From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: inductors, was RE: Sizing capacitors
Date: Tue, 20 Jun 2006 16:56:07 -0600
Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>
Nick,
These are great abundance at any irrigation supply for marking sprinkler
head location on the left coast. Great idea!
Jim Mora
-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Tuesday, June 20, 2006 8:11 AM
To: tesla@xxxxxxxxxx
Subject: RE: Sizing capacitors
Original poster: "Nick Andrews" <nicothefabulous@xxxxxxxxxxx>
Another thing that is a little more difficult to find that would be
excellent are the wires from the pin flags used in construction and
utility locate marking. They are roughly 24" long and maybe 18ga
steel wire. You would need to remove the vinyl flag portion. They
are also sold with those underground radio fences for dogs and cats.
Nick A
>From: "Tesla list" <tesla@xxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: RE: Sizing capacitors
>Date: Mon, 19 Jun 2006 17:26:13 -0600
>
>Original poster: "Terry Oxandale" <Toxandale@xxxxxxx>
>
>I used 3/32" (different diameters are available) flux coated welding
>rods inserted snuggly into a PVC tube, and then epoxied them in
>place (poured epoxy into both ends). It warms up a little at 5 kva,
>but worked very well for its purpose.
>
>________________________________
>
>From: Tesla list [mailto:tesla@xxxxxxxxxx]
>Sent: Mon 6/19/2006 3:19 PM
>To: tesla@xxxxxxxxxx
>Subject: Re: Sizing capacitors
>
>
>
>Original poster: "Nick Andrews" <nicothefabulous@xxxxxxxxxxx>
>
>For a decent-size core, you could go down to Home Repot or Lowe's or
>any lumberyard (or a construction site) and get some steel form
>pins. They are ~1/2" dia steel and smooth, unlike rebar and fairly
>cheap. Plenty long to rig up a control mechanism for adjustment, and
>can be cut shorter easily with a hacksaw.
>
>Nick A
>
>
>
>
>
> >From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: tesla@xxxxxxxxxx
> >Subject: Re: Sizing capacitors
> >Date: Sun, 18 Jun 2006 14:39:42 -0600
> >
> >Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>
> >
> >
> >
> >Did you dip each rod into an insulating varnish before bundling to
> >reduce eddy currents? If not, did the core get hot?
> >
> >This sounds like a reasonable solution to an expensive problem. I
> >will also try it perhaps with 1/4 inch steel rods.
> >
> >Dr. Resonance
> >----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: <tesla@xxxxxxxxxx>
> >Sent: Sunday, June 18, 2006 1:27 PM
> >Subject: RE: Sizing capacitors
> >
> >
> >>Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>
> >>
> >>Hi Dr. R, et al,
> >>
> >>I made 2 of your 3" X 20" last year using 18" of #10awg solid wire and
mild
> >>steel 3/8 rods of this length cut by a local steel supplier(fairly
cheap)
> >>and using two part marine epoxy. I shook them around abit but they were
> >>always vertical. Surprising, the core moved fairly easily after 1/2 hour
of
> >>set, no very freely inside the 3" sch 40 tubes. I drilled a bolt
> through the
> >>bottom of 18" to prevent them from slipping and mounted them vertically
> >>inside a network punch down cage. Hmmm. Very adjustable core.. and
fairly
> >>cheap to make. Pics and inductance and minor temp rise @
> 10KW with static R
> >>240v are in the archives or maybe Terry will need to bring them
> back. Thanks
> >>Terry, I want to use these on the fourth.
> >>
> >>Regards to all,
> >>Jim Mora
> >>
> >>-----Original Message-----
> >>From: Tesla list [mailto:tesla@xxxxxxxxxx]
> >>Sent: Saturday, June 17, 2006 8:50 PM
> >>To: tesla@xxxxxxxxxx
> >>Subject: Re: Sizing capacitors
> >>
> >>Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>
> >>
> >>
> >>
> >>
> >>I'm presently experimenting with some neat 2 x 2 x 12 inch supercil
> >>M6 grain oriented cores to develop a straight core type of current
> >>limiter for MOTs and PTs. The final design may contain 200-300 turns
> >>of #12 or # 14 AWG wire but should provide good series current
> >>limiting reactance for PT powered systems.
> >>
> >>I also have made up some 3 x 3 x 20 inch long straight cores that I
> >>will be winding up with some #10 AWG for current limiting testing
> >>with pole pigs. The bad news is these cores are not cheap due to the
> >>high price of this special steel --- over $200 per core!
