I limit my SSTCs to 240VAC now.
 >
 > As for power vs. voltage, I still think voltage is the decided factor for
 > "directly" driven SSTCs.  Perhaps with DRSSTCs, it would be different, or
an
 > SSTC where there was an actual
 > primary tank circuit, but with a direct driven primary SSTC, voltage is
 > where its at!
 >
 > On example regarding power input is the following experiments I've run:
 >
 > HALF-RECTIFIED - NO CAP FILTER
 > HALF-RECTIFIED - SMALL CAP FILTER
 > HALF-RECTIFIED - LARGE CAP FILTER
 > HALF-RECTIFIED - VERY LARGE CAP BANK
 >
 > Each of these tests were used with 240VAC input.  Peak voltage was
constant
 > except at each step of increasing size capacitor bank, the input waveform
 > had decreasing ripple (with
 > capacitor filters) so that at the last step, the input voltage was about
 > equal to a DC value of the half-rectified peak voltage value.
 >
 > Each step, power input was significantly higher than the previous step.
 >
 > HOWEVER, even though the range of power was about 1kW to 3kW, output arc
 > length remained CONSTANT.  The arcs grew much thicker and nastier looking
 > but overall length
 > wasn't increased with increased power input.
 >
 > In the next step, I would increase the input voltage a bit (using my
 > autotransformer variac), and the arc output grows nicely!
 >
 >  > Again, even with spark gap TC's, it's input power that is necessary
 >  > for huge arcs. This is a very well known concept. For instance: a 7kV
 >  > 100mA coil can arc just as far as a 50kV 14mA coil. Same power (700W)
 >  > for both coils.
 >
 > Yes, I do agree with you on that statement.  Basically because you are
 > charging up a primary tank circuit and discharging this energy into the
 > primary.
 > BUT, with a direct driven primary SSTC, there is no energy storing tank
 > circuit.  Again, perhaps with a DRSSTC this would be different, but I
 > haven't explored
 > that area yet.
 >
 >  > To finalize my thoughts, I will add that my friend Aron Koscho's SSTC
 >  > achieved a measured sparklength of 32" (Dan, no offense to that extra
 >  > 2", it's just what it happened to be), using an H-bridge running off
 >  > of 240V. The reason it's not smeared across our website is because it
 >  > only lasted about 3 seconds due to using only 20A parts (IRFP460's -at-
 >  > 20A Id). Aron used a 4 turn primary wound 5" tall, coupled to a 4"
 >  > secondary wound with #28.
 >
 > Sounds cool.  Has he made any progress to replace the FETs with higher
 > current ones?
 >
 > In summary, my point wasn't meant to say large arcs are impossible with
 > full-bridge driven SSTCs, but that it can be fairly difficult as proven in
 > your friends Aron Koscho's design.
 > I'm merely saying by starting off with a higher input voltage for "direct
 > driven" SSTCs one can make life much more easier can obtain those longs
arcs
 > much easier than working with
 > a lower voltage full-bridge circuit.
 >
 >
 >  > Regards,
 >  >
 >  > Justin Hays
 >  > KC5PNP
 >  > Email: justin-at-hvguy-dot-com
 >  > Website: www.hvguy-dot-com
 >  >
 >  >
 >  >
 >  >
 >  >
 >
 >
 >