Re: [TCML] srsg to vari speed rsg

[Scott Bogard <sdbogard@xxxxxxxxx>]

     You cannot use a Freu adjuster with an async spark gap, as phase angle
changes constantly, as it is asynch.  Firstly before you waste your time
building a new spark gap a few questions to ask yourself, firstly why are
you making it?  Are you unsatisfied with your coils performance?  Why is it
unsatisfactory, will this correct it?  Or do you simply want to build
something different for the sake of curiosity and building something new?
 Let us look at asynch Vs sync spark gaps a moment.  What is the purpose of
a spark gap?  Well it is to allow the tank capacitor to discharge into the
primary, after it has been charged by the "step up" transformers of course,
and providing a low impedance path for resonance to occur.  Why is the rate
at which it does that important?  Well it has to do with optimizing power
flow from the transformers, into the primary, you don't want to fully
charge your cap and then wait before discharging, that doesn't use as much
power as you can, and by the same token, you don't want to charge to a low
voltage and discharge rapidly, that will prevent proper resonance.
     Ok, the reason I am telling you this (and I apologize if I sound
"school teacher"-ish) is that without knowing why break rate is important,
you cannot make an informed decision about which gap is best for a given
system.  Sync gaps with Freu adjusters are well suited for systems with
huge tank capacitors, that can take advantage of longest possible charge
times by the step up transformers, if your system was designed this way,
and performed well, switching to a rapid firing async gap will ruin your
performance and leave you thinking async is bad tasting, which it is not.
 Async systems are AWESOME for coils with small tank capacitors, as they
charge to the optimum 70% tank capacitor charge before firing, and have the
advantage of a high break rate for better spark growth and brightness.  If
you are hoping for better spark growth and brightness but have a big
capacitor, you will be very disappointed, as your capacitor will not charge
high enough and your sparks will dwindle.  The other alternative is running
an async slow, and this is very bad as you will slowly move in and out of
phase, leading to noticeable beating of the arcs, which looks a bit neat
granted, but makes dangerous transients for your transformers and will
promptly fry them, and all the electronics in your house (potentially).
     Anyway, sorry for ranting, it's just I'm unsure what your plans are,
and don't want you to be disappointed and not sure why.  To actually answer
your questions, you can use a DC motor or an AC motor, provided you use the
correct controller.  I like 3-phase AC with VFD, but will probably opt for
DC next time around, because it is easier and potentially much cheaper
(junkyard DC treadmill motor with an eBay variac and full bridge diode).
 That would be my recommendation, as if you lurk eBay you can get your
parts for next to nothing.  The problem with treadmill motors I have found
so far is they have an obnoxious flywheel attached that seems difficult to
get off, but you can always incorporate that into your design if you are
clever.  But anyway as David said, no, you cannot tweak electrode position,
that is purely an SRSG thing, and does not apply to ASRSG.  A thing to note
is that if you go the three phase VFD rout, sometimes you can make a gap
that does both sync and async via programming, but that is useless really
unless you have a way to disconnect half your your cap bank, (or preferably
more)  though now that I think about that, that would be awesome!  But if
you did go that route you may need a Freu adjuster when in Sync mode,
though I'm not sure how you would do that with a three phase motor, and I'm
also unsure if the VFD would be able to dynamically shift phase anyway,
eliminating the need for it.  Snyway some food for thought, if you would
like to discuss your plans in more detail (coil specs) we can better help
you choose your options, and help you grant a more firm understanding of
what is going on also.  Hope this was helpful!!!

Scott Bogard.


On Thu, Jul 25, 2013 at 8:25 PM, <coils@xxxxxxxxx> wrote:

> Hey everyone, I have been using an srsg and a Freu phase shifter for some
> time now, with great results. I am planning a new rsg with variable speed.
> My
> question; with vari speed, will I still need to tweek the angle of the
> moving electrodes to stationary electrodes? I have not decided on ac or dc
> vari speed, but if I were to
> go with ac, could I use a Freu phase shifter with something like a vfd, or
> one of the ACTech speed controlers?
>
> thanks for your thoughts,
>
> Cheers
>
>
>
>
>
>
>
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