RE: [TCML] Taming the Beast: Inductive Ballast vs. Variac, PFC

["Lau, Gary" <Gary.Lau@xxxxxx>]

Before going too much further, consider this.

If using a .03uF cap with a 120BPS SRSG and a 14.4kV xfmr, your theoretical maximum power throughput is:
120BPS * .5*C*V^2 = 120 * .5 * .03E-6 * (14,400*1.414)^2 = 746 Watts
You can use the biggest baddest pig available, but that cap and gap can't pull any more power than above.  This is why pig-powered coils typically use async RSG's - to permit higher break rates and pull more power.

Regards, Gary Lau
MA, USA



> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of David Rieben
> Sent: Tuesday, May 27, 2008 8:55 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Taming the Beast: Inductive Ballast vs. Variac, PFC
>
> Hi Jeremy,
>
>
> ----- Original Message -----
> From: "Jeremy Scott" <supertux1@xxxxxxxxx>
>
> > That sounds interesting, and I may just take you up on
> > it. I have another option as well that I'd like to
> > explore too.
> >
> > I've got 225 amp lincoln arc welder (240VAC@50A input)
> > which I was going to use but I have some safety
> > concerns. 1) What kind of current limiting will it
> > provide at 120V as opposed to 240V and 2) Does this
> > work if the welding leads are shorted vs. not? (The
> > switching mechanism temporarily breaks the secondary
> > welding circuit and I am worried that this will
> > translated to 'full blast' if I am running the coil
> > in between clicks.)
>
>
> I would assume that Ohm's law would apply and that
> the arc welder would limit the current at 120 volts 4X
> what it does at 240 volts. Shorting the welding leads
> allows for the maximum current throughput since that's
> effectively what you are doing when you weld with it.
> Switching the tap selector switch will only disconnect
> the power in between clicks, not run at full blast. How-
> ever, you will find a label that states to NOT switch
> the selector while it's under a load, as this would quick-
> ly errode the switch contacts.
>
>
> > I may settle for it being adjustable only when the
> > main power is off, but I really like the idea of
> > ramping up slowly by pulling a core.
>
>  This type of welder does not utilize the sliding core to
> adjust the current. There are simply multiple taps.
>
>
> > Okay now that's interesting. I originally wanted a
> > small 5kV pole pig. But I settled for a PT as an
> > intermediate stepping stone from the NST.
> >
> > I take it these things are much more robust than the
> > typical NST? (Fried my first one, like everyone else
> > :) ) Are RC protection circuits on the secondary a
> > good thing to have for it?
>
>
> Yes, PTs along with pigs are much more robust than
> fragile NSTs and do not require RC circuit protection
> although you can still use circuit protection, if desired.
> I believe the HV side of all 14.4 kV pigs and PTs are
> rated at 110 kV BIL, so they typically have no problems
> standing up to the nasty kickbacks of a Tesla tank circuit.
>
>
> > I will probably not run that high a kVA on my coils,
> > as I haven't sized the other components for it. (The
> > spark gap I'm planning on using is a 120bps 1/4"
> > electrode SRSG 'propeller' style with tungsten rods
> > and the secondary is a 25"x6.5" form. Caps are going
> > to be MMC or a series of one, two or three Maxwell
> > .03uf units.)
>
> >From your description of your proposed SRSG design,
> I'd say that your coil should easily handle 4.2 kVA. Just
> make sure that you run enough strings of your MMCs (if
> you choose the MMC route) to handle the RMS currents.
> I woud opt for a (4) sereised-parallel configuration of those
> .03 uf, 35 kV Maxwells (for a total of .03 uFd at 70 kV)
> as these have been known to fail from overvoltage with 15
> kV NSTs. This will also spread the RMS currents over the
> 4 of them to share the load.
>
> What size toriod terminal do you plan to employ? A good rule
> of thumb is to make it about the same demensions of the
> secondary coil, which in your case would be 25" x 6.5".
>
>
> > I have to play with javatc a bit more to figure out
> > the specs exactly, and to start that I need to know
> > what I can put into it.
> >
> >
> > Do you have any issues balancing them? For example,
> > can one core be left in while the other is out or do
> > you have to move them in parallel?
>
> >From what others have stated, balancing is not that big of
> an issue in this situation.
>
>
> David Rieben

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