> >>
> >>Dr. Resonance
> >>
> >>
> >>
> >>
> >> >Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
> >> >
> >> >Thanks Dr. R., Terry, this is great stuff! I'm
> >> >finally beginning to understand "LTR" and "STR" :-)
> >> >For my DC (non-resonant-charging) project, as Terry
> >> >mentioned, I ought not to have to worry about
> >> >transformer/cap resonance, which is goodness, I
> >> >suppose!
> >> >
> >> >Now I'm left to play with ballasting the little PT for
> >> >200-300VA. I had originally thought about using some
> >> >of the adjustable 5k 100W resistors I have all over
> >> >the place, but what a waste! The problem with using a
> >> >PT this small is that a pair of 3kV 30mA NSTs would be
> >> >smaller, especially after adding a ballast. Still,
> >> >the little PT looks "cool", so I'll see what I can
> >> >come up with :-)
> >> >
> >> >Thanks again,
> >> >Aaron
> >> >
> >> >
> >> >--- Tesla list <tesla@xxxxxxxxxx> wrote:
> >> >
> >> > > Original poster: "Dr. Resonance"
> >> > > <resonance@xxxxxxxxxx>
> >> > >
> >> > >
> >> > >
> >> > > Another interesting formulation is matching the
> >> > > transformer to the
> >> > > capacitor size.
> >> > >
> >> > > Imagine if you have a variac to adjust the voltage
> >> > > and another variac
> >> > > to adjust the current, ie, an adjustable series
> >> > > inductor on the
> >> > > primary side of your pole xmfr / PT xmfr.
> >> > >
> >> > > For initial testing you might set the xmfrs
> >> > > impedance equal to the
> >> > > impedance of the capacitor bank. Use a climbing arc
> >> > > to set the
> >> > > current to a certain value, ie, perhaps 30 Amperes.
> >> > > Knowing the 30
> >> > > amp current value on the primary side using 220
> >> > > volts you can calc.
> >> > > the power in the system The, using the 14,400 volt
> >> > > sec xmfr value
> >> > > you find the sec. current value. You then use this
> >> > > value to match
> >> > > the capacitive reactance value and you have the
> >> > > resonant match value
> >> > > for the xmfr - cap bank. Go slightly above this
> >> > > value to prevent
> >> > > undesireable xmfr to cap resonance, usually 1.3 to
> >> > > 1.4 times the
> >> > > capacitive match value at resonance.
> >> > >
> >> > > Now, here is where the interesting part begins.
> >> > >
> >> > > Set up a current meter on the primary side and
> >> > > monitor the primary
> >> > > amps. Increase the voltage control variac to 89-90%
> >> > > and then adjust
> >> > > the current control (series variac) for 25-30 amps.
> >> > > As power is
> >> > > applied to the coil system, at some point, you will
> >> > > notice the
> >> > > current actually begin to decrease even as you
> >> > > increase the voltage
> >> > > control variac. In ham radio, tuning linear amps,
> >> > > this was referred
> >> > > to as "dipping the plate current at resonance". The
> >> > > current will
> >> > > decrease as the voltage variac (power into the
> >> > > system is
> >> > > increased). There is a "tuning dip" on the ammeter
> >> > > at this point.
> >> > >
> >> > > This tuning point is the most efficient operating
> >> > > point for a classic
> >> > > spark gap Tesla coil system. As you increase the
> >> > > power into the
> >> > > system the amps will again start to rise. Slightly
> >> > > above the "tuning
> >> > > dip" point is the point at which the sparks will be
> >> > > their longest
> >> > > with a reasonable minimum of input power for any
> >> > > given
> >> > > system. Longer sparks can be produced above this
> >> > > current input
> >> > > point, however, a lot more power is required and the
> >> > > system is not
> >> > > operating in an efficient mode, ie, you have
> >> > > increased the power
> >> > > factor above the unity point and this is an area
> >> > > where classic Tesla
> >> > > coils do not operate very smooth. They become
> >> > > current hogs and try
> >> > > to saturate the current controller and produce audio
> >> > > "thumps" in the
> >> > > current and voltage variacs.
> >> > >
> >> > > This is what I refer to as "tuning the power supply
> >> > > to the system"
> >> > > and will give you a reliable indication of the most
> >> > > efficient power
> >> > > input (current level especially) for your given
> >> > > system. It's an
> >> > > experiment worth doing at least once to determine
> >> > > where the "resonant
> >> > > current dip" point is for your system. Then you can
> >> > > adjust the
> >> > > number of turns on your series power reactor to
> >> > > prodvide this proper
> >> > > level of current just as your voltage variac reaches
> >> > > 100% on it's scale.
