Sooooo, I tried option #3, the snubber approach, and
it kinda worked.
I used some of the (1 uF) capacitors & diodes from
my aborted Microwave oven power supply project and a
bunch of 160K 2 watts R's wired in series parallel for
an effective 240K discharge R.
This generally suppressed the arcing on the two
highest power settings when running at 3KV but,
switching to the lowest setting still arced fairly
repeatably. This also happens to be at the point
where the power supply transistions out of true choke
input operation and jumps from 2950 to 3050 volts. I
guess with the geometries involved it is a magic (or
tragic!) point. I then increased the suppressor cap.
on this pole to 2uF and that did the trick.
The switch still must be turned briskly. Now if I
just had one of those spring operated mechanisms used
on the realllllly high power switches....
If this was for more than just a test load it would
best be done with vacuum relays.
73 & Good morning,
Marv WC6W
http://wc6w.50webs.com/
--- Radio WC6W <wc6w_amps@yahoo.com> wrote:
> I recently reconfigured a 3KW load bank, which I
> use
> for amplifier power supply testing, by adding a 4
> position progressively shorting switch to select 1
> thru 4, 12K paths resulting in a selectable 12K, 6K,
> 4K, or 3K ohm load.
>
> This worked well until I ran the voltage up around
> 3KV where I noticed a disturbing tendency for the
> switch, even though it has 1/4" spacing between the
> terminals, to arc when the load is hot switched to a
> higher resistance. Said arc is maintained and is
> only extinguished by removing power.
>
> My first thru fourth thoughts to remedy this
> anomally are:
>
> 1. Reposition the switch vertically and put an
> oil filled jar over the terminals.
>
> 2. Use compressed air or a fast fan to blow the
> arc(s) out.
>
> 3. Add Capacitor/Diode/Resistor snubbing
> networks
> across the terminals, using something on the order
> of 1uF for the C.
>
> 4. Use a vacuum relay to switch the load bank
> out when the switch is in transit. This requires an
> external power source for the relay.
>
> Does anyone have a better idea? Or experience
> with a similar situation??
>
> 73 & Good afternoon,
> Marv WC6W
>
> http://wc6w.50webs.com/
>
>
>
>
>
>
>
> *
>
>
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