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Re: NST Shunt Removal (fwd)
---------- Forwarded message ----------
Date: Tue, 12 Jun 2007 14:28:17 -0700 (PDT)
From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: NST Shunt Removal (fwd)
Would you want to set it on a fixed current range
instead of auto-range? Mine can do either.
To read mine, I simply bought an analog panel milliamp
meter from eBay.
Adam
--- Tesla list <tesla@xxxxxxxxxx> wrote:
>
> ---------- Forwarded message ----------
> Date: Mon, 11 Jun 2007 17:56:09 -0700
> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: NST Shunt Removal (fwd)
>
> Hi Jim,
>
> Ever measured what the current is now? Easy to do if
> your interested.
> The transformer is rated for "open circuit" voltage
> and "short circuit"
> current. So, short the two HV terminals through a
> digital ammeter and
> set the dial to mA (most of these meters are capable
> of about 300 to 500
> mA). Plug in the NST and read the output. The shunts
> are current
> limiting the NST, so this type of test is real easy
> for this
> transformer. You might be surprised at the short
> circuit current value
> as I was.
>
> SAFETY NOTE: You must ensure there is a good
> connection between meter
> and hv terminals. If for some reason there isn't,
> then the output
> voltage would be felt across the meter and the meter
> would likely die.
> With a good connection, the hv side is shorted out
> through the meter and
> the HV is not present. If you want to test how the
> NST reacts, sounds,
> etc.. with the hv shorted, simply connect a piece of
> wire between both
> hv terminals and plug in the NST. You'll then get a
> feel for what to
> expect. After that, just connect the meter ready to
> read milliamps and
> ensuring you've plugged in the leads to the
> appropriate receptacle on
> the meter.
>
> Take care,
> Bart
>
> Tesla list wrote:
>
> >---------- Forwarded message ----------
> >Date: Sun, 10 Jun 2007 18:33:34 -0700
> >From: Jim Mora <jmora@xxxxxxxxxxx>
> >To: 'Tesla list' <tesla@xxxxxxxxxx>
> >Subject: RE: NST Shunt Removal (fwd)
> >
> >Hello,
> >
> >I too modified a France 12/30 removing half the
> shunts and potting it a
> >mixture of melted Vaseline and paraffin. It arcs a
> Really hot flame!
> >
> >Jim Mora
> >
> >-----Original Message-----
> >From: Tesla list [mailto:tesla@xxxxxxxxxx]
> >Sent: Sunday, June 10, 2007 3:51 PM
> >To: tesla@xxxxxxxxxx
> >Subject: NST Shunt Removal (fwd)
> >
> >
> >---------- Forwarded message ----------
> >Date: Sun, 10 Jun 2007 16:05:07 -0700
> >From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> >To: Tesla list <tesla@xxxxxxxxxx>
> >Subject: NST Shunt Removal
> >
> >Hi All,
> >
> >My 4.5" diameter coil spark lengths are far beyond
> a 12/60 NST capability.
> >http://www.classictesla.com/photos/ba45/ba45.html
> >And these pics don't really show the lengths I've
> seen with this coil.
> >
> >The NST I use was modified by fixing some hv
> windings and removing 1/2
> >of the shunts (back when I documented the NST
> depotting procedure. So,
> >the 12/60 Franceformer is no longer a 12/60. At the
> time, I never
> >finished the measurements on the NST. Well, I
> rebuilt my hv divider
> >today using 6 100Meg HV resistors (mfg p/n
> EX2G1006, $1.66ea). These are
> >made by Ohmite and good for 7.5KV each (I have 3 in
> series on each leg
> >for 22.5KV at 300Meg). Anyway, following
> calibration, I tested an
> >unmodified 15/30 Franceformer. All came out as it
> should. Here's the
> >data for the unmodified 15/30 NST.
> >Rp=0.8 ohms, Rs=16230 ohms.
> >
> >OPEN CIRCUIT MEASUREMENTS:
> >V_pri = 124.1 V
> >I_pri = 0.74 A
> >P_pri = 24 W
> >VA_pri = 91 VA
> >PF = 0.27
> >V_sec = 15340 V
> >
> >SHORT CIRCUIT MEASUREMENTS:
> >V_pri = 124.0 V
> >I_pri = 3.83 A
> >P_pri = 39 W
> >VA_pri = 474 VA
> >PF = 0.08
> >I_sec = 25.74 mA
> >
> >
> >Knowing that the hv divider is working well, I
> decided to unbolt the
> >modified 12/60 and run it through both open and
> short circuit
> >measurements. Here is what I found: btw, Rp=0.45
> ohms, Rs=4660 ohms.
> >
> >OPEN CIRCUIT MEASUREMENTS:
> >V_pri = 124.2 V
> >I_pri = 1.53 A
> >P_pri = 50 W
> >VA_pri = 190 VA
> >PF = 0.26
> >V_sec = 13380 V
> >
> >SHORT CIRCUIT MEASUREMENTS:
> >V_pri = 121.3 V
> >I_pri = 20.3 A
> >P_pri = 428 W
> >VA_pri = 2457 VA
> >PF = 0.18
> >I_sec = 206.7 mA
> >
> >So, as you can see, this NST is no longer a 12/60,
> closer to a 13/200
> >and that explains the arc lengths being so good, or
> really, "not that
> >good" considering I am about 20" shorter than I
> should be for this power.
> >
> >Dr. Resonance was wondering why the little coil was
> doing so well and
> >had asked me offline. I let him know the NST was
> modified, but I didn't
> >have the data to give him at the time. I've
> probably pushed that NST to
> >the brink of saturation, but, it has held up well,
> it just keeps on
> >running. It's reliability is a pleasant surprise
> considering what I know
> >"now" about the modifications.
> >
> >I took out exactly 1/2 the shunts. I_sec jumped
> from 60mA to 200mA (more
> >current than I intended). I was hoping removing 1/2
> the shunts would be
> >a linear jump to 120mA, but that was just a shot in
> the dark. If I were
> >to modify an NST again by removing shunts, I would
> only remove 1/4 of
> >the shunts. 1/2 seems a bit much. This NST is more
> like a PT or
> >bombarder now. I really don't know how long it will
> last. Last week, I
> >lost an XBOX 360 and my main computer (video
> section on motherboard
> >committed suicide). This was due to a small 2" coil
> that I ran without
> >an RF ground. Big mistake. However, my NST Terry
> Filter smoked with this
> >4.5" coil Thursday. The coil and NST still run
> great, but the Terry
> >Filter has some burnt resistors. Looks like I'll
> have to check all those
> >MOV's!
> >
> >Just thought this data might be of interest to
> anyone considering shunt
> >modifications. I know those that happen to manage
> NST shunt removal like
> >the fact they have (more power, baby!), but not
> everyone makes the
> >measurements following the modification. And
> considering what I found,
> >1/2 the shunts removed might be stretching (or not
> depending on your
> >view of things).
> >
> >Take care,
> >Bart
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
>
>
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