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RE: Measuring HV capacitor voltage (fwd)
---------- Forwarded message ----------
Date: Tue, 24 Jul 2007 21:57:37 +0000
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Cc: drieben@xxxxxxxxxxx
Subject: RE: Measuring HV capacitor voltage (fwd)
Hi Jim,
Not too sure as I haven't actually hooked the big caps up yet.
I've been calibrating it with a 75 nFd, 40 kVDC Maxwell pulse
cap and of course, I can charge it up just about instantly. I was
charging these huge caps before with a neon bombarder and
was able to charge them to their full rated voltage without
blowing the fuse on the variac within 15 seconds when I last
had it set up last year.
David Rieben
-------------- Original message --------------
From: "Tesla list" <tesla@xxxxxxxxxx>
>
> ---------- Forwarded message ----------
> Date: Sat, 21 Jul 2007 18:59:48 -0700
> From: Jim Mora
> To: 'Tesla list'
> Subject: RE: Measuring HV capacitor voltage (fwd)
>
> Hi David,
>
> How long does it take to charge the caps via this method?
>
> Jim Mora
>
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Saturday, July 21, 2007 8:14 AM
> To: tesla@xxxxxxxxxx
> Subject: Re: Measuring HV capacitor voltage (fwd)
>
>
> ---------- Forwarded message ----------
> Date: Sat, 21 Jul 2007 00:46:01 +0000
> From: David Rieben
> To: Tesla list
> Cc: drieben@xxxxxxxxxxx
> Subject: Re: Measuring HV capacitor voltage (fwd)
>
> Hi Adam,
>
> No, actually I am going to be charging them with the "dry" core
> of a 125 kVp, 500 mA transformer, removed from its tank
> of oil, through a 120/140 volt variac. Since the HV output
> of this x-ray transformer, like most of them, is center tapped
> to its grounded core, just like an NST on steroids, I simply
> run the two "hot" HV output leads to the rectifiers facing the
> same way and use the ground the return, so I get full wave
> rectification but at only half of the rated output voltage of the
> transformer. That still gives me access to more than enough
> voltage to charge the caps, to charge them in a timely manner.
> Of course, careful metering of the voltage at the capacitors' ter-
> minals is of paramount importance to insure against overvolting them.
> Also, since I will never be pushing the x-ray transformer to even
> half of its rated output voltage, it won't matter that it's no longer
> submerged in oil.
>
> David Rieben
>
> -------------- Original message --------------
> From: "Tesla list"
>
> >
> > ---------- Forwarded message ----------
> > Date: Fri, 20 Jul 2007 14:01:15 -0700 (PDT)
> > From: Yurtle Turtle
> > To: Tesla list
> > Subject: Re: Measuring HV capacitor voltage (fwd)
> >
> > Do you charge it from an NST with rectifiers and a
> > variac? If so, you could measure variac output, and
> > calibrate the scaling using your HV probe. Of course
> > this wouldn't tell you when you're fully charged.
> >
> > I use the 5 volt output from my HVDC YAG PSU in my
> > canabalized VTVM:
> >
> > http://hot-streamer.com/adam/garage/psu_34kV_1.jpg
> > http://hot-streamer.com/adam/garage/psu_34kV_2.jpg
> > http://hot-streamer.com/adam/garage/psu_34kV_3.jpg
> >
> > Adam
> >
> > --- Tesla list wrote:
> >
> > >
> > > ---------- Forwarded message ----------
> > > Date: Fri, 20 Jul 2007 14:29:51 +0000
> > > From: David Rieben
> > > To: Tesla list
> > > Cc: drieben@xxxxxxxxxxx
> > > Subject: Re: Measuring HV capacitor voltage (fwd)
> > >
> > > Hi Bart,
> > >
> > > Yes, a high voltage probe that plugs directly into
> > > your DVM
> > > is the most convinient way to measure HV. I do
> > > already have
> > > one of these and was using it to try to calibrate my
> > > "attempts"
> > > at a voltage divider. However, I need a more
> > > permanent panel
> > > mount meter for measuring the voltage across my huge
> > > quar-
> > > ter shrinker caps so that I don't overvolt them. I'd
> > > really ra-
> > > ther not have to be sticking that probe by hand onto
> > > the
> > > "hot" terminal of a fully charged 20 kJ capacitor
> > > bank each
> > > tiem that I charge them up ;^() I need a safer and
> > > more per-
> > > manent hardwired metering setup.
