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Scoped? primary
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From: Harri Suomalainen [SMTP:haba-at-cc.hut.fi]
Sent: Tuesday, August 18, 1998 12:20 PM
To: tesla-at-pupman-dot-com
Subject: Re: Scoped? primary
>>14 turns on this one, I took the free end and connected about 5meg onto
it
>>and then went to my probe. I didn't connect the ground I left it
floating.
>
>to transformer action with the tap you mention. Be absolutely sure the 5
>meg resistor will withstand that voltage.
That is really a must. Further, do notice that a properly dc-rated
resistor
might not work at ac ringing primary. It may work or may fail in time.
Reasons behind this danger are related to capasitive effects of the
resistor
which may cause uneven voltage stress to different parts of the resistor.
With large long resistors (hv resistors or long resistor chains) this is
very
real. With high-voltage transients this is very likely to cause problems
sooner or later.
> The ground lead should be
>grounded by the scope's ground.
Scope should definately be solidly grounded. A floating scope connected to
some point of hv circuits might be very dangerous!
> You probably graounded yourself when you
>touched it and drained you body's charge (you were in the E field of the
5Meg resistor leaks about 2mA at 10kV. You feel that very well.
Capasitance
from scope to ground might also be charged to some voltage. Touching
scope chassis should shock you as well.
If the pole pig (or whatever) had a floating output then the capasitance
of
the transformer might also be one shocking you.
It is very important to ground scope properly! Floating scopes connected
improperly to systems are very very dangerous things around!
--
Harri Suomalainen mailto:haba-at-cc.hut.fi
We have phone numbers, why'd we need IP-numbers? - a person in a bus