RE: Common mode voltage & Safety Gaps

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

Original poster: "Steve K by way of Terry Fritz <teslalist-at-qwest-dot-net>" <teslainnovations-at-yahoo-dot-com>

Gary,
Thanks... So you are saying that when arc touches the
primary, there will be a stress potential between the
insulation of the NST secondary and grounded core? If
that's the case, then wouldn't the potential rather
arc across either side of the safety gap instead of
through the secondary's insulation? I guess having
only one side of the safety gap fire would explain
your common mode voltage explanation, since it is
attracted to ground instead of the other high voltage
lead. I would think that safety gaps would be
sufficient protection against primary stikes, so long
as they were properly spaced. The capacitors shouldn't
be stressed as you explained before, so the only other
thing that should be bad about primary stiking is
connecting the high voltage to the 60hz of the
primary. Let's forget about RF interference too...

Steve Klec
--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Lau, Gary by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>
 >
 > Consider the two wire mains cable - hot and neutral.
 >  Common mode refers to
 > a signal that is pretty much the same on hot &
 > neutral.  The voltage of
 > interest is relative to ground, not between the two
 > conductors.
 >
 > The opposite of common mode is differential.  Here
 > the voltage of interest
 > is measured between the two conductors, and ground
 > is irrelevant.
 >
 > What I was getting at is that high voltage
 > transients exist not between the
 > two NST primary leads, but rather equally between
 > each of the two leads and
 > ground.
 >
 > My "definition" may not be clinically precise, but I
 > hope it helps.
 >
 > Regards, Gary Lau
 > MA, USA
 >
 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Thursday, May 15, 2003 10:57 PM
 > To: tesla-at-pupman-dot-com
 > Subject: Common mode voltage
 >
 >
 > Original poster: "Steve K by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>"
 > <teslainnovations-at-yahoo-dot-com>
 >
 > I am not very advanced with electrical terms and
 > such... I was just wondering what "common mode
 > voltage" means.
 >
 > Steve
 >
 >


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