> > >
> > >
> > > David Rieben
> > >
> > > -------------- Original message --------------
> > > From: "Tesla list"
> > >
> > > >
> > > > ---------- Forwarded message ----------
> > > > Date: Thu, 19 Jul 2007 01:21:24 -0700
> > > > From: Barton B. Anderson
> > > > To: Tesla list
> > > > Subject: Re: Measuring HV capacitor voltage (fwd)
> > > >
> > > > Hi David,
> > > >
> > > > A little while back I documented a hv divider:
> > > >
> > > http://www.classictesla.com/download/hvacdivider.pdf
> > >
> > > >
> > > > I however broke one of the resistors and decided
> > > to simply buy some hv
> > > > resistors and give them a try. I ordered from
> > > Allied Electronics p/n =
> > > > 296-0171 (the manufacturer is Ohmite who's p/n is
> > > EX2G1006). I just
> > > > checked the website and it seems that part number
> > > is no longer listed?
> > > > Odd. It's a pc board mount type. If you can
> > > imagine a 10 pin sip
> > > > resistor with only pin 1 and pin 10 at their ends,
> > > this is what the
> > > > resistor looked like. Was good for a hefty 10kV
> > > however. I think it was
> > > > about 300M. It may not be available any longer?
> > > Anyway, something along
> > > > that line can be used. You just have to alter the
> > > center voltage divider
> > > > to suit.
> > > >
> > > > Of course, the best way to measure is just to do
> > > an eBay search for a
> > > > high voltage measurement probe for high "AC"
> > > volts. Their out there. A
> > > > lot easier than building a divider and the cost is
> > > likely pretty similar
> > > > in the end.
> > > >
> > > > Take care,
> > > > Bart
> > > >
> > > >
> > > >
> > > > Tesla list wrote:
> > > >
> > > > >---------- Forwarded message ----------
> > > > >Date: Thu, 19 Jul 2007 15:15:51 +0000
> > > > >From: David Rieben
> > > > >To: Tesla list
> > > > >Cc: drieben@xxxxxxxxxx
> > > > >Subject: Measuring HV capacitor voltage
> > > > >
> > > > >Hi all,
> > > > >
> > > > >I'm having a little issue with measuring up to 10
> > > kV across a capacitor
> > > > >on a standard panel mount, analog 0-15 VDC
> > > voltmeter from Radio
> > > > >Shack. Obviously, I was trying to make it read 1
> > > volt for each measured
> > > > >1000 volts. I tried using a voltage divider of 10
> > > seriesed 10 meg resistors
> > > > >and a 100 K pot but found that the 100 megs was
> > > just too much resist-
> > > > >ance to allow for sufficient current for reliable
> > > movement of the volt meter.
> > > > >I then tried a series-parallel arrangment of
> > > 10x10 of the 10 meg resistors
> > > > >for a total of 10 meg and then still used the 100
> > > K pot and varied it to try
> > > > >to bring in the proper calibration. I was
> > > checking the voltage measurement
> > > > >with my HV probe and DVM. The resistors didn't
> > > like being bunched up
> > > > >10 at a time and started flashing over
> > > externally. Also, I was having trouble
> > > > >getting the analog meter readings to be accurate
> > > throughout the 0 - 15 volt
> > > > >range according to the measurement of the HV
> > > probe. I think the meter is
> > > > >designed for 10 meg impedance and it also comes
> > > with a 15 K resistor that
> > > > >is supposed to be in series with the voltage
> > > source. Anyone have any sug-
> > > > >gestions for reliable and reasonably accurate
> > > measurement of high voltage
> > > > >through a low voltage analog voltmeter via a
> > > voltage divider network?
> > > > >
> > > > >Thanks
> > > > >David Rieben
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
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