Re: Arcing and current
Subject: Re: Arcing and current
From: chip (Chip Atkinson)
Date: Mon, 2 May 1994 13:09:45 +0700
>>>> I would think that this would screw up the tuning. When your secondary
>>>> is not arcing, you would have one inductance, and when it arcs, it would
>>>> be like removing a section of the coil and replacing it with a resistance.
>>>> I would think that this would change the inductance (and resistance) and
>>>> consequently the tuning would change depending on whether it's arcing
>>>> or not.
That sounds like it makes sense. I "fixed" the secondary that we are talking
about with a bunch of epoxy on the outside and between the windings. Once
it cured, I was ready. This saturday I fired the thing up and noticed several
things (I don't remember the exact order though): What looked like a cobweb
type of discharge between the tap clamp on the primary and the outside of the
secondary. Then I heard this strange hollow sparking sound. Later, I saw
a bunch of sparks all over the secondary. After a bit of investigation, I
discovered that the hollow sparking sound was an arc inside the secondary.
The arc was about 2" long and left a small carbon track on the cardboard.
Therefore, I think that I will replace the entire secondary with a plastic
tube. I have heard that using concrete forms is bad because they are
somewhat conductive. Based on saturday's experience, I would have to
agree. I think I will try using a PVC or HDPE tube next time.
>>>> Hooked up normally, a variac is simply a transformer that allows you to
>>>> vary the turns ratio, which will vary the voltage directly, not limit your
Does this mean that the current that can be drawn from a variac is limited
only by the "meltdown current"?