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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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