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[Amps] Arcing

To: <amps@contesting.com>
Subject: [Amps] Arcing
From: w8ji at contesting.com (Tom Rauch)
Date: Fri Mar 7 13:08:29 2003
> immediately. The CT was probably about 2ft in diameter and 10" thick, with
a
> ratio of 1200:5.  I was really lucky (blessed) that my knuckle on the same
> hand was touching ground, as the voltage was tremendous and I don't think
I
> would have survived that potential across my chest.

This is a different situation than the flyback or energy storage situation I
outlined Jeff, because it probably was a sinewave source causing a
time-varying flux that did not result in an abrupt collapse of field. An
ignition coil or tank driven by a less-than-class A tube, or an ohmmeter
across a transformer would have an extra kick (as do relays and motors)
unless something shorted the backpulse.

In your case the current transformer acts like a normal transformer rather
than an energy storage system, unless someone broke the line abruptly at a
sinewave peak. The problem is you can have considerable voltage drop across
the primary impedance, because the primary impedance can be high if the
secondary is unterminated. With a sinewave signal you could have had
hundreds of volts across the primary, which would be stepped up to many
thousands of secondary volts.

As you learned, an open termination on a current transformer can produce
some large voltages!! But no more that the turns ratio of the transformer
and operating voltage would indicate. A system with an abrupt drop in
primary excitation, especially if flux density was high, would be a
different matter.

73 Tom

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