> >> > >
> >> > > Up to approx 35 Amps a single variac provides
> >> > > voltage control for
> >> > > this experiment while a single variac in series with
> >> > > the pole xmfr
> >> > > pri provides the current control. If you are
> >> > > running a 0.1 uF to 0.2
> >> > > uF cap bank then you will need a dual variac for the
> >> > > voltage control
> >> > > and another dual variac for the current control to
> >> > > determine this
> >> > > tuning point. After this experiment is conducted
> >> > > you will know the
> >> > > best current for your system and the second current
> >> > > control variac is
> >> > > eliminated and the turns are adjusted on the primary
> >> > > series reactor
> >> > > to provide this "dip current" or slightly above (10%
> >> > > is usually very
> >> > > good for performance). This is the best way to
> >> > > determine the proper
> >> > > amount of current your current reactor / pole xmfr
> >> > > system should be
> >> > > providing to your system.
> >> > >
> >> > > Then, matching the impedance to determine the
> >> > > resonant value
> >> > > capacitance, and increase this value by 1.3 x Cres
> >> > > and you will have
> >> > > a very nice performing system. Values up to 1.6
> >> > > Cres do work but
> >> > > they produce sparks with more of a "capacitive
> >> > > discharge" and don't
> >> > > seem to be as active as the sparks off a toroid at
> >> > > 1.3 x Cres value.
> >> > >
> >> > > Dr. Resonance
> >> > >
> >> > >
> >> > >
> >> > >
> >> > > >Original poster: "J. Aaron Holmes"
> >> > > <jaholmes@xxxxxxxxxxxxxxxxxx>
> >> > > >
> >> > > >Thanks, Terry! Very helpful as usual. I suppose
> >> > > my
> >> > > >doubts about the transformer <==> capacitor
> >> > > >formulation come about because it seems to me that
> >> > > a
> >> > > >capacitive load on the transformer is going to have
> >> > > a
> >> > > >crummy power factor, thus rendering the transformer
> >> > > VA
> >> > > >incompatible with the coil Watts value.
> >> > > >
> >> > > >Is that true? In other words, to use 290nF would
> >> > > mean
> >> > > >200W effective power from the transformer, but the
> >> > > VA
> >> > > >would be higher, right? If I'm way off, just shut
> >> > > me
> >> > > >up! :-)) Otherwise, what I guess I was asking was
> >> > > >this: How would one go about choosing a cap for a
> >> > > >given VA, or otherwise so as to avoid exceeding
> >> > > some
> >> > > >rated peak current. Again, this is a PT and
> >> > > probably
> >> > > >can take a few times its rated 200VA...guess I'm
> >> > > just
> >> > > >interested in "getting the math" instead of
> >> > > surviving
> >> > > >on "rules of thumb" as I have for years now.
> >> > > >
> >> > > >Regarding "resonance" and "DC"...duh! My brain was
> >> > > >obviously already in bed when I went off on
> >> > > LTR/STR.
> >> > > >I'd actually *love* to know how those values were
> >> > > >computed for NSTs, etc., but if you recall sending
> >> > > it
> >> > > >to the list or posting it somewhere, I'll just look
> >> > > >harder :-)
> >> > > >
> >> > > >Good night (for me!) -
> >> > > >Aaron, N7OE
> >> > > >
> >> > > >--- Tesla list <tesla@xxxxxxxxxx> wrote:
> >> > > >
> >> > > > > Original poster: Vardan
> >> > > > > <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
> >> > > > >
> >> > > > > Hi,
> >> > > > >
> >> > > > > At 10:14 PM 6/16/2006, you wrote:
> >> > > > > >I've built coils before using caps that were
> >> > > > > obviously
> >> > > > > >"way STR" (e.g., 30nF on a 15kVA pig), and so
> >> > > never
> >> > > > > >bothered to really understand how one sizes a
> >> > > cap
> >> > > > > to
> >> > > > > >take maximum advantage of one's transformer
> >> > > (didn't
> >> > > > > >have room in my garage to do that with a pig
> >> > > > > anyway!),
> >> > > > > >but now I'm working on a coil based on a tiny
> >> > > 200VA
> >> > > > > PT
> >> > >
> >> >=== message truncated ===
> >> >
> >> >
> >
> >
>