Re: Polarized HV/ what's + and what's -

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S&JY" <youngsters-at-konnections-dot-net> 

David,

You should be able to directly measure the polarity with an ordinary
voltmeter on it highest DC scale (typically 1000 V).  You just have to very
carefully ramp up the AC input until you get a meter indication.

For better ramp-up control, you can run your variac into an AC arc welder,
MOT run backwards or large filament transformer and use the low voltage
output to more carefully run your X-ray power supply and have less chance of
burning out your voltmeter.

This only works if the HV diodes are semiconductors.  If they are tubes,
don't try this method!
--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, August 07, 2004 9:34 AM
Subject: Polarized HV/ what's + and what's -


 > Original poster: "David Rieben" <drieben-at-midsouth.rr-dot-com>
 >
 > Hi all,
 >
 > I recently scored a pretty nice x-ray transformer. I think it's
 > rated around 150 kV -at- ~ 600 mA. I've already repaired a
 > carbon tracked phenolic rectifier mount twice. The new
 > phenolic mounting block also carbon tracked after the
 > first repair but so far the second repair has held up (keep-
 > ing my fingers crossed). Anyway, I'm wanting to keep
 > the rectifiers intact in this transformer since I'm wanting
 > this one as a very high DC voltage source. Since I have
 > it all back together after the last repair I really don't want
 > to dig into the oily mess again just to get a close look at
 > the diodes to determine the polarity of the HV outputs. I
 > have heard that one polarity tends to form corona easier
 > and actually arc further at a given voltage than the other.
 > I've noticed this phenomena from the output leads of this
 > transformer as I slowly ramp up the input voltage to it with
 > a big variac. Of course I'm also seriesing the variac's out-
 > put to it with a ballast assembly since x-ray trannies are
 > NOT current limited. Anyway, I was thinking that the ne-
 > gative terminal would be the one that would most likely
 > tend to more corona and arc further at a given voltage
 > but I simply can't remeber for sure. I think Antonio de
 > Quieros was talking about this once. Can anyone tell
 > me which polarity will form more corona and arc further
 > at a given DC voltage?
 >
 > Thanks,
 > David Rieben
 >
 >
 >