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

["DC Cox" <resonance@xxxxxxxxxxxx>]

If running a pole xmfr, gear down your treadmill slightly with belts
and pulleys and pillow blocks, allowing for around 450 pps for
excellent performance with good quenching.  Keep your electrode dia at
least 3/8" (preferably 1/2") so the tips don't overheat and spoil the
quenching action.

Dr. Resonance




On 5/27/08, Jeremy Scott <supertux1@xxxxxxxxx> wrote:
> I'm not sure what I'm going to make yet,  but an ASRG
> is an option. I have one of those massive DC treadmill
> motors plus the speed
> control for it. Could swing a 12" Garolite disc easily
> :)
>
>
> --- "Lau, Gary" <Gary.Lau@xxxxxx> wrote:
>
>> 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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>
>
>
